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| author | Laurent Pinchart <laurent.pinchart@ideasonboard.com> | 2012-07-13 02:57:26 +0400 |
|---|---|---|
| committer | Laurent Pinchart <laurent.pinchart@ideasonboard.com> | 2012-08-23 14:02:53 +0400 |
| commit | 9cad9c95d7e8d6d61d8c9729e0b6bbd18f47d86d (patch) | |
| tree | 75e06ef26bb69e1676f31e13bd461a0e26e45a07 /Documentation/DocBook | |
| parent | 269b62db0e52bf2656aa762d61cfe67f3705fdff (diff) | |
| download | linux-9cad9c95d7e8d6d61d8c9729e0b6bbd18f47d86d.tar.xz | |
Documentation: DocBook DRM framework documentation
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Rob Clark <rob.clark@linaro.org>
Diffstat (limited to 'Documentation/DocBook')
| -rw-r--r-- | Documentation/DocBook/drm.tmpl | 2835 |
1 files changed, 2226 insertions, 609 deletions
diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl index 196b8b9dba11..b0300529ab13 100644 --- a/Documentation/DocBook/drm.tmpl +++ b/Documentation/DocBook/drm.tmpl @@ -6,11 +6,36 @@ <bookinfo> <title>Linux DRM Developer's Guide</title> + <authorgroup> + <author> + <firstname>Jesse</firstname> + <surname>Barnes</surname> + <contrib>Initial version</contrib> + <affiliation> + <orgname>Intel Corporation</orgname> + <address> + <email>jesse.barnes@intel.com</email> + </address> + </affiliation> + </author> + <author> + <firstname>Laurent</firstname> + <surname>Pinchart</surname> + <contrib>Driver internals</contrib> + <affiliation> + <orgname>Ideas on board SPRL</orgname> + <address> + <email>laurent.pinchart@ideasonboard.com</email> + </address> + </affiliation> + </author> + </authorgroup> + <copyright> <year>2008-2009</year> - <holder> - Intel Corporation (Jesse Barnes <jesse.barnes@intel.com>) - </holder> + <year>2012</year> + <holder>Intel Corporation</holder> + <holder>Laurent Pinchart</holder> </copyright> <legalnotice> @@ -20,6 +45,17 @@ the kernel source COPYING file. </para> </legalnotice> + + <revhistory> + <!-- Put document revisions here, newest first. --> + <revision> + <revnumber>1.0</revnumber> + <date>2012-07-13</date> + <authorinitials>LP</authorinitials> + <revremark>Added extensive documentation about driver internals. + </revremark> + </revision> + </revhistory> </bookinfo> <toc></toc> @@ -72,342 +108,361 @@ submission & fencing, suspend/resume support, and DMA services. </para> - <para> - The core of every DRM driver is struct drm_driver. Drivers - typically statically initialize a drm_driver structure, - then pass it to drm_init() at load time. - </para> <!-- Internals: driver init --> <sect1> - <title>Driver initialization</title> - <para> - Before calling the DRM initialization routines, the driver must - first create and fill out a struct drm_driver structure. - </para> - <programlisting> - static struct drm_driver driver = { - /* Don't use MTRRs here; the Xserver or userspace app should - * deal with them for Intel hardware. - */ - .driver_features = - DRIVER_USE_AGP | DRIVER_REQUIRE_AGP | - DRIVER_HAVE_IRQ | DRIVER_IRQ_SHARED | DRIVER_MODESET, - .load = i915_driver_load, - .unload = i915_driver_unload, - .firstopen = i915_driver_firstopen, - .lastclose = i915_driver_lastclose, - .preclose = i915_driver_preclose, - .save = i915_save, - .restore = i915_restore, - .device_is_agp = i915_driver_device_is_agp, - .get_vblank_counter = i915_get_vblank_counter, - .enable_vblank = i915_enable_vblank, - .disable_vblank = i915_disable_vblank, - .irq_preinstall = i915_driver_irq_preinstall, - .irq_postinstall = i915_driver_irq_postinstall, - .irq_uninstall = i915_driver_irq_uninstall, - .irq_handler = i915_driver_irq_handler, - .reclaim_buffers = drm_core_reclaim_buffers, - .get_map_ofs = drm_core_get_map_ofs, - .get_reg_ofs = drm_core_get_reg_ofs, - .fb_probe = intelfb_probe, - .fb_remove = intelfb_remove, - .fb_resize = intelfb_resize, - .master_create = i915_master_create, - .master_destroy = i915_master_destroy, -#if defined(CONFIG_DEBUG_FS) - .debugfs_init = i915_debugfs_init, - .debugfs_cleanup = i915_debugfs_cleanup, -#endif - .gem_init_object = i915_gem_init_object, - .gem_free_object = i915_gem_free_object, - .gem_vm_ops = &i915_gem_vm_ops, - .ioctls = i915_ioctls, - .fops = { - .owner = THIS_MODULE, - .open = drm_open, - .release = drm_release, - .ioctl = drm_ioctl, - .mmap = drm_mmap, - .poll = drm_poll, - .fasync = drm_fasync, -#ifdef CONFIG_COMPAT - .compat_ioctl = i915_compat_ioctl, -#endif - .llseek = noop_llseek, - }, - .pci_driver = { - .name = DRIVER_NAME, - .id_table = pciidlist, - .probe = probe, - .remove = __devexit_p(drm_cleanup_pci), - }, - .name = DRIVER_NAME, - .desc = DRIVER_DESC, - .date = DRIVER_DATE, - .major = DRIVER_MAJOR, - .minor = DRIVER_MINOR, - .patchlevel = DRIVER_PATCHLEVEL, - }; - </programlisting> - <para> - In the example above, taken from the i915 DRM driver, the driver - sets several flags indicating what core features it supports; - we go over the individual callbacks in later sections. Since - flags indicate which features your driver supports to the DRM - core, you need to set most of them prior to calling drm_init(). Some, - like DRIVER_MODESET can be set later based on user supplied parameters, - but that's the exception rather than the rule. - </para> - <variablelist> - <title>Driver flags</title> - <varlistentry> - <term>DRIVER_USE_AGP</term> - <listitem><para> - Driver uses AGP interface - </para></listitem> - </varlistentry> - <varlistentry> - <term>DRIVER_REQUIRE_AGP</term> - <listitem><para> - Driver needs AGP interface to function. - </para></listitem> - </varlistentry> - <varlistentry> - <term>DRIVER_USE_MTRR</term> - <listitem> - <para> - Driver uses MTRR interface for mapping memory. Deprecated. - </para> - </listitem> - </varlistentry> - <varlistentry> - <term>DRIVER_PCI_DMA</term> - <listitem><para> - Driver is capable of PCI DMA. Deprecated. - </para></listitem> - </varlistentry> - <varlistentry> - <term>DRIVER_SG</term> - <listitem><para> - Driver can perform scatter/gather DMA. Deprecated. - </para></listitem> - </varlistentry> - <varlistentry> - <term>DRIVER_HAVE_DMA</term> - <listitem><para>Driver supports DMA. Deprecated.</para></listitem> - </varlistentry> - <varlistentry> - <term>DRIVER_HAVE_IRQ</term><term>DRIVER_IRQ_SHARED</term> - <listitem> - <para> - DRIVER_HAVE_IRQ indicates whether the driver has an IRQ - handler. DRIVER_IRQ_SHARED indicates whether the device & - handler support shared IRQs (note that this is required of - PCI drivers). - </para> - </listitem> - </varlistentry> - <varlistentry> - <term>DRIVER_DMA_QUEUE</term> - <listitem> - <para> - Should be set if the driver queues DMA requests and completes them - asynchronously. Deprecated. - </para> - </listitem> - </varlistentry> - <varlistentry> - <term>DRIVER_FB_DMA</term> - <listitem> - <para> - Driver supports DMA to/from the framebuffer. Deprecated. - </para> - </listitem> - </varlistentry> - <varlistentry> - <term>DRIVER_MODESET</term> - <listitem> - <para> - Driver supports mode setting interfaces. - </para> - </listitem> - </varlistentry> - </variablelist> - <para> - In this specific case, the driver requires AGP and supports - IRQs. DMA, as discussed later, is handled by device-specific ioctls - in this case. It also supports the kernel mode setting APIs, though - unlike in the actual i915 driver source, this example unconditionally - exports KMS capability. + <title>Driver Initialization</title> + <para> + At the core of every DRM driver is a <structname>drm_driver</structname> + structure. Drivers typically statically initialize a drm_driver structure, + and then pass it to one of the <function>drm_*_init()</function> functions + to register it with the DRM subsystem. </para> - </sect1> - - <!-- Internals: driver load --> - - <sect1> - <title>Driver load</title> - <para> - In the previous section, we saw what a typical drm_driver - structure might look like. One of the more important fields in - the structure is the hook for the load function. - </para> - <programlisting> - static struct drm_driver driver = { - ... - .load = i915_driver_load, - ... - }; - </programlisting> - <para> - The load function has many responsibilities: allocating a driver - private structure, specifying supported performance counters, - configuring the device (e.g. mapping registers & command - buffers), initializing the memory manager, and setting up the - initial output configuration. - </para> - <para> - If compatibility is a concern (e.g. with drivers converted over - to the new interfaces from the old ones), care must be taken to - prevent device initialization and control that is incompatible with - currently active userspace drivers. For instance, if user - level mode setting drivers are in use, it would be problematic - to perform output discovery & configuration at load time. - Likewise, if user-level drivers unaware of memory management are - in use, memory management and command buffer setup may need to - be omitted. These requirements are driver-specific, and care - needs to be taken to keep both old and new applications and - libraries working. The i915 driver supports the "modeset" - module parameter to control whether advanced features are - enabled at load time or in legacy fashion. + <para> + The <structname>drm_driver</structname> structure contains static + information that describes the driver and features it supports, and + pointers to methods that the DRM core will call to implement the DRM API. + We will first go through the <structname>drm_driver</structname> static + information fields, and will then describe individual operations in + details as they get used in later sections. </para> - <sect2> - <title>Driver private & performance counters</title> - <para> - The driver private hangs off the main drm_device structure and - can be used for tracking various device-specific bits of - information, like register offsets, command buffer status, - register state for suspend/resume, etc. At load time, a - driver may simply allocate one and set drm_device.dev_priv - appropriately; it should be freed and drm_device.dev_priv set - to NULL when the driver is unloaded. - </para> + <title>Driver Information</title> + <sect3> + <title>Driver Features</title> + <para> + Drivers inform the DRM core about their requirements and supported + features by setting appropriate flags in the + <structfield>driver_features</structfield> field. Since those flags + influence the DRM core behaviour since registration time, most of them + must be set to registering the <structname>drm_driver</structname> + instance. + </para> + <synopsis>u32 driver_features;</synopsis> + <variablelist> + <title>Driver Feature Flags</title> + <varlistentry> + <term>DRIVER_USE_AGP</term> + <listitem><para> + Driver uses AGP interface, the DRM core will manage AGP resources. + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRIVER_REQUIRE_AGP</term> + <listitem><para> + Driver needs AGP interface to function. AGP initialization failure + will become a fatal error. + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRIVER_USE_MTRR</term> + <listitem><para> + Driver uses MTRR interface for mapping memory, the DRM core will + manage MTRR resources. Deprecated. + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRIVER_PCI_DMA</term> + <listitem><para> + Driver is capable of PCI DMA, mapping of PCI DMA buffers to + userspace will be enabled. Deprecated. + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRIVER_SG</term> + <listitem><para> + Driver can perform scatter/gather DMA, allocation and mapping of + scatter/gather buffers will be enabled. Deprecated. + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRIVER_HAVE_DMA</term> + <listitem><para> + Driver supports DMA, the userspace DMA API will be supported. + Deprecated. + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRIVER_HAVE_IRQ</term><term>DRIVER_IRQ_SHARED</term> + <listitem><para> + DRIVER_HAVE_IRQ indicates whether the driver has an IRQ handler. The + DRM core will automatically register an interrupt handler when the + flag is set. DRIVER_IRQ_SHARED indicates whether the device & + handler support shared IRQs (note that this is required of PCI + drivers). + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRIVER_IRQ_VBL</term> + <listitem><para>Unused. Deprecated.</para></listitem> + </varlistentry> + <varlistentry> + <term>DRIVER_DMA_QUEUE</term> + <listitem><para> + Should be set if the driver queues DMA requests and completes them + asynchronously. Deprecated. + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRIVER_FB_DMA</term> + <listitem><para> + Driver supports DMA to/from the framebuffer, mapping of frambuffer + DMA buffers to userspace will be supported. Deprecated. + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRIVER_IRQ_VBL2</term> + <listitem><para>Unused. Deprecated.</para></listitem> + </varlistentry> + <varlistentry> + <term>DRIVER_GEM</term> + <listitem><para> + Driver use the GEM memory manager. + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRIVER_MODESET</term> + <listitem><para> + Driver supports mode setting interfaces (KMS). + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRIVER_PRIME</term> + <listitem><para> + Driver implements DRM PRIME buffer sharing. + </para></listitem> + </varlistentry> + </variablelist> + </sect3> + <sect3> + <title>Major, Minor and Patchlevel</title> + <synopsis>int major; +int minor; +int patchlevel;</synopsis> + <para> + The DRM core identifies driver versions by a major, minor and patch + level triplet. The information is printed to the kernel log at + initialization time and passed to userspace through the + DRM_IOCTL_VERSION ioctl. + </para> + <para> + The major and minor numbers are also used to verify the requested driver + API version passed to DRM_IOCTL_SET_VERSION. When the driver API changes + between minor versions, applications can call DRM_IOCTL_SET_VERSION to + select a specific version of the API. If the requested major isn't equal + to the driver major, or the requested minor is larger than the driver + minor, the DRM_IOCTL_SET_VERSION call will return an error. Otherwise + the driver's set_version() method will be called with the requested + version. + </para> + </sect3> + <sect3> + <title>Name, Description and Date</title> + <synopsis>char *name; +char *desc; +char *date;</synopsis> + <para> + The driver name is printed to the kernel log at initialization time, + used for IRQ registration and passed to userspace through + DRM_IOCTL_VERSION. + </para> + <para> + The driver description is a purely informative string passed to + userspace through the DRM_IOCTL_VERSION ioctl and otherwise unused by + the kernel. + </para> + <para> + The driver date, formatted as YYYYMMDD, is meant to identify the date of + the latest modification to the driver. However, as most drivers fail to + update it, its value is mostly useless. The DRM core prints it to the + kernel log at initialization time and passes it to userspace through the + DRM_IOCTL_VERSION ioctl. + </para> + </sect3> + </sect2> + <sect2> + <title>Driver Load</title> <para> - The DRM supports several counters which may be used for rough - performance characterization. Note that the DRM stat counter - system is not often used by applications, and supporting - additional counters is completely optional. + The <methodname>load</methodname> method is the driver and device + initialization entry point. The method is responsible for allocating and + initializing driver private data, specifying supported performance + counters, performing resource allocation and mapping (e.g. acquiring + clocks, mapping registers or allocating command buffers), initializing + the memory manager (<xref linkend="drm-memory-management"/>), installing + the IRQ handler (<xref linkend="drm-irq-registration"/>), setting up + vertical blanking handling (<xref linkend="drm-vertical-blank"/>), mode + setting (<xref linkend="drm-mode-setting"/>) and initial output + configuration (<xref linkend="drm-kms-init"/>). </para> + <note><para> + If compatibility is a concern (e.g. with drivers converted over from + User Mode Setting to Kernel Mode Setting), care must be taken to prevent + device initialization and control that is incompatible with currently + active userspace drivers. For instance, if user level mode setting + drivers are in use, it would be problematic to perform output discovery + & configuration at load time. Likewise, if user-level drivers + unaware of memory management are in use, memory management and command + buffer setup may need to be omitted. These requirements are + driver-specific, and care needs to be taken to keep both old and new + applications and libraries working. + </para></note> + <synopsis>int (*load) (struct drm_device *, unsigned long flags);</synopsis> <para> - These interfaces are deprecated and should not be used. If performance - monitoring is desired, the developer should investigate and - potentially enhance the kernel perf and tracing infrastructure to export - GPU related performance information for consumption by performance - monitoring tools and applications. + The method takes two arguments, a pointer to the newly created + <structname>drm_device</structname> and flags. The flags are used to + pass the <structfield>driver_data</structfield> field of the device id + corresponding to the device passed to <function>drm_*_init()</function>. + Only PCI devices currently use this, USB and platform DRM drivers have + their <methodname>load</methodname> method called with flags to 0. </para> + <sect3> + <title>Driver Private & Performance Counters</title> + <para> + The driver private hangs off the main + <structname>drm_device</structname> structure and can be used for + tracking various device-specific bits of information, like register + offsets, command buffer status, register state for suspend/resume, etc. + At load time, a driver may simply allocate one and set + <structname>drm_device</structname>.<structfield>dev_priv</structfield> + appropriately; it should be freed and + <structname>drm_device</structname>.<structfield>dev_priv</structfield> + set to NULL when the driver is unloaded. + </para> + <para> + DRM supports several counters which were used for rough performance + characterization. This stat counter system is deprecated and should not + be used. If performance monitoring is desired, the developer should + investigate and potentially enhance the kernel perf and tracing + infrastructure to export GPU related performance information for + consumption by performance monitoring tools and applications. + </para> + </sect3> + <sect3 id="drm-irq-registration"> + <title>IRQ Registration</title> + <para> + The DRM core tries to facilitate IRQ handler registration and + unregistration by providing <function>drm_irq_install</function> and + <function>drm_irq_uninstall</function> functions. Those functions only + support a single interrupt per device. + </para> + <!--!Fdrivers/char/drm/drm_irq.c drm_irq_install--> + <para> + Both functions get the device IRQ by calling + <function>drm_dev_to_irq</function>. This inline function will call a + bus-specific operation to retrieve the IRQ number. For platform devices, + <function>platform_get_irq</function>(..., 0) is used to retrieve the + IRQ number. + </para> + <para> + <function>drm_irq_install</function> starts by calling the + <methodname>irq_preinstall</methodname> driver operation. The operation + is optional and must make sure that the interrupt will not get fired by + clearing all pending interrupt flags or disabling the interrupt. + </para> + <para> + The IRQ will then be requested by a call to + <function>request_irq</function>. If the DRIVER_IRQ_SHARED driver + feature flag is set, a shared (IRQF_SHARED) IRQ handler will be + requested. + </para> + <para> + The IRQ handler function must be provided as the mandatory irq_handler + driver operation. It will get passed directly to + <function>request_irq</function> and thus has the same prototype as all + IRQ handlers. It will get called with a pointer to the DRM device as the + second argument. + </para> + <para> + Finally the function calls the optional + <methodname>irq_postinstall</methodname> driver operation. The operation + usually enables interrupts (excluding the vblank interrupt, which is + enabled separately), but drivers may choose to enable/disable interrupts + at a different time. + </para> + <para> + <function>drm_irq_uninstall</function> is similarly used to uninstall an + IRQ handler. It starts by waking up all processes waiting on a vblank + interrupt to make sure they don't hang, and then calls the optional + <methodname>irq_uninstall</methodname> driver operation. The operation + must disable all hardware interrupts. Finally the function frees the IRQ + by calling <function>free_irq</function>. + </para> + </sect3> + <sect3> + <title>Memory Manager Initialization</title> + <para> + Every DRM driver requires a memory manager which must be initialized at + load time. DRM currently contains two memory managers, the Translation + Table Manager (TTM) and the Graphics Execution Manager (GEM). + This document describes the use of the GEM memory manager only. See + <xref linkend="drm-memory-management"/> for details. + </para> + </sect3> + <sect3> + <title>Miscellaneous Device Configuration</title> + <para> + Another task that may be necessary for PCI devices during configuration + is mapping the video BIOS. On many devices, the VBIOS describes device + configuration, LCD panel timings (if any), and contains flags indicating + device state. Mapping the BIOS can be done using the pci_map_rom() call, + a convenience function that takes care of mapping the actual ROM, + whether it has been shadowed into memory (typically at address 0xc0000) + or exists on the PCI device in the ROM BAR. Note that after the ROM has + been mapped and any necessary information has been extracted, it should + be unmapped; on many devices, the ROM address decoder is shared with + other BARs, so leaving it mapped could cause undesired behaviour like + hangs or memory corruption. + <!--!Fdrivers/pci/rom.c pci_map_rom--> + </para> + </sect3> </sect2> + </sect1> - <sect2> - <title>Configuring the device</title> - <para> - Obviously, device configuration is device-specific. - However, there are several common operations: finding a - device's PCI resources, mapping them, and potentially setting - up an IRQ handler. - </para> - <para> - Finding & mapping resources is fairly straightforward. The - DRM wrapper functions, drm_get_resource_start() and - drm_get_resource_len(), may be used to find BARs on the given - drm_device struct. Once those values have been retrieved, the - driver load function can call drm_addmap() to create a new - mapping for the BAR in question. Note that you probably want a - drm_local_map_t in your driver private structure to track any - mappings you create. -<!-- !Fdrivers/gpu/drm/drm_bufs.c drm_get_resource_* --> -<!-- !Finclude/drm/drmP.h drm_local_map_t --> - </para> - <para> - if compatibility with other operating systems isn't a concern - (DRM drivers can run under various BSD variants and OpenSolaris), - native Linux calls may be used for the above, e.g. pci_resource_* - and iomap*/iounmap. See the Linux device driver book for more - info. - </para> - <para> - Once you have a register map, you may use the DRM_READn() and - DRM_WRITEn() macros to access the registers on your device, or - use driver-specific versions to offset into your MMIO space - relative to a driver-specific base pointer (see I915_READ for - an example). - </para> - <para> - If your device supports interrupt generation, you may want to - set up an interrupt handler when the driver is loaded. This - is done using the drm_irq_install() function. If your device - supports vertical blank interrupts, it should call - drm_vblank_init() to initialize the core vblank handling code before - enabling interrupts on your device. This ensures the vblank related - structures are allocated and allows the core to handle vblank events. - </para> -<!--!Fdrivers/char/drm/drm_irq.c drm_irq_install--> - <para> - Once your interrupt handler is registered (it uses your - drm_driver.irq_handler as the actual interrupt handling - function), you can safely enable interrupts on your device, - assuming any other state your interrupt handler uses is also - initialized. - </para> - <para> - Another task that may be necessary during configuration is - mapping the video BIOS. On many devices, the VBIOS describes - device configuration, LCD panel timings (if any), and contains - flags indicating device state. Mapping the BIOS can be done - using the pci_map_rom() call, a convenience function that - takes care of mapping the actual ROM, whether it has been - shadowed into memory (typically at address 0xc0000) or exists - on the PCI device in the ROM BAR. Note that after the ROM - has been mapped and any necessary information has been extracted, - it should be unmapped; on many devices, the ROM address decoder is - shared with other BARs, so leaving it mapped could cause - undesired behavior like hangs or memory corruption. -<!--!Fdrivers/pci/rom.c pci_map_rom--> - </para> - </sect2> + <!-- Internals: memory management --> + <sect1 id="drm-memory-management"> + <title>Memory management</title> + <para> + Modern Linux systems require large amount of graphics memory to store + frame buffers, textures, vertices and other graphics-related data. Given + the very dynamic nature of many of that data, managing graphics memory + efficiently is thus crucial for the graphics stack and plays a central + role in the DRM infrastructure. + </para> + <para> + The DRM core includes two memory managers, namely Translation Table Maps + (TTM) and Graphics Execution Manager (GEM). TTM was the first DRM memory + manager to be developed and tried to be a one-size-fits-them all + solution. It provides a single userspace API to accomodate the need of + all hardware, supporting both Unified Memory Architecture (UMA) devices + and devices with dedicated video RAM (i.e. most discrete video cards). + This resulted in a large, complex piece of code that turned out to be + hard to use for driver development. + </para> + <para> + GEM started as an Intel-sponsored project in reaction to TTM's + complexity. Its design philosophy is completely different: instead of + providing a solution to every graphics memory-related problems, GEM + identified common code between drivers and created a support library to + share it. GEM has simpler initialization and execution requirements than + TTM, but has no video RAM management capabitilies and is thus limited to + UMA devices. + </para> <sect2> - <title>Memory manager initialization</title> - <para> - In order to allocate command buffers, cursor memory, scanout - buffers, etc., as well as support the latest features provided - by packages like Mesa and the X.Org X server, your driver - should support a memory manager. - </para> + <title>The Translation Table Manager (TTM)</title> <para> - If your driver supports memory management (it should!), you - need to set that up at load time as well. How you initialize - it depends on which memory manager you're using: TTM or GEM. + TTM design background and information belongs here. </para> <sect3> <title>TTM initialization</title> - <para> - TTM (for Translation Table Manager) manages video memory and - aperture space for graphics devices. TTM supports both UMA devices - and devices with dedicated video RAM (VRAM), i.e. most discrete - graphics devices. If your device has dedicated RAM, supporting - TTM is desirable. TTM also integrates tightly with your - driver-specific buffer execution function. See the radeon - driver for examples. - </para> - <para> - The core TTM structure is the ttm_bo_driver struct. It contains - several fields with function pointers for initializing the TTM, - allocating and freeing memory, waiting for command completion - and fence synchronization, and memory migration. See the - radeon_ttm.c file for an example of usage. + <warning><para>This section is outdated.</para></warning> + <para> + Drivers wishing to support TTM must fill out a drm_bo_driver + structure. The structure contains several fields with function + pointers for initializing the TTM, allocating and freeing memory, + waiting for command completion and fence synchronization, and memory + migration. See the radeon_ttm.c file for an example of usage. </para> <para> The ttm_global_reference structure is made up of several fields: @@ -445,82 +500,1081 @@ count for the TTM, which will call your initialization function. </para> </sect3> + </sect2> + <sect2 id="drm-gem"> + <title>The Graphics Execution Manager (GEM)</title> + <para> + The GEM design approach has resulted in a memory manager that doesn't + provide full coverage of all (or even all common) use cases in its + userspace or kernel API. GEM exposes a set of standard memory-related + operations to userspace and a set of helper functions to drivers, and let + drivers implement hardware-specific operations with their own private API. + </para> + <para> + The GEM userspace API is described in the + <ulink url="http://lwn.net/Articles/283798/"><citetitle>GEM - the Graphics + Execution Manager</citetitle></ulink> article on LWN. While slightly + outdated, the document provides a good overview of the GEM API principles. + Buffer allocation and read and write operations, described as part of the + common GEM API, are currently implemented using driver-specific ioctls. + </para> + <para> + GEM is data-agnostic. It manages abstract buffer objects without knowing + what individual buffers contain. APIs that require knowledge of buffer + contents or purpose, such as buffer allocation or synchronization + primitives, are thus outside of the scope of GEM and must be implemented + using driver-specific ioctls. + </para> + <para> + On a fundamental level, GEM involves several operations: + <itemizedlist> + <listitem>Memory allocation and freeing</listitem> + <listitem>Command execution</listitem> + <listitem>Aperture management at command execution time</listitem> + </itemizedlist> + Buffer object allocation is relatively straightforward and largely + provided by Linux's shmem layer, which provides memory to back each + object. + </para> + <para> + Device-specific operations, such as command execution, pinning, buffer + read & write, mapping, and domain ownership transfers are left to + driver-specific ioctls. + </para> + <sect3> + <title>GEM Initialization</title> + <para> + Drivers that use GEM must set the DRIVER_GEM bit in the struct + <structname>drm_driver</structname> + <structfield>driver_features</structfield> field. The DRM core will + then automatically initialize the GEM core before calling the + <methodname>load</methodname> operation. Behind the scene, this will + create a DRM Memory Manager object which provides an address space + pool for object allocation. + </para> + <para> + In a KMS configuration, drivers need to allocate and initialize a + command ring buffer following core GEM initialization if required by + the hardware. UMA devices usually have what is called a "stolen" + memory region, which provides space for the initial framebuffer and + large, contiguous memory regions required by the device. This space is + typically not managed by GEM, and must be initialized separately into + its own DRM MM object. + </para> + </sect3> <sect3> - <title>GEM initialization</title> - <para> - GEM is an alternative to TTM, designed specifically for UMA - devices. It has simpler initialization and execution requirements - than TTM, but has no VRAM management capability. Core GEM - is initialized by calling drm_mm_init() to create - a GTT DRM MM object, which provides an address space pool for - object allocation. In a KMS configuration, the driver - needs to allocate and initialize a command ring buffer following - core GEM initialization. A UMA device usually has what is called a - "stolen" memory region, which provides space for the initial - framebuffer and large, contiguous memory regions required by the - device. This space is not typically managed by GEM, and it must - be initialized separately into its own DRM MM object. - </para> - <para> - Initialization is driver-specific. In the case of Intel - integrated graphics chips like 965GM, GEM initialization can - be done by calling the internal GEM init function, - i915_gem_do_init(). Since the 965GM is a UMA device - (i.e. it doesn't have dedicated VRAM), GEM manages - making regular RAM available for GPU operations. Memory set - aside by the BIOS (called "stolen" memory by the i915 - driver) is managed by the DRM memrange allocator; the - rest of the aperture is managed by GEM. - <programlisting> - /* Basic memrange allocator for stolen space (aka vram) */ - drm_memrange_init(&dev_priv->vram, 0, prealloc_size); - /* Let GEM Manage from end of prealloc space to end of aperture */ - i915_gem_do_init(dev, prealloc_size, agp_size); - </programlisting> -<!--!Edrivers/char/drm/drm_memrange.c--> - </para> - <para> - Once the memory manager has been set up, we may allocate the - command buffer. In the i915 case, this is also done with a - GEM function, i915_gem_init_ringbuffer(). - </para> + <title>GEM Objects Creation</title> + <para> + GEM splits creation of GEM objects and allocation of the memory that + backs them in two distinct operations. + </para> + <para> + GEM objects are represented by an instance of struct + <structname>drm_gem_object</structname>. Drivers usually need to extend + GEM objects with private information and thus create a driver-specific + GEM object structure type that embeds an instance of struct + <structname>drm_gem_object</structname>. + </para> + <para> + To create a GEM object, a driver allocates memory for an instance of its + specific GEM object type and initializes the embedded struct + <structname>drm_gem_object</structname> with a call to + <function>drm_gem_object_init</function>. The function takes a pointer to + the DRM device, a pointer to the GEM object and the buffer object size + in bytes. + </para> + <para> + GEM uses shmem to allocate anonymous pageable memory. + <function>drm_gem_object_init</function> will create an shmfs file of + the requested size and store it into the struct + <structname>drm_gem_object</structname> <structfield>filp</structfield> + field. The memory is used as either main storage for the object when the + graphics hardware uses system memory directly or as a backing store + otherwise. + </para> + <para> + Drivers are responsible for the actual physical pages allocation by + calling <function>shmem_read_mapping_page_gfp</function> for each page. + Note that they can decide to allocate pages when initializing the GEM + object, or to delay allocation until the memory is needed (for instance + when a page fault occurs as a result of a userspace memory access or + when the driver needs to start a DMA transfer involving the memory). + </para> + <para> + Anonymous pageable memory allocation is not always desired, for instance + when the hardware requires physically contiguous system memory as is + often the case in embedded devices. Drivers can create GEM objects with + no shmfs backing (called private GEM objects) by initializing them with + a call to <function>drm_gem_private_object_init</function> instead of + <function>drm_gem_object_init</function>. Storage for private GEM + objects must be managed by drivers. + </para> + <para> + Drivers that do not need to extend GEM objects with private information + can call the <function>drm_gem_object_alloc</function> function to + allocate and initialize a struct <structname>drm_gem_object</structname> + instance. The GEM core will call the optional driver + <methodname>gem_init_object</methodname> operation after initializing + the GEM object with <function>drm_gem_object_init</function>. + <synopsis>int (*gem_init_object) (struct drm_gem_object *obj);</synopsis> + </para> + <para> + No alloc-and-init function exists for private GEM objects. + </para> + </sect3> + <sect3> + <title>GEM Objects Lifetime</title> + <para> + All GEM objects are reference-counted by the GEM core. References can be + acquired and release by <function>calling drm_gem_object_reference</function> + and <function>drm_gem_object_unreference</function> respectively. The + caller must hold the <structname>drm_device</structname> + <structfield>struct_mutex</structfield> lock. As a convenience, GEM + provides the <function>drm_gem_object_reference_unlocked</function> and + <function>drm_gem_object_unreference_unlocked</function> functions that + can be called without holding the lock. + </para> + <para> + When the last reference to a GEM object is released the GEM core calls + the <structname>drm_driver</structname> + <methodname>gem_free_object</methodname> operation. That operation is + mandatory for GEM-enabled drivers and must free the GEM object and all + associated resources. + </para> + <para> + <synopsis>void (*gem_free_object) (struct drm_gem_object *obj);</synopsis> + Drivers are responsible for freeing all GEM object resources, including + the resources created by the GEM core. If an mmap offset has been + created for the object (in which case + <structname>drm_gem_object</structname>::<structfield>map_list</structfield>::<structfield>map</structfield> + is not NULL) it must be freed by a call to + <function>drm_gem_free_mmap_offset</function>. The shmfs backing store + must be released by calling <function>drm_gem_object_release</function> + (that function can safely be called if no shmfs backing store has been + created). + </para> + </sect3> + <sect3> + <title>GEM Objects Naming</title> + <para> + Communication between userspace and the kernel refers to GEM objects + using local handles, global names or, more recently, file descriptors. + All of those are 32-bit integer values; the usual Linux kernel limits + apply to the file descriptors. + </para> + <para> + GEM handles are local to a DRM file. Applications get a handle to a GEM + object through a driver-specific ioctl, and can use that handle to refer + to the GEM object in other standard or driver-specific ioctls. Closing a + DRM file handle frees all its GEM handles and dereferences the + associated GEM objects. + </para> + <para> + To create a handle for a GEM object drivers call + <function>drm_gem_handle_create</function>. The function takes a pointer + to the DRM file and the GEM object and returns a locally unique handle. + When the handle is no longer needed drivers delete it with a call to + <function>drm_gem_handle_delete</function>. Finally the GEM object + associated with a handle can be retrieved by a call to + <function>drm_gem_object_lookup</function>. + </para> + <para> + Handles don't take ownership of GEM objects, they only take a reference + to the object that will be dropped when the handle is destroyed. To + avoid leaking GEM objects, drivers must make sure they drop the + reference(s) they own (such as the initial reference taken at object + creation time) as appropriate, without any special consideration for the + handle. For example, in the particular case of combined GEM object and + handle creation in the implementation of the + <methodname>dumb_create</methodname> operation, drivers must drop the + initial reference to the GEM object before returning the handle. + </para> + <para> + GEM names are similar in purpose to handles but are not local to DRM + files. They can be passed between processes to reference a GEM object + globally. Names can't be used directly to refer to objects in the DRM + API, applications must convert handles to names and names to handles + using the DRM_IOCTL_GEM_FLINK and DRM_IOCTL_GEM_OPEN ioctls + respectively. The conversion is handled by the DRM core without any + driver-specific support. + </para> + <para> + Similar to global names, GEM file descriptors are also used to share GEM + objects across processes. They offer additional security: as file + descriptors must be explictly sent over UNIX domain sockets to be shared + between applications, they can't be guessed like the globally unique GEM + names. + </para> + <para> + Drivers that support GEM file descriptors, also known as the DRM PRIME + API, must set the DRIVER_PRIME bit in the struct + <structname>drm_driver</structname> + <structfield>driver_features</structfield> field, and implement the + <methodname>prime_handle_to_fd</methodname> and + <methodname>prime_fd_to_handle</methodname> operations. + </para> + <para> + <synopsis>int (*prime_handle_to_fd)(struct drm_device *dev, + struct drm_file *file_priv, uint32_t handle, + uint32_t flags, int *prime_fd); + int (*prime_fd_to_handle)(struct drm_device *dev, + struct drm_file *file_priv, int prime_fd, + uint32_t *handle);</synopsis> + Those two operations convert a handle to a PRIME file descriptor and + vice versa. Drivers must use the kernel dma-buf buffer sharing framework + to manage the PRIME file descriptors. + </para> + <para> + While non-GEM drivers must implement the operations themselves, GEM + drivers must use the <function>drm_gem_prime_handle_to_fd</function> + and <function>drm_gem_prime_fd_to_handle</function> helper functions. + Those helpers rely on the driver + <methodname>gem_prime_export</methodname> and + <methodname>gem_prime_import</methodname> operations to create a dma-buf + instance from a GEM object (dma-buf exporter role) and to create a GEM + object from a dma-buf instance (dma-buf importer role). + </para> + <para> + <synopsis>struct dma_buf * (*gem_prime_export)(struct drm_device *dev, + struct drm_gem_object *obj, + int flags); + struct drm_gem_object * (*gem_prime_import)(struct drm_device *dev, + struct dma_buf *dma_buf);</synopsis> + These two operations are mandatory for GEM drivers that support DRM + PRIME. + </para> + </sect3> + <sect3 id="drm-gem-objects-mapping"> + <title>GEM Objects Mapping</title> + <para> + Because mapping operations are fairly heavyweight GEM favours + read/write-like access to buffers, implemented through driver-specific + ioctls, over mapping buffers to userspace. However, when random access + to the buffer is needed (to perform software rendering for instance), + direct access to the object can be more efficient. + </para> + <para> + The mmap system call can't be used directly to map GEM objects, as they + don't have their own file handle. Two alternative methods currently + co-exist to map GEM objects to userspace. The first method uses a + driver-specific ioctl to perform the mapping operation, calling + <function>do_mmap</function> under the hood. This is often considered + dubious, seems to be discouraged for new GEM-enabled drivers, and will + thus not be described here. + </para> + <para> + The second method uses the mmap system call on the DRM file handle. + <synopsis>void *mmap(void *addr, size_t length, int prot, int flags, int fd, + off_t offset);</synopsis> + DRM identifies the GEM object to be mapped by a fake offset passed + through the mmap offset argument. Prior to being mapped, a GEM object + must thus be associated with a fake offset. To do so, drivers must call + <function>drm_gem_create_mmap_offset</function> on the object. The + function allocates a fake offset range from a pool and stores the + offset divided by PAGE_SIZE in + <literal>obj->map_list.hash.key</literal>. Care must be taken not to + call <function>drm_gem_create_mmap_offset</function> if a fake offset + has already been allocated for the object. This can be tested by + <literal>obj->map_list.map</literal> being non-NULL. + </para> + <para> + Once allocated, the fake offset value + (<literal>obj->map_list.hash.key << PAGE_SHIFT</literal>) + must be passed to the application in a driver-specific way and can then + be used as the mmap offset argument. + </para> + <para> + The GEM core provides a helper method <function>drm_gem_mmap</function> + to handle object mapping. The method can be set directly as the mmap + file operation handler. It will look up the GEM object based on the + offset value and set the VMA operations to the + <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield> + field. Note that <function>drm_gem_mmap</function> doesn't map memory to + userspace, but relies on the driver-provided fault handler to map pages + individually. + </para> + <para> + To use <function>drm_gem_mmap</function>, drivers must fill the struct + <structname>drm_driver</structname> <structfield>gem_vm_ops</structfield> + field with a pointer to VM operations. + </para> + <para> + <synopsis>struct vm_operations_struct *gem_vm_ops + + struct vm_operations_struct { + void (*open)(struct vm_area_struct * area); + void (*close)(struct vm_area_struct * area); + int (*fault)(struct vm_area_struct *vma, struct vm_fault *vmf); + };</synopsis> + </para> + <para> + The <methodname>open</methodname> and <methodname>close</methodname> + operations must update the GEM object reference count. Drivers can use + the <function>drm_gem_vm_open</function> and + <function>drm_gem_vm_close</function> helper functions directly as open + and close handlers. + </para> + <para> + The fault operation handler is responsible for mapping individual pages + to userspace when a page fault occurs. Depending on the memory + allocation scheme, drivers can allocate pages at fault time, or can + decide to allocate memory for the GEM object at the time the object is + created. + </para> + <para> + Drivers that want to map the GEM object upfront instead of handling page + faults can implement their own mmap file operation handler. + </para> + </sect3> + <sect3> + <title>Dumb GEM Objects</title> + <para> + The GEM API doesn't standardize GEM objects creation and leaves it to + driver-specific ioctls. While not an issue for full-fledged graphics + stacks that include device-specific userspace components (in libdrm for + instance), this limit makes DRM-based early boot graphics unnecessarily + complex. + </para> + <para> + Dumb GEM objects partly alleviate the problem by providing a standard + API to create dumb buffers suitable for scanout, which can then be used + to create KMS frame buffers. + </para> + <para> + To support dumb GEM objects drivers must implement the + <methodname>dumb_create</methodname>, + <methodname>dumb_destroy</methodname> and + <methodname>dumb_map_offset</methodname> operations. + </para> + <itemizedlist> + <listitem> + <synopsis>int (*dumb_create)(struct drm_file *file_priv, struct drm_device *dev, + struct drm_mode_create_dumb *args);</synopsis> + <para> + The <methodname>dumb_create</methodname> operation creates a GEM + object suitable for scanout based on the width, height and depth + from the struct <structname>drm_mode_create_dumb</structname> + argument. It fills the argument's <structfield>handle</structfield>, + <structfield>pitch</structfield> and <structfield>size</structfield> + fields with a handle for the newly created GEM object and its line + pitch and size in bytes. + </para> + </listitem> + <listitem> + <synopsis>int (*dumb_destroy)(struct drm_file *file_priv, struct drm_device *dev, + uint32_t handle);</synopsis> + <para> + The <methodname>dumb_destroy</methodname> operation destroys a dumb + GEM object created by <methodname>dumb_create</methodname>. + </para> + </listitem> + <listitem> + <synopsis>int (*dumb_map_offset)(struct drm_file *file_priv, struct drm_device *dev, + uint32_t handle, uint64_t *offset);</synopsis> + <para> + The <methodname>dumb_map_offset</methodname> operation associates an + mmap fake offset with the GEM object given by the handle and returns + it. Drivers must use the + <function>drm_gem_create_mmap_offset</function> function to + associate the fake offset as described in + <xref linkend="drm-gem-objects-mapping"/>. + </para> + </listitem> + </itemizedlist> + </sect3> + <sect3> + <title>Memory Coherency</title> + <para> + When mapped to the device or used in a command buffer, backing pages + for an object are flushed to memory and marked write combined so as to + be coherent with the GPU. Likewise, if the CPU accesses an object + after the GPU has finished rendering to the object, then the object + must be made coherent with the CPU's view of memory, usually involving + GPU cache flushing of various kinds. This core CPU<->GPU + coherency management is provided by a device-specific ioctl, which + evaluates an object's current domain and performs any necessary + flushing or synchronization to put the object into the desired + coherency domain (note that the object may be busy, i.e. an active + render target; in that case, setting the domain blocks the client and + waits for rendering to complete before performing any necessary + flushing operations). + </para> + </sect3> + <sect3> + <title>Command Execution</title> + <para> + Perhaps the most important GEM function for GPU devices is providing a + command execution interface to clients. Client programs construct + command buffers containing references to previously allocated memory + objects, and then submit them to GEM. At that point, GEM takes care to + bind all the objects into the GTT, execute the buffer, and provide + necessary synchronization between clients accessing the same buffers. + This often involves evicting some objects from the GTT and re-binding + others (a fairly expensive operation), and providing relocation + support which hides fixed GTT offsets from clients. Clients must take + care not to submit command buffers that reference more objects than + can fit in the GTT; otherwise, GEM will reject them and no rendering + will occur. Similarly, if several objects in the buffer require fence + registers to be allocated for correct rendering (e.g. 2D blits on + pre-965 chips), care must be taken not to require more fence registers + than are available to the client. Such resource management should be + abstracted from the client in libdrm. + </para> </sect3> </sect2> + </sect1> + + <!-- Internals: mode setting --> + <sect1 id="drm-mode-setting"> + <title>Mode Setting</title> + <para> + Drivers must initialize the mode setting core by calling + <function>drm_mode_config_init</function> on the DRM device. The function + initializes the <structname>drm_device</structname> + <structfield>mode_config</structfield> field and never fails. Once done, + mode configuration must be setup by initializing the following fields. + </para> + <itemizedlist> + <listitem> + <synopsis>int min_width, min_height; +int max_width, max_height;</synopsis> + <para> + Minimum and maximum width and height of the frame buffers in pixel + units. + </para> + </listitem> + <listitem> + <synopsis>struct drm_mode_config_funcs *funcs;</synopsis> + <para>Mode setting functions.</para> + </listitem> + </itemizedlist> <sect2> - <title>Output configuration</title> + <title>Frame Buffer Creation</title> + <synopsis>struct drm_framebuffer *(*fb_create)(struct drm_device *dev, + struct drm_file *file_priv, + struct drm_mode_fb_cmd2 *mode_cmd);</synopsis> <para> - The final initialization task is output configuration. This involves: - <itemizedlist> - <listitem> - Finding and initializing the CRTCs, encoders, and connectors - for the device. - </listitem> - <listitem> - Creating an initial configuration. - </listitem> - <listitem> - Registering a framebuffer console driver. - </listitem> - </itemizedlist> + Frame buffers are abstract memory objects that provide a source of + pixels to scanout to a CRTC. Applications explicitly request the + creation of frame buffers through the DRM_IOCTL_MODE_ADDFB(2) ioctls and + receive an opaque handle that can be passed to the KMS CRTC control, + plane configuration and page flip functions. + </para> + <para> + Frame buffers rely on the underneath memory manager for low-level memory + operations. When creating a frame buffer applications pass a memory + handle (or a list of memory handles for multi-planar formats) through + the <parameter>drm_mode_fb_cmd2</parameter> argument. This document + assumes that the driver uses GEM, those handles thus reference GEM + objects. + </para> + <para> + Drivers must first validate the requested frame buffer parameters passed + through the mode_cmd argument. In particular this is where invalid + sizes, pixel formats or pitches can be caught. + </para> + <para> + If the parameters are deemed valid, drivers then create, initialize and + return an instance of struct <structname>drm_framebuffer</structname>. + If desired the instance can be embedded in a larger driver-specific + structure. The new instance is initialized with a call to + <function>drm_framebuffer_init</function> which takes a pointer to DRM + frame buffer operations (struct + <structname>drm_framebuffer_funcs</structname>). Frame buffer operations are + <itemizedlist> + <listitem> + <synopsis>int (*create_handle)(struct drm_framebuffer *fb, + struct drm_file *file_priv, unsigned int *handle);</synopsis> + <para> + Create a handle to the frame buffer underlying memory object. If + the frame buffer uses a multi-plane format, the handle will + reference the memory object associated with the first plane. + </para> + <para> + Drivers call <function>drm_gem_handle_create</function> to create + the handle. + </para> + </listitem> + <listitem> + <synopsis>void (*destroy)(struct drm_framebuffer *framebuffer);</synopsis> + <para> + Destroy the frame buffer object and frees all associated + resources. Drivers must call + <function>drm_framebuffer_cleanup</function> to free resources + allocated by the DRM core for the frame buffer object, and must + make sure to unreference all memory objects associated with the + frame buffer. Handles created by the + <methodname>create_handle</methodname> operation are released by + the DRM core. + </para> + </listitem> + <listitem> + <synopsis>int (*dirty)(struct drm_framebuffer *framebuffer, + struct drm_file *file_priv, unsigned flags, unsigned color, + struct drm_clip_rect *clips, unsigned num_clips);</synopsis> + <para> + This optional operation notifies the driver that a region of the + frame buffer has changed in response to a DRM_IOCTL_MODE_DIRTYFB + ioctl call. + </para> + </listitem> + </itemizedlist> + </para> + <para> + After initializing the <structname>drm_framebuffer</structname> + instance drivers must fill its <structfield>width</structfield>, + <structfield>height</structfield>, <structfield>pitches</structfield>, + <structfield>offsets</structfield>, <structfield>depth</structfield>, + <structfield>bits_per_pixel</structfield> and + <structfield>pixel_format</structfield> fields from the values passed + through the <parameter>drm_mode_fb_cmd2</parameter> argument. They + should call the <function>drm_helper_mode_fill_fb_struct</function> + helper function to do so. + </para> + </sect2> + <sect2> + <title>Output Polling</title> + <synopsis>void (*output_poll_changed)(struct drm_device *dev);</synopsis> + <para> + This operation notifies the driver that the status of one or more + connectors has changed. Drivers that use the fb helper can just call the + <function>drm_fb_helper_hotplug_event</function> function to handle this + operation. + </para> + </sect2> + </sect1> + + <!-- Internals: kms initialization and cleanup --> + + <sect1 id="drm-kms-init"> + <title>KMS Initialization and Cleanup</title> + <para> + A KMS device is abstracted and exposed as a set of planes, CRTCs, encoders + and connectors. KMS drivers must thus create and initialize all those + objects at load time after initializing mode setting. + </para> + <sect2> + <title>CRTCs (struct <structname>drm_crtc</structname>)</title> + <para> + A CRTC is an abstraction representing a part of the chip that contains a + pointer to a scanout buffer. Therefore, the number of CRTCs available + determines how many independent scanout buffers can be active at any + given time. The CRTC structure contains several fields to support this: + a pointer to some video memory (abstracted as a frame buffer object), a + display mode, and an (x, y) offset into the video memory to support + panning or configurations where one piece of video memory spans multiple + CRTCs. </para> <sect3> - <title>Output discovery and initialization</title> - <para> - Several core functions exist to create CRTCs, encoders, and - connectors, namely: drm_crtc_init(), drm_connector_init(), and - drm_encoder_init(), along with several "helper" functions to - perform common tasks. - </para> - <para> - Connectors should be registered with sysfs once they've been - detected and initialized, using the - drm_sysfs_connector_add() function. Likewise, when they're - removed from the system, they should be destroyed with - drm_sysfs_connector_remove(). - </para> - <programlisting> -<![CDATA[ + <title>CRTC Initialization</title> + <para> + A KMS device must create and register at least one struct + <structname>drm_crtc</structname> instance. The instance is allocated + and zeroed by the driver, possibly as part of a larger structure, and + registered with a call to <function>drm_crtc_init</function> with a + pointer to CRTC functions. + </para> + </sect3> + <sect3> + <title>CRTC Operations</title> + <sect4> + <title>Set Configuration</title> + <synopsis>int (*set_config)(struct drm_mode_set *set);</synopsis> + <para> + Apply a new CRTC configuration to the device. The configuration + specifies a CRTC, a frame buffer to scan out from, a (x,y) position in + the frame buffer, a display mode and an array of connectors to drive + with the CRTC if possible. + </para> + <para> + If the frame buffer specified in the configuration is NULL, the driver + must detach all encoders connected to the CRTC and all connectors + attached to those encoders and disable them. + </para> + <para> + This operation is called with the mode config lock held. + </para> + <note><para> + FIXME: How should set_config interact with DPMS? If the CRTC is + suspended, should it be resumed? + </para></note> + </sect4> + <sect4> + <title>Page Flipping</title> + <synopsis>int (*page_flip)(struct drm_crtc *crtc, struct drm_framebuffer *fb, + struct drm_pending_vblank_event *event);</synopsis> + <para> + Schedule a page flip to the given frame buffer for the CRTC. This + operation is called with the mode config mutex held. + </para> + <para> + Page flipping is a synchronization mechanism that replaces the frame + buffer being scanned out by the CRTC with a new frame buffer during + vertical blanking, avoiding tearing. When an application requests a page + flip the DRM core verifies that the new frame buffer is large enough to + be scanned out by the CRTC in the currently configured mode and then + calls the CRTC <methodname>page_flip</methodname> operation with a + pointer to the new frame buffer. + </para> + <para> + The <methodname>page_flip</methodname> operation schedules a page flip. + Once any pending rendering targetting the new frame buffer has + completed, the CRTC will be reprogrammed to display that frame buffer + after the next vertical refresh. The operation must return immediately + without waiting for rendering or page flip to complete and must block + any new rendering to the frame buffer until the page flip completes. + </para> + <para> + If a page flip is already pending, the + <methodname>page_flip</methodname> operation must return + -<errorname>EBUSY</errorname>. + </para> + <para> + To synchronize page flip to vertical blanking the driver will likely + need to enable vertical blanking interrupts. It should call + <function>drm_vblank_get</function> for that purpose, and call + <function>drm_vblank_put</function> after the page flip completes. + </para> + <para> + If the application has requested to be notified when page flip completes + the <methodname>page_flip</methodname> operation will be called with a + non-NULL <parameter>event</parameter> argument pointing to a + <structname>drm_pending_vblank_event</structname> instance. Upon page + flip completion the driver must fill the + <parameter>event</parameter>::<structfield>event</structfield> + <structfield>sequence</structfield>, <structfield>tv_sec</structfield> + and <structfield>tv_usec</structfield> fields with the associated + vertical blanking count and timestamp, add the event to the + <parameter>drm_file</parameter> list of events to be signaled, and wake + up any waiting process. This can be performed with + <programlisting><![CDATA[ + struct timeval now; + + event->event.sequence = drm_vblank_count_and_time(..., &now); + event->event.tv_sec = now.tv_sec; + event->event.tv_usec = now.tv_usec; + + spin_lock_irqsave(&dev->event_lock, flags); + list_add_tail(&event->base.link, &event->base.file_priv->event_list); + wake_up_interruptible(&event->base.file_priv->event_wait); + spin_unlock_irqrestore(&dev->event_lock, flags); + ]]></programlisting> + </para> + <note><para> + FIXME: Could drivers that don't need to wait for rendering to complete + just add the event to <literal>dev->vblank_event_list</literal> and + let the DRM core handle everything, as for "normal" vertical blanking + events? + </para></note> + <para> + While waiting for the page flip to complete, the + <literal>event->base.link</literal> list head can be used freely by + the driver to store the pending event in a driver-specific list. + </para> + <para> + If the file handle is closed before the event is signaled, drivers must + take care to destroy the event in their + <methodname>preclose</methodname> operation (and, if needed, call + <function>drm_vblank_put</function>). + </para> + </sect4> + <sect4> + <title>Miscellaneous</title> + <itemizedlist> + <listitem> + <synopsis>void (*gamma_set)(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b, + uint32_t start, uint32_t size);</synopsis> + <para> + Apply a gamma table to the device. The operation is optional. + </para> + </listitem> + <listitem> + <synopsis>void (*destroy)(struct drm_crtc *crtc);</synopsis> + <para> + Destroy the CRTC when not needed anymore. See + <xref linkend="drm-kms-init"/>. + </para> + </listitem> + </itemizedlist> + </sect4> + </sect3> + </sect2> + <sect2> + <title>Planes (struct <structname>drm_plane</structname>)</title> + <para> + A plane represents an image source that can be blended with or overlayed + on top of a CRTC during the scanout process. Planes are associated with + a frame buffer to crop a portion of the image memory (source) and + optionally scale it to a destination size. The result is then blended + with or overlayed on top of a CRTC. + </para> + <sect3> + <title>Plane Initialization</title> + <para> + Planes are optional. To create a plane, a KMS drivers allocates and + zeroes an instances of struct <structname>drm_plane</structname> + (possibly as part of a larger structure) and registers it with a call + to <function>drm_plane_init</function>. The function takes a bitmask + of the CRTCs that can be associated with the plane, a pointer to the + plane functions and a list of format supported formats. + </para> + </sect3> + <sect3> + <title>Plane Operations</title> + <itemizedlist> + <listitem> + <synopsis>int (*update_plane)(struct drm_plane *plane, struct drm_crtc *crtc, + struct drm_framebuffer *fb, int crtc_x, int crtc_y, + unsigned int crtc_w, unsigned int crtc_h, + uint32_t src_x, uint32_t src_y, + uint32_t src_w, uint32_t src_h);</synopsis> + <para> + Enable and configure the plane to use the given CRTC and frame buffer. + </para> + <para> + The source rectangle in frame buffer memory coordinates is given by + the <parameter>src_x</parameter>, <parameter>src_y</parameter>, + <parameter>src_w</parameter> and <parameter>src_h</parameter> + parameters (as 16.16 fixed point values). Devices that don't support + subpixel plane coordinates can ignore the fractional part. + </para> + <para> + The destination rectangle in CRTC coordinates is given by the + <parameter>crtc_x</parameter>, <parameter>crtc_y</parameter>, + <parameter>crtc_w</parameter> and <parameter>crtc_h</parameter> + parameters (as integer values). Devices scale the source rectangle to + the destination rectangle. If scaling is not supported, and the source + rectangle size doesn't match the destination rectangle size, the + driver must return a -<errorname>EINVAL</errorname> error. + </para> + </listitem> + <listitem> + <synopsis>int (*disable_plane)(struct drm_plane *plane);</synopsis> + <para> + Disable the plane. The DRM core calls this method in response to a + DRM_IOCTL_MODE_SETPLANE ioctl call with the frame buffer ID set to 0. + Disabled planes must not be processed by the CRTC. + </para> + </listitem> + <listitem> + <synopsis>void (*destroy)(struct drm_plane *plane);</synopsis> + <para> + Destroy the plane when not needed anymore. See + <xref linkend="drm-kms-init"/>. + </para> + </listitem> + </itemizedlist> + </sect3> + </sect2> + <sect2> + <title>Encoders (struct <structname>drm_encoder</structname>)</title> + <para> + An encoder takes pixel data from a CRTC and converts it to a format + suitable for any attached connectors. On some devices, it may be + possible to have a CRTC send data to more than one encoder. In that + case, both encoders would receive data from the same scanout buffer, + resulting in a "cloned" display configuration across the connectors + attached to each encoder. + </para> + <sect3> + <title>Encoder Initialization</title> + <para> + As for CRTCs, a KMS driver must create, initialize and register at + least one struct <structname>drm_encoder</structname> instance. The + instance is allocated and zeroed by the driver, possibly as part of a + larger structure. + </para> + <para> + Drivers must initialize the struct <structname>drm_encoder</structname> + <structfield>possible_crtcs</structfield> and + <structfield>possible_clones</structfield> fields before registering the + encoder. Both fields are bitmasks of respectively the CRTCs that the + encoder can be connected to, and sibling encoders candidate for cloning. + </para> + <para> + After being initialized, the encoder must be registered with a call to + <function>drm_encoder_init</function>. The function takes a pointer to + the encoder functions and an encoder type. Supported types are + <itemizedlist> + <listitem> + DRM_MODE_ENCODER_DAC for VGA and analog on DVI-I/DVI-A + </listitem> + <listitem> + DRM_MODE_ENCODER_TMDS for DVI, HDMI and (embedded) DisplayPort + </listitem> + <listitem> + DRM_MODE_ENCODER_LVDS for display panels + </listitem> + <listitem> + DRM_MODE_ENCODER_TVDAC for TV output (Composite, S-Video, Component, + SCART) + </listitem> + <listitem> + DRM_MODE_ENCODER_VIRTUAL for virtual machine displays + </listitem> + </itemizedlist> + </para> + <para> + Encoders must be attached to a CRTC to be used. DRM drivers leave + encoders unattached at initialization time. Applications (or the fbdev + compatibility layer when implemented) are responsible for attaching the + encoders they want to use to a CRTC. + </para> + </sect3> + <sect3> + <title>Encoder Operations</title> + <itemizedlist> + <listitem> + <synopsis>void (*destroy)(struct drm_encoder *encoder);</synopsis> + <para> + Called to destroy the encoder when not needed anymore. See + <xref linkend="drm-kms-init"/>. + </para> + </listitem> + </itemizedlist> + </sect3> + </sect2> + <sect2> + <title>Connectors (struct <structname>drm_connector</structname>)</title> + <para> + A connector is the final destination for pixel data on a device, and + usually connects directly to an external display device like a monitor + or laptop panel. A connector can only be attached to one encoder at a + time. The connector is also the structure where information about the + attached display is kept, so it contains fields for display data, EDID + data, DPMS & connection status, and information about modes + supported on the attached displays. + </para> + <sect3> + <title>Connector Initialization</title> + <para> + Finally a KMS driver must create, initialize, register and attach at + least one struct <structname>drm_connector</structname> instance. The + instance is created as other KMS objects and initialized by setting the + following fields. + </para> + <variablelist> + <varlistentry> + <term><structfield>interlace_allowed</structfield></term> + <listitem><para> + Whether the connector can handle interlaced modes. + </para></listitem> + </varlistentry> + <varlistentry> + <term><structfield>doublescan_allowed</structfield></term> + <listitem><para> + Whether the connector can handle doublescan. + </para></listitem> + </varlistentry> + <varlistentry> + <term><structfield>display_info + </structfield></term> + <listitem><para> + Display information is filled from EDID information when a display + is detected. For non hot-pluggable displays such as flat panels in + embedded systems, the driver should initialize the + <structfield>display_info</structfield>.<structfield>width_mm</structfield> + and + <structfield>display_info</structfield>.<structfield>height_mm</structfield> + fields with the physical size of the display. + </para></listitem> + </varlistentry> + <varlistentry> + <term id="drm-kms-connector-polled"><structfield>polled</structfield></term> + <listitem><para> + Connector polling mode, a combination of + <variablelist> + <varlistentry> + <term>DRM_CONNECTOR_POLL_HPD</term> + <listitem><para> + The connector generates hotplug events and doesn't need to be + periodically polled. The CONNECT and DISCONNECT flags must not + be set together with the HPD flag. + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_CONNECTOR_POLL_CONNECT</term> + <listitem><para> + Periodically poll the connector for connection. + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_CONNECTOR_POLL_DISCONNECT</term> + <listitem><para> + Periodically poll the connector for disconnection. + </para></listitem> + </varlistentry> + </variablelist> + Set to 0 for connectors that don't support connection status + discovery. + </para></listitem> + </varlistentry> + </variablelist> + <para> + The connector is then registered with a call to + <function>drm_connector_init</function> with a pointer to the connector + functions and a connector type, and exposed through sysfs with a call to + <function>drm_sysfs_connector_add</function>. + </para> + <para> + Supported connector types are + <itemizedlist> + <listitem>DRM_MODE_CONNECTOR_VGA</listitem> + <listitem>DRM_MODE_CONNECTOR_DVII</listitem> + <listitem>DRM_MODE_CONNECTOR_DVID</listitem> + <listitem>DRM_MODE_CONNECTOR_DVIA</listitem> + <listitem>DRM_MODE_CONNECTOR_Composite</listitem> + <listitem>DRM_MODE_CONNECTOR_SVIDEO</listitem> + <listitem>DRM_MODE_CONNECTOR_LVDS</listitem> + <listitem>DRM_MODE_CONNECTOR_Component</listitem> + <listitem>DRM_MODE_CONNECTOR_9PinDIN</listitem> + <listitem>DRM_MODE_CONNECTOR_DisplayPort</listitem> + <listitem>DRM_MODE_CONNECTOR_HDMIA</listitem> + <listitem>DRM_MODE_CONNECTOR_HDMIB</listitem> + <listitem>DRM_MODE_CONNECTOR_TV</listitem> + <listitem>DRM_MODE_CONNECTOR_eDP</listitem> + <listitem>DRM_MODE_CONNECTOR_VIRTUAL</listitem> + </itemizedlist> + </para> + <para> + Connectors must be attached to an encoder to be used. For devices that + map connectors to encoders 1:1, the connector should be attached at + initialization time with a call to + <function>drm_mode_connector_attach_encoder</function>. The driver must + also set the <structname>drm_connector</structname> + <structfield>encoder</structfield> field to point to the attached + encoder. + </para> + <para> + Finally, drivers must initialize the connectors state change detection + with a call to <function>drm_kms_helper_poll_init</function>. If at + least one connector is pollable but can't generate hotplug interrupts + (indicated by the DRM_CONNECTOR_POLL_CONNECT and + DRM_CONNECTOR_POLL_DISCONNECT connector flags), a delayed work will + automatically be queued to periodically poll for changes. Connectors + that can generate hotplug interrupts must be marked with the + DRM_CONNECTOR_POLL_HPD flag instead, and their interrupt handler must + call <function>drm_helper_hpd_irq_event</function>. The function will + queue a delayed work to check the state of all connectors, but no + periodic polling will be done. + </para> + </sect3> + <sect3> + <title>Connector Operations</title> + <note><para> + Unless otherwise state, all operations are mandatory. + </para></note> + <sect4> + <title>DPMS</title> + <synopsis>void (*dpms)(struct drm_connector *connector, int mode);</synopsis> + <para> + The DPMS operation sets the power state of a connector. The mode + argument is one of + <itemizedlist> + <listitem><para>DRM_MODE_DPMS_ON</para></listitem> + <listitem><para>DRM_MODE_DPMS_STANDBY</para></listitem> + <listitem><para>DRM_MODE_DPMS_SUSPEND</para></listitem> + <listitem><para>DRM_MODE_DPMS_OFF</para></listitem> + </itemizedlist> + </para> + <para> + In all but DPMS_ON mode the encoder to which the connector is attached + should put the display in low-power mode by driving its signals + appropriately. If more than one connector is attached to the encoder + care should be taken not to change the power state of other displays as + a side effect. Low-power mode should be propagated to the encoders and + CRTCs when all related connectors are put in low-power mode. + </para> + </sect4> + <sect4> + <title>Modes</title> + <synopsis>int (*fill_modes)(struct drm_connector *connector, uint32_t max_width, + uint32_t max_height);</synopsis> + <para> + Fill the mode list with all supported modes for the connector. If the + <parameter>max_width</parameter> and <parameter>max_height</parameter> + arguments are non-zero, the implementation must ignore all modes wider + than <parameter>max_width</parameter> or higher than + <parameter>max_height</parameter>. + </para> + <para> + The connector must also fill in this operation its + <structfield>display_info</structfield> + <structfield>width_mm</structfield> and + <structfield>height_mm</structfield> fields with the connected display + physical size in millimeters. The fields should be set to 0 if the value + isn't known or is not applicable (for instance for projector devices). + </para> + </sect4> + <sect4> + <title>Connection Status</title> + <para> + The connection status is updated through polling or hotplug events when + supported (see <xref linkend="drm-kms-connector-polled"/>). The status + value is reported to userspace through ioctls and must not be used + inside the driver, as it only gets initialized by a call to + <function>drm_mode_getconnector</function> from userspace. + </para> + <synopsis>enum drm_connector_status (*detect)(struct drm_connector *connector, + bool force);</synopsis> + <para> + Check to see if anything is attached to the connector. The + <parameter>force</parameter> parameter is set to false whilst polling or + to true when checking the connector due to user request. + <parameter>force</parameter> can be used by the driver to avoid + expensive, destructive operations during automated probing. + </para> + <para> + Return connector_status_connected if something is connected to the + connector, connector_status_disconnected if nothing is connected and + connector_status_unknown if the connection state isn't known. + </para> + <para> + Drivers should only return connector_status_connected if the connection + status has really been probed as connected. Connectors that can't detect + the connection status, or failed connection status probes, should return + connector_status_unknown. + </para> + </sect4> + <sect4> + <title>Miscellaneous</title> + <itemizedlist> + <listitem> + <synopsis>void (*destroy)(struct drm_connector *connector);</synopsis> + <para> + Destroy the connector when not needed anymore. See + <xref linkend="drm-kms-init"/>. + </para> + </listitem> + </itemizedlist> + </sect4> + </sect3> + </sect2> + <sect2> + <title>Cleanup</title> + <para> + The DRM core manages its objects' lifetime. When an object is not needed + anymore the core calls its destroy function, which must clean up and + free every resource allocated for the object. Every + <function>drm_*_init</function> call must be matched with a + corresponding <function>drm_*_cleanup</function> call to cleanup CRTCs + (<function>drm_crtc_cleanup</function>), planes + (<function>drm_plane_cleanup</function>), encoders + (<function>drm_encoder_cleanup</function>) and connectors + (<function>drm_connector_cleanup</function>). Furthermore, connectors + that have been added to sysfs must be removed by a call to + <function>drm_sysfs_connector_remove</function> before calling + <function>drm_connector_cleanup</function>. + </para> + <para> + Connectors state change detection must be cleanup up with a call to + <function>drm_kms_helper_poll_fini</function>. + </para> + </sect2> + <sect2> + <title>Output discovery and initialization example</title> + <programlisting><![CDATA[ void intel_crt_init(struct drm_device *dev) { struct drm_connector *connector; @@ -556,252 +1610,741 @@ void intel_crt_init(struct drm_device *dev) drm_connector_helper_add(connector, &intel_crt_connector_helper_funcs); drm_sysfs_connector_add(connector); -} -]]> - </programlisting> - <para> - In the example above (again, taken from the i915 driver), a - CRT connector and encoder combination is created. A device-specific - i2c bus is also created for fetching EDID data and - performing monitor detection. Once the process is complete, - the new connector is registered with sysfs to make its - properties available to applications. - </para> - <sect4> - <title>Helper functions and core functions</title> - <para> - Since many PC-class graphics devices have similar display output - designs, the DRM provides a set of helper functions to make - output management easier. The core helper routines handle - encoder re-routing and the disabling of unused functions following - mode setting. Using the helpers is optional, but recommended for - devices with PC-style architectures (i.e. a set of display planes - for feeding pixels to encoders which are in turn routed to - connectors). Devices with more complex requirements needing - finer grained management may opt to use the core callbacks - directly. - </para> - <para> - [Insert typical diagram here.] [Insert OMAP style config here.] - </para> - </sect4> - <para> - Each encoder object needs to provide: - <itemizedlist> - <listitem> - A DPMS (basically on/off) function. - </listitem> - <listitem> - A mode-fixup function (for converting requested modes into - native hardware timings). - </listitem> - <listitem> - Functions (prepare, set, and commit) for use by the core DRM - helper functions. - </listitem> - </itemizedlist> - Connector helpers need to provide functions (mode-fetch, validity, - and encoder-matching) for returning an ideal encoder for a given - connector. The core connector functions include a DPMS callback, - save/restore routines (deprecated), detection, mode probing, - property handling, and cleanup functions. - </para> -<!--!Edrivers/char/drm/drm_crtc.h--> -<!--!Edrivers/char/drm/drm_crtc.c--> -<!--!Edrivers/char/drm/drm_crtc_helper.c--> - </sect3> +}]]></programlisting> + <para> + In the example above (taken from the i915 driver), a CRTC, connector and + encoder combination is created. A device-specific i2c bus is also + created for fetching EDID data and performing monitor detection. Once + the process is complete, the new connector is registered with sysfs to + make its properties available to applications. + </para> </sect2> </sect1> - <!-- Internals: vblank handling --> + <!-- Internals: mid-layer helper functions --> <sect1> - <title>VBlank event handling</title> + <title>Mid-layer Helper Functions</title> <para> - The DRM core exposes two vertical blank related ioctls: - <variablelist> - <varlistentry> - <term>DRM_IOCTL_WAIT_VBLANK</term> - <listitem> - <para> - This takes a struct drm_wait_vblank structure as its argument, - and it is used to block or request a signal when a specified - vblank event occurs. - </para> - </listitem> - </varlistentry> - <varlistentry> - <term>DRM_IOCTL_MODESET_CTL</term> - <listitem> - <para> - This should be called by application level drivers before and - after mode setting, since on many devices the vertical blank - counter is reset at that time. Internally, the DRM snapshots - the last vblank count when the ioctl is called with the - _DRM_PRE_MODESET command, so that the counter won't go backwards - (which is dealt with when _DRM_POST_MODESET is used). - </para> - </listitem> - </varlistentry> - </variablelist> -<!--!Edrivers/char/drm/drm_irq.c--> + The CRTC, encoder and connector functions provided by the drivers + implement the DRM API. They're called by the DRM core and ioctl handlers + to handle device state changes and configuration request. As implementing + those functions often requires logic not specific to drivers, mid-layer + helper functions are available to avoid duplicating boilerplate code. + </para> + <para> + The DRM core contains one mid-layer implementation. The mid-layer provides + implementations of several CRTC, encoder and connector functions (called + from the top of the mid-layer) that pre-process requests and call + lower-level functions provided by the driver (at the bottom of the + mid-layer). For instance, the + <function>drm_crtc_helper_set_config</function> function can be used to + fill the struct <structname>drm_crtc_funcs</structname> + <structfield>set_config</structfield> field. When called, it will split + the <methodname>set_config</methodname> operation in smaller, simpler + operations and call the driver to handle them. </para> <para> - To support the functions above, the DRM core provides several - helper functions for tracking vertical blank counters, and - requires drivers to provide several callbacks: - get_vblank_counter(), enable_vblank() and disable_vblank(). The - core uses get_vblank_counter() to keep the counter accurate - across interrupt disable periods. It should return the current - vertical blank event count, which is often tracked in a device - register. The enable and disable vblank callbacks should enable - and disable vertical blank interrupts, respectively. In the - absence of DRM clients waiting on vblank events, the core DRM - code uses the disable_vblank() function to disable - interrupts, which saves power. They are re-enabled again when - a client calls the vblank wait ioctl above. + To use the mid-layer, drivers call <function>drm_crtc_helper_add</function>, + <function>drm_encoder_helper_add</function> and + <function>drm_connector_helper_add</function> functions to install their + mid-layer bottom operations handlers, and fill the + <structname>drm_crtc_funcs</structname>, + <structname>drm_encoder_funcs</structname> and + <structname>drm_connector_funcs</structname> structures with pointers to + the mid-layer top API functions. Installing the mid-layer bottom operation + handlers is best done right after registering the corresponding KMS object. </para> <para> - A device that doesn't provide a count register may simply use an - internal atomic counter incremented on every vertical blank - interrupt (and then treat the enable_vblank() and disable_vblank() - callbacks as no-ops). + The mid-layer is not split between CRTC, encoder and connector operations. + To use it, a driver must provide bottom functions for all of the three KMS + entities. </para> + <sect2> + <title>Helper Functions</title> + <itemizedlist> + <listitem> + <synopsis>int drm_crtc_helper_set_config(struct drm_mode_set *set);</synopsis> + <para> + The <function>drm_crtc_helper_set_config</function> helper function + is a CRTC <methodname>set_config</methodname> implementation. It + first tries to locate the best encoder for each connector by calling + the connector <methodname>best_encoder</methodname> helper + operation. + </para> + <para> + After locating the appropriate encoders, the helper function will + call the <methodname>mode_fixup</methodname> encoder and CRTC helper + operations to adjust the requested mode, or reject it completely in + which case an error will be returned to the application. If the new + configuration after mode adjustment is identical to the current + configuration the helper function will return without performing any + other operation. + </para> + <para> + If the adjusted mode is identical to the current mode but changes to + the frame buffer need to be applied, the + <function>drm_crtc_helper_set_config</function> function will call + the CRTC <methodname>mode_set_base</methodname> helper operation. If + the adjusted mode differs from the current mode, or if the + <methodname>mode_set_base</methodname> helper operation is not + provided, the helper function performs a full mode set sequence by + calling the <methodname>prepare</methodname>, + <methodname>mode_set</methodname> and + <methodname>commit</methodname> CRTC and encoder helper operations, + in that order. + </para> + </listitem> + <listitem> + <synopsis>void drm_helper_connector_dpms(struct drm_connector *connector, int mode);</synopsis> + <para> + The <function>drm_helper_connector_dpms</function> helper function + is a connector <methodname>dpms</methodname> implementation that + tracks power state of connectors. To use the function, drivers must + provide <methodname>dpms</methodname> helper operations for CRTCs + and encoders to apply the DPMS state to the device. + </para> + <para> + The mid-layer doesn't track the power state of CRTCs and encoders. + The <methodname>dpms</methodname> helper operations can thus be + called with a mode identical to the currently active mode. + </para> + </listitem> + <listitem> + <synopsis>int drm_helper_probe_single_connector_modes(struct drm_connector *connector, + uint32_t maxX, uint32_t maxY);</synopsis> + <para> + The <function>drm_helper_probe_single_connector_modes</function> helper + function is a connector <methodname>fill_modes</methodname> + implementation that updates the connection status for the connector + and then retrieves a list of modes by calling the connector + <methodname>get_modes</methodname> helper operation. + </para> + <para> + The function filters out modes larger than + <parameter>max_width</parameter> and <parameter>max_height</parameter> + if specified. It then calls the connector + <methodname>mode_valid</methodname> helper operation for each mode in + the probed list to check whether the mode is valid for the connector. + </para> + </listitem> + </itemizedlist> + </sect2> + <sect2> + <title>CRTC Helper Operations</title> + <itemizedlist> + <listitem id="drm-helper-crtc-mode-fixup"> + <synopsis>bool (*mode_fixup)(struct drm_crtc *crtc, + const struct drm_display_mode *mode, + struct drm_display_mode *adjusted_mode);</synopsis> + <para> + Let CRTCs adjust the requested mode or reject it completely. This + operation returns true if the mode is accepted (possibly after being + adjusted) or false if it is rejected. + </para> + <para> + The <methodname>mode_fixup</methodname> operation should reject the + mode if it can't reasonably use it. The definition of "reasonable" + is currently fuzzy in this context. One possible behaviour would be + to set the adjusted mode to the panel timings when a fixed-mode + panel is used with hardware capable of scaling. Another behaviour + would be to accept any input mode and adjust it to the closest mode + supported by the hardware (FIXME: This needs to be clarified). + </para> + </listitem> + <listitem> + <synopsis>int (*mode_set_base)(struct drm_crtc *crtc, int x, int y, + struct drm_framebuffer *old_fb)</synopsis> + <para> + Move the CRTC on the current frame buffer (stored in + <literal>crtc->fb</literal>) to position (x,y). Any of the frame + buffer, x position or y position may have been modified. + </para> + <para> + This helper operation is optional. If not provided, the + <function>drm_crtc_helper_set_config</function> function will fall + back to the <methodname>mode_set</methodname> helper operation. + </para> + <note><para> + FIXME: Why are x and y passed as arguments, as they can be accessed + through <literal>crtc->x</literal> and + <literal>crtc->y</literal>? + </para></note> + </listitem> + <listitem> + <synopsis>void (*prepare)(struct drm_crtc *crtc);</synopsis> + <para> + Prepare the CRTC for mode setting. This operation is called after + validating the requested mode. Drivers use it to perform + device-specific operations required before setting the new mode. + </para> + </listitem> + <listitem> + <synopsis>int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode, + struct drm_display_mode *adjusted_mode, int x, int y, + struct drm_framebuffer *old_fb);</synopsis> + <para> + Set a new mode, position and frame buffer. Depending on the device + requirements, the mode can be stored internally by the driver and + applied in the <methodname>commit</methodname> operation, or + programmed to the hardware immediately. + </para> + <para> + The <methodname>mode_set</methodname> operation returns 0 on success + or a negative error code if an error occurs. + </para> + </listitem> + <listitem> + <synopsis>void (*commit)(struct drm_crtc *crtc);</synopsis> + <para> + Commit a mode. This operation is called after setting the new mode. + Upon return the device must use the new mode and be fully + operational. + </para> + </listitem> + </itemizedlist> + </sect2> + <sect2> + <title>Encoder Helper Operations</title> + <itemizedlist> + <listitem> + <synopsis>bool (*mode_fixup)(struct drm_encoder *encoder, + const struct drm_display_mode *mode, + struct drm_display_mode *adjusted_mode);</synopsis> + <note><para> + FIXME: The mode argument be const, but the i915 driver modifies + mode->clock in <function>intel_dp_mode_fixup</function>. + </para></note> + <para> + Let encoders adjust the requested mode or reject it completely. This + operation returns true if the mode is accepted (possibly after being + adjusted) or false if it is rejected. See the + <link linkend="drm-helper-crtc-mode-fixup">mode_fixup CRTC helper + operation</link> for an explanation of the allowed adjustments. + </para> + </listitem> + <listitem> + <synopsis>void (*prepare)(struct drm_encoder *encoder);</synopsis> + <para> + Prepare the encoder for mode setting. This operation is called after + validating the requested mode. Drivers use it to perform + device-specific operations required before setting the new mode. + </para> + </listitem> + <listitem> + <synopsis>void (*mode_set)(struct drm_encoder *encoder, + struct drm_display_mode *mode, + struct drm_display_mode *adjusted_mode);</synopsis> + <para> + Set a new mode. Depending on the device requirements, the mode can + be stored internally by the driver and applied in the + <methodname>commit</methodname> operation, or programmed to the + hardware immediately. + </para> + </listitem> + <listitem> + <synopsis>void (*commit)(struct drm_encoder *encoder);</synopsis> + <para> + Commit a mode. This operation is called after setting the new mode. + Upon return the device must use the new mode and be fully + operational. + </para> + </listitem> + </itemizedlist> + </sect2> + <sect2> + <title>Connector Helper Operations</title> + <itemizedlist> + <listitem> + <synopsis>struct drm_encoder *(*best_encoder)(struct drm_connector *connector);</synopsis> + <para> + Return a pointer to the best encoder for the connecter. Device that + map connectors to encoders 1:1 simply return the pointer to the + associated encoder. This operation is mandatory. + </para> + </listitem> + <listitem> + <synopsis>int (*get_modes)(struct drm_connector *connector);</synopsis> + <para> + Fill the connector's <structfield>probed_modes</structfield> list + by parsing EDID data with <function>drm_add_edid_modes</function> or + calling <function>drm_mode_probed_add</function> directly for every + supported mode and return the number of modes it has detected. This + operation is mandatory. + </para> + <para> + When adding modes manually the driver creates each mode with a call to + <function>drm_mode_create</function> and must fill the following fields. + <itemizedlist> + <listitem> + <synopsis>__u32 type;</synopsis> + <para> + Mode type bitmask, a combination of + <variablelist> + <varlistentry> + <term>DRM_MODE_TYPE_BUILTIN</term> + <listitem><para>not used?</para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_TYPE_CLOCK_C</term> + <listitem><para>not used?</para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_TYPE_CRTC_C</term> + <listitem><para>not used?</para></listitem> + </varlistentry> + <varlistentry> + <term> + DRM_MODE_TYPE_PREFERRED - The preferred mode for the connector + </term> + <listitem> + <para>not used?</para> + </listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_TYPE_DEFAULT</term> + <listitem><para>not used?</para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_TYPE_USERDEF</term> + <listitem><para>not used?</para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_TYPE_DRIVER</term> + <listitem> + <para> + The mode has been created by the driver (as opposed to + to user-created modes). + </para> + </listitem> + </varlistentry> + </variablelist> + Drivers must set the DRM_MODE_TYPE_DRIVER bit for all modes they + create, and set the DRM_MODE_TYPE_PREFERRED bit for the preferred + mode. + </para> + </listitem> + <listitem> + <synopsis>__u32 clock;</synopsis> + <para>Pixel clock frequency in kHz unit</para> + </listitem> + <listitem> + <synopsis>__u16 hdisplay, hsync_start, hsync_end, htotal; + __u16 vdisplay, vsync_start, vsync_end, vtotal;</synopsis> + <para>Horizontal and vertical timing information</para> + <screen><![CDATA[ + Active Front Sync Back + Region Porch Porch + <-----------------------><----------------><-------------><--------------> + + //////////////////////| + ////////////////////// | + ////////////////////// |.................. ................ + _______________ + + <----- [hv]display -----> + <------------- [hv]sync_start ------------> + <--------------------- [hv]sync_end ---------------------> + <-------------------------------- [hv]total -----------------------------> +]]></screen> + </listitem> + <listitem> + <synopsis>__u16 hskew; + __u16 vscan;</synopsis> + <para>Unknown</para> + </listitem> + <listitem> + <synopsis>__u32 flags;</synopsis> + <para> + Mode flags, a combination of + <variablelist> + <varlistentry> + <term>DRM_MODE_FLAG_PHSYNC</term> + <listitem><para> + Horizontal sync is active high + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_FLAG_NHSYNC</term> + <listitem><para> + Horizontal sync is active low + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_FLAG_PVSYNC</term> + <listitem><para> + Vertical sync is active high + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_FLAG_NVSYNC</term> + <listitem><para> + Vertical sync is active low + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_FLAG_INTERLACE</term> + <listitem><para> + Mode is interlaced + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_FLAG_DBLSCAN</term> + <listitem><para> + Mode uses doublescan + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_FLAG_CSYNC</term> + <listitem><para> + Mode uses composite sync + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_FLAG_PCSYNC</term> + <listitem><para> + Composite sync is active high + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_FLAG_NCSYNC</term> + <listitem><para> + Composite sync is active low + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_FLAG_HSKEW</term> + <listitem><para> + hskew provided (not used?) + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_FLAG_BCAST</term> + <listitem><para> + not used? + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_FLAG_PIXMUX</term> + <listitem><para> + not used? + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_FLAG_DBLCLK</term> + <listitem><para> + not used? + </para></listitem> + </varlistentry> + <varlistentry> + <term>DRM_MODE_FLAG_CLKDIV2</term> + <listitem><para> + ? + </para></listitem> + </varlistentry> + </variablelist> + </para> + <para> + Note that modes marked with the INTERLACE or DBLSCAN flags will be + filtered out by + <function>drm_helper_probe_single_connector_modes</function> if + the connector's <structfield>interlace_allowed</structfield> or + <structfield>doublescan_allowed</structfield> field is set to 0. + </para> + </listitem> + <listitem> + <synopsis>char name[DRM_DISPLAY_MODE_LEN];</synopsis> + <para> + Mode name. The driver must call + <function>drm_mode_set_name</function> to fill the mode name from + <structfield>hdisplay</structfield>, + <structfield>vdisplay</structfield> and interlace flag after + filling the corresponding fields. + </para> + </listitem> + </itemizedlist> + </para> + <para> + The <structfield>vrefresh</structfield> value is computed by + <function>drm_helper_probe_single_connector_modes</function>. + </para> + <para> + When parsing EDID data, <function>drm_add_edid_modes</function> fill the + connector <structfield>display_info</structfield> + <structfield>width_mm</structfield> and + <structfield>height_mm</structfield> fields. When creating modes + manually the <methodname>get_modes</methodname> helper operation must + set the <structfield>display_info</structfield> + <structfield>width_mm</structfield> and + <structfield>height_mm</structfield> fields if they haven't been set + already (for instance at initilization time when a fixed-size panel is + attached to the connector). The mode <structfield>width_mm</structfield> + and <structfield>height_mm</structfield> fields are only used internally + during EDID parsing and should not be set when creating modes manually. + </para> + </listitem> + <listitem> + <synopsis>int (*mode_valid)(struct drm_connector *connector, + struct drm_display_mode *mode);</synopsis> + <para> + Verify whether a mode is valid for the connector. Return MODE_OK for + supported modes and one of the enum drm_mode_status values (MODE_*) + for unsupported modes. This operation is mandatory. + </para> + <para> + As the mode rejection reason is currently not used beside for + immediately removing the unsupported mode, an implementation can + return MODE_BAD regardless of the exact reason why the mode is not + valid. + </para> + <note><para> + Note that the <methodname>mode_valid</methodname> helper operation is + only called for modes detected by the device, and + <emphasis>not</emphasis> for modes set by the user through the CRTC + <methodname>set_config</methodname> operation. + </para></note> + </listitem> + </itemizedlist> + </sect2> </sect1> - <sect1> - <title>Memory management</title> + <!-- Internals: vertical blanking --> + + <sect1 id="drm-vertical-blank"> + <title>Vertical Blanking</title> + <para> + Vertical blanking plays a major role in graphics rendering. To achieve + tear-free display, users must synchronize page flips and/or rendering to + vertical blanking. The DRM API offers ioctls to perform page flips + synchronized to vertical blanking and wait for vertical blanking. + </para> + <para> + The DRM core handles most of the vertical blanking management logic, which + involves filtering out spurious interrupts, keeping race-free blanking + counters, coping with counter wrap-around and resets and keeping use + counts. It relies on the driver to generate vertical blanking interrupts + and optionally provide a hardware vertical blanking counter. Drivers must + implement the following operations. + </para> + <itemizedlist> + <listitem> + <synopsis>int (*enable_vblank) (struct drm_device *dev, int crtc); +void (*disable_vblank) (struct drm_device *dev, int crtc);</synopsis> + <para> + Enable or disable vertical blanking interrupts for the given CRTC. + </para> + </listitem> + <listitem> + <synopsis>u32 (*get_vblank_counter) (struct drm_device *dev, int crtc);</synopsis> + <para> + Retrieve the value of the vertical blanking counter for the given + CRTC. If the hardware maintains a vertical blanking counter its value + should be returned. Otherwise drivers can use the + <function>drm_vblank_count</function> helper function to handle this + operation. + </para> + </listitem> + </itemizedlist> <para> - The memory manager lies at the heart of many DRM operations; it - is required to support advanced client features like OpenGL - pbuffers. The DRM currently contains two memory managers: TTM - and GEM. + Drivers must initialize the vertical blanking handling core with a call to + <function>drm_vblank_init</function> in their + <methodname>load</methodname> operation. The function will set the struct + <structname>drm_device</structname> + <structfield>vblank_disable_allowed</structfield> field to 0. This will + keep vertical blanking interrupts enabled permanently until the first mode + set operation, where <structfield>vblank_disable_allowed</structfield> is + set to 1. The reason behind this is not clear. Drivers can set the field + to 1 after <function>calling drm_vblank_init</function> to make vertical + blanking interrupts dynamically managed from the beginning. </para> + <para> + Vertical blanking interrupts can be enabled by the DRM core or by drivers + themselves (for instance to handle page flipping operations). The DRM core + maintains a vertical blanking use count to ensure that the interrupts are + not disabled while a user still needs them. To increment the use count, + drivers call <function>drm_vblank_get</function>. Upon return vertical + blanking interrupts are guaranteed to be enabled. + </para> + <para> + To decrement the use count drivers call + <function>drm_vblank_put</function>. Only when the use count drops to zero + will the DRM core disable the vertical blanking interrupts after a delay + by scheduling a timer. The delay is accessible through the vblankoffdelay + module parameter or the <varname>drm_vblank_offdelay</varname> global + variable and expressed in milliseconds. Its default value is 5000 ms. + </para> + <para> + When a vertical blanking interrupt occurs drivers only need to call the + <function>drm_handle_vblank</function> function to account for the + interrupt. + </para> + <para> + Resources allocated by <function>drm_vblank_init</function> must be freed + with a call to <function>drm_vblank_cleanup</function> in the driver + <methodname>unload</methodname> operation handler. + </para> + </sect1> + + <!-- Internals: open/close, file operations and ioctls --> + <sect1> + <title>Open/Close, File Operations and IOCTLs</title> <sect2> - <title>The Translation Table Manager (TTM)</title> + <title>Open and Close</title> + <synopsis>int (*firstopen) (struct drm_device *); +void (*lastclose) (struct drm_device *); +int (*open) (struct drm_device *, struct drm_file *); +void (*preclose) (struct drm_device *, struct drm_file *); +void (*postclose) (struct drm_device *, struct drm_file *);</synopsis> + <abstract>Open and close handlers. None of those methods are mandatory. + </abstract> <para> - TTM was developed by Tungsten Graphics, primarily by Thomas - Hellström, and is intended to be a flexible, high performance - graphics memory manager. + The <methodname>firstopen</methodname> method is called by the DRM core + when an application opens a device that has no other opened file handle. + Similarly the <methodname>lastclose</methodname> method is called when + the last application holding a file handle opened on the device closes + it. Both methods are mostly used for UMS (User Mode Setting) drivers to + acquire and release device resources which should be done in the + <methodname>load</methodname> and <methodname>unload</methodname> + methods for KMS drivers. </para> <para> - Drivers wishing to support TTM must fill out a drm_bo_driver - structure. + Note that the <methodname>lastclose</methodname> method is also called + at module unload time or, for hot-pluggable devices, when the device is + unplugged. The <methodname>firstopen</methodname> and + <methodname>lastclose</methodname> calls can thus be unbalanced. </para> <para> - TTM design background and information belongs here. + The <methodname>open</methodname> method is called every time the device + is opened by an application. Drivers can allocate per-file private data + in this method and store them in the struct + <structname>drm_file</structname> <structfield>driver_priv</structfield> + field. Note that the <methodname>open</methodname> method is called + before <methodname>firstopen</methodname>. + </para> + <para> + The close operation is split into <methodname>preclose</methodname> and + <methodname>postclose</methodname> methods. Drivers must stop and + cleanup all per-file operations in the <methodname>preclose</methodname> + method. For instance pending vertical blanking and page flip events must + be cancelled. No per-file operation is allowed on the file handle after + returning from the <methodname>preclose</methodname> method. + </para> + <para> + Finally the <methodname>postclose</methodname> method is called as the + last step of the close operation, right before calling the + <methodname>lastclose</methodname> method if no other open file handle + exists for the device. Drivers that have allocated per-file private data + in the <methodname>open</methodname> method should free it here. + </para> + <para> + The <methodname>lastclose</methodname> method should restore CRTC and + plane properties to default value, so that a subsequent open of the + device will not inherit state from the previous user. </para> </sect2> - <sect2> - <title>The Graphics Execution Manager (GEM)</title> + <title>File Operations</title> + <synopsis>const struct file_operations *fops</synopsis> + <abstract>File operations for the DRM device node.</abstract> <para> - GEM is an Intel project, authored by Eric Anholt and Keith - Packard. It provides simpler interfaces than TTM, and is well - suited for UMA devices. + Drivers must define the file operations structure that forms the DRM + userspace API entry point, even though most of those operations are + implemented in the DRM core. The <methodname>open</methodname>, + <methodname>release</methodname> and <methodname>ioctl</methodname> + operations are handled by + <programlisting> + .owner = THIS_MODULE, + .open = drm_open, + .release = drm_release, + .unlocked_ioctl = drm_ioctl, + #ifdef CONFIG_COMPAT + .compat_ioctl = drm_compat_ioctl, + #endif + </programlisting> </para> <para> - GEM-enabled drivers must provide gem_init_object() and - gem_free_object() callbacks to support the core memory - allocation routines. They should also provide several driver-specific - ioctls to support command execution, pinning, buffer - read & write, mapping, and domain ownership transfers. + Drivers that implement private ioctls that requires 32/64bit + compatibility support must provide their own + <methodname>compat_ioctl</methodname> handler that processes private + ioctls and calls <function>drm_compat_ioctl</function> for core ioctls. </para> <para> - On a fundamental level, GEM involves several operations: - <itemizedlist> - <listitem>Memory allocation and freeing</listitem> - <listitem>Command execution</listitem> - <listitem>Aperture management at command execution time</listitem> - </itemizedlist> - Buffer object allocation is relatively - straightforward and largely provided by Linux's shmem layer, which - provides memory to back each object. When mapped into the GTT - or used in a command buffer, the backing pages for an object are - flushed to memory and marked write combined so as to be coherent - with the GPU. Likewise, if the CPU accesses an object after the GPU - has finished rendering to the object, then the object must be made - coherent with the CPU's view - of memory, usually involving GPU cache flushing of various kinds. - This core CPU<->GPU coherency management is provided by a - device-specific ioctl, which evaluates an object's current domain and - performs any necessary flushing or synchronization to put the object - into the desired coherency domain (note that the object may be busy, - i.e. an active render target; in that case, setting the domain - blocks the client and waits for rendering to complete before - performing any necessary flushing operations). - </para> - <para> - Perhaps the most important GEM function is providing a command - execution interface to clients. Client programs construct command - buffers containing references to previously allocated memory objects, - and then submit them to GEM. At that point, GEM takes care to bind - all the objects into the GTT, execute the buffer, and provide - necessary synchronization between clients accessing the same buffers. - This often involves evicting some objects from the GTT and re-binding - others (a fairly expensive operation), and providing relocation - support which hides fixed GTT offsets from clients. Clients must - take care not to submit command buffers that reference more objects - than can fit in the GTT; otherwise, GEM will reject them and no rendering - will occur. Similarly, if several objects in the buffer require - fence registers to be allocated for correct rendering (e.g. 2D blits - on pre-965 chips), care must be taken not to require more fence - registers than are available to the client. Such resource management - should be abstracted from the client in libdrm. + The <methodname>read</methodname> and <methodname>poll</methodname> + operations provide support for reading DRM events and polling them. They + are implemented by + <programlisting> + .poll = drm_poll, + .read = drm_read, + .fasync = drm_fasync, + .llseek = no_llseek, + </programlisting> + </para> + <para> + The memory mapping implementation varies depending on how the driver + manages memory. Pre-GEM drivers will use <function>drm_mmap</function>, + while GEM-aware drivers will use <function>drm_gem_mmap</function>. See + <xref linkend="drm-gem"/>. + <programlisting> + .mmap = drm_gem_mmap, + </programlisting> + </para> + <para> + No other file operation is supported by the DRM API. + </para> + </sect2> + <sect2> + <title>IOCTLs</title> + <synopsis>struct drm_ioctl_desc *ioctls; +int num_ioctls;</synopsis> + <abstract>Driver-specific ioctls descriptors table.</abstract> + <para> + Driver-specific ioctls numbers start at DRM_COMMAND_BASE. The ioctls + descriptors table is indexed by the ioctl number offset from the base + value. Drivers can use the DRM_IOCTL_DEF_DRV() macro to initialize the + table entries. + </para> + <para> + <programlisting>DRM_IOCTL_DEF_DRV(ioctl, func, flags)</programlisting> + <para> + <parameter>ioctl</parameter> is the ioctl name. Drivers must define + the DRM_##ioctl and DRM_IOCTL_##ioctl macros to the ioctl number + offset from DRM_COMMAND_BASE and the ioctl number respectively. The + first macro is private to the device while the second must be exposed + to userspace in a public header. + </para> + <para> + <parameter>func</parameter> is a pointer to the ioctl handler function + compatible with the <type>drm_ioctl_t</type> type. + <programlisting>typedef int drm_ioctl_t(struct drm_device *dev, void *data, + struct drm_file *file_priv);</programlisting> + </para> + <para> + <parameter>flags</parameter> is a bitmask combination of the following + values. It restricts how the ioctl is allowed to be called. + <itemizedlist> + <listitem><para> + DRM_AUTH - Only authenticated callers allowed + </para></listitem> + <listitem><para> + DRM_MASTER - The ioctl can only be called on the master file + handle + </para></listitem> + <listitem><para> + DRM_ROOT_ONLY - Only callers with the SYSADMIN capability allowed + </para></listitem> + <listitem><para> + DRM_CONTROL_ALLOW - The ioctl can only be called on a control + device + </para></listitem> + <listitem><para> + DRM_UNLOCKED - The ioctl handler will be called without locking + the DRM global mutex + </para></listitem> + </itemizedlist> + </para> </para> </sect2> - - </sect1> - - <!-- Output management --> - <sect1> - <title>Output management</title> - <para> - At the core of the DRM output management code is a set of - structures representing CRTCs, encoders, and connectors. - </para> - <para> - A CRTC is an abstraction representing a part of the chip that - contains a pointer to a scanout buffer. Therefore, the number - of CRTCs available determines how many independent scanout - buffers can be active at any given time. The CRTC structure - contains several fields to support this: a pointer to some video - memory, a display mode, and an (x, y) offset into the video - memory to support panning or configurations where one piece of - video memory spans multiple CRTCs. - </para> - <para> - An encoder takes pixel data from a CRTC and converts it to a - format suitable for any attached connectors. On some devices, - it may be possible to have a CRTC send data to more than one - encoder. In that case, both encoders would receive data from - the same scanout buffer, resulting in a "cloned" display - configuration across the connectors attached to each encoder. - </para> - <para> - A connector is the final destination for pixel data on a device, - and usually connects directly to an external display device like - a monitor or laptop panel. A connector can only be attached to - one encoder at a time. The connector is also the structure - where information about the attached display is kept, so it - contains fields for display data, EDID data, DPMS & - connection status, and information about modes supported on the - attached displays. - </para> -<!--!Edrivers/char/drm/drm_crtc.c--> - </sect1> - - <sect1> - <title>Framebuffer management</title> - <para> - Clients need to provide a framebuffer object which provides a source - of pixels for a CRTC to deliver to the encoder(s) and ultimately the - connector(s). A framebuffer is fundamentally a driver-specific memory - object, made into an opaque handle by the DRM's addfb() function. - Once a framebuffer has been created this way, it may be passed to the - KMS mode setting routines for use in a completed configuration. - </para> </sect1> <sect1> @@ -812,15 +2355,24 @@ void intel_crt_init(struct drm_device *dev) </para> </sect1> + <!-- Internals: suspend/resume --> + <sect1> - <title>Suspend/resume</title> + <title>Suspend/Resume</title> + <para> + The DRM core provides some suspend/resume code, but drivers wanting full + suspend/resume support should provide save() and restore() functions. + These are called at suspend, hibernate, or resume time, and should perform + any state save or restore required by your device across suspend or + hibernate states. + </para> + <synopsis>int (*suspend) (struct drm_device *, pm_message_t state); +int (*resume) (struct drm_device *);</synopsis> <para> - The DRM core provides some suspend/resume code, but drivers - wanting full suspend/resume support should provide save() and - restore() functions. These are called at suspend, - hibernate, or resume time, and should perform any state save or - restore required by your device across suspend or hibernate - states. + Those are legacy suspend and resume methods. New driver should use the + power management interface provided by their bus type (usually through + the struct <structname>device_driver</structname> dev_pm_ops) and set + these methods to NULL. </para> </sect1> @@ -833,6 +2385,35 @@ void intel_crt_init(struct drm_device *dev) </sect1> </chapter> +<!-- TODO + +- Add a glossary +- Document the struct_mutex catch-all lock +- Document connector properties + +- Why is the load method optional? +- What are drivers supposed to set the initial display state to, and how? + Connector's DPMS states are not initialized and are thus equal to + DRM_MODE_DPMS_ON. The fbcon compatibility layer calls + drm_helper_disable_unused_functions(), which disables unused encoders and + CRTCs, but doesn't touch the connectors' DPMS state, and + drm_helper_connector_dpms() in reaction to fbdev blanking events. Do drivers + that don't implement (or just don't use) fbcon compatibility need to call + those functions themselves? +- KMS drivers must call drm_vblank_pre_modeset() and drm_vblank_post_modeset() + around mode setting. Should this be done in the DRM core? +- vblank_disable_allowed is set to 1 in the first drm_vblank_post_modeset() + call and never set back to 0. It seems to be safe to permanently set it to 1 + in drm_vblank_init() for KMS driver, and it might be safe for UMS drivers as + well. This should be investigated. +- crtc and connector .save and .restore operations are only used internally in + drivers, should they be removed from the core? +- encoder mid-layer .save and .restore operations are only used internally in + drivers, should they be removed from the core? +- encoder mid-layer .detect operation is only used internally in drivers, + should it be removed from the core? +--> + <!-- External interfaces --> <chapter id="drmExternals"> @@ -853,6 +2434,42 @@ void intel_crt_init(struct drm_device *dev) Cover generic ioctls and sysfs layout here. We only need high-level info, since man pages should cover the rest. </para> + + <!-- External: vblank handling --> + + <sect1> + <title>VBlank event handling</title> + <para> + The DRM core exposes two vertical blank related ioctls: + <variablelist> + <varlistentry> + <term>DRM_IOCTL_WAIT_VBLANK</term> + <listitem> + <para> + This takes a struct drm_wait_vblank structure as its argument, + and it is used to block or request a signal when a specified + vblank event occurs. + </para> + </listitem> + </varlistentry> + <varlistentry> + <term>DRM_IOCTL_MODESET_CTL</term> + <listitem> + <para> + This should be called by application level drivers before and + after mode setting, since on many devices the vertical blank + counter is reset at that time. Internally, the DRM snapshots + the last vblank count when the ioctl is called with the + _DRM_PRE_MODESET command, so that the counter won't go backwards + (which is dealt with when _DRM_POST_MODESET is used). + </para> + </listitem> + </varlistentry> + </variablelist> +<!--!Edrivers/char/drm/drm_irq.c--> + </para> + </sect1> + </chapter> <!-- API reference --> |