From 59f5989ad42b6edd089b47895986ef15259822dc Mon Sep 17 00:00:00 2001 From: Thomas Zimmermann Date: Wed, 8 May 2019 10:26:18 +0200 Subject: drm: Integrate VRAM MM into struct drm_device There's now a pointer to struct drm_vram_mm stored in struct drm_device. DRM drivers that use VRAM MM should use this field to refer to their instance of the data structure. Appropriate helpers are now provided as well. Adding struct drm_vram_mm to struct drm_device further avoids wrappers and boilerplate code in drivers. This patch implements default functions for callbacks in struct drm_driver and struct file_operations that use the struct drm_vram_mm stored in struct drm_device. Drivers that need to provide their own implementations can still do so. The patch also adds documentation for the VRAM helper library in general. v5: * set .llseek to no_llseek() from DRM_VRAM_MM_FILE_OPERATIONS v4: * cleanups from checkpatch.pl * document VRAM helper library Signed-off-by: Thomas Zimmermann Link: http://patchwork.freedesktop.org/patch/msgid/20190508082630.15116-9-tzimmermann@suse.de Signed-off-by: Gerd Hoffmann --- drivers/gpu/drm/drm_vram_helper_common.c | 92 ++++++++++++++++++++++++++++++++ 1 file changed, 92 insertions(+) (limited to 'drivers/gpu/drm/drm_vram_helper_common.c') diff --git a/drivers/gpu/drm/drm_vram_helper_common.c b/drivers/gpu/drm/drm_vram_helper_common.c index 7c25daca18d0..3b47f7002115 100644 --- a/drivers/gpu/drm/drm_vram_helper_common.c +++ b/drivers/gpu/drm/drm_vram_helper_common.c @@ -2,5 +2,97 @@ #include +/** + * DOC: overview + * + * This library provides &struct drm_gem_vram_object (GEM VRAM), a GEM + * buffer object that is backed by video RAM. It can be used for + * framebuffer devices with dedicated memory. The video RAM can be + * managed with &struct drm_vram_mm (VRAM MM). Both data structures are + * supposed to be used together, but can also be used individually. + * + * With the GEM interface userspace applications create, manage and destroy + * graphics buffers, such as an on-screen framebuffer. GEM does not provide + * an implementation of these interfaces. It's up to the DRM driver to + * provide an implementation that suits the hardware. If the hardware device + * contains dedicated video memory, the DRM driver can use the VRAM helper + * library. Each active buffer object is stored in video RAM. Active + * buffer are used for drawing the current frame, typically something like + * the frame's scanout buffer or the cursor image. If there's no more space + * left in VRAM, inactive GEM objects can be moved to system memory. + * + * The easiest way to use the VRAM helper library is to call + * drm_vram_helper_alloc_mm(). The function allocates and initializes an + * instance of &struct drm_vram_mm in &struct drm_device.vram_mm . Use + * &DRM_GEM_VRAM_DRIVER to initialize &struct drm_driver and + * &DRM_VRAM_MM_FILE_OPERATIONS to initialize &struct file_operations; + * as illustrated below. + * + * .. code-block:: c + * + * struct file_operations fops ={ + * .owner = THIS_MODULE, + * DRM_VRAM_MM_FILE_OPERATION + * }; + * struct drm_driver drv = { + * .driver_feature = DRM_ ... , + * .fops = &fops, + * DRM_GEM_VRAM_DRIVER + * }; + * + * int init_drm_driver() + * { + * struct drm_device *dev; + * uint64_t vram_base; + * unsigned long vram_size; + * int ret; + * + * // setup device, vram base and size + * // ... + * + * ret = drm_vram_helper_alloc_mm(dev, vram_base, vram_size, + * &drm_gem_vram_mm_funcs); + * if (ret) + * return ret; + * return 0; + * } + * + * This creates an instance of &struct drm_vram_mm, exports DRM userspace + * interfaces for GEM buffer management and initializes file operations to + * allow for accessing created GEM buffers. With this setup, the DRM driver + * manages an area of video RAM with VRAM MM and provides GEM VRAM objects + * to userspace. + * + * To clean up the VRAM memory management, call drm_vram_helper_release_mm() + * in the driver's clean-up code. + * + * .. code-block:: c + * + * void fini_drm_driver() + * { + * struct drm_device *dev = ...; + * + * drm_vram_helper_release_mm(dev); + * } + * + * For drawing or scanout operations, buffer object have to be pinned in video + * RAM. Call drm_gem_vram_pin() with &DRM_GEM_VRAM_PL_FLAG_VRAM or + * &DRM_GEM_VRAM_PL_FLAG_SYSTEM to pin a buffer object in video RAM or system + * memory. Call drm_gem_vram_unpin() to release the pinned object afterwards. + * If you have to evict a buffer object from video RAM (e.g., for freeing up + * memory), unpin the buffer and call drm_gem_vram_push_to_system(). + * + * A buffer object that is pinned in video RAM has a fixed address within that + * memory region. Call drm_gem_vram_offset() to retrieve this value. Typically + * it's used to program the hardware's scanout engine for framebuffers, set + * the cursor overlay's image for a mouse cursor, or use it as input to the + * hardware's draing engine. + * + * To access a buffer object's memory from the DRM driver, call + * drm_gem_vram_kmap(). It (optionally) maps the buffer into kernel address + * space and returns the memory address. Use drm_gem_vram_kunmap() to + * release the mapping. + */ + MODULE_DESCRIPTION("DRM VRAM memory-management helpers"); MODULE_LICENSE("GPL"); -- cgit v1.2.3