kernel/linux.git/drivers/video/fbdev/udlfb.c, branch linux-4.20.y

udlfb: handle unplug properly

2018-10-08T10:57:34+00:00

The udlfb driver maintained an open count and cleaned up itself when the count reached zero. But the console is also counted in the reference count - so, if the user unplugged the device, the open count would not drop to zero and the driver stayed loaded with console attached. If the user re-plugged the adapter, it would create a device /dev/fb1, show green screen and the access to the console would be lost. The framebuffer subsystem has reference counting on its own - in order to fix the unplug bug, we rely the framebuffer reference counting. When the user unplugs the adapter, we call unregister_framebuffer unconditionally. unregister_framebuffer will unbind the console, wait until all users stop using the framebuffer and then call the fb_destroy method. The fb_destroy cleans up the USB driver. This patch makes the following changes: * Drop dlfb->kref and rely on implicit framebuffer reference counting instead. * dlfb_usb_disconnect calls unregister_framebuffer, the rest of driver cleanup is done in the function dlfb_ops_destroy. dlfb_ops_destroy will be called by the framebuffer subsystem when no processes have the framebuffer open or mapped. * We don't use workqueue during initialization, but initialize directly from dlfb_usb_probe. The workqueue could race with dlfb_usb_disconnect and this racing would produce various kinds of memory corruption. * We use usb_get_dev and usb_put_dev to make sure that the USB subsystem doesn't free the device under us. Signed-off-by: Mikulas Patocka cc: Dave Airlie Cc: Bernie Thompson , Cc: Ladislav Michl Signed-off-by: Bartlomiej Zolnierkiewicz

udlfb: use spin_lock_irq instead of spin_lock_irqsave

2018-07-25T13:41:57+00:00

spin_lock_irqsave and spin_unlock_irqrestore is inteded to be called from a context where it is unknown if interrupts are enabled or disabled (such as interrupt handlers). From a process context, we should call spin_lock_irq and spin_unlock_irq, that avoids the costly pushf and popf instructions. Signed-off-by: Mikulas Patocka Signed-off-by: Bartlomiej Zolnierkiewicz

udlfb: avoid prefetch

2018-07-25T13:41:57+00:00

Modern processors can detect linear memory accesses and prefetch data automatically, so there's no need to use prefetch. Signed-off-by: Mikulas Patocka Signed-off-by: Bartlomiej Zolnierkiewicz

udlfb: optimization - test the backing buffer

2018-07-25T13:41:56+00:00

Currently, the udlfb driver only tests for identical bytes at the beginning or at the end of a page and renders anything between the first and last mismatching pixel. But pages are not the same as lines, so this is quite suboptimal - if there is something modified at the beginning of a page and at the end of a page, the whole page is rendered, even if most of the page is not modified. This patch makes it test for identical pixels at the beginning and end of each rendering command. This patch improves identical byte detection by 41% when playing video in a window. This patch also fixes a possible screen corruption if the user is writing to the framebuffer while dlfb_render_hline is in progress - the pixel data that is copied to the backbuffer with memcpy may be different from the pixel data that is actually rendered to the hardware (because the content of the framebuffer may change between memcpy and the rendering command). We must make sure that we copy exactly the same pixel as the pixel that is being rendered. Signed-off-by: Mikulas Patocka [b.zolnierkie: fix code indent] Signed-off-by: Bartlomiej Zolnierkiewicz

udlfb: allow reallocating the framebuffer

2018-07-25T13:41:56+00:00

This patch changes udlfb so that it may reallocate the framebuffer when setting higher-resolution mode. If we boot the system without monitor attached, udlfb creates a framebuffer with the size 800x600. This patch makes it possible to select higher videomode with the fbset command when a monitor is attached. Note that there is no reliable way to prevent the system from touching the old framebuffer, so we must not free it. We add it to the list dlfb->deferred_free and free it when the driver is unloaded. Signed-off-by: Mikulas Patocka [b.zolnierkie: sparse fixes] Signed-off-by: Bartlomiej Zolnierkiewicz

udlfb: set line_length in dlfb_ops_set_par

2018-07-25T13:41:56+00:00

Set the variable "line_length" in the function dlfb_ops_set_par. Without this, we get garbage if we select different videomode with fbset. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org Signed-off-by: Bartlomiej Zolnierkiewicz

udlfb: handle allocation failure

2018-07-25T13:41:56+00:00

Allocations larger than PAGE_ALLOC_COSTLY_ORDER are unreliable and they may fail anytime. This patch fixes the udlfb driver so that when a large alloactions fails, it tries to do multiple smaller allocations. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org Signed-off-by: Bartlomiej Zolnierkiewicz

udlfb: make a local copy of fb_ops

2018-07-25T13:41:55+00:00

The defio subsystem overwrites the method fb_osp->mmap. That method is stored in module's static data - and that means that if we have multiple diplaylink adapters, they will over write each other's method. In order to avoid interference between multiple adapters, we copy the fb_ops structure to a device-local memory. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org Signed-off-by: Bartlomiej Zolnierkiewicz

udlfb: don't switch if we are switching to the same videomode

2018-07-25T13:41:55+00:00

The udlfb driver reprograms the hardware everytime the user switches the console, that makes quite unusable when working on the console. This patch makes the driver remember the videomode we are in and avoid reprogramming the hardware if we switch to the same videomode. We mask the "activate" field and the "FB_VMODE_SMOOTH_XPAN" flag when comparing the videomode, because they cause spurious switches when switching to and from the Xserver. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org Signed-off-by: Bartlomiej Zolnierkiewicz

udlfb: fix display corruption of the last line

2018-07-25T13:41:54+00:00

The displaylink hardware has such a peculiarity that it doesn't render a command until next command is received. This produces occasional corruption, such as when setting 22x11 font on the console, only the first line of the cursor will be blinking if the cursor is located at some specific columns. When we end up with a repeating pixel, the driver has a bug that it leaves one uninitialized byte after the command (and this byte is enough to flush the command and render it - thus it fixes the screen corruption), however whe we end up with a non-repeating pixel, there is no byte appended and this results in temporary screen corruption. This patch fixes the screen corruption by always appending a byte 0xAF at the end of URB. It also removes the uninitialized byte. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org Signed-off-by: Bartlomiej Zolnierkiewicz