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fbdev: Prevent probing generic drivers if a FB is already registered

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The efifb and simplefb drivers just render to a pre-allocated frame buffer
and rely on the display hardware being initialized before the kernel boots.

But if another driver already probed correctly and registered a fbdev, the
generic drivers shouldn't be probed since an actual driver for the display
hardware is already present.

This is more likely to occur after commit d391c58271 ("drivers/firmware:
move x86 Generic System Framebuffers support") since the "efi-framebuffer"
and "simple-framebuffer" platform devices are registered at a later time.

Link: https://lore.kernel.org/r/20211110200253.rfudkt3edbd3nsyj@lahvuun/
Fixes: d391c58271 ("drivers/firmware: move x86 Generic System Framebuffers support")
Reported-by: Ilya Trukhanov <lahvuun@gmail.com>
Cc: <stable@vger.kernel.org> # 5.15.x
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: Ilya Trukhanov <lahvuun@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211111115757.1351045-1-javierm@redhat.com
This commit is contained in:
Javier Martinez Canillas 2021-11-11 12:57:57 +01:00
parent 963d0b3569
commit fb561bf9ab
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2 changed files with 22 additions and 0 deletions
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11
drivers/video/fbdev/efifb.c
View File

@ -351,6 +351,17 @@ static int efifb_probe(struct platform_device *dev)
char *option = NULL;
efi_memory_desc_t md;
/*
* Generic drivers must not be registered if a framebuffer exists.
* If a native driver was probed, the display hardware was already
* taken and attempting to use the system framebuffer is dangerous.
*/
if (num_registered_fb > 0) {
dev_err(&dev->dev,
"efifb: a framebuffer is already registered\n");
return -EINVAL;
}
if (screen_info.orig_video_isVGA != VIDEO_TYPE_EFI || pci_dev_disabled)
return -ENODEV;

11
drivers/video/fbdev/simplefb.c
View File

@ -407,6 +407,17 @@ static int simplefb_probe(struct platform_device *pdev)
struct simplefb_par *par;
struct resource *mem;
/*
* Generic drivers must not be registered if a framebuffer exists.
* If a native driver was probed, the display hardware was already
* taken and attempting to use the system framebuffer is dangerous.
*/
if (num_registered_fb > 0) {
dev_err(&pdev->dev,
"simplefb: a framebuffer is already registered\n");
return -EINVAL;
}
if (fb_get_options("simplefb", NULL))
return -ENODEV;