Hi Javier,
On Thu, Nov 11, 2021 at 12:13 PM Javier Martinez Canillas javierm@redhat.com wrote:
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 d391c5827107 ("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: d391c5827107 ("drivers/firmware: move x86 Generic System Framebuffers support") Reported-by: Ilya Trukhanov lahvuun@gmail.com Signed-off-by: Javier Martinez Canillas javierm@redhat.com Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
Changes in v2:
- Add a Link: tag with a reference to the bug report (Thorsten Leemhuis).
- Add a comment explaining why the probe fails earlier (Daniel Vetter).
- Add a Fixes: tag for stable to pick the fix (Daniel Vetter).
- Add Daniel Vetter's Reviewed-by: tag.
- Improve the commit message and mention the culprit commit
drivers/video/fbdev/efifb.c | 11 +++++++++++ drivers/video/fbdev/simplefb.c | 11 +++++++++++ 2 files changed, 22 insertions(+)
diff --git drivers/video/fbdev/efifb.c drivers/video/fbdev/efifb.c index edca3703b964..ea42ba6445b2 100644 --- drivers/video/fbdev/efifb.c +++ drivers/video/fbdev/efifb.c @@ -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) {
Who says this registered fbdev is driving the same hardware as efifb? This might be e.g. a small external display connected to i2c or spi.
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;diff --git drivers/video/fbdev/simplefb.c drivers/video/fbdev/simplefb.c index 62f0ded70681..b63074fd892e 100644 --- drivers/video/fbdev/simplefb.c +++ drivers/video/fbdev/simplefb.c @@ -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) {
Likewise.
dev_err(&pdev->dev,"simplefb: a framebuffer is already registered\n");return -EINVAL;}if (fb_get_options("simplefb", NULL)) return -ENODEV;
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds