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

[Javier Martinez Canillas]

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.

Reported-by: Ilya Trukhanov <lahv...@gmail.com>
Signed-off-by: Javier Martinez Canillas <javi...@redhat.com>
---

 drivers/video/fbdev/efifb.c    | 6 ++++++
 drivers/video/fbdev/simplefb.c | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git drivers/video/fbdev/efifb.c drivers/video/fbdev/efifb.c
index edca3703b964..76325c07cf0c 100644
--- drivers/video/fbdev/efifb.c
+++ drivers/video/fbdev/efifb.c
@@ -351,6 +351,12 @@ static int efifb_probe(struct platform_device *dev)
        char *option = NULL;
        efi_memory_desc_t md;
 
+       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;
 
diff --git drivers/video/fbdev/simplefb.c drivers/video/fbdev/simplefb.c
index 62f0ded70681..55c1f54d7663 100644
--- drivers/video/fbdev/simplefb.c
+++ drivers/video/fbdev/simplefb.c
@@ -407,6 +407,12 @@ static int simplefb_probe(struct platform_device *pdev)
        struct simplefb_par *par;
        struct resource *mem;
 
+       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;
 
-- 
2.33.1