[PATCH] fbdev: Fix logic error in "offb" name match

[PATCH] fbdev: Fix logic error in "offb" name match

[Finn Thain]

A regression was reported to me recently whereby /dev/fb0 had disappeared
from a PowerBook G3 Series "Wallstreet". The problem shows up when the
"video=ofonly" parameter is passed to the kernel, which is what the
bootloader does when "no video driver" is selected. The cause of the
problem is the "offb" string comparison, which got mangled when it got
refactored. Fix it.

Cc: stable@vger.kernel.org
Fixes: 93604a5ade3a ("fbdev: Handle video= parameter in video/cmdline.c")
Reported-and-tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
---
 drivers/video/fbdev/core/fb_cmdline.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/core/fb_cmdline.c b/drivers/video/fbdev/core/fb_cmdline.c
index 4d1634c492ec..594b60424d1c 100644
--- a/drivers/video/fbdev/core/fb_cmdline.c
+++ b/drivers/video/fbdev/core/fb_cmdline.c
@@ -40,7 +40,7 @@ int fb_get_options(const char *name, char **option)
 	bool enabled;
 
 	if (name)
-		is_of = strncmp(name, "offb", 4);
+		is_of = !strncmp(name, "offb", 4);
 
 	enabled = __video_get_options(name, &options, is_of);
 
-- 
2.49.1

Re: [PATCH] fbdev: Fix logic error in "offb" name match

[Helge Deller]

On 10/9/25 00:56, Finn Thain wrote:
> A regression was reported to me recently whereby /dev/fb0 had disappeared
> from a PowerBook G3 Series "Wallstreet". The problem shows up when the
> "video=ofonly" parameter is passed to the kernel, which is what the
> bootloader does when "no video driver" is selected. The cause of the
> problem is the "offb" string comparison, which got mangled when it got
> refactored. Fix it.
> 
> Cc: stable@vger.kernel.org
> Fixes: 93604a5ade3a ("fbdev: Handle video= parameter in video/cmdline.c")
> Reported-and-tested-by: Stan Johnson <userm57@yahoo.com>
> Signed-off-by: Finn Thain <fthain@linux-m68k.org>
> ---
>   drivers/video/fbdev/core/fb_cmdline.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)

applied.

Thanks!
Helge

Re: [PATCH] fbdev: Fix logic error in "offb" name match

[Thomas Zimmermann]

Am 09.10.25 um 00:56 schrieb Finn Thain:
> A regression was reported to me recently whereby /dev/fb0 had disappeared
> from a PowerBook G3 Series "Wallstreet". The problem shows up when the
> "video=ofonly" parameter is passed to the kernel, which is what the
> bootloader does when "no video driver" is selected. The cause of the
> problem is the "offb" string comparison, which got mangled when it got
> refactored. Fix it.
>
> Cc: stable@vger.kernel.org
> Fixes: 93604a5ade3a ("fbdev: Handle video= parameter in video/cmdline.c")
> Reported-and-tested-by: Stan Johnson <userm57@yahoo.com>
> Signed-off-by: Finn Thain <fthain@linux-m68k.org>

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>

> ---
>   drivers/video/fbdev/core/fb_cmdline.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/core/fb_cmdline.c b/drivers/video/fbdev/core/fb_cmdline.c
> index 4d1634c492ec..594b60424d1c 100644
> --- a/drivers/video/fbdev/core/fb_cmdline.c
> +++ b/drivers/video/fbdev/core/fb_cmdline.c
> @@ -40,7 +40,7 @@ int fb_get_options(const char *name, char **option)
>   	bool enabled;
>   
>   	if (name)
> -		is_of = strncmp(name, "offb", 4);
> +		is_of = !strncmp(name, "offb", 4);
>   
>   	enabled = __video_get_options(name, &options, is_of);
>   

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)