Re: [PATCH] drivers: video: fbmem: add signed type cast for comparation.

[Chen Gang <gang.chen@asianux.com>]

On 07/22/2013 07:16 PM, Geert Uytterhoeven wrote:
> On Mon, Jul 22, 2013 at 10:07 AM, Chen Gang <gang.chen@asianux.com> wrote:
>> For 'con2fb.framebuffer', it can be '-1' as an invalid value, so it
>> need related type cast for its comparing.
>>
>> The related warning:
>>
>>   drivers/video/fbmem.c:1169:3: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
>>
>>
>> Signed-off-by: Chen Gang <gang.chen@asianux.com>
>> ---
>>  drivers/video/fbmem.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
>> index 36e1fe2..8e8225c 100644
>> --- a/drivers/video/fbmem.c
>> +++ b/drivers/video/fbmem.c
>> @@ -1166,7 +1166,7 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
>>                         return -EFAULT;
>>                 if (con2fb.console < 1 || con2fb.console > MAX_NR_CONSOLES)
>>                         return -EINVAL;
>> -               if (con2fb.framebuffer < 0 || con2fb.framebuffer >= FB_MAX)
>> +               if ((int)con2fb.framebuffer < 0 || con2fb.framebuffer >= FB_MAX)
>>                         return -EINVAL;
> 
> Instead of adding the cast, you can also just remove the check, as it's useless.
> If it's `-1' for invalid, after conversion to unsigned, it will
> trigger the check
> ">= FB_MAX".
> 

OH, yes, thanks.

Original implementation is no issue (the compiler will skip the first
checking automatically).

If suitable, I should send patch v2.

Thanks.

> 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
> 
> 


-- 
Chen Gang