From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chen Gang Date: Tue, 23 Jul 2013 00:04:16 +0000 Subject: Re: [PATCH] drivers: video: fbmem: add signed type cast for comparation. Message-Id: <51EDC880.40000@asianux.com> List-Id: References: <51ECE851.4030002@asianux.com> In-Reply-To: <51ECE851.4030002@asianux.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-fbdev@vger.kernel.org On 07/22/2013 07:16 PM, Geert Uytterhoeven wrote: > On Mon, Jul 22, 2013 at 10:07 AM, Chen Gang 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 >> --- >> 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