On Tue, Sep 18, 2012 at 08:35:09PM +0200, Jean Delvare wrote: > Hi Mauro, > > On Tue, 18 Sep 2012 12:49:53 -0300, Mauro Carvalho Chehab wrote: > > Em 01-09-2012 15:53, Jean Delvare escreveu: > > > DIV_ROUND_CLOSEST is faster if the compiler knows it will only be > > > dealing with unsigned dividends. > > > > > > Signed-off-by: Jean Delvare <khali@xxxxxxxxxxxx> > > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > > Cc: Guenter Roeck <linux@xxxxxxxxxxxx> > > > Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxx> > > > --- > > > drivers/media/rc/mceusb.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > --- linux-3.6-rc3.orig/drivers/media/rc/mceusb.c 2012-08-04 21:49:27.000000000 +0200 > > > +++ linux-3.6-rc3/drivers/media/rc/mceusb.c 2012-09-01 18:53:32.053042123 +0200 > > > @@ -627,7 +627,7 @@ static void mceusb_dev_printdata(struct > > > break; > > > case MCE_RSP_EQIRCFS: > > > period = DIV_ROUND_CLOSEST( > > > - (1 << data1 * 2) * (data2 + 1), 10); > > > + (1U << data1 * 2) * (data2 + 1), 10); > > > if (!period) > > > break; > > > carrier = (1000 * 1000) / period; > > > > Hmm... this generates the following warning with "W=1": > > > > drivers/media/rc/mceusb.c:629:4: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits] > > drivers/media/rc/mceusb.c:629:4: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits] > > I doubt this is the only warning of that kind. There must be a reason > why -Wextra isn't enabled by default. > > > Perhaps it makes sense to use an optimized version for unsigned, or to > > change the macro to take the data types into account. > > This was discussed before, but Andrew said he preferred a single macro. > And I agree with him, having two macros would induce a risk of the > wrong one being called. > > If you can come up with a variant of DIV_ROUND_CLOSEST which performs > the same and doesn't trigger the warning above, we'll be happy to see > it, but neither Guenter nor myself could come up with one. > I did some more research, and I think I found a fix. I'll send out a patch in a minute for people to try. Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
