On Tue, Jul 18, 2023 at 2:44 PM Nathan Chancellor <nathan@xxxxxxxxxx> wrote: > > A proposed update to clang's -Wconstant-logical-operand to warn when the > left hand side is a constant shows the following instance in > nsecs_to_jiffies_timeout() when NSEC_PER_SEC is not a multiple of HZ, > such as CONFIG_HZ=300: > > In file included from drivers/gpu/drm/v3d/v3d_debugfs.c:12: > drivers/gpu/drm/v3d/v3d_drv.h:343:24: warning: use of logical '&&' with constant operand [-Wconstant-logical-operand] > 343 | if (NSEC_PER_SEC % HZ && > | ~~~~~~~~~~~~~~~~~ ^ > drivers/gpu/drm/v3d/v3d_drv.h:343:24: note: use '&' for a bitwise operation > 343 | if (NSEC_PER_SEC % HZ && > | ^~ > | & > drivers/gpu/drm/v3d/v3d_drv.h:343:24: note: remove constant to silence this warning > 1 warning generated. > > Turn this into an explicit comparison against zero to make the > expression a boolean to make it clear this should be a logical check, > not a bitwise one. > > Link: https://reviews.llvm.org/D142609 > Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx> Thanks for the patch! Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > --- > drivers/gpu/drm/v3d/v3d_drv.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/v3d/v3d_drv.h b/drivers/gpu/drm/v3d/v3d_drv.h > index b74b1351bfc8..7f664a4b2a75 100644 > --- a/drivers/gpu/drm/v3d/v3d_drv.h > +++ b/drivers/gpu/drm/v3d/v3d_drv.h > @@ -340,7 +340,7 @@ struct v3d_submit_ext { > static inline unsigned long nsecs_to_jiffies_timeout(const u64 n) > { > /* nsecs_to_jiffies64() does not guard against overflow */ > - if (NSEC_PER_SEC % HZ && > + if ((NSEC_PER_SEC % HZ) != 0 && > div_u64(n, NSEC_PER_SEC) >= MAX_JIFFY_OFFSET / HZ) > return MAX_JIFFY_OFFSET; > > > -- > 2.41.0 > -- Thanks, ~Nick Desaulniers
