(Adding Hans) Hi Nathan, Nick, Thanks for the patch (and the patience). On Mon, 2019-11-04 at 21:59 -0700, Nathan Chancellor wrote: > When building with Clang + -Wtautological-constant-compare, several of > the ivtv drivers warn along the lines of: > Nitpick: s/ivtv/ivtv and cx18 > drivers/media/pci/cx18/cx18-driver.c:1005:21: warning: converting the > result of '<<' to a boolean always evaluates to true > [-Wtautological-constant-compare] > cx18_call_hw(cx, CX18_HW_GPIO_RESET_CTRL, > ^ > drivers/media/pci/cx18/cx18-cards.h:18:37: note: expanded from macro > 'CX18_HW_GPIO_RESET_CTRL' > #define CX18_HW_GPIO_RESET_CTRL (1 << 6) > ^ > 1 warning generated. > > This is because the shift operation is implicitly converted to a boolean > in v4l2_device_mask_call_all before being negated. This can be solved by > just comparing the mask result to 0 explicitly so that there is no > boolean conversion. > Perhaps it's interesting to mention the reason for this change, which you mentioned as a comment before: """ The ultimate goal is to get -Wtautological-compare enabled because there are several subwarnings that would be helpful to have and right now they are all disabled. """ > Link: https://github.com/ClangBuiltLinux/linux/issues/752 > Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx> > --- > > v1 -> v2: https://lore.kernel.org/lkml/20191024201240.49063-1-natechancellor@xxxxxxxxx/ > > * Fix typo in commit message > * Add Nick's Reviewed-by. > > include/media/v4l2-device.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/include/media/v4l2-device.h b/include/media/v4l2-device.h > index e0b8f2602670..8564b3227887 100644 > --- a/include/media/v4l2-device.h > +++ b/include/media/v4l2-device.h > @@ -431,8 +431,8 @@ static inline bool v4l2_device_supports_requests(struct v4l2_device *v4l2_dev) > struct v4l2_subdev *__sd; \ > \ > __v4l2_device_call_subdevs_p(v4l2_dev, __sd, \ > - !(grpmsk) || (__sd->grp_id & (grpmsk)), o, f , \ > - ##args); \ > + (grpmsk) == 0 || (__sd->grp_id & (grpmsk)), o, \ > + f , ##args); \ > } while (0) > > /** The change is small enough and if it helps enabling helpful warnings, then it seems a good idea. Reviewed-by: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx> For consistency, it would be good to also patch the other case(s). Thanks, Ezequiel
