Re: [PATCH 0/2] Avoid -Wconstant-logical-operand in nsecs_to_jiffies_timeout()

[Maira Canal <mcanal@igalia.com>]

On 7/18/23 18:44, Nathan Chancellor wrote:
> Hi all,
> 
> A proposed update to clang's -Wconstant-logical-operand [1] to warn when
> the left hand side is a constant as well now triggers with the modulo
> expression in nsecs_to_jiffies_timeout() when NSEC_PER_SEC is not a
> multiple of HZ, such as CONFIG_HZ=300:
> 
>    drivers/gpu/drm/i915/gem/i915_gem_wait.c:189:24: warning: use of logical '&&' with constant operand [-Wconstant-logical-operand]
>      189 |         if (NSEC_PER_SEC % HZ &&
>          |             ~~~~~~~~~~~~~~~~~ ^
>    drivers/gpu/drm/i915/gem/i915_gem_wait.c:189:24: note: use '&' for a bitwise operation
>      189 |         if (NSEC_PER_SEC % HZ &&
>          |                               ^~
>          |                               &
>    drivers/gpu/drm/i915/gem/i915_gem_wait.c:189:24: note: remove constant to silence this warning
>    1 warning generated.
> 
>    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.
> 
> These patches add an explicit comparison to zero to make the
> expression a boolean, which clears up the warning.
> 
> The patches have no real dependency on each other but I felt like they
> made send together since it is the same code.
> 
> If these could go into mainline sooner rather than later to avoid
> breaking builds that can hit this with CONFIG_WERROR, that would be
> nice, but I won't insist since I don't think our own CI has builds that
> has those conditions, but others might.
> 
> ---
> Nathan Chancellor (2):
>        drm/v3d: Avoid -Wconstant-logical-operand in nsecs_to_jiffies_timeout()
>        drm/i915: Avoid -Wconstant-logical-operand in nsecs_to_jiffies_timeout()

Applied both patches to drm-misc/drm-misc-next!

Best Regards,
- Maíra

> 
>   drivers/gpu/drm/i915/gem/i915_gem_wait.c | 2 +-
>   drivers/gpu/drm/v3d/v3d_drv.h            | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
> ---
> base-commit: fdf0eaf11452d72945af31804e2a1048ee1b574c
> change-id: 20230718-nsecs_to_jiffies_timeout-constant-logical-operand-4a944690f3e9
> 
> Best regards,