Re: [PATCH v2 3/3] Move IS_CONFIG_NONZERO() to kconfig.h

[Lucas De Marchi]

On Thu, Sep 30, 2021 at 11:01:36PM +0900, Masahiro Yamada wrote:
> On Thu, Sep 30, 2021 at 3:34 AM Lucas De Marchi
> <lucas.demarchi@xxxxxxxxx> wrote:
> > The check for config value doesn't really belong to i915_utils.h - we
> > are trying to eliminate that utils helper and share them when possible
> > with other drivers and subsystems.
> >
> > Rationale for having such macro is in commit
> > babaab2f4738 ("drm/i915: Encapsulate kconfig constant values inside boolean predicates")
> > whereas later it is improved to not break the build if used with
> > undefined configs. The caveat is detailed in the documentation: unlike
> > IS_ENABLED(): it's not preprocessor-only logic so can't be used for
> > things like `#if IS_CONFIG_NONZERO(...)`
> >
> > Signed-off-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
>
>
> Hypothetical "it would be nice to have ..." is really unneeded.
>
>       if (context && CONFIG_DRM_I915_FENCE_TIMEOUT > 0)
>                     return
> msecs_to_jiffies_timeout(CONFIG_DRM_I915_FENCE_TIMEOUT);
>
>
> is enough, and much cleaner.
>
>
>
> This warning is shown only when a constant is used
> together with '&&'.
>
> Most of IS_ACTIVE can go away.
>
> Given that, there are not many places where the IS_ACTIVE macro
> is useful, even in the i915 driver.
>
> For a few sources of the warnings,
> replacing it with  != 0 or > 0 is just fine.

humn... maybe. Let me do a conversion in that direction and see what is
the outcome.

My original intention was to make IS_ENABLED() even uglier to cover the
int case, but after some tries it seems impossible to do on preprocessor
context, so I thought maybe it would be ok as a separate one.

> Of course, such an ugly macro is not worth being moved to <linux/kconfig.h>

if we don't handle the undefined case and only worry about encapsulating
it inside a boolean predicate, the macro would be very simple. Would
that be worth having in kconfig.h maybe?


thanks
Lucas De Marchi