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

From: Lucas De Marchi
Date: Thu Sep 30 2021 - 11:55:52 EST


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