Re: [PATCH] kconfig.h: remove config_enabled() macro

From: Masahiro Yamada
Date: Thu Oct 20 2016 - 08:07:15 EST

Hi Paul,

2016-10-20 19:04 GMT+09:00 Paul Bolle <pebolle@xxxxxxxxxx>:
> Masahiro,
> A few comments regarding, I guess, future work.
> On Sun, 2016-10-16 at 20:07 +0900, Masahiro Yamada wrote:
>> The use of config_enabled() is ambiguous. For config options,
>> IS_ENABLED(), IS_REACHABLE(), etc. will make intention clearer.
>> Sometimes config_enabled() has been used for non-config options
>> because it is useful to check whether the given symbol is defined
>> or not.
>> I have been tackling on deprecating config_enabled(), and now is the
>> time to finish this work.
>> Some new users have appeared for v4.9-rc1, but it is trivial to
>> replace them:
>> - arch/x86/mm/kaslr.c
>> replace config_enabled() with IS_ENABLED() because
>> CONFIG_X86_ESPFIX64 and CONFIG_EFI are boolean.
>> - include/asm-generic/export.h
>> replace config_enabled() with __is_defined().
>> Then, config_enabled() can be removed now.
>> Going forward, please use IS_ENABLED(), IS_REACHABLE(), etc. for
>> config options, and __is_defined() for non-config symbols.
> There are about a dozen instances of IS_ENABLED() that target something
> other than a kconfig macros. Are you planning to convert those to
> __is_defined() too?

I did not notice that, but looks like there are some to be checked.

$ git grep '[^A-Za-z0-9_]IS_ENABLED([^C]'
arch/arc/include/asm/setup.h:#define IS_USED_CFG(cfg)
arch/arm64/include/asm/alternative.h: __ALTERNATIVE_CFG(oldinstr,
newinstr, feature, IS_ENABLED(cfg))
arch/arm64/include/asm/alternative.h: alternative_insn insn1, insn2,
cap, IS_ENABLED(cfg)
drivers/crypto/sahara.c: if (!IS_ENABLED(DEBUG))
drivers/crypto/sahara.c: if (!IS_ENABLED(DEBUG))
drivers/crypto/sahara.c: if (!IS_ENABLED(DEBUG))
drivers/gpu/drm/exynos/exynos_drm_drv.c:#define DRV_PTR(drv, cond)
(IS_ENABLED(cond) ? &drv : NULL)
include/asm-generic/ OF_TABLE(cfg, name)
__OF_TABLE(IS_ENABLED(cfg), name)
include/linux/init.h: int var = IS_ENABLED(config);
include/linux/kconfig.h: * This is similar to IS_ENABLED(), but
returns false when invoked from
include/linux/kconfig.h:#define IS_ENABLED(option)
__or(IS_BUILTIN(option), IS_MODULE(option))
kernel/locking/locktorture.c:int torture_runnable = IS_ENABLED(MODULE);
kernel/rcu/rcuperf.c:static int perf_runnable = IS_ENABLED(MODULE);
kernel/rcu/rcutorture.c:static int torture_runnable = IS_ENABLED(MODULE);
scripts/ "Prefer
scripts/ $fixed[$fixlinenr] =
"\+#if IS_ENABLED($config)";

>> --- a/include/linux/kconfig.h
>> +++ b/include/linux/kconfig.h
>> @@ -31,7 +31,6 @@
>> * When CONFIG_BOOGER is not defined, we generate a (... 1, 0) pair, and when
>> * the last step cherry picks the 2nd arg, we get a zero.
>> */
>> -#define config_enabled(cfg) ___is_defined(cfg)
> Is there a reason to keep using the double underscore prefix?

I followed the suggestion in the following message:

>> #define __is_defined(x) ___is_defined(x)
>> #define ___is_defined(val) ____is_defined(__ARG_PLACEHOLDER_##val)
>> #define ____is_defined(arg1_or_junk) __take_second_arg(arg1_or_junk 1, 0)
> __is_defined() is now meant to be used generally, and not just on
> kconfig macros. Can it be moved into another header?

Currently, __is_defined() is only used in two places:


Even if we fix something like IS_ENABLED(DEBUG),
we do not have many for now,
but perhaps will it be used more widely in the future?

If so, do we need to add IS_DEFINED() or is_defined()?

in include/linux/kconfig.h ? or include/linux/kernel.h ?

Best Regards
Masahiro Yamada