| Message ID | 20210505174515.87565-1-masahiroy@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] linux/kconfig.h: replace IF_ENABLED() with PTR_IF() in <linux/kernel.h> | expand |
On Thu, May 06, 2021 at 02:45:15AM +0900, Masahiro Yamada wrote: > <linux/kconfig.h> is included from all the kernel-space source files, > including C, assembly, linker scripts. It is intended to contain a > minimal set of macros to evaluate CONFIG options. > > IF_ENABLED() is an intruder here because (x ? y : z) is C code, which > should not be included from assembly files or linker scripts. > > Also, <linux/kconfig.h> is no longer self-contained because NULL is > defined in <linux/stddef.h>. > > Move IF_ENABLED() out to <linux/kernel.h> as PTR_IF(). PTF_IF() > takes the general boolean expression instead of a CONFIG option > so that it fits better in <linux/kernel.h>. > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Kees Cook <keescook@chromium.org>
Hi Masahiro, On Thu, 6 May 2021 02:45:15 +0900 Masahiro Yamada <masahiroy@kernel.org> wrote: > > <linux/kconfig.h> is included from all the kernel-space source files, > including C, assembly, linker scripts. It is intended to contain a > minimal set of macros to evaluate CONFIG options. > > IF_ENABLED() is an intruder here because (x ? y : z) is C code, which > should not be included from assembly files or linker scripts. Except it doesn't matter unless IF_ENABLED() is used by one of those. > Also, <linux/kconfig.h> is no longer self-contained because NULL is > defined in <linux/stddef.h>. Again, it doesn't matter unless IF_ENABLED() is used. > Move IF_ENABLED() out to <linux/kernel.h> as PTR_IF(). PTF_IF() > takes the general boolean expression instead of a CONFIG option > so that it fits better in <linux/kernel.h>. > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> > --- > > Changes in v2: > - Keep PTF_IF macro in pinctrl-ingenic.c > > drivers/pinctrl/pinctrl-ingenic.c | 2 ++ > include/linux/kconfig.h | 6 ------ > include/linux/kernel.h | 2 ++ > 3 files changed, 4 insertions(+), 6 deletions(-) > > diff --git a/drivers/pinctrl/pinctrl-ingenic.c b/drivers/pinctrl/pinctrl-ingenic.c > index 651a36b9dcc0..0ee69f8e20b2 100644 > --- a/drivers/pinctrl/pinctrl-ingenic.c > +++ b/drivers/pinctrl/pinctrl-ingenic.c > @@ -3854,6 +3854,8 @@ static int __init ingenic_pinctrl_probe(struct platform_device *pdev) > return 0; > } > > +#define IF_ENABLED(cfg, ptr) PTR_IF(IS_ENABLED(cfg), (ptr)) > + > static const struct of_device_id ingenic_pinctrl_of_match[] = { > { > .compatible = "ingenic,jz4730-pinctrl", You also need to include linux/kernel.h in drivers/pinctrl/pinctrl-ingenic.c (for completeness). Also, I don't understand why the use of IF_ENABLED doesn't produce "defined but not used" warnings (if the function "ptr" is not marked as __maybe_unused) ... Also, if there is only one user of IF_ENABLED (and therefore PTR_IF), why not just put it in that file and save me rebuilding the world again every day because kernel.h is changed (again). I guess that is going to happen just because kconfig.h is being changed and that is also included by everything :-( Also, is anyone else ever going to use PTR_IF() without having to also use IS_ENABLED()? So, in case it is not obvious, I consider this patch unnecessary churn (as was probably the patch that introduced IF_ENABLED in the first place). As an aside, this should not have been added to the kbuild tree in linux-next until after -rc1 was released ...
Hi Stephen, On Sat, May 8, 2021 at 10:59 AM Stephen Rothwell <sfr@canb.auug.org.au> wrote: > > Hi Masahiro, > > On Thu, 6 May 2021 02:45:15 +0900 Masahiro Yamada <masahiroy@kernel.org> wrote: > > > > <linux/kconfig.h> is included from all the kernel-space source files, > > including C, assembly, linker scripts. It is intended to contain a > > minimal set of macros to evaluate CONFIG options. > > > > IF_ENABLED() is an intruder here because (x ? y : z) is C code, which > > should not be included from assembly files or linker scripts. > > Except it doesn't matter unless IF_ENABLED() is used by one of those. Yes. This is rather coding policy of <linux/kconfig.h> > > Also, <linux/kconfig.h> is no longer self-contained because NULL is > > defined in <linux/stddef.h>. > > Again, it doesn't matter unless IF_ENABLED() is used. If you want to use IF_ENABLED(), you must understand that it is internally using NULL and include <linux/stddef.h>. It is the reason why we should make headers self-contained. > > > Move IF_ENABLED() out to <linux/kernel.h> as PTR_IF(). PTF_IF() > > takes the general boolean expression instead of a CONFIG option > > so that it fits better in <linux/kernel.h>. > > > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> > > --- > > > > Changes in v2: > > - Keep PTF_IF macro in pinctrl-ingenic.c > > > > drivers/pinctrl/pinctrl-ingenic.c | 2 ++ > > include/linux/kconfig.h | 6 ------ > > include/linux/kernel.h | 2 ++ > > 3 files changed, 4 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/pinctrl/pinctrl-ingenic.c b/drivers/pinctrl/pinctrl-ingenic.c > > index 651a36b9dcc0..0ee69f8e20b2 100644 > > --- a/drivers/pinctrl/pinctrl-ingenic.c > > +++ b/drivers/pinctrl/pinctrl-ingenic.c > > @@ -3854,6 +3854,8 @@ static int __init ingenic_pinctrl_probe(struct platform_device *pdev) > > return 0; > > } > > > > +#define IF_ENABLED(cfg, ptr) PTR_IF(IS_ENABLED(cfg), (ptr)) > > + > > static const struct of_device_id ingenic_pinctrl_of_match[] = { > > { > > .compatible = "ingenic,jz4730-pinctrl", > > You also need to include linux/kernel.h in > drivers/pinctrl/pinctrl-ingenic.c (for completeness). <linux/kernel.h> is too widely used, so some other headers would have already included it eventually. But, correct, it is better to include it explicitly for completeness. > > Also, I don't understand why the use of IF_ENABLED doesn't produce > "defined but not used" warnings (if the function "ptr" is not marked as > __maybe_unused) ... The function is optimized out by the compiler, not by the pre-processor. So, -Wunused-but-set-variable does not complain about it. > Also, if there is only one user of IF_ENABLED (and therefore PTR_IF), > why not just put it in that file and save me rebuilding the world again > every day because kernel.h is changed (again). I guess that is going > to happen just because kconfig.h is being changed and that is also > included by everything :-( I understand, but this is a one-time fix. <linux/kconfig.h> is not changed so often. I believe this will be useful for SET_SYSTEM_SLEEP_PM_OPS cleanups. So, the macro must be placed in a public header. > Also, is anyone else ever going to use PTR_IF() without having to also > use IS_ENABLED()? Yes or no. I am not sure about the future of this. I prefer this in a more general expression, so IS_REACHABLE or the combination of two CONFIG options will work. PTR_IF(IS_REACHABLE(CONFIG_FOO), ...) PTR_IF( IS_ENABLED(CONFIG_FOO) && IS_ENABLED(CONFIG_BAR), ...) > > So, in case it is not obvious, I consider this patch unnecessary churn > (as was probably the patch that introduced IF_ENABLED in the first > place). > > As an aside, this should not have been added to the kbuild tree in > linux-next until after -rc1 was released ... Rather, I was considering sending a pull req before -rc1. Otherwise, other drivers may start to use it. > > -- > Cheers, > Stephen Rothwell -- Best Regards Masahiro Yamada
diff --git a/drivers/pinctrl/pinctrl-ingenic.c b/drivers/pinctrl/pinctrl-ingenic.c index 651a36b9dcc0..0ee69f8e20b2 100644 --- a/drivers/pinctrl/pinctrl-ingenic.c +++ b/drivers/pinctrl/pinctrl-ingenic.c @@ -3854,6 +3854,8 @@ static int __init ingenic_pinctrl_probe(struct platform_device *pdev) return 0; } +#define IF_ENABLED(cfg, ptr) PTR_IF(IS_ENABLED(cfg), (ptr)) + static const struct of_device_id ingenic_pinctrl_of_match[] = { { .compatible = "ingenic,jz4730-pinctrl", diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h index 24a59cb06963..cc8fa109cfa3 100644 --- a/include/linux/kconfig.h +++ b/include/linux/kconfig.h @@ -70,10 +70,4 @@ */ #define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option)) -/* - * IF_ENABLED(CONFIG_FOO, ptr) evaluates to (ptr) if CONFIG_FOO is set to 'y' - * or 'm', NULL otherwise. - */ -#define IF_ENABLED(option, ptr) (IS_ENABLED(option) ? (ptr) : NULL) - #endif /* __LINUX_KCONFIG_H */ diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 5b7ed6dc99ac..8685ca4cf287 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -38,6 +38,8 @@ #define PTR_ALIGN_DOWN(p, a) ((typeof(p))ALIGN_DOWN((unsigned long)(p), (a))) #define IS_ALIGNED(x, a) (((x) & ((typeof(x))(a) - 1)) == 0) +#define PTR_IF(cond, ptr) ((cond) ? (ptr) : NULL) + /* generic data direction definitions */ #define READ 0 #define WRITE 1
<linux/kconfig.h> is included from all the kernel-space source files, including C, assembly, linker scripts. It is intended to contain a minimal set of macros to evaluate CONFIG options. IF_ENABLED() is an intruder here because (x ? y : z) is C code, which should not be included from assembly files or linker scripts. Also, <linux/kconfig.h> is no longer self-contained because NULL is defined in <linux/stddef.h>. Move IF_ENABLED() out to <linux/kernel.h> as PTR_IF(). PTF_IF() takes the general boolean expression instead of a CONFIG option so that it fits better in <linux/kernel.h>. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> --- Changes in v2: - Keep PTF_IF macro in pinctrl-ingenic.c drivers/pinctrl/pinctrl-ingenic.c | 2 ++ include/linux/kconfig.h | 6 ------ include/linux/kernel.h | 2 ++ 3 files changed, 4 insertions(+), 6 deletions(-)