Re: [PATCH 1/2] if_enabled.h: Add IF_ENABLED_OR_ELSE() and IF_ENABLED() macros

[Paul Cercueil]

Hi Randy,

Le mar. 8 déc. 2020 à 9:39, Randy Dunlap <rdunlap@xxxxxxxxxxxxx> a 
écrit :
> On 12/8/20 8:48 AM, Paul Cercueil wrote:
> >  Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
>
> Hi Paul,
>
> Why not just add these 2 new macros to <linux/kconfig.h> ?
>
> Maybe you don't want to add the other 2 headers there also?

That means including <linux/compiler.h> in <linux/kconfig.h>, which 
causes build failures:

 LD      vmlinux
 SORTTAB vmlinux
 SYSMAP  System.map
 AS      arch/mips/boot/compressed/head.o
 CC      arch/mips/boot/compressed/decompress.o
 CC      arch/mips/boot/compressed/string.o
 CC      arch/mips/boot/compressed/dummy.o
 OBJCOPY arch/mips/boot/compressed/vmlinux.bin
 HOSTCC  arch/mips/boot/compressed/calc_vmlinuz_load_addr
 GZIP    arch/mips/boot/compressed/vmlinux.bin.z
In file included from ./include/linux/kcsan-checks.h:7,
                from ./include/asm-generic/rwonce.h:27,
                from ./arch/mips/include/generated/asm/rwonce.h:1,
                from ./include/linux/compiler.h:246,
                from ././include/linux/kconfig.h:8,
                from <command-line>:32:
/include/linux/compiler_attributes.h:64: warning: "__always_inline" 
redefined
  64 | #define __always_inline                 inline 
__attribute__((__always_inline__))
     |
In file included from ./include/linux/stddef.h:5,
                from ./include/uapi/linux/posix_types.h:5,
                from ./include/uapi/linux/types.h:14,
                from ./include/linux/types.h:6,
                from ./include/linux/kasan-checks.h:5,
                from ./include/asm-generic/rwonce.h:26,
                from ./arch/mips/include/generated/asm/rwonce.h:1,
                from ./include/linux/compiler.h:246,
                from ././include/linux/kconfig.h:8,
                from <command-line>:32:
/include/uapi/linux/stddef.h:5: note: this is the location of the 
previous definition
   5 | #define __always_inline inline
     |
In file included from ./arch/mips/include/generated/asm/rwonce.h:1,
                from ./include/linux/compiler.h:246,
                from ././include/linux/kconfig.h:8,
                from <command-line>:32:
/include/asm-generic/rwonce.h:64:31: error: expected ‘;’ before 
‘unsigned’
  64 | static __no_sanitize_or_inline
     |                               ^
     |                               ;
  65 | unsigned long __read_once_word_nocheck(const void *addr)
     | ~~~~~~~~
/include/asm-generic/rwonce.h:65:15: warning: no previous prototype 
for ‘__read_once_word_nocheck’ [-Wmissing-prototypes]
  65 | unsigned long __read_once_word_nocheck(const void *addr)
     |               ^~~~~~~~~~~~~~~~~~~~~~~~
/include/asm-generic/rwonce.h:82:28: error: expected ‘;’ before 
‘unsigned’
  82 | static __no_kasan_or_inline
     |                            ^
     |                            ;
  83 | unsigned long read_word_at_a_time(const void *addr)
     | ~~~~~~~~
/include/asm-generic/rwonce.h:83:15: warning: no previous prototype 
for ‘read_word_at_a_time’ [-Wmissing-prototypes]
  83 | unsigned long read_word_at_a_time(const void *addr)
     |               ^~~~~~~~~~~~~~~~~~~


That's why I opted for a new header.

Cheers,
-Paul

> >  ---
> >   include/linux/if_enabled.h | 22 ++++++++++++++++++++++
> >   1 file changed, 22 insertions(+)
> >   create mode 100644 include/linux/if_enabled.h
> >
> >  diff --git a/include/linux/if_enabled.h b/include/linux/if_enabled.h
> >  new file mode 100644
> >  index 000000000000..8189d1402340
> >  --- /dev/null
> >  +++ b/include/linux/if_enabled.h
> >  @@ -0,0 +1,22 @@
> >  +/* SPDX-License-Identifier: GPL-2.0 */
> >  +#ifndef __LINUX_IF_ENABLED_H
> >  +#define __LINUX_IF_ENABLED_H
> >  +
> >  +#include <linux/build_bug.h>
> >  +#include <linux/compiler_types.h>
> >  +#include <linux/kconfig.h>
> >  +
> >  +/*
> >  + * IF_ENABLED_OR_ELSE(CONFIG_FOO, a, b) evaluates to (a) if 
> > CONFIG_FOO is set
> >  + * to 'y' or 'm', (b) otherwise.
> >  + */
> >  +#define IF_ENABLED_OR_ELSE(option, a, b) \
> >  +	(BUILD_BUG_ON_ZERO(__same_type((a), (b))) || IS_ENABLED(option) ? 
> > (a) : (b))
> >  +
> >  +/*
> >  + * IF_ENABLED(CONFIG_FOO, ptr) evaluates to (ptr) if CONFIG_FOO is 
> > set to 'y'
> >  + * or 'm', NULL otherwise.
> >  + */
> >  +#define IF_ENABLED(option, ptr) IF_ENABLED_OR_ELSE(option, ptr, 
> > NULL)
> >  +
> >  +#endif /* __LINUX_IF_ENABLED_H */
>
>
> thanks.
> --
> ~Randy