on 2024/8/5 20:55, Simon Horman wrote:

Hi,

I may well be wrong but I think that FIELD_PREP can only be used with
a compile-time constant as the mask.

In any case, with Clang-18 W=1 allmodconfig builds on x86_64 I see:

Thanks， I'll fix this warning in V2.

   CC      drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.o
    CC      drivers/net/ethernet/hisilicon/hibmcge/hbg_main.o
In file included from drivers/net/ethernet/hisilicon/hibmcge/hbg_main.c:8:
drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.h:31:15: warning: result of comparison of constant 18446744073709551615 with expression of type 'typeof (_Generic((mask), char: (unsigned char)0, unsigned char: (unsigned char)0, signed char: (unsigned char)0, unsigned short: (unsigned short)0, short: (unsigned short)0, unsigned int: (unsigned int)0, int: (unsigned int)0, unsigned long: (unsigned long)0, long: (unsigned long)0, unsigned long long: (unsigned long long)0, long long: (unsigned long long)0, default: (mask)))' (aka 'unsigned int') is always false [-Wtautological-constant-out-of-range-compare]
    31 |         reg_value |= FIELD_PREP(mask, val);
       |                      ^~~~~~~~~~~~~~~~~~~~~
./include/linux/bitfield.h:115:3: note: expanded from macro 'FIELD_PREP'
   115 |                 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: ");    \
       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./include/linux/bitfield.h:72:53: note: expanded from macro '__BF_FIELD_CHECK'
    72 |                 BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) >     \
       |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
    73 |                                  __bf_cast_unsigned(_reg, ~0ull),       \
       |                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    74 |                                  _pfx "type of reg too small for mask"); \
       |                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./include/linux/build_bug.h:39:58: note: expanded from macro 'BUILD_BUG_ON_MSG'
    39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
       |                                     ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
././include/linux/compiler_types.h:510:22: note: expanded from macro 'compiletime_assert'
   510 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
       |         ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
././include/linux/compiler_types.h:498:23: note: expanded from macro '_compiletime_assert'
   498 |         __compiletime_assert(condition, msg, prefix, suffix)
       |         ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
././include/linux/compiler_types.h:490:9: note: expanded from macro '__compiletime_assert'
   490 |                 if (!(condition))                                       \
       |                       ^~~~~~~~~
1 warning generated.
In file included from drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.c:8:
drivers/net/ethernet/hisilicon/hibmcge/hbg_hw.h:31:15: warning: result of comparison of constant 18446744073709551615 with expression of type 'typeof (_Generic((mask), char: (unsigned char)0, unsigned char: (unsigned char)0, signed char: (unsigned char)0, unsigned short: (unsigned short)0, short: (unsigned short)0, unsigned int: (unsigned int)0, int: (unsigned int)0, unsigned long: (unsigned long)0, long: (unsigned long)0, unsigned long long: (unsigned long long)0, long long: (unsigned long long)0, default: (mask)))' (aka 'unsigned int') is always false [-Wtautological-constant-out-of-range-compare]
    31 |         reg_value |= FIELD_PREP(mask, val);
       |                      ^~~~~~~~~~~~~~~~~~~~~
./include/linux/bitfield.h:115:3: note: expanded from macro 'FIELD_PREP'
   115 |                 __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: ");    \
       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./include/linux/bitfield.h:72:53: note: expanded from macro '__BF_FIELD_CHECK'
    72 |                 BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) >     \
       |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
    73 |                                  __bf_cast_unsigned(_reg, ~0ull),       \
       |                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    74 |                                  _pfx "type of reg too small for mask"); \
       |                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./include/linux/build_bug.h:39:58: note: expanded from macro 'BUILD_BUG_ON_MSG'
    39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
       |                                     ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
././include/linux/compiler_types.h:510:22: note: expanded from macro 'compiletime_assert'
   510 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
       |         ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
././include/linux/compiler_types.h:498:23: note: expanded from macro '_compiletime_assert'
   498 |         __compiletime_assert(condition, msg, prefix, suffix)
       |         ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
././include/linux/compiler_types.h:490:9: note: expanded from macro '__compiletime_assert'
   490 |                 if (!(condition))                                       \
       |                       ^~~~~~~~~
1 warning generated.

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