[PATCH v2 0/16] bitfield: tidy up bitfield.h

david.laight.linux
2025-12-12T20:04:56Z

From: David Laight <david.laight.linux@gmail.com>

I noticed some very long (18KB) error messages from the compiler.
Turned out they were errors on lines that passed GENMASK() to FIELD_PREP().
Since most of the #defines are already statement functions the values
can be copied to locals so the actual parameters only get expanded once.

The 'bloat' is reduced further by using a simple test to ensure 'reg'
is large enough, slightly simplifying the test for constant 'val' and
only checking 'reg' and 'val' when the parameters are present.

The first two patches are slightly problematic.

drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp_eth.c manages to use
a #define that should be an internal to bitfield.h, the changed file
is actually more similar to the previous version.

drivers/thunderbolt/tb.h passes a bifield to FIELD_GET(), these can't
be used with sizeof, typeof or __auto_type.
The existing FIELD_GET() uses _Generic(); gcc treats 'u32 foo:8' as
'unsigned char' and clang treats 'u32 foo:n' as 'unsigned int'.
So the code currentyly compiles 'by accident', pass 'u32 foo:6' and
gcc will error the attempt to use typeof with a bitfield.
For v2 fixed by changing the structure definition to use u8 for the
relevant field.

Both changes may need to to through the same tree as the header file changes.

The changes are based on 'next' and contain the addition of field_prep()
and field_get() for non-constant values.

I also know it is the merge window.
I expect to be generating a v3 in the new year (someone always has a comment).

Changes for v2:
- Change thunderbolt header (see above).
- Fix variable name re-use in FIELD_PREP_WM16()
- Use 'mask' (not _mask) in __BF_SHIFT().
The changes to bitfield.h have been split into multiple patches,
but the actual final file only has whitespace differences.

David Laight (16):
nfp: Call FIELD_PREP() in NFP_ETH_SET_BIT_CONFIG() wrapper
thunderbolt: Don't pass a bitfield to FIELD_GET
bitmap: Use FIELD_PREP() in expansion of FIELD_PREP_WM16()
bitfield: Copy #define parameters to locals
bitfield: Merge __field_prep/get() into field_prep/get()
bitfield: Remove some pointless casts
bitfield: FIELD_MODIFY: Only do a single read/write on the target
bitfield: Simplify __BF_FIELD_CHECK_REG()
bitfield: Rename __FIELD_PREP/GET() to __BF_FIELD_PREP/GET()
bitfield: Split the 'val' check out of __BF_FIELD_CHECK_MASK()
bitfield: Common up validation of the mask parameter
bitfield: Remove leading _ from #define formal parameter names
bitfield: Reduce indentation
bitfield: Add comment block for the host/fixed endian functions
bitfield: Update comments for le/be functions
build_bug.h; Remove __BUILD_BUG_ON_NOT_POWER_OF_2()

.../netronome/nfp/nfpcore/nfp_nsp_eth.c | 16 +-
drivers/thunderbolt/tb_regs.h | 16 +-
include/linux/bitfield.h | 278 ++++++++++--------
include/linux/build_bug.h | 2 -
include/linux/hw_bitfield.h | 21 +-
5 files changed, 175 insertions(+), 158 deletions(-)

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2.39.5