Introduce some fixed width variant of the GENMASK() and the BIT() macros in bits.h. Note that the main goal is not to get the correct type, but rather to enforce more checks at compile time. For example: GENMASK_U16(16, 0) will raise a build bug. This series is a continuation of: https://lore.kernel.org/intel-xe/20240208074521.577076-1-lucas.demarchi@xxxxxxxxx from Lucas De Marchi. Above series is one year old. I really think that this was a good idea and I do not want this series to die. So I am volunteering to revive it. Meanwhile, many changes occurred in bits.h. The most significant change is that __GENMASK() was moved to the uapi headers. For this reason, a new GENMASK_TYPE() is introduced instead and the uapi __GENMASK() is left untouched. Finally, I do not think it makes sense to expose the fixed width variants to the asm. The fixed width integers type are a C concept. So the GENMASK_U*() are only visible to the non-asm code. For asm, the long and long long variants seems sufficient. This series does not modify the actual GENMASK(), GENMASK_ULL() and GENMASK_U128(). A consolidation of the existing genmasks will be proposed later on in a separate series. As requested, here are the bloat-o-meter stats: $ ./scripts/bloat-o-meter vmlinux_before.o vmlinux_after.o add/remove: 0/0 grow/shrink: 0/0 up/down: 0/0 (0) Function old new delta Total: Before=22723481, After=22723481, chg +0.00% (done with GCC 12.4.1 on an x86_64 defconfig) -- 2.43.0 --- Changes from v6: - Split the series in two: this series leave any existing GENMASK*() unmodified. The consolidation will be done in a separate series. - Collect some Reviewed-by tag. - Address miscellaneous nitpick on the code comments and the line wrapping (details in each patch). - Link to v6: https://lore.kernel.org/r/20250308-fixed-type-genmasks-v6-0-f59315e73c29@xxxxxxxxxx Changes from v5: - Update the cover letter message. I was still refering to GENMASK_t() instead of GENMASK_TYPE(). - Add a comment in the cover letter to explain that a common GENMASK_TYPE() for C and asm wouldn't allow to generate the u128 variant. - Restore the comment saying that BUILD_BUG_ON() is not available in asm code. - Add a FIXME message to highlight the absence of the asm GENMASK*() unit tests. - Use git's histogram diff algorithm - Link to v5: https://lore.kernel.org/r/20250306-fixed-type-genmasks-v5-0-b443e9dcba63@xxxxxxxxxx Changes from v4: - Rebase on https://github.com/norov/linux/tree/bitmap-for-next - Rename GENMASK_t() to GENMASK_TYPE() - First patch of v4 (the typo fix 'init128' -> 'int128') is removed because it was resent separately in: https://lore.kernel.org/all/20250305-fix_init128_typo-v1-1-cbe5b8e54e7d@xxxxxxxxxx - Replace the (t)~ULL(0) by type_max(t). This way, GENMASK_TYPE() can now be used to generate GENMASK_U128(). - Get rid of the unsigned int cast for the U8 and U16 variants. - Add the BIT_TYPE() helper macro. - Link to v4: https://lore.kernel.org/r/20250305-fixed-type-genmasks-v4-0-1873dcdf6723@xxxxxxxxxx Changes from v3: - Rebase on v6.14-rc5 - Fix a typo in GENMASK_U128() comment. - Split the asm and non-asm definition of - Replace ~0ULL by ~ULL(0) - Since v3, __GENMASK() was moved to the uapi and people started using directly. Introduce GENMASK_t() instead. - Link to v3: https://lore.kernel.org/intel-xe/20240208074521.577076-1-lucas.demarchi@xxxxxxxxx Changes from v2: - Document both in commit message and code about the strict type checking and give examples how it´d break with invalid params. - Link to v2: https://lore.kernel.org/intel-xe/20240124050205.3646390-1-lucas.demarchi@xxxxxxxxx Link to v1: https://lore.kernel.org/intel-xe/20230509051403.2748545-1-lucas.demarchi@xxxxxxxxx --- Lucas De Marchi (3): bits: introduce fixed-type BIT_U*() drm/i915: Convert REG_GENMASK*() to fixed-width GENMASK_U*() test_bits: add tests for GENMASK_U*() Vincent Mailhol (2): bits: introduce fixed-type GENMASK_U*() test_bits: add tests for BIT_U*() drivers/gpu/drm/i915/i915_reg_defs.h | 108 ++++------------------------------- include/linux/bitops.h | 1 - include/linux/bits.h | 57 +++++++++++++++++- lib/test_bits.c | 30 ++++++++++ 4 files changed, 96 insertions(+), 100 deletions(-) --- base-commit: e3f42c436d7e0cb432935fe3ae275dd8d9b60f71 change-id: 20250228-fixed-type-genmasks-8d1a555f34e8 Best regards, -- Vincent Mailhol <mailhol.vincent@xxxxxxxxxx>
