On Sat, Mar 22, 2025 at 06:23:11PM +0900, Vincent Mailhol via B4 Relay wrote: > 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:
You say this, and then typecast both BIT and GENMASK. This may confuse readers. Maybe add few words about promotion rules in C standard, or just drop this note entirely? Doesn't require new submission, of course. > 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.demar...@intel.com > > 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-f59315e73...@wanadoo.fr > > 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-b443e9dcb...@wanadoo.fr > > 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-cbe5b8e54...@wanadoo.fr > > - 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-v4-0-1873dcdf6...@wanadoo.fr > > 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.demar...@intel.com > > 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.demar...@intel.com > > Link to v1: > https://lore.kernel.org/intel-xe/20230509051403.2748545-1-lucas.demar...@intel.com > > --- > 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.vinc...@wanadoo.fr> >
