Quoting Yury Norov (2024-01-24 12:27:58-03:00) >On Wed, Jan 24, 2024 at 08:03:53AM -0600, Lucas De Marchi wrote: >> On Wed, Jan 24, 2024 at 09:58:26AM +0200, Jani Nikula wrote: >> > On Tue, 23 Jan 2024, Lucas De Marchi <lucas.demarchi@xxxxxxxxx> wrote: >> > > From: Yury Norov <yury.norov@xxxxxxxxx> >> > > >> > > Generalize __GENMASK() to support different types, and implement >> > > fixed-types versions of GENMASK() based on it. The fixed-type version >> > > allows more strict checks to the min/max values accepted, which is >> > > useful for defining registers like implemented by i915 and xe drivers >> > > with their REG_GENMASK*() macros. >> > >> > Mmh, the commit message says the fixed-type version allows more strict >> > checks, but none are actually added. GENMASK_INPUT_CHECK() remains the >> > same. >> > >> > Compared to the i915 and xe versions, this is more lax now. You could >> > specify GENMASK_U32(63,32) without complaints. >> >> Doing this on top of the this series: >> >> -#define XELPDP_PORT_M2P_COMMAND_TYPE_MASK REG_GENMASK(30, 27) >> +#define XELPDP_PORT_M2P_COMMAND_TYPE_MASK REG_GENMASK(62, 32) >> >> and I do get a build failure: >> >> ../drivers/gpu/drm/i915/display/intel_cx0_phy.c: In function ‘__intel_cx0_read_once’: >> ../include/linux/bits.h:41:31: error: left shift count >= width of type [-Werror=shift-count-overflow] >> 41 | (((t)~0ULL - ((t)(1) << (l)) + 1) & \ >> | ^~ > >I would better include this in commit message to avoid people's >confusion. If it comes to v2, can you please do it and mention that >this trick relies on shift-count-overflow compiler check? Wouldn't it be better to have explicit check that l and h are not out of bounds based on BITS_PER_TYPE() than relying on a compiler flag that could be turned off (maybe for some questionable reason, but even so)? -- Gustavo Sousa
