On Tue, 07 Jul 2020, Pierre-Louis Bossart wrote:
On 7/7/20 2:39 PM, Jerome Brunet wrote:
On Tue 07 Jul 2020 at 21:23, Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com wrote:
This is a much smaller set of cleanups, all related to warnings thrown by the use of GENMASK() with an unsigned variable. I just made the warning go away but I wonder if there's a better fix in the definition of GENMASK() itself?
Looking at the patch I was going to ask the same thing. It does not make much sense to me to force GENMASK arguments to be integer (instead of unsigned integer) to then check there are positive ...
Agree, it's just that the following macro isn't exactly simple to change:
#define GENMASK_INPUT_CHECK(h, l) \ (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ __builtin_constant_p((l) > (h)), (l) > (h), 0)))
I couldn't find a means to avoid the comparison.
I just realized this is a fairly recent addition in 295bcca84916 ('linux/bits.h: add compile time sanity check of GENMASK inputs'), adding the author Rikard Falkeborn in CC:
include/linux/bits.h:26:28: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits] 26 | __builtin_constant_p((l) > (h)), (l) > (h), 0)))
Linus recently complained about the type-limits warning, saying that it was invalid. He preferred the warning to be bumped from W=1 to W=2, although I haven't seen a patch doing this yet.
Rikard also tried to fix GENMASK directly; however, Linus did not approve of this either.