On Mon, Jun 17, 2024 at 02:58:59PM +0200, Alexander Lobakin wrote: > From: Simon Horman <ho...@kernel.org> > Date: Sat, 15 Jun 2024 16:16:41 +0100 > > > On Fri, Jun 14, 2024 at 11:43:38AM +0200, Petr Oros wrote: > >> Do not use _test_bit() macro for testing bit. The proper macro for this > >> is one without underline. > > > > Hi Petr, > > > > it might be nice to include a brief explanation as to > > why test_bit() is correct. > > Let me explain this as the author of all those bitops wrappers :D > Petr is free to include either this or his own brief into v2. > > _test_bit() is what test_bit() was prior to my const-optimization. It > directly calls arch_test_bit(), i.e. the arch-specific implementation > (or the generic one). It's strictly _internal_ and shouldn't be used > anywhere outside the actual test_bit() macro. > > test_bit() is a wrapper which checks whether the bitmap and the bit > number are compile-time constants and if so, it calls the optimized > function which evaluates this call to a compile-time constant as well. > If either of them is not a compile-time constant, it just calls _test_bit(). > test_bit() is the actual function to use anywhere in the kernel. > > IOW, calling _test_bit() avoids potential compile-time optimizations. > > >From what I see in the code, &sensors is not a compile-time constant, > thus most probably there are no object code changes before and after > the patch. But anyway, we shouldn't call internal wrappers instead of > the actual API, so this fix is correct.
Thanks for this very comprehensive description, now I know :) > >> Fixes: 4da71a77fc3b ("ice: read internal temperature sensor") > >> Signed-off-by: Petr Oros <po...@redhat.com> > >> Acked-by: Ivan Vecera <ivec...@redhat.com> > > To be added to v2: > > Reviewed-by: Alexander Lobakin <aleksander.loba...@intel.com> > > Thanks, > Olek >