On Tue, May 05, 2020 at 04:51:56PM +0300, Andy Shevchenko wrote: > On Mon, May 4, 2020 at 5:41 PM William Breathitt Gray > <vilhelm.gray@xxxxxxxxx> wrote: > > On Mon, May 04, 2020 at 02:41:09PM +0300, Andy Shevchenko wrote: > > > On Sun, May 03, 2020 at 04:38:36AM +0530, Syed Nayyar Waris wrote: > > ... > > > > Looking into the last patches where we have examples I still do not see a > > > benefit of variadic clump sizes. power of 2 sizes would make sense (and be > > > optimized accordingly (64-bit, 32-bit). > > > > > > -- > > > With Best Regards, > > > Andy Shevchenko > > > > There is of course benefit in defining for_each_set_clump with clump > > sizes of powers of 2 (we can optimize for 32 and 64 bit sizes and avoid > > boundary checks that we know will not occur), but at the very least the > > variable size bitmap_set_value and bitmap_get_value provide significant > > benefit for the readability of the gpio-xilinx code: > > > > bitmap_set_value(old, state[0], 0, width[0]); > > bitmap_set_value(old, state[1], width[0], width[1]); > > ... > > state[0] = bitmap_get_value(new, 0, width[0]); > > state[1] = bitmap_get_value(new, width[0], width[1]); > > > > These lines are simple and clear to read: we know immediately what they > > do. But if we did not have bitmap_set_value/bitmap_get_value, we'd have > > to use several bitwise operations for each line; the obfuscation of the > > code would be an obvious hinderance here. > > Do I understand correctly that width[0] and width[1] may not be power > of two and it's actually the case? > > -- > With Best Regards, > Andy Shevchenko I'm under the impression that width[0] and width[1] are arbitrarily chosen by the user and could be any integer. I have never used this hardware so I'm hoping one of the gpio-xilinx or GPIO subsystem maintainers in this thread will respond with some guidance. If the values of width[0] and width[1] are restricted to powers of 2, then I agree that there is no need for generic bitmap_set_value and bitmap_get_value functions and we can instead use more optimized power of 2 versions. William Breathitt Gray
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