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Date: Tue, 5 May 2020 16:51:56 +0300 From: Andy Shevchenko <andy.shevchenko@...il.com> To: William Breathitt Gray <vilhelm.gray@...il.com> Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Syed Nayyar Waris <syednwaris@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, Michal Simek <michal.simek@...inx.com>, Arnd Bergmann <arnd@...db.de>, rrichter@...vell.com, Linus Walleij <linus.walleij@...aro.org>, Bartosz Golaszewski <bgolaszewski@...libre.com>, Masahiro Yamada <yamada.masahiro@...ionext.com>, "Zhang, Rui" <rui.zhang@...el.com>, Daniel Lezcano <daniel.lezcano@...aro.org>, Amit Kucheria <amit.kucheria@...durent.com>, Linux-Arch <linux-arch@...r.kernel.org>, "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>, Linux PM <linux-pm@...r.kernel.org> Subject: Re: [PATCH v5 0/4] Introduce the for_each_set_clump macro On Mon, May 4, 2020 at 5:41 PM William Breathitt Gray <vilhelm.gray@...il.com> 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
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