From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga05.intel.com ([192.55.52.43]:30067 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727285AbeJBPEG (ORCPT ); Tue, 2 Oct 2018 11:04:06 -0400 Date: Tue, 2 Oct 2018 11:21:42 +0300 From: Andy Shevchenko Subject: Re: [RESEND PATCH v4 1/8] bitops: Introduce the for_each_set_clump macro Message-ID: <20181002082142.GC15943@smile.fi.intel.com> References: <40ecad49-2797-0d30-b52d-a2e6838dc1ab@rasmusvillemoes.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <40ecad49-2797-0d30-b52d-a2e6838dc1ab@rasmusvillemoes.dk> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Rasmus Villemoes Cc: William Breathitt Gray , linus.walleij@linaro.org, akpm@linux-foundation.org, linux-gpio@vger.kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Arnd Bergmann Message-ID: <20181002082142.O-z0SvFFOcI5EN2J_t8K56DPZ2l4yNLd_YKeMmwcPe8@z> On Tue, Oct 02, 2018 at 09:42:48AM +0200, Rasmus Villemoes wrote: > On 2018-10-02 03:13, William Breathitt Gray wrote: > The cover letter says > > The clump_size argument can be an arbitrary number of bits and is not > required to be a multiple of 2. > > by which I assume you mean "power of 2", but either way, the above code > does not seem to take into account the case where bits_offset + > clump_size straddles a word boundary, so it wouldn't work for a > clump_size that does not divide BITS_PER_LONG. E.g. 3 bits in a clump? Hmm... Why would we need that? I mean some real use case? > May I suggest another approach: You may, of course, but see above and my comments below. > unsigned long bitmap_get_value(const unsigned long *bitmap, unsigned > start, unsigned width): Get the value of bitmap[start:start+width] for > 1<=width<=BITS_PER_LONG (it's up to the caller to ensure this is within > the defined region). That can almost be an inline > > bitmap_get_value(const unsigned long *bitmap, unsigned start, unsigned > width) > { > unsigned idx = BIT_WORD(start); > unsigned offset = start % BITS_PER_LONG; > unsigned long lower = bitmap[idx] >> offset; > unsigned long upper = offset <= BITS_PER_LONG - width ? 0 : > bitmap[idx+1] << (BITS_PER_LONG - offset); > return (lower | upper) & GENMASK(width-1, 0) > } > > Then you can implement the for_each_set_clump by a (IMO) more readable > > for (i = 0, start = 0; i < num_ports; i++, start += gpio_reg_size) { > word_mask = bitmap_get_value(mask, start, gpio_reg_size); > if (!word_mask) > continue; > ... > } I would rather go with two prototypes to get()/set() a clump in the bitmap in a way when it's aligned and BITS_PER_LONG % clump_size == 0. unsigned long bitmap_get_clump(unsigned long *src, unsigned int start, unsigned int clump_size) { unsigned int index = BIT_WORD(start); unsigned int offset = start % BITS_PER_LONG; /* These just for spelling the restrictions */ WARN_ON(BITS_PER_LONG % clump_size); WARN_ON(offset % clump_size); /* TODO: take care of clump_size == 64 */ return (bitmap[index] >> offset) & GENMASK(clump_size - 1, 0); } Something similar with set with additional parameter unsigned long value which has MSB cleared till we reach [clump_size - 1 : 0]. -- With Best Regards, Andy Shevchenko