From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail-pf1-x42b.google.com ([2607:f8b0:4864:20::42b]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qLQV4-004SUi-39 for linux-arm-kernel@lists.infradead.org; Mon, 17 Jul 2023 15:51:04 +0000 Received: by mail-pf1-x42b.google.com with SMTP id d2e1a72fcca58-666e6ecb52dso2858732b3a.2 for ; Mon, 17 Jul 2023 08:51:01 -0700 (PDT) Date: Mon, 17 Jul 2023 08:50:59 -0700 From: Yury Norov Subject: Re: [PATCH v3 1/5] lib/bitmap: add bitmap_{set,get}_value() Message-ID: References: <20230717113709.328671-1-glider@google.com> <20230717113709.328671-2-glider@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20230717113709.328671-2-glider@google.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+lwn-linux-arm-kernel=archive.lwn.net@lists.infradead.org List-Archive: To: Alexander Potapenko Cc: catalin.marinas@arm.com, will@kernel.org, pcc@google.com, andreyknvl@gmail.com, andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, eugenis@google.com, syednwaris@gmail.com, william.gray@linaro.org, Arnd Bergmann On Mon, Jul 17, 2023 at 01:37:04PM +0200, Alexander Potapenko wrote: > The two new functions allow setting/getting values of length up to > BITS_PER_LONG bits at arbitrary position in the bitmap. > > The code was taken from "bitops: Introduce the for_each_set_clump macro" > by Syed Nayyar Waris with a couple of minor changes: > - instead of using roundup(), which adds an unnecessary dependency > on , we calculate space as BITS_PER_LONG-offset; > - indentation is reduced by not using else-clauses (suggested by > checkpatch for bitmap_get_value()) Please preserve Syed's authorship ('From' field in git log). > Cc: Arnd Bergmann > Signed-off-by: Syed Nayyar Waris > Signed-off-by: William Breathitt Gray > Link: https://lore.kernel.org/lkml/fe12eedf3666f4af5138de0e70b67a07c7f40338.1592224129.git.syednwaris@gmail.com/ > Suggested-by: Yury Norov > Signed-off-by: Alexander Potapenko > --- > include/linux/bitmap.h | 57 ++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 57 insertions(+) > > diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h > index 03644237e1efb..4559366084988 100644 > --- a/include/linux/bitmap.h > +++ b/include/linux/bitmap.h > @@ -76,7 +76,11 @@ struct device; > * bitmap_to_arr32(buf, src, nbits) Copy nbits from buf to u32[] dst > * bitmap_to_arr64(buf, src, nbits) Copy nbits from buf to u64[] dst > * bitmap_get_value8(map, start) Get 8bit value from map at start > + * bitmap_get_value(map, start, nbits) Get bit value of size 'nbits' > + * from map at start > * bitmap_set_value8(map, value, start) Set 8bit value to map at start > + * bitmap_set_value(map, value, start, nbits) Set bit value of size 'nbits' > + * of map at start The 'bit value of size' sounds more confusing than it should. The size of bit is actually a bit... Can you rephrase? Moreover, 'set bits' has a meaning of actually setting them, i.e. switching to '1'. Maybe: "Copy 'nbits' to bitmap starting at 'start'"? > * > * Note, bitmap_zero() and bitmap_fill() operate over the region of > * unsigned longs, that is, bits behind bitmap till the unsigned long > @@ -583,6 +587,31 @@ static inline unsigned long bitmap_get_value8(const unsigned long *map, > return (map[index] >> offset) & 0xFF; > } > > +/** > + * bitmap_get_value - get a value of n-bits from the memory region > + * @map: address to the bitmap memory region > + * @start: bit offset of the n-bit value > + * @nbits: size of value in bits * @nbits: size of value in bits, up to BITS_PER_LONG > + * > + * Returns value of nbits located at the @start bit offset within the @map > + * memory region. > + */ > +static inline unsigned long bitmap_get_value(const unsigned long *map, > + unsigned long start, > + unsigned long nbits) > +{ > + const size_t index = BIT_WORD(start); > + const unsigned long offset = start % BITS_PER_LONG; > + const unsigned long space = BITS_PER_LONG - offset; > + unsigned long value_low, value_high; > + > + if (space >= nbits) > + return (map[index] >> offset) & GENMASK(nbits - 1, 0); > + value_low = map[index] & BITMAP_FIRST_WORD_MASK(start); > + value_high = map[index + 1] & BITMAP_LAST_WORD_MASK(start + nbits); > + return (value_low >> offset) | (value_high << space); > +} When nbits == 0, copy-like functions shouldn't touch any memory. See how other bitmap and find_bit functions hold it. Thanks, Yury _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel