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From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, andriy.shevchenko@linux.intel.com,
	andy.shevchenko@gmail.com, arnd@arndb.de,
	bgolaszewski@baylibre.com, geert+renesas@glider.be,
	geert@linux-m68k.org, gustavo@embeddedor.com,
	linus.walleij@linaro.org, linux-mm@kvack.org,
	linux@rasmusvillemoes.dk, lukas@wunner.de, m.duckeck@kunbus.de,
	mm-commits@vger.kernel.org, morten.tiljeset@prevas.dk,
	preid@electromag.com.au, sean.nyekjaer@prevas.dk,
	torvalds@linux-foundation.org, vilhelm.gray@gmail.com,
	yamada.masahiro@socionext.com
Subject: [patch 24/86] bitops: introduce the for_each_set_clump8 macro
Date: Wed, 04 Dec 2019 16:50:57 -0800
Message-ID: <20191205005057.gUdhyBVHB%akpm@linux-foundation.org> (raw)
In-Reply-To: <20191204164858.fe4ed8886e34ad9f3b34ea00@linux-foundation.org>

From: William Breathitt Gray <vilhelm.gray@gmail.com>
Subject: bitops: introduce the for_each_set_clump8 macro

Pach series "Introduce the for_each_set_clump8 macro", v18.

While adding GPIO get_multiple/set_multiple callback support for various
drivers, I noticed a pattern of looping manifesting that would be useful
standardized as a macro.

This patchset introduces the for_each_set_clump8 macro and utilizes it in
several GPIO drivers.  The for_each_set_clump macro8 facilitates a
for-loop syntax that iterates over a memory region entire groups of set
bits at a time.

For example, suppose you would like to iterate over a 32-bit integer 8
bits at a time, skipping over 8-bit groups with no set bit, where XXXXXXXX
represents the current 8-bit group:

    Example:        10111110 00000000 11111111 00110011
    First loop:     10111110 00000000 11111111 XXXXXXXX
    Second loop:    10111110 00000000 XXXXXXXX 00110011
    Third loop:     XXXXXXXX 00000000 11111111 00110011

Each iteration of the loop returns the next 8-bit group that has at
least one set bit.

The for_each_set_clump8 macro has four parameters:

    * start: set to the bit offset of the current clump
    * clump: set to the current clump value
    * bits: bitmap to search within
    * size: bitmap size in number of bits

In this version of the patchset, the for_each_set_clump macro has been
reimplemented and simplified based on the suggestions provided by Rasmus
Villemoes and Andy Shevchenko in the version 4 submission.

In particular, the function of the for_each_set_clump macro has been
restricted to handle only 8-bit clumps; the drivers that use the
for_each_set_clump macro only handle 8-bit ports so a generic
for_each_set_clump implementation is not necessary.  Thus, a solution for
large clumps (i.e.  those larger than the width of a bitmap word) can be
postponed until a driver appears that actually requires such a generic
for_each_set_clump implementation.

For what it's worth, a semi-generic for_each_set_clump (i.e.  for clumps
smaller than the width of a bitmap word) can be implemented by simply
replacing the hardcoded '8' and '0xFF' instances with respective
variables.  I have not yet had a need for such an implementation, and
since it falls short of a true generic for_each_set_clump function, I have
decided to forgo such an implementation for now.

In addition, the bitmap_get_value8 and bitmap_set_value8 functions are
introduced to get and set 8-bit values respectively.  Their use is based
on the behavior suggested in the patchset version 4 review.


This patch (of 14):

This macro iterates for each 8-bit group of bits (clump) with set bits,
within a bitmap memory region.  For each iteration, "start" is set to the
bit offset of the found clump, while the respective clump value is stored
to the location pointed by "clump".  Additionally, the bitmap_get_value8
and bitmap_set_value8 functions are introduced to respectively get and set
an 8-bit value in a bitmap memory region.

[gustavo@embeddedor.com: fix potential sign-extension overflow]
  Link: http://lkml.kernel.org/r/20191015184657.GA26541@embeddedor
[akpm@linux-foundation.org: s/ULL/UL/, per Joe]
[vilhelm.gray@gmail.com: add for_each_set_clump8 documentation]
  Link: http://lkml.kernel.org/r/20191016161825.301082-1-vilhelm.gray@gmail.com
Link: http://lkml.kernel.org/r/893c3b4f03266c9496137cc98ac2b1bd27f92c73.1570641097.git.vilhelm.gray@gmail.com
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Suggested-by: Lukas Wunner <lukas@wunner.de>
Tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Phil Reid <preid@electromag.com.au>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Mathias Duckeck <m.duckeck@kunbus.de>
Cc: Morten Hein Tiljeset <morten.tiljeset@prevas.dk>
Cc: Sean Nyekjaer <sean.nyekjaer@prevas.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/asm-generic/bitops/find.h |   17 +++++++++++++
 include/linux/bitmap.h            |   35 ++++++++++++++++++++++++++++
 include/linux/bitops.h            |   12 +++++++++
 lib/find_bit.c                    |   14 +++++++++++
 4 files changed, 78 insertions(+)

--- a/include/asm-generic/bitops/find.h~bitops-introduce-the-for_each_set_clump8-macro
+++ a/include/asm-generic/bitops/find.h
@@ -80,4 +80,21 @@ extern unsigned long find_first_zero_bit
 
 #endif /* CONFIG_GENERIC_FIND_FIRST_BIT */
 
+/**
+ * find_next_clump8 - find next 8-bit clump with set bits in a memory region
+ * @clump: location to store copy of found clump
+ * @addr: address to base the search on
+ * @size: bitmap size in number of bits
+ * @offset: bit offset at which to start searching
+ *
+ * Returns the bit offset for the next set clump; the found clump value is
+ * copied to the location pointed by @clump. If no bits are set, returns @size.
+ */
+extern unsigned long find_next_clump8(unsigned long *clump,
+				      const unsigned long *addr,
+				      unsigned long size, unsigned long offset);
+
+#define find_first_clump8(clump, bits, size) \
+	find_next_clump8((clump), (bits), (size), 0)
+
 #endif /*_ASM_GENERIC_BITOPS_FIND_H_ */
--- a/include/linux/bitmap.h~bitops-introduce-the-for_each_set_clump8-macro
+++ a/include/linux/bitmap.h
@@ -66,6 +66,8 @@
  *  bitmap_allocate_region(bitmap, pos, order)  Allocate specified bit region
  *  bitmap_from_arr32(dst, buf, nbits)          Copy nbits from u32[] buf to dst
  *  bitmap_to_arr32(buf, src, nbits)            Copy nbits from buf to u32[] dst
+ *  bitmap_get_value8(map, start)               Get 8bit value from map at start
+ *  bitmap_set_value8(map, value, start)        Set 8bit value to map at start
  *
  * Note, bitmap_zero() and bitmap_fill() operate over the region of
  * unsigned longs, that is, bits behind bitmap till the unsigned long
@@ -489,6 +491,39 @@ static inline void bitmap_from_u64(unsig
 		dst[1] = mask >> 32;
 }
 
+/**
+ * bitmap_get_value8 - get an 8-bit value within a memory region
+ * @map: address to the bitmap memory region
+ * @start: bit offset of the 8-bit value; must be a multiple of 8
+ *
+ * Returns the 8-bit value located at the @start bit offset within the @src
+ * memory region.
+ */
+static inline unsigned long bitmap_get_value8(const unsigned long *map,
+					      unsigned long start)
+{
+	const size_t index = BIT_WORD(start);
+	const unsigned long offset = start % BITS_PER_LONG;
+
+	return (map[index] >> offset) & 0xFF;
+}
+
+/**
+ * bitmap_set_value8 - set an 8-bit value within a memory region
+ * @map: address to the bitmap memory region
+ * @value: the 8-bit value; values wider than 8 bits may clobber bitmap
+ * @start: bit offset of the 8-bit value; must be a multiple of 8
+ */
+static inline void bitmap_set_value8(unsigned long *map, unsigned long value,
+				     unsigned long start)
+{
+	const size_t index = BIT_WORD(start);
+	const unsigned long offset = start % BITS_PER_LONG;
+
+	map[index] &= ~(0xFFUL << offset);
+	map[index] |= value << offset;
+}
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* __LINUX_BITMAP_H */
--- a/include/linux/bitops.h~bitops-introduce-the-for_each_set_clump8-macro
+++ a/include/linux/bitops.h
@@ -47,6 +47,18 @@ extern unsigned long __sw_hweight64(__u6
 	     (bit) < (size);					\
 	     (bit) = find_next_zero_bit((addr), (size), (bit) + 1))
 
+/**
+ * for_each_set_clump8 - iterate over bitmap for each 8-bit clump with set bits
+ * @start: bit offset to start search and to store the current iteration offset
+ * @clump: location to store copy of current 8-bit clump
+ * @bits: bitmap address to base the search on
+ * @size: bitmap size in number of bits
+ */
+#define for_each_set_clump8(start, clump, bits, size) \
+	for ((start) = find_first_clump8(&(clump), (bits), (size)); \
+	     (start) < (size); \
+	     (start) = find_next_clump8(&(clump), (bits), (size), (start) + 8))
+
 static inline int get_bitmask_order(unsigned int count)
 {
 	int order;
--- a/lib/find_bit.c~bitops-introduce-the-for_each_set_clump8-macro
+++ a/lib/find_bit.c
@@ -214,3 +214,17 @@ EXPORT_SYMBOL(find_next_bit_le);
 #endif
 
 #endif /* __BIG_ENDIAN */
+
+unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,
+			       unsigned long size, unsigned long offset)
+{
+	offset = find_next_bit(addr, size, offset);
+	if (offset == size)
+		return size;
+
+	offset = round_down(offset, 8);
+	*clump = bitmap_get_value8(addr, offset);
+
+	return offset;
+}
+EXPORT_SYMBOL(find_next_clump8);
_


  parent reply index

Thread overview: 88+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-05  0:48 incoming Andrew Morton
2019-12-05  0:49 ` [patch 01/86] mm/kasan/common.c: fix compile error Andrew Morton
2019-12-05  0:49 ` [patch 02/86] mm: memcg/slab: wait for !root kmem_cache refcnt killing on root kmem_cache destruction Andrew Morton
2019-12-05  0:49 ` [patch 03/86] mm/vmstat: add helpers to get vmstat item names for each enum type Andrew Morton
2019-12-05  0:49 ` [patch 04/86] mm/memcontrol: use vmstat names for printing statistics Andrew Morton
2019-12-05  0:49 ` [patch 05/86] mm/memory.c: replace is_zero_pfn with is_huge_zero_pmd for thp Andrew Morton
2019-12-05  0:49 ` [patch 06/86] proc: change ->nlink under proc_subdir_lock Andrew Morton
2019-12-05  0:50 ` [patch 07/86] fs/proc/generic.c: delete useless "len" variable Andrew Morton
2019-12-05  0:50 ` [patch 08/86] fs/proc/internal.h: shuffle "struct pde_opener" Andrew Morton
2019-12-05  0:50 ` [patch 09/86] include/linux/proc_fs.h: fix confusing macro arg name Andrew Morton
2019-12-05  0:50 ` [patch 10/86] fs/proc/Kconfig: fix indentation Andrew Morton
2019-12-05  0:50 ` [patch 11/86] include/linux/sysctl.h: inline braces for ctl_table and ctl_table_header Andrew Morton
2019-12-05  0:50 ` [patch 12/86] .gitattributes: use 'dts' diff driver for dts files Andrew Morton
2019-12-05  1:00   ` Frank Rowand
2019-12-05  0:50 ` [patch 13/86] linux/build_bug.h: change type to int Andrew Morton
2019-12-05  0:50 ` [patch 14/86] linux/scc.h: make uapi linux/scc.h self-contained Andrew Morton
2019-12-05  0:50 ` [patch 15/86] arch/Kconfig: fix indentation Andrew Morton
2019-12-05  0:50 ` [patch 16/86] scripts/get_maintainer.pl: add signatures from Fixes: <badcommit> lines in commit message Andrew Morton
2019-12-05  0:50 ` [patch 17/86] kernel.h: update comment about simple_strto<foo>() functions Andrew Morton
2019-12-05  0:50 ` [patch 18/86] auxdisplay: charlcd: deduplicate simple_strtoul() Andrew Morton
2019-12-05  0:50 ` [patch 19/86] kernel/notifier.c: intercept duplicate registrations to avoid infinite loops Andrew Morton
2019-12-05  0:50 ` [patch 20/86] kernel/notifier.c: remove notifier_chain_cond_register() Andrew Morton
2019-12-05  0:50 ` [patch 21/86] kernel/notifier.c: remove blocking_notifier_chain_cond_register() Andrew Morton
2019-12-05  0:50 ` [patch 22/86] kernel/profile.c: use cpumask_available to check for NULL cpumask Andrew Morton
2019-12-05  0:50 ` [patch 23/86] kernel/sys.c: avoid copying possible padding bytes in copy_to_user Andrew Morton
2019-12-05  0:50 ` Andrew Morton [this message]
2019-12-05  0:51 ` [patch 25/86] lib/test_bitmap.c: add for_each_set_clump8 test cases Andrew Morton
2019-12-05  0:51 ` [patch 26/86] gpio: 104-dio-48e: utilize for_each_set_clump8 macro Andrew Morton
2019-12-05  0:51 ` [patch 27/86] gpio: 104-idi-48: " Andrew Morton
2019-12-05  0:51 ` [patch 28/86] gpio: gpio-mm: " Andrew Morton
2019-12-05  0:51 ` [patch 29/86] gpio: ws16c48: " Andrew Morton
2019-12-05  0:51 ` [patch 30/86] gpio: pci-idio-16: " Andrew Morton
2019-12-05  0:51 ` [patch 31/86] gpio: pcie-idio-24: " Andrew Morton
2019-12-05  0:51 ` [patch 32/86] gpio: uniphier: " Andrew Morton
2019-12-05  0:51 ` [patch 33/86] gpio: 74x164: utilize the " Andrew Morton
2019-12-05  0:51 ` [patch 34/86] thermal: intel: intel_soc_dts_iosf: Utilize " Andrew Morton
2019-12-05  0:51 ` [patch 35/86] gpio: pisosr: utilize the " Andrew Morton
2019-12-05  0:51 ` [patch 36/86] gpio: max3191x: " Andrew Morton
2019-12-05  0:51 ` [patch 37/86] gpio: pca953x: " Andrew Morton
2019-12-05  0:51 ` [patch 38/86] lib/rbtree: set successor's parent unconditionally Andrew Morton
2019-12-05  0:51 ` [patch 39/86] lib/rbtree: get successor's color directly Andrew Morton
2019-12-05  0:51 ` [patch 40/86] lib/test_meminit.c: add bulk alloc/free tests Andrew Morton
2019-12-05  0:51 ` [patch 41/86] lib/math/rational.c: fix possible incorrect result from rational fractions helper Andrew Morton
2019-12-05  0:52 ` [patch 42/86] lib/genalloc.c: export symbol addr_in_gen_pool Andrew Morton
2019-12-05  0:52 ` [patch 43/86] lib/genalloc.c: rename addr_in_gen_pool to gen_pool_has_addr Andrew Morton
2019-12-05  0:52 ` [patch 44/86] checkpatch: improve ignoring CamelCase SI style variants like mA Andrew Morton
2019-12-05  0:52 ` [patch 45/86] checkpatch: reduce is_maintained_obsolete lookup runtime Andrew Morton
2019-12-05  0:52 ` [patch 46/86] epoll: simplify ep_poll_safewake() for CONFIG_DEBUG_LOCK_ALLOC Andrew Morton
2019-12-05  0:52 ` [patch 47/86] fs/epoll: remove unnecessary wakeups of nested epoll Andrew Morton
2019-12-05  0:52 ` [patch 48/86] selftests: add epoll selftests Andrew Morton
2019-12-05  0:52 ` [patch 49/86] fs/binfmt_elf.c: delete unused "interp_map_addr" argument Andrew Morton
2019-12-05  0:52 ` [patch 50/86] fs/binfmt_elf.c: extract elf_read() function Andrew Morton
2019-12-05  0:52 ` [patch 51/86] init/Kconfig: fix indentation Andrew Morton
2019-12-05  0:52 ` [patch 52/86] drivers/rapidio/rio-driver.c: fix missing include of <linux/rio_drv.h> Andrew Morton
2019-12-05  0:52 ` [patch 53/86] drivers/rapidio/rio-access.c: " Andrew Morton
2019-12-05  0:52 ` [patch 54/86] drm: limit to INT_MAX in create_blob ioctl Andrew Morton
2019-12-05  0:52 ` [patch 55/86] uaccess: disallow > INT_MAX copy sizes Andrew Morton
2019-12-05  0:52 ` [patch 56/86] kcov: remote coverage support Andrew Morton
2019-12-05  0:52 ` [patch 57/86] usb, kcov: collect coverage from hub_event Andrew Morton
2019-12-05  0:52 ` [patch 58/86] vhost, kcov: collect coverage from vhost_worker Andrew Morton
2019-12-05  0:52 ` [patch 59/86] lib/ubsan: don't serialize UBSAN report Andrew Morton
2019-12-05  0:52 ` [patch 60/86] arch: ipcbuf.h: make uapi asm/ipcbuf.h self-contained Andrew Morton
2019-12-05  0:53 ` [patch 61/86] arch: msgbuf.h: make uapi asm/msgbuf.h self-contained Andrew Morton
2019-12-05  0:53 ` [patch 62/86] arch: sembuf.h: make uapi asm/sembuf.h self-contained Andrew Morton
2019-12-05  0:53 ` [patch 63/86] lib/test_bitmap: force argument of bitmap_parselist_user() to proper address space Andrew Morton
2019-12-05  0:53 ` [patch 64/86] lib/test_bitmap: undefine macros after use Andrew Morton
2019-12-05  0:53 ` [patch 65/86] lib/test_bitmap: name EXP_BYTES properly Andrew Morton
2019-12-05  0:53 ` [patch 66/86] lib/test_bitmap: rename exp to exp1 to avoid ambiguous name Andrew Morton
2019-12-05  0:53 ` [patch 67/86] lib/test_bitmap: move exp1 and exp2 upper for others to use Andrew Morton
2019-12-05  0:53 ` [patch 68/86] lib/test_bitmap: fix comment about this file Andrew Morton
2019-12-05  0:53 ` [patch 69/86] lib/bitmap: introduce bitmap_replace() helper Andrew Morton
2019-12-05  0:53 ` [patch 70/86] gpio: pca953x: remove redundant variable and check in IRQ handler Andrew Morton
2019-12-05  0:53 ` [patch 71/86] gpio: pca953x: use input from regs structure in pca953x_irq_pending() Andrew Morton
2019-12-05  0:53 ` [patch 72/86] gpio: pca953x: convert to use bitmap API Andrew Morton
2019-12-05  0:53 ` [patch 73/86] gpio: pca953x: tighten up indentation Andrew Morton
2019-12-05  0:53 ` [patch 74/86] alpha: use pgtable-nopud instead of 4level-fixup Andrew Morton
2019-12-05  0:53 ` [patch 75/86] arm: nommu: " Andrew Morton
2019-12-05  0:53 ` [patch 76/86] c6x: " Andrew Morton
2019-12-05  0:53 ` [patch 77/86] m68k: nommu: " Andrew Morton
2019-12-05  0:53 ` [patch 78/86] m68k: mm: use pgtable-nopXd " Andrew Morton
2019-12-05  0:54 ` [patch 79/86] microblaze: use pgtable-nopmd " Andrew Morton
2019-12-05  0:54 ` [patch 80/86] nds32: " Andrew Morton
2019-12-05  0:54 ` [patch 81/86] parisc: use pgtable-nopXd " Andrew Morton
2019-12-05  0:54 ` [patch 82/86] parisc/hugetlb: " Andrew Morton
2019-12-05  0:54 ` [patch 83/86] sparc32: use pgtable-nopud " Andrew Morton
2019-12-05  0:54 ` [patch 84/86] um: remove unused pxx_offset_proc() and addr_pte() functions Andrew Morton
2019-12-05  0:54 ` [patch 85/86] um: add support for folded p4d page tables Andrew Morton
2019-12-05  0:54 ` [patch 86/86] mm: remove __ARCH_HAS_4LEVEL_HACK and include/asm-generic/4level-fixup.h Andrew Morton

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