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authorWilliam Breathitt Gray <vilhelm.gray@gmail.com>2019-12-05 03:50:57 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2019-12-05 06:44:12 +0300
commit169c474fb22d8a5e909e172f177b957546d0519d (patch)
treea76e7a577e0bd2fdc9bb1da1a4f522d0ef013740 /include/asm-generic
parent5e1aada08cd19ea652b2d32a250501d09b02ff2e (diff)
downloadlinux-169c474fb22d8a5e909e172f177b957546d0519d.tar.xz
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> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/asm-generic')
-rw-r--r--include/asm-generic/bitops/find.h17
1 files changed, 17 insertions, 0 deletions
diff --git a/include/asm-generic/bitops/find.h b/include/asm-generic/bitops/find.h
index 8a1ee10014de..9fdf21302fdf 100644
--- a/include/asm-generic/bitops/find.h
+++ b/include/asm-generic/bitops/find.h
@@ -80,4 +80,21 @@ extern unsigned long find_first_zero_bit(const unsigned long *addr,
#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_ */