From 79c53b31376101ed5d82955d5ba09757e84937ce Mon Sep 17 00:00:00 2001 From: William Breathitt Gray Date: Wed, 23 Oct 2019 11:25:10 +1100 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. Link: http://lkml.kernel.org/r/893c3b4f03266c9496137cc98ac2b1bd27f92c73.1570641097.git.vilhelm.gray@gmail.com Signed-off-by: William Breathitt Gray Suggested-by: Andy Shevchenko Suggested-by: Rasmus Villemoes Suggested-by: Lukas Wunner Tested-by: Andy Shevchenko Cc: Arnd Bergmann Cc: Linus Walleij Cc: Bartosz Golaszewski Cc: Masahiro Yamada Cc: Geert Uytterhoeven Cc: Phil Reid Cc: Geert Uytterhoeven Cc: Mathias Duckeck Cc: Morten Hein Tiljeset Cc: Sean Nyekjaer Signed-off-by: Andrew Morton Signed-off-by: Stephen Rothwell --- include/linux/bitops.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux/bitops.h') diff --git a/include/linux/bitops.h b/include/linux/bitops.h index c94a9ff9f082..dd83cd8a0683 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -47,6 +47,11 @@ extern unsigned long __sw_hweight64(__u64 w); (bit) < (size); \ (bit) = find_next_zero_bit((addr), (size), (bit) + 1)) +#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; -- cgit v1.2.3 From 75b105964fd493f35d45d0a44a58b99b779626e8 Mon Sep 17 00:00:00 2001 From: William Breathitt Gray Date: Wed, 23 Oct 2019 11:25:11 +1100 Subject: linux/bitopts.h: Add for_each_set_clump8 documentation Document in kerneldoc form the for_each_set_clump8 macro. Link: http://lkml.kernel.org/r/20191016161825.301082-1-vilhelm.gray@gmail.com Signed-off-by: William Breathitt Gray Signed-off-by: Andrew Morton Signed-off-by: Stephen Rothwell --- include/linux/bitops.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'include/linux/bitops.h') diff --git a/include/linux/bitops.h b/include/linux/bitops.h index dd83cd8a0683..e479067c202c 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -47,6 +47,13 @@ extern unsigned long __sw_hweight64(__u64 w); (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); \ -- cgit v1.2.3