On Wed, May 16, 2018 at 11:08:28PM +0300, Andy Shevchenko wrote: >On Wed, May 16, 2018 at 5:03 PM, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: >> On Tue, May 15, 2018 at 6:22 PM, William Breathitt Gray >> <vilhelm.gray@xxxxxxxxx> wrote: >> >>> For example, suppose you would like to iterate over a 16-bit integer 4 >>> bits at a time, skipping over 4-bit groups with no set bit, where XXXX >>> represents the current 4-bit group: >>> >>> Example: 1011 1110 0000 1111 >>> First loop: 1011 1110 0000 XXXX >>> Second loop: 1011 XXXX 0000 1111 >>> Third loop: XXXX 1110 0000 1111 >>> >>> Each iteration of the loop returns the next 4-bit group that has at >>> least one set bit. >>> >>> The for_each_set_clump macro has six parameters: >>> >>> * clump: set to current clump index for the iteration >>> * index: set to current bitmap word index for the iteration >>> * offset: bits offset of the found clump in the bitmap word >>> * bits: bitmap to search within >>> * size: bitmap size in number of clumps >>> * clump_size: clump size in number of bits >>> >>> The clump_size argument can be an arbitrary number of bits and is not >>> required to be a multiple of 2. >> >> I must say I'm impressed. Very nice arithmetics going on there. >> >> If I can get some ACK for the bitops patch I'd be happy to merge >> it all through the GPIO tree. The users are pretty clear cut. > >Give me also some time to go through proposed API, I think it might >have needed more alignment with existing find_* and for_* helpers. Hi Andy, Are there any additional changes you would like me to make before this patchset is merged through the GPIO tree? William Breathitt Gray > >> BTW: if I could, I would pull out Donald Knuth's "The Art of Computer >> Programming vol 4A" chapter 7.1.3 "Bitwise Tricks and Techniques" >> to see what he has to say about the subject, but I don't have >> that book as it turns out. > >I can also add the Standford collection of bit algos here: > >https://graphics.stanford.edu/~seander/bithacks.html > >-- >With Best Regards, >Andy Shevchenko
