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SubjectRe: [PATCH v4 0/8] Introduce the for_each_set_clump macro
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@linaro.org> wrote:
>> On Tue, May 15, 2018 at 6:22 PM, William Breathitt Gray
>> <vilhelm.gray@gmail.com> 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

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