From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: William Breathitt Gray <vilhelm.gray@gmail.com>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
Linux-Arch <linux-arch@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 0/8] Introduce the for_each_set_clump macro
Date: Wed, 16 May 2018 23:08:28 +0300 [thread overview]
Message-ID: <CAHp75VcGuJ0+qzUZZW=1VSeXmf_rht0tJvCH+yBsXPZz0z8qHA@mail.gmail.com> (raw)
In-Reply-To: <CACRpkdbRH-Bz3BoczD+YmaSGqtoeCwtvGj4dGm8PKRKYFXTdKA@mail.gmail.com>
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.
> 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
next prev parent reply other threads:[~2018-05-16 20:08 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-15 16:22 [PATCH v4 0/8] Introduce the for_each_set_clump macro William Breathitt Gray
2018-05-15 16:22 ` William Breathitt Gray
2018-05-15 16:22 ` [PATCH v4 1/8] bitops: " William Breathitt Gray
2018-05-15 16:22 ` William Breathitt Gray
2018-05-15 16:22 ` [PATCH v4 2/8] lib/test_bitmap.c: Add for_each_set_clump test cases William Breathitt Gray
2018-05-15 16:22 ` William Breathitt Gray
2018-05-15 16:22 ` [PATCH v4 3/8] gpio: 104-dio-48e: Utilize for_each_set_clump macro William Breathitt Gray
2018-05-15 16:22 ` William Breathitt Gray
2018-05-15 16:22 ` [PATCH v4 4/8] gpio: 104-idi-48: " William Breathitt Gray
2018-05-15 16:22 ` William Breathitt Gray
2018-05-15 16:23 ` [PATCH v4 5/8] gpio: gpio-mm: " William Breathitt Gray
2018-05-15 16:23 ` William Breathitt Gray
2018-05-15 16:23 ` [PATCH v4 6/8] gpio: ws16c48: " William Breathitt Gray
2018-05-15 16:23 ` William Breathitt Gray
2018-05-15 16:23 ` [PATCH v4 7/8] gpio: pci-idio-16: " William Breathitt Gray
2018-05-15 16:23 ` William Breathitt Gray
2018-05-15 16:23 ` [PATCH v4 8/8] gpio: pcie-idio-24: " William Breathitt Gray
2018-05-15 16:23 ` William Breathitt Gray
2018-05-16 14:03 ` [PATCH v4 0/8] Introduce the " Linus Walleij
2018-05-16 14:03 ` Linus Walleij
2018-05-16 20:08 ` Andy Shevchenko [this message]
2018-05-16 20:08 ` Andy Shevchenko
2018-06-16 19:16 ` William Breathitt Gray
2018-06-16 19:16 ` William Breathitt Gray
2018-09-05 15:04 ` William Breathitt Gray
2018-09-05 15:04 ` William Breathitt Gray
2018-09-10 7:54 ` Linus Walleij
2018-09-10 7:54 ` Linus Walleij
2018-09-10 14:47 ` Andy Shevchenko
2018-09-10 14:47 ` Andy Shevchenko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAHp75VcGuJ0+qzUZZW=1VSeXmf_rht0tJvCH+yBsXPZz0z8qHA@mail.gmail.com' \
--to=andy.shevchenko@gmail.com \
--cc=linus.walleij@linaro.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-gpio@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=vilhelm.gray@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).