linux-kernel - Re: [RESEND PATCH v4 1/8] bitops: Introduce the for_each_set

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Message-ID: <20181003114804.GE15943@smile.fi.intel.com>
Date:   Wed, 3 Oct 2018 14:48:04 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     William Breathitt Gray <vilhelm.gray@...il.com>,
        linus.walleij@...aro.org, akpm@...ux-foundation.org,
        linux-gpio@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>
Subject: Re: [RESEND PATCH v4 1/8] bitops: Introduce the for_each_set_clump
 macro

On Tue, Oct 02, 2018 at 11:21:42AM +0300, Andy Shevchenko wrote:

> I would rather go with two prototypes to get()/set() a clump in the bitmap
> in a way when it's aligned and BITS_PER_LONG % clump_size == 0.

To make things much easier, restrict clump_size to the one
from the following set:

1, 2, 4, 8, 16, 32 even on 64-bit platforms.

If it would be simpler solution to add 64 here (implying 32-bit platform),
I would vote for that.

For the generic case we might need something like:

unsigned long bitmap_get_bits(unsigned long *src, unsigned int start, unsigned int nbits)
{
	assert(nbits > BITS_PER_LONG);

	/* Something like Rasmus proposed earlier */
}

And similar to setter.


-- 
With Best Regards,
Andy Shevchenko