linux-kernel - Re: [PATCH v12 01/11] bitops: Introduce the for_each_set

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Date:   Mon, 25 Mar 2019 10:38:54 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     William Breathitt Gray <vilhelm.gray@...il.com>
Cc:     linus.walleij@...aro.org, bgolaszewski@...libre.com,
        akpm@...ux-foundation.org, linux-gpio@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        andriy.shevchenko@...ux.intel.com, linux@...musvillemoes.dk,
        yamada.masahiro@...ionext.com,
        linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
        geert@...ux-m68k.org, preid@...ctromag.com.au,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v12 01/11] bitops: Introduce the for_each_set_clump8 macro

On Mon, Mar 25, 2019 at 03:22:23PM +0900, William Breathitt Gray wrote:
> +/**
> + * find_next_clump8 - find next 8-bit clump with set bits in a memory region
> + * @clump: location to store copy of found clump
> + * @addr: address to base the search on
> + * @offset: bit offset at which to start searching
> + * @size: bitmap size in number of bits
> + *
> + * Returns the bit offset for the next set clump; the found clump value is
> + * copied to the location pointed by @clump. If no bits are set, returns @size.
> + */
> +unsigned int find_next_clump8(unsigned long *const clump,
> +			      const unsigned long *const addr,
> +			      unsigned int offset, const unsigned int size)
> +{
> +	for (; offset < size; offset += 8) {
> +		*clump = bitmap_get_value8(addr, size, offset);
> +		if (!*clump)
> +			continue;
> +
> +		return offset;
> +	}
> +
> +	return size;
> +}
> +EXPORT_SYMBOL(find_next_clump8);

Just use find_first_bit() / find_next_bit() to use optimized arch-specific
bitops instead of open-coding the iteration over the bitmap.

See max3191x_get_multiple() for an example.

Thanks,

Lukas