Re: [PATCH v12 01/11] bitops: Introduce the for_each_set_clump8 macro

[Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>]

On Mon, Mar 25, 2019 at 03:22:23PM +0900, William Breathitt Gray wrote:
> This macro iterates for each 8-bit group of bits (clump) with set bits,
> within a bitmap memory region. For each iteration, "start" is set to the
> bit offset of the found clump, while the respective clump value is
> stored to the location pointed by "clump". Additionally, the
> bitmap_get_value8 and bitmap_set_value8 functions are introduced to
> respectively get and set an 8-bit value in a bitmap memory region.


This seems to miss Randy's (IIRC) comment about too many const specifiers.

> Suggested-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> Suggested-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Acked-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@xxxxxxxxx>
> ---
>  include/asm-generic/bitops/find.h | 14 ++++++
>  include/linux/bitops.h            |  5 ++
>  lib/find_bit.c                    | 81 +++++++++++++++++++++++++++++++
>  3 files changed, 100 insertions(+)
> 
> diff --git a/include/asm-generic/bitops/find.h b/include/asm-generic/bitops/find.h
> index 8a1ee10014de..9a76adff59c6 100644
> --- a/include/asm-generic/bitops/find.h
> +++ b/include/asm-generic/bitops/find.h
> @@ -80,4 +80,18 @@ extern unsigned long find_first_zero_bit(const unsigned long *addr,
>  
>  #endif /* CONFIG_GENERIC_FIND_FIRST_BIT */
>  
> +unsigned long bitmap_get_value8(const unsigned long *const bitmap,
> +				const unsigned int size,
> +				const unsigned int start);
> +
> +void bitmap_set_value8(unsigned long *const bitmap, const unsigned int size,
> +		       const unsigned long value, const unsigned int start);
> +
> +unsigned int find_next_clump8(unsigned long *const clump,
> +			      const unsigned long *const addr,
> +			      unsigned int offset, const unsigned int size);
> +
> +#define find_first_clump8(clump, bits, size) \
> +	find_next_clump8((clump), (bits), 0, (size))
> +
>  #endif /*_ASM_GENERIC_BITOPS_FIND_H_ */
> diff --git a/include/linux/bitops.h b/include/linux/bitops.h
> index 602af23b98c7..f19a7bc8f559 100644
> --- a/include/linux/bitops.h
> +++ b/include/linux/bitops.h
> @@ -40,6 +40,11 @@ extern unsigned long __sw_hweight64(__u64 w);
>  	     (bit) < (size);					\
>  	     (bit) = find_next_zero_bit((addr), (size), (bit) + 1))
>  
> +#define for_each_set_clump8(start, clump, bits, size) \
> +	for ((start) = find_first_clump8(&(clump), (bits), (size)); \
> +	     (start) < (size); \
> +	     (start) = find_next_clump8(&(clump), (bits), (start) + 8, (size)))
> +
>  static inline int get_bitmask_order(unsigned int count)
>  {
>  	int order;
> diff --git a/lib/find_bit.c b/lib/find_bit.c
> index ee3df93ba69a..1b6f8a6f1957 100644
> --- a/lib/find_bit.c
> +++ b/lib/find_bit.c
> @@ -218,3 +218,84 @@ EXPORT_SYMBOL(find_next_bit_le);
>  #endif
>  
>  #endif /* __BIG_ENDIAN */
> +
> +/**
> + * bitmap_get_value8 - get an 8-bit value within a memory region
> + * @bitmap: address to the bitmap memory region
> + * @size: bitmap size in number of bits
> + * @start: bit offset of the 8-bit value
> + *
> + * Returns the 8-bit value located at the @start bit offset within the @bitmap
> + * memory region.
> + */
> +unsigned long bitmap_get_value8(const unsigned long *const bitmap,
> +				const unsigned int size,
> +				const unsigned int start)
> +{
> +	const size_t index = BIT_WORD(start);
> +	const unsigned int offset = start % BITS_PER_LONG;
> +	const unsigned int low_width = (offset + 8 > BITS_PER_LONG) ?
> +				       BITS_PER_LONG - offset : 8;
> +	const unsigned long low = bitmap[index] >> offset;
> +	const unsigned long high = (low_width < 8 && start + 8 <= size) ?
> +				   bitmap[index + 1] << low_width : 0;
> +
> +	return (low | high) & 0xFF;
> +}
> +EXPORT_SYMBOL(bitmap_get_value8);
> +
> +/**
> + * bitmap_set_value8 - set an 8-bit value within a memory region
> + * @bitmap: address to the bitmap memory region
> + * @size: bitmap size in number of bits
> + * @value: the 8-bit value; values wider than 8 bits may clobber bitmap
> + * @start: bit offset of the 8-bit value
> + */
> +void bitmap_set_value8(unsigned long *const bitmap, const unsigned int size,
> +		       const unsigned long value, const unsigned int start)
> +{
> +	const size_t index = BIT_WORD(start);
> +	const unsigned int offset = start % BITS_PER_LONG;
> +	const unsigned int low_width = (offset + 8 > BITS_PER_LONG) ?
> +				       BITS_PER_LONG - offset : 8;
> +	const unsigned long low_mask = GENMASK(low_width - 1, 0) << offset;
> +	const unsigned int high_width = 8 - low_width;
> +	const unsigned long high_mask = GENMASK(high_width - 1, 0);
> +
> +	/* set lower portion */
> +	bitmap[index] &= ~low_mask;
> +	bitmap[index] |= value << offset;
> +
> +	/* set higher portion if space available in bitmap */
> +	if (high_width && start + 8 <= size) {
> +		bitmap[index + 1] &= ~high_mask;
> +		bitmap[index + 1] |= value >> low_width;
> +	}
> +}
> +EXPORT_SYMBOL(bitmap_set_value8);
> +
> +/**
> + * 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);
> -- 
> 2.21.0
> 

-- 
With Best Regards,
Andy Shevchenko