Re: [PATCH v17 01/14] bitops: Introduce the for_each_set_clump8 macro

[Masahiro Yamada]

On Thu, Oct 10, 2019 at 12:27 AM William Breathitt Gray
<vilhelm.gray@xxxxxxxxx> 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.
>
> Suggested-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> Suggested-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
> Suggested-by: Lukas Wunner <lukas@xxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@xxxxxxxxx>
> ---
>  include/asm-generic/bitops/find.h | 17 +++++++++++++++
>  include/linux/bitmap.h            | 35 +++++++++++++++++++++++++++++++
>  include/linux/bitops.h            |  5 +++++
>  lib/find_bit.c                    | 14 +++++++++++++
>  4 files changed, 71 insertions(+)
>
> diff --git a/include/asm-generic/bitops/find.h b/include/asm-generic/bitops/find.h
> index 8a1ee10014de..9fdf21302fdf 100644
> --- a/include/asm-generic/bitops/find.h
> +++ b/include/asm-generic/bitops/find.h
> @@ -80,4 +80,21 @@ extern unsigned long find_first_zero_bit(const unsigned long *addr,
>
>  #endif /* CONFIG_GENERIC_FIND_FIRST_BIT */
>
> +/**
> + * 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
> + * @size: bitmap size in number of bits
> + * @offset: bit offset at which to start searching
> + *
> + * 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.
> + */
> +extern unsigned long find_next_clump8(unsigned long *clump,
> +                                     const unsigned long *addr,
> +                                     unsigned long size, unsigned long offset);
> +
> +#define find_first_clump8(clump, bits, size) \
> +       find_next_clump8((clump), (bits), (size), 0)
> +
>  #endif /*_ASM_GENERIC_BITOPS_FIND_H_ */
> diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
> index 90528f12bdfa..761fab5b60a7 100644
> --- a/include/linux/bitmap.h
> +++ b/include/linux/bitmap.h
> @@ -66,6 +66,8 @@
>   *  bitmap_allocate_region(bitmap, pos, order)  Allocate specified bit region
>   *  bitmap_from_arr32(dst, buf, nbits)          Copy nbits from u32[] buf to dst
>   *  bitmap_to_arr32(buf, src, nbits)            Copy nbits from buf to u32[] dst
> + *  bitmap_get_value8(map, start)               Get 8bit value from map at start
> + *  bitmap_set_value8(map, value, start)        Set 8bit value to map at start
>   *
>   * Note, bitmap_zero() and bitmap_fill() operate over the region of
>   * unsigned longs, that is, bits behind bitmap till the unsigned long
> @@ -488,6 +490,39 @@ static inline void bitmap_from_u64(unsigned long *dst, u64 mask)
>                 dst[1] = mask >> 32;
>  }
>
> +/**
> + * bitmap_get_value8 - get an 8-bit value within a memory region
> + * @map: address to the bitmap memory region
> + * @start: bit offset of the 8-bit value; must be a multiple of 8
> + *
> + * Returns the 8-bit value located at the @start bit offset within the @src
> + * memory region.
> + */
> +static inline unsigned long bitmap_get_value8(const unsigned long *map,
> +                                             unsigned long start)

Why is the return type "unsigned long" where you know
it return the 8-bit value ?

u8?



> +{
> +       const size_t index = BIT_WORD(start);
> +       const unsigned long offset = start % BITS_PER_LONG;
> +
> +       return (map[index] >> offset) & 0xFF;
> +}
> +
> +/**
> + * bitmap_set_value8 - set an 8-bit value within a memory region
> + * @map: address to the bitmap memory region
> + * @value: the 8-bit value; values wider than 8 bits may clobber bitmap
> + * @start: bit offset of the 8-bit value; must be a multiple of 8
> + */
> +static inline void bitmap_set_value8(unsigned long *map, unsigned long value,


Same here,   "u8 value"



> +                                    unsigned long start)
> +{
> +       const size_t index = BIT_WORD(start);
> +       const unsigned long offset = start % BITS_PER_LONG;
> +
> +       map[index] &= ~(0xFF << offset);
> +       map[index] |= value << offset;
> +}
> +
>  #endif /* __ASSEMBLY__ */
>
>  #endif /* __LINUX_BITMAP_H */
> diff --git a/include/linux/bitops.h b/include/linux/bitops.h
> index cf074bce3eb3..fb94a10f7853 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), (size), (start) + 8))
> +
>  static inline int get_bitmask_order(unsigned int count)
>  {
>         int order;
> diff --git a/lib/find_bit.c b/lib/find_bit.c
> index 5c51eb45178a..e35a76b291e6 100644
> --- a/lib/find_bit.c
> +++ b/lib/find_bit.c
> @@ -214,3 +214,17 @@ EXPORT_SYMBOL(find_next_bit_le);
>  #endif
>
>  #endif /* __BIG_ENDIAN */
> +
> +unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,


Ditto.   "u8 *clump"




> +                              unsigned long size, unsigned long offset)
> +{
> +       offset = find_next_bit(addr, size, offset);
> +       if (offset == size)
> +               return size;
> +
> +       offset = round_down(offset, 8);
> +       *clump = bitmap_get_value8(addr, offset);
> +
> +       return offset;
> +}
> +EXPORT_SYMBOL(find_next_clump8);
> --
> 2.23.0
>


--
Best Regards

Masahiro Yamada