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Date: Thu, 10 Oct 2019 01:28:08 +0900
From: Masahiro Yamada <yamada.masahiro@...ionext.com>
To: William Breathitt Gray <vilhelm.gray@...il.com>
Cc: Linus Walleij <linus.walleij@...aro.org>,
Bartosz Golaszewski <bgolaszewski@...libre.com>,
Andrew Morton <akpm@...ux-foundation.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-arch <linux-arch@...r.kernel.org>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
Linux PM mailing list <linux-pm@...r.kernel.org>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
preid@...ctromag.com.au, Lukas Wunner <lukas@...ner.de>,
sean.nyekjaer@...vas.dk, morten.tiljeset@...vas.dk,
Andy Shevchenko <andy.shevchenko@...il.com>,
Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v17 01/14] bitops: Introduce the for_each_set_clump8 macro
On Thu, Oct 10, 2019 at 12:27 AM William Breathitt Gray
<vilhelm.gray@...il.com> 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@...il.com>
> Suggested-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> Suggested-by: Lukas Wunner <lukas@...ner.de>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Andy Shevchenko <andy.shevchenko@...il.com>
> Cc: Linus Walleij <linus.walleij@...aro.org>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@...il.com>
> ---
> 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
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