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Message-ID: <xhsmhedwnb15r.mognet@vschneid.remote.csb>
Date: Wed, 07 Sep 2022 17:27:12 +0100
From: Valentin Schneider <vschneid@...hat.com>
To: Yury Norov <yury.norov@...il.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-kernel@...r.kernel.org
Cc: Yury Norov <yury.norov@...il.com>,
Alexey Klimov <klimov.linux@...il.com>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Andy Whitcroft <apw@...onical.com>,
Catalin Marinas <catalin.marinas@....com>,
David Laight <David.Laight@...LAB.COM>,
Dennis Zhou <dennis@...nel.org>,
Guenter Roeck <linux@...ck-us.net>,
Kees Cook <keescook@...omium.org>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
Russell King <linux@...linux.org.uk>
Subject: Re: [PATCH v3 2/4] lib/find_bit: create find_first_zero_bit_le()
On 27/08/22 10:58, Yury Norov wrote:
> find_first_zero_bit_le() is an alias to find_next_zero_bit_le(),
> despite that 'next' is known to be slower than 'first' version.
>
> Now that we have common FIND_FIRST_BIT() macro helper, it's trivial
> to implement find_first_zero_bit_le() as a real function.
>
> Signed-off-by: Yury Norov <yury.norov@...il.com>
Declaration ordering nit below, otherwise:
Reviewed-by: Valentin Schneider <vschneid@...hat.com>
> ---
> include/linux/find.h | 23 ++++++++++++++++++-----
> lib/find_bit.c | 14 ++++++++++++++
> 2 files changed, 32 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/find.h b/include/linux/find.h
> index 424ef67d4a42..a1861d0ba533 100644
> --- a/include/linux/find.h
> +++ b/include/linux/find.h
> @@ -17,6 +17,10 @@ extern unsigned long _find_first_and_bit(const unsigned long *addr1,
> extern unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size);
> extern unsigned long _find_last_bit(const unsigned long *addr, unsigned long size);
>
> +#ifdef __BIG_ENDIAN
> +unsigned long _find_first_zero_bit_le(const unsigned long *addr, unsigned long size);
> +#endif
> +
> #ifndef find_next_bit
> /**
> * find_next_bit - find the next set bit in a memory region
> @@ -251,6 +255,20 @@ unsigned long find_next_zero_bit_le(const void *addr, unsigned
> }
> #endif
>
> +#ifndef find_first_zero_bit_le
> +static inline
> +unsigned long find_first_zero_bit_le(const unsigned long *addr, unsigned long size)
> +{
> + if (small_const_nbits(size)) {
> + unsigned long val = swab(*addr) | ~GENMASK(size - 1, 0);
> +
> + return val == ~0UL ? size : ffz(val);
> + }
> +
> + return _find_first_zero_bit_le(addr, size);
> +}
> +#endif
> +
Nit: this should be placed after the declaration of find_next_bit_le() to
match the __LITTLE_ENDIAN declaration order above.
> #ifndef find_next_bit_le
> static inline
> unsigned long find_next_bit_le(const void *addr, unsigned
> @@ -270,11 +288,6 @@ unsigned long find_next_bit_le(const void *addr, unsigned
> }
> #endif
>
> -#ifndef find_first_zero_bit_le
> -#define find_first_zero_bit_le(addr, size) \
> - find_next_zero_bit_le((addr), (size), 0)
> -#endif
> -
> #else
> #error "Please fix <asm/byteorder.h>"
> #endif
> diff --git a/lib/find_bit.c b/lib/find_bit.c
> index 894b656f6836..f4d9b9684811 100644
> --- a/lib/find_bit.c
> +++ b/lib/find_bit.c
> @@ -160,3 +160,17 @@ unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,
> return offset;
> }
> EXPORT_SYMBOL(find_next_clump8);
> +
> +#ifdef __BIG_ENDIAN
> +#ifndef find_first_zero_bit_le
> +/*
> + * Find the first cleared bit in an LE memory region.
> + */
> +unsigned long _find_first_zero_bit_le(const unsigned long *addr, unsigned long size)
> +{
> + return FIND_FIRST_BIT(~addr[idx], swab, size);
> +}
> +EXPORT_SYMBOL(_find_first_zero_bit_le);
> +#endif
> +
> +#endif /* __BIG_ENDIAN */
> --
> 2.34.1
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