Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <a31155a7-d7f4-2825-1e84-bb8a51815edd@infradead.org>
Date:   Sat, 18 Jun 2022 18:29:18 -0700
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.9.1
Subject: Re: [PATCH v2 4/5] rslib: Improve the performance of encode_rs.c
Content-Language: en-US
To:     Zhang Boyang <zhangboyang.id@gmail.com>,
        linux-kernel@vger.kernel.org
Cc:     Ferdinand Blomqvist <ferdinand.blomqvist@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Kees Cook <keescook@chromium.org>,
        Ivan Djelic <ivan.djelic@parrot.com>,
        Boris Brezillon <boris.brezillon@bootlin.com>,
        Miquel Raynal <miquel.raynal@bootlin.com>
References: <20220617144624.158973-1-zhangboyang.id@gmail.com>
 <20220617144624.158973-5-zhangboyang.id@gmail.com>
From:   Randy Dunlap <rdunlap@infradead.org>
In-Reply-To: <20220617144624.158973-5-zhangboyang.id@gmail.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

Hi--

On 6/17/22 07:46, Zhang Boyang wrote:
> Signed-off-by: Zhang Boyang <zhangboyang.id@gmail.com>
> ---
>  include/linux/rslib.h        | 14 +++++++++++++-
>  lib/reed_solomon/encode_rs.c | 21 ++++++++++-----------
>  2 files changed, 23 insertions(+), 12 deletions(-)
> 
> diff --git a/include/linux/rslib.h b/include/linux/rslib.h
> index cd0b5a7a5698..44ec7c6f24b2 100644
> --- a/include/linux/rslib.h
> +++ b/include/linux/rslib.h
> @@ -110,7 +110,7 @@ void free_rs(struct rs_control *rs);
>  /** modulo replacement for galois field arithmetics
>   *
>   *  @rs:	Pointer to the RS codec
> - *  @x:		the value to reduce
> + *  @x:		x >= 0 ; the value to reduce
>   *
>   *  where
>   *  rs->mm = number of bits per symbol
> @@ -127,4 +127,16 @@ static inline int rs_modnn(struct rs_codec *rs, int x)
>  	return x;
>  }
>  
> +/** modulo replacement for galois field arithmetics

/**
 * rs_modnn_fast() - modulo replacement for galois field arithmetics

> + *
> + *  @rs:	Pointer to the RS codec
> + *  @x:		0 <= x < 2*nn ; the value to reduce
> + *
> + *  Same as rs_modnn(x), but faster, at the cost of limited value range of @x
> +*/
> +static inline int rs_modnn_fast(struct rs_codec *rs, int x)
> +{
> +	return x - rs->nn < 0 ? x : x - rs->nn;
> +}
> +
>  #endif

-- 
~Randy