linux-kernel - Re: [RFC PATCH 2/7] rslib: Fix decoding of shortened codes

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Message-ID: <alpine.DEB.2.21.1906172244450.1963@nanos.tec.linutronix.de>
Date:   Mon, 17 Jun 2019 22:46:18 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Ferdinand Blomqvist <ferdinand.blomqvist@...il.com>
cc:     linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 2/7] rslib: Fix decoding of shortened codes

Ferdinand,

On Sat, 30 Mar 2019, Ferdinand Blomqvist wrote:

> The decoder is broken. It only works with full length codes.

A short explanation what is missing and what is done to fix it would be
appreciated.

> Signed-off-by: Ferdinand Blomqvist <ferdinand.blomqvist@...il.com>
> ---
>  lib/reed_solomon/decode_rs.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/reed_solomon/decode_rs.c b/lib/reed_solomon/decode_rs.c
> index 1db74eb098d0..3313bf944ff1 100644
> --- a/lib/reed_solomon/decode_rs.c
> +++ b/lib/reed_solomon/decode_rs.c
> @@ -99,9 +99,9 @@
>  	if (no_eras > 0) {
>  		/* Init lambda to be the erasure locator polynomial */
>  		lambda[1] = alpha_to[rs_modnn(rs,
> -					      prim * (nn - 1 - eras_pos[0]))];
> +					prim * (nn - 1 - (eras_pos[0] + pad)))];
>  		for (i = 1; i < no_eras; i++) {
> -			u = rs_modnn(rs, prim * (nn - 1 - eras_pos[i]));
> +			u = rs_modnn(rs, prim * (nn - 1 - (eras_pos[i] + pad)));
>  			for (j = i + 1; j > 0; j--) {
>  				tmp = index_of[lambda[j - 1]];
>  				if (tmp != nn) {

Code looks fine as is.

Thanks,

	tglx