linux-kernel - Re: [PATCH 6/7] mtd: rawnand: sunxi: Update OOB layout to match hardware

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Date:   Mon, 2 Jan 2023 10:21:23 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Samuel Holland <samuel@...lland.org>
Cc:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        Brian Norris <computersforpeace@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mtd@...ts.infradead.org, linux-sunxi@...ts.linux.dev
Subject: Re: [PATCH 6/7] mtd: rawnand: sunxi: Update OOB layout to match
 hardware

Hi Samuel,

samuel@...lland.org wrote on Thu, 29 Dec 2022 12:15:25 -0600:

> When using the hardware ECC engine, the OOB data is made available in
> the NFC_REG_USER_DATA registers, one 32-bit word per ECC step. Any
> additional bytes are only accessible through raw reads and software
> descrambling. For efficiency, and to match the vendor driver, ignore
> these extra bytes.
> 
> Signed-off-by: Samuel Holland <samuel@...lland.org>
> ---
> 
>  drivers/mtd/nand/raw/sunxi_nand.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/mtd/nand/raw/sunxi_nand.c b/drivers/mtd/nand/raw/sunxi_nand.c
> index 8e873f4fec9a..a3bc9f7f9e5a 100644
> --- a/drivers/mtd/nand/raw/sunxi_nand.c
> +++ b/drivers/mtd/nand/raw/sunxi_nand.c
> @@ -1604,6 +1604,13 @@ static int sunxi_nand_ooblayout_free(struct mtd_info *mtd, int section,
>  		return 0;
>  	}
>  
> +	/*
> +	 * The controller does not provide access to OOB bytes
> +	 * past the end of the ECC data.
> +	 */
> +	if (section == ecc->steps && ecc->engine_type == NAND_ECC_ENGINE_TYPE_ON_HOST)
> +		return -ERANGE;

Again, I am sorry but I cannot take this change, it would typically
break jffs2 users (if any?) :(

>  	oobregion->offset = section * (ecc->bytes + 4);
>  
>  	if (section < ecc->steps)


Thanks,
Miquèl