linux-kernel - Re: [PATCH] mtd: nand: fix lack of oob layout when using no ecc

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Message-ID: <20170710133556.23e48f54@bbrezillon>
Date:   Mon, 10 Jul 2017 13:35:56 +0200
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Miquel Raynal <miquel.raynal@...e-electrons.com>
Cc:     Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        linux-mtd@...ts.infradead.org (open list:NAND FLASH SUBSYSTEM),
        linux-kernel@...r.kernel.org (open list)
Subject: Re: [PATCH] mtd: nand: fix lack of oob layout when using no ecc

On Mon, 10 Jul 2017 12:37:26 +0200
Miquel Raynal <miquel.raynal@...e-electrons.com> wrote:

> Fix nand core lack of OOB layout when:
> - the NFC driver does not provide any OOB layout,
> - ECC operations are disabled (using NAND_ECC_NONE).
> Using this configuration leads to a crash during the probe.
> 
> Add layout functions for small and large pages with mainly free bytes
> plus reserved space for bad block markers.
> 
> Check the configuration and eventually assign this OOB layout in
> nand_scan_tail().
> 
> Bad block markers position was extracted from the existing OOB layouts
> by assigning as free all the bytes marked as ECC.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@...e-electrons.com>
> ---
>  drivers/mtd/nand/nand_base.c | 75 +++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 74 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index c5221795a1e8..28ff58e4385f 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -53,7 +53,45 @@ static int nand_get_device(struct mtd_info *mtd, int new_state);
>  static int nand_do_write_oob(struct mtd_info *mtd, loff_t to,
>  			     struct mtd_oob_ops *ops);
>  
> -/* Define default oob placement schemes for large and small page devices */
> +/*
> + * Define default OOB placement schemes for:
> + *   - no ECC or software ECC
> + *   - small or large page devices
> + */
> +static int nand_ooblayout_ecc_sp_bbm_only(struct mtd_info *mtd, int section,
> +					  struct mtd_oob_region *oobregion)
> +{
> +	return -ERANGE;
> +}
> +
> +static int nand_ooblayout_free_sp_bbm_only(struct mtd_info *mtd, int section,
> +					   struct mtd_oob_region *oobregion)
> +{
> +	if (section > 1)
> +		return -ERANGE;
> +
> +	if (!section) {
> +		if (mtd->oobsize == 16) {
> +			oobregion->offset = 0;
> +			oobregion->length = 4;
> +		} else {
> +			oobregion->offset = 0;
> +			oobregion->length = 5;
> +		}
> +	} else {
> +		oobregion->offset = 6;
> +		oobregion->length = mtd->oobsize - oobregion->offset;
> +	}
> +
> +	return 0;
> +}
> +
> +const struct mtd_ooblayout_ops nand_ooblayout_sp_bbm_only_ops = {
> +	.ecc = nand_ooblayout_ecc_sp_bbm_only,

Actually, you don't have to implement ->ecc() in this case, just leave
it to NULL, the core takes care of returning -ENOTSUPP in this case [1].

[1]http://elixir.free-electrons.com/linux/latest/source/drivers/mtd/mtdcore.c#L1143