Re: [PATCH v2 05/51] mtd: add mtd_ooblayout_xxx() helper functions

Boris Brezillon
2016-02-05T09:27:22Z

On Thu, 4 Feb 2016 11:06:28 +0100
Boris Brezillon <boris.brezillon@free-electrons.com> wrote:

> In order to make the ecclayout definition completely dynamic we need to
> rework the way the OOB layout are defined and iterated.
>
> Create a few mtd_ooblayout_xxx() helpers to ease OOB bytes manipulation
> and hide ecclayout internals to their users.
>
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> ---
> drivers/mtd/mtdcore.c | 401 ++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/mtd/mtd.h | 33 ++++
> 2 files changed, 434 insertions(+)
>
> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> index 3096251..14e46ca 100644
> --- a/drivers/mtd/mtdcore.c
> +++ b/drivers/mtd/mtdcore.c
> @@ -997,6 +997,407 @@ int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
> }
> EXPORT_SYMBOL_GPL(mtd_read_oob);
>
> +/**
> + * mtd_ooblayout_ecc - Get the OOB region definition of a specific ECC section
> + * @mtd: MTD device structure
> + * @section: ECC section. Depending on the layout you may have all the ECC
> + * bytes stored in a single contiguous section, or one section
> + * per ECC chunk (and sometime several sections for a single ECC
> + * ECC chunk)
> + * @oobecc: OOB region struct filled with the appropriate ECC position
> + * information
> + *
> + * This functions return ECC section information in the OOB area. I you want
> + * to get all the ECC bytes information, then you should call
> + * mtd_ooblayout_ecc(mtd, section++, oobecc) until it returns -ERANGE.
> + *
> + * Returns zero on success, a negative error code otherwise.
> + */
> +int mtd_ooblayout_ecc(struct mtd_info *mtd, int section,
> + struct mtd_oob_region *oobecc)
> +{
> + int eccbyte = 0, cursection = 0, length = 0, eccpos = 0;
> +
> + memset(oobecc, 0, sizeof(*oobecc));
> +
> + if (!mtd || section < 0)
> + return -EINVAL;
> +
> + if (!mtd->ecclayout)
> + return -ENOTSUPP;
> +
> + if (mtd->ecclayout->eccbytes < 1)
> + return -ERANGE;
> +
> + /*
> + * This logic allows us to reuse the ->ecclayout information and
> + * expose them as ECC regions (as done for the OOB free regions).
> + *
> + * TODO: this should be dropped as soon as we get rid of the
> + * ->ecclayout field.
> + */
> + for (eccbyte = 0; eccbyte < mtd->ecclayout->eccbytes; eccbyte++) {
> + eccpos = mtd->ecclayout->eccpos[eccbyte];
> +
> + if (eccbyte < mtd->ecclayout->eccbytes - 1) {
> + int neccpos = mtd->ecclayout->eccpos[eccbyte + 1];
> +
> + if (eccpos + 1 == neccpos) {
> + length++;
> + continue;
> + }
> + }
> +
> + if (section == cursection)
> + break;
> +
> + length = 0;
> + cursection++;
> + }
> +
> + if (cursection != section)

Should be
if (cursection != section ||
eccbyte >= mtd->ecclayout->eccbytes)

Will fix that too.

> + return -ERANGE;
> +
> + oobecc->length = length + 1;
> + oobecc->offset = eccpos - length;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(mtd_ooblayout_ecc);

--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering