[U-Boot] [PATCH v6 04/31] mtd: Fallback to ->_read/write() when ->_read/write_oob() is missing

[Boris Brezillon]

On Thu, 16 Aug 2018 17:30:02 +0200
Miquel Raynal <miquel.raynal at bootlin.com> wrote:

> Some MTD sublayers/drivers are implementing ->_read/write() and
> not ->_read/write_oob().
> 
> While for NAND devices both are usually valid, for NOR devices, using
> the _oob variant has no real meaning. But, as the MTD layer is supposed
> to hide as much as possible the flash complexity to the user, there is
> no reason to error out while it is just a matter of rewritting things
> internally.
> 
> Add a fallback on mtd->_read() (resp. mtd->_write()) when the user calls
> mtd_read_oob() (resp. mtd_write_oob()) while mtd->_read_oob() (resp.
> mtd->_write_oob) is not implemented. There is already a fallback on the
> _oob variant if the former is used.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>

Reviewed-by: Boris Brezillon <boris.brezillon at bootlin.com>

> ---
>  drivers/mtd/mtdcore.c | 26 ++++++++++++++++++++------
>  1 file changed, 20 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> index 9a3efe95df..fb1d68d5e2 100644
> --- a/drivers/mtd/mtdcore.c
> +++ b/drivers/mtd/mtdcore.c
> @@ -1047,20 +1047,27 @@ int mtd_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
>  {
>  	int ret_code;
>  	ops->retlen = ops->oobretlen = 0;
> -	if (!mtd->_read_oob)
> -		return -EOPNOTSUPP;
>  
>  	ret_code = mtd_check_oob_ops(mtd, from, ops);
>  	if (ret_code)
>  		return ret_code;
>  
> +	/* Check the validity of a potential fallback on mtd->_read */
> +	if (!mtd->_read_oob && (!mtd->_read || ops->oobbuf))
> +		return -EOPNOTSUPP;
> +
> +	if (mtd->_read_oob)
> +		ret_code = mtd->_read_oob(mtd, from, ops);
> +	else
> +		ret_code = mtd->_read(mtd, from, ops->len, &ops->retlen,
> +				      ops->datbuf);
> +
>  	/*
>  	 * In cases where ops->datbuf != NULL, mtd->_read_oob() has semantics
>  	 * similar to mtd->_read(), returning a non-negative integer
>  	 * representing max bitflips. In other cases, mtd->_read_oob() may
>  	 * return -EUCLEAN. In all cases, perform similar logic to mtd_read().
>  	 */
> -	ret_code = mtd->_read_oob(mtd, from, ops);
>  	if (unlikely(ret_code < 0))
>  		return ret_code;
>  	if (mtd->ecc_strength == 0)
> @@ -1075,8 +1082,7 @@ int mtd_write_oob(struct mtd_info *mtd, loff_t to,
>  	int ret;
>  
>  	ops->retlen = ops->oobretlen = 0;
> -	if (!mtd->_write_oob)
> -		return -EOPNOTSUPP;
> +
>  	if (!(mtd->flags & MTD_WRITEABLE))
>  		return -EROFS;
>  
> @@ -1084,7 +1090,15 @@ int mtd_write_oob(struct mtd_info *mtd, loff_t to,
>  	if (ret)
>  		return ret;
>  
> -	return mtd->_write_oob(mtd, to, ops);
> +	/* Check the validity of a potential fallback on mtd->_write */
> +	if (!mtd->_write_oob && (!mtd->_write || ops->oobbuf))
> +		return -EOPNOTSUPP;
> +
> +	if (mtd->_write_oob)
> +		return mtd->_write_oob(mtd, to, ops);
> +	else
> +		return mtd->_write(mtd, to, ops->len, &ops->retlen,
> +				   ops->datbuf);
>  }
>  EXPORT_SYMBOL_GPL(mtd_write_oob);
>