Re: [PATCH v2] mtd: fsl-quadspi: Distinguish the mtd device names

[Boris Brezillon <boris.brezillon@free-electrons.com>]

On Thu, 11 Jan 2018 11:15:04 -0200
Fabio Estevam <fabio.estevam@nxp.com> wrote:

> Currently on a imx6sx-sdb board, which has two SPI NOR chips connected
> to QSPI2 the following output from /proc/mtd is seen:
> 
> # cat /proc/mtd 
> dev:    size   erasesize  name
> mtd0: 01000000 00010000 "21e4000.qspi"
> mtd1: 01000000 00010000 "21e4000.qspi"
> 
> Attempts to partition them on the kernel command line result in both
> chips with identical (and identically named) partitions, which is
> an inconvenient behavior.
> 
> Assign a different mtd->name for each mtd device to avoid this problem.
> 
> After this change the output from /proc/mtd becomes:
> 
> # cat /proc/mtd 
> dev:    size   erasesize  name
> mtd0: 01000000 00010000 "21e4000.qspi-0"
> mtd1: 01000000 00010000 "21e4000.qspi-1"
> 
> Reported-by: David Wolfe <david.wolfe@nxp.com>
> Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
> ---
> Changes since v1:
> - Use 'spiflash_idx' for the variable name
> - Use the mtd->name in the format 21e4000.qspi-0
> - Do not assing the mtd name relying on the dts ordering and use the reg
> property instead
> - Call devm_kasprintf() after spi_nor_set_flash_node().
> 
>  drivers/mtd/spi-nor/fsl-quadspi.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/spi-nor/fsl-quadspi.c b/drivers/mtd/spi-nor/fsl-quadspi.c
> index 2901c7b..b28ad8b 100644
> --- a/drivers/mtd/spi-nor/fsl-quadspi.c
> +++ b/drivers/mtd/spi-nor/fsl-quadspi.c
> @@ -967,7 +967,7 @@ static int fsl_qspi_probe(struct platform_device *pdev)
>  	struct resource *res;
>  	struct spi_nor *nor;
>  	struct mtd_info *mtd;
> -	int ret, i = 0;
> +	int ret, i = 0, spiflash_idx;
>  
>  	q = devm_kzalloc(dev, sizeof(*q), GFP_KERNEL);
>  	if (!q)
> @@ -1051,6 +1051,22 @@ static int fsl_qspi_probe(struct platform_device *pdev)
>  		spi_nor_set_flash_node(nor, np);
>  		nor->priv = q;
>  
> +		ret = of_property_read_u32(np, "reg", &spiflash_idx);
> +		if (ret) {
> +			dev_err(dev, "could not get reg property: %d\n", ret);
> +			ret = -EINVAL;
> +			goto mutex_failed;

Was reg already mandatory before this commit? If it's not the case,
you're breaking backward compat.

> +		}

You can move the above block

> +
> +		if (!mtd->name) {

here.

> +			mtd->name = devm_kasprintf(dev, GFP_KERNEL, "%s-%d",
> +						   dev_name(dev), spiflash_idx);

By changing the name you're breaking existing users that pass
mtdparts=21e4000.qspi:<parts> :-(.

There's no easy solution for the problem you're trying to solve, but
maybe you can make reg optional, and if it's not present set
mtd->name to dev_name(dev).
And, you should complain when you have more than one child node and reg
is missing.

> +			if (!mtd->name) {
> +				ret = -ENOMEM;
> +				goto mutex_failed;
> +			}
> +		}
> +
>  		/* fill the hooks */
>  		nor->read_reg = fsl_qspi_read_reg;
>  		nor->write_reg = fsl_qspi_write_reg;