Re: [PATCH v3] mtd: limit OTP NVMEM Cell parse to non Nand devices

[Rafał Miłecki]

On 22.03.2024 05:09, Christian Marangi wrote:
> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> index 5887feb347a4..0de87bc63840 100644
> --- a/drivers/mtd/mtdcore.c
> +++ b/drivers/mtd/mtdcore.c
> @@ -900,7 +900,7 @@ static struct nvmem_device *mtd_otp_nvmem_register(struct mtd_info *mtd,
>   	config.name = compatible;
>   	config.id = NVMEM_DEVID_AUTO;
>   	config.owner = THIS_MODULE;
> -	config.add_legacy_fixed_of_cells = true;
> +	config.add_legacy_fixed_of_cells = !mtd_type_is_nand(mtd);
>   	config.type = NVMEM_TYPE_OTP;
>   	config.root_only = true;
>   	config.ignore_wp = true;

I think there may be even more unwanted behaviour here. If
mtd_otp_nvmem_register() fails to find node with "user-otp" /
"factory-otp" compatible then it sets "config.of_node" to NULL but that
means NVMEM core still looks for NVMEM cells in device's "of_node".

I believe we should not look for OTP NVMEM cells out of the "user-otp" /
"factory-otp" compatible nodes.

So maybe what we need in the first place is just:
config.add_legacy_fixed_of_cells = !!np;
?

Any extra limitation of .add_legacy_fixed_of_cells should probably be
used only if we want to prevent new users of the legacy syntax. The
problem is that mtd.yaml binding allowed "user-otp" and "factory-otp"
with old syntax cells. It means every MTD device was allowed to have
them.

No in-kernel DTS even used "user-otp" or "factory-otp" with NVMEM legacy
cells but I'm not sure about downstream DTS files. Ideally we would do
config.add_legacy_fixed_of_cells = false;
but that could break compatibility with some downstream DTS files.