Re: [PATCH] mtd: core: handle flashes without OTP gracefully

From: <Tudor.Ambarus@microchip.com>
To: <michael@walle.cc>, <linux-mtd@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>
Cc: <miquel.raynal@bootlin.com>, <richard@nod.at>, <vigneshr@ti.com>,
	<linux@roeck-us.net>
Subject: Re: [PATCH] mtd: core: handle flashes without OTP gracefully
Date: Sat, 3 Jul 2021 09:56:14 +0000	[thread overview]
Message-ID: <9bb2acac-aeb8-d2b2-8df0-9acfd972ec5d@microchip.com> (raw)
In-Reply-To: <20210702093841.32307-1-michael@walle.cc>

On 7/2/21 12:38 PM, Michael Walle wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> There are flash drivers which registers the OTP callbacks although the
> flash doesn't support OTP regions and return -ENODATA for these
> callbacks if there is no OTP. If this happens, the probe of the whole

why do they register the OTP callback if they don't support OTP?

> flash will fail. Fix it by handling the ENODATA return code and skip
> the OTP region nvmem setup.
> 
> Fixes: 4b361cfa8624 ("mtd: core: add OTP nvmem provider support")
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Signed-off-by: Michael Walle <michael@walle.cc>
> ---
>  drivers/mtd/mtdcore.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> index b5ccd3037788..6881d1423dd6 100644
> --- a/drivers/mtd/mtdcore.c
> +++ b/drivers/mtd/mtdcore.c
> @@ -880,7 +880,10 @@ static int mtd_otp_nvmem_add(struct mtd_info *mtd)
> 
>         if (mtd->_get_user_prot_info && mtd->_read_user_prot_reg) {
>                 size = mtd_otp_size(mtd, true);
> -               if (size < 0)
> +               /* ENODATA means there is no OTP region */
> +               if (size == -ENODATA)

If no OTP data, maybe it's more appropriate for the clients to just
return a retlen of 0.

> +                       size = 0;
> +               else if (size < 0)
>                         return size;
> 
>                 if (size > 0) {
> @@ -896,7 +899,10 @@ static int mtd_otp_nvmem_add(struct mtd_info *mtd)
> 
>         if (mtd->_get_fact_prot_info && mtd->_read_fact_prot_reg) {
>                 size = mtd_otp_size(mtd, false);
> -               if (size < 0) {
> +               /* ENODATA means there is no OTP region */
> +               if (size == -ENODATA) {
> +                       size = 0;
> +               } else if (size < 0) {
>                         err = size;
>                         goto err;
>                 }
> --
> 2.20.1
> 
> 
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