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

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Message-ID: <9F46D75C-D00D-4577-A337-7411049EC7D9@walle.cc>
Date:   Sat, 03 Jul 2021 18:08:38 +0200
From:   Michael Walle <michael@...le.cc>
To:     Tudor.Ambarus@...rochip.com, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org
CC:     miquel.raynal@...tlin.com, richard@....at, vigneshr@...com,
        linux@...ck-us.net
Subject: Re: [PATCH] mtd: core: handle flashes without OTP gracefully

Am 3. Juli 2021 11:56:14 MESZ schrieb Tudor.Ambarus@...rochip.com:
>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?

I don't know. But I certainly won't touch that code :p

>> 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@...ck-us.net>
>> Signed-off-by: Michael Walle <michael@...le.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.

you mean already checking ENODATA in mtd_otp_size() and return 0. That would also make the hunk below unnecessary. I'll change it. 

-michael

>
>
>> +                       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
>> 
>> 
>> ______________________________________________________
>> Linux MTD discussion mailing list
>> http://lists.infradead.org/mailman/listinfo/linux-mtd/
>> 

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