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

[<Tudor.Ambarus@microchip.com>]

On 7/3/21 7:08 PM, Michael Walle wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Am 3. Juli 2021 11:56:14 MESZ schrieb Tudor.Ambarus@microchip.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

why? :D

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

I've thought about:

diff --git a/drivers/mtd/chips/cfi_cmdset_0001.c b/drivers/mtd/chips/cfi_cmdset_0001.c
index 54f92d09d9cf..9419b33d7238 100644
--- a/drivers/mtd/chips/cfi_cmdset_0001.c
+++ b/drivers/mtd/chips/cfi_cmdset_0001.c
@@ -2314,7 +2314,7 @@ static int cfi_intelext_otp_walk(struct mtd_info *mtd, loff_t from, size_t len,
 
        /* Check that we actually have some OTP registers */
        if (!extp || !(extp->FeatureSupport & 64) || !extp->NumProtectionFields)
-               return -ENODATA;
+               return 0;

> 
> -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
>>>
>>>
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>