2021-07-02 09:40:05

by Michael Walle

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

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
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 <[email protected]>
Signed-off-by: Michael Walle <[email protected]>
---
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)
+ 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

2021-07-02 13:51:39

by Guenter Roeck

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

On 7/2/21 2:38 AM, Michael Walle wrote:
> 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
> 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 <[email protected]>
> Signed-off-by: Michael Walle <[email protected]>

Tested-by: Guenter Roeck <[email protected]>

> ---
> 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)
> + 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;
> }
>

2021-07-02 13:54:37

by Michael Walle

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

Am 2021-07-02 15:49, schrieb Guenter Roeck:
> On 7/2/21 2:38 AM, Michael Walle wrote:
>> 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
>> 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 <[email protected]>
>> Signed-off-by: Michael Walle <[email protected]>
>
> Tested-by: Guenter Roeck <[email protected]>

Thanks for confirming, and sorry for the inconvenience.

-michael

2021-07-03 09:58:13

by Tudor Ambarus

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

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 <[email protected]>
> Signed-off-by: Michael Walle <[email protected]>
> ---
> 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
>
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
>

2021-07-03 16:26:59

by Michael Walle

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

Am 3. Juli 2021 11:56:14 MESZ schrieb [email protected]:
>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 <[email protected]>
>> Signed-off-by: Michael Walle <[email protected]>
>> ---
>> 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/
>>

2021-07-03 16:45:16

by Tudor Ambarus

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

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 [email protected]:
>> 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 <[email protected]>
>>> Signed-off-by: Michael Walle <[email protected]>
>>> ---
>>> 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
>>>
>>>
>>> ______________________________________________________
>>> Linux MTD discussion mailing list
>>> http://lists.infradead.org/mailman/listinfo/linux-mtd/
>>>
>

2021-07-03 17:27:41

by Guenter Roeck

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

On 7/3/21 9:42 AM, [email protected] wrote:
> 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 [email protected]:
>>> 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 <[email protected]>
>>>> Signed-off-by: Michael Walle <[email protected]>
>>>> ---
>>>> 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;
>

There are various places where this is called, including code returning information
to userspace. That means you'd be changing the ABI to userspace which would now suddenly
return 0 instead of -ENODATA.

Guenter

2021-07-06 16:31:08

by Miquel Raynal

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

Hi Guenter,

Guenter Roeck <[email protected]> wrote on Sat, 3 Jul 2021 10:26:06
-0700:

> On 7/3/21 9:42 AM, [email protected] wrote:
> > 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 [email protected]:
> >>> 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 <[email protected]>
> >>>> Signed-off-by: Michael Walle <[email protected]>
> >>>> ---
> >>>> 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;
> >
>
> There are various places where this is called, including code returning information
> to userspace. That means you'd be changing the ABI to userspace which would now suddenly
> return 0 instead of -ENODATA.

Yeah let's avoid this if possible, even though I liked Tudor's approach.

Would Michael proposal of checking it in mtd_otp_size() still affect
userspace? If not, having a single check over the -ENODATA return code
seems attractive.

Thanks,
Miquèl

2021-07-06 18:24:03

by Guenter Roeck

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

On 7/6/21 9:29 AM, Miquel Raynal wrote:
> Hi Guenter,
>
> Guenter Roeck <[email protected]> wrote on Sat, 3 Jul 2021 10:26:06
> -0700:
>
>> On 7/3/21 9:42 AM, [email protected] wrote:
>>> 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 [email protected]:
>>>>> 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 <[email protected]>
>>>>>> Signed-off-by: Michael Walle <[email protected]>
>>>>>> ---
>>>>>> 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;
>>>
>>
>> There are various places where this is called, including code returning information
>> to userspace. That means you'd be changing the ABI to userspace which would now suddenly
>> return 0 instead of -ENODATA.
>
> Yeah let's avoid this if possible, even though I liked Tudor's approach.
>
> Would Michael proposal of checking it in mtd_otp_size() still affect
> userspace? If not, having a single check over the -ENODATA return code
> seems attractive.
>

The check in mtd_otp_nvmem_add() does not affect userspace.

Guenter