Greg/Brian/Arnd,
We have OTP device drivers for accessing OTP memory in our SoCs.
I looking for the right place and model to place such OTP device drivers.
1) Should we follow the bfin-otp model in drivers/char? This doesn't
seem like the right place to put it although following the bfin example
is quite simple to implement. We actually had a custom set of Ioctl's
that I changed to use the standard file access model used by the bfin
driver. But a custom util is still needed to issue an OTPLOCK command.
I'm guess mtd-utils has such abilities (or should).
2) Instead, should we start adding OTP-only drivers into the MTD
subsystem? Onenand and CFI based MTD devices already have OTP
programmable regions. If we created a new OTP device type in the MTD
subsystem this looks like a good thing to do. mtd-utils could/should be
used to access the OTP device then along with standard fileio operations.
3) Or some other suggestion of where to place OTP device drivers?
Regards,
Scott
On Monday 28 December 2015 15:21:08 Scott Branden wrote:
> Greg/Brian/Arnd,
>
> We have OTP device drivers for accessing OTP memory in our SoCs.
>
> I looking for the right place and model to place such OTP device drivers.
>
> 1) Should we follow the bfin-otp model in drivers/char? This doesn't
> seem like the right place to put it although following the bfin example
> is quite simple to implement. We actually had a custom set of Ioctl's
> that I changed to use the standard file access model used by the bfin
> driver. But a custom util is still needed to issue an OTPLOCK command.
> I'm guess mtd-utils has such abilities (or should).
>
> 2) Instead, should we start adding OTP-only drivers into the MTD
> subsystem? Onenand and CFI based MTD devices already have OTP
> programmable regions. If we created a new OTP device type in the MTD
> subsystem this looks like a good thing to do. mtd-utils could/should be
> used to access the OTP device then along with standard fileio operations.
>
> 3) Or some other suggestion of where to place OTP device drivers?
I think drivers/nvmem is now the right place for this.
Arnd
+Srinivas/Maxime
On 15-12-28 03:38 PM, Arnd Bergmann wrote:
> On Monday 28 December 2015 15:21:08 Scott Branden wrote:
>> Greg/Brian/Arnd,
>>
>> We have OTP device drivers for accessing OTP memory in our SoCs.
>>
>> I looking for the right place and model to place such OTP device drivers.
>>
>> 1) Should we follow the bfin-otp model in drivers/char? This doesn't
>> seem like the right place to put it although following the bfin example
>> is quite simple to implement. We actually had a custom set of Ioctl's
>> that I changed to use the standard file access model used by the bfin
>> driver. But a custom util is still needed to issue an OTPLOCK command.
>> I'm guess mtd-utils has such abilities (or should).
>>
>> 2) Instead, should we start adding OTP-only drivers into the MTD
>> subsystem? Onenand and CFI based MTD devices already have OTP
>> programmable regions. If we created a new OTP device type in the MTD
>> subsystem this looks like a good thing to do. mtd-utils could/should be
>> used to access the OTP device then along with standard fileio operations.
>>
>> 3) Or some other suggestion of where to place OTP device drivers?
>
> I think drivers/nvmem is now the right place for this.
Thanks for the pointer Arnd. Too bad an extension wasn't added in MTD
but at least there is some sort of a model in place now. The mtd-abi.h
would have been a good thing to use for OTPLOCK as well as the remainder
of the functionality in MTD OTP. The mapping of nvmem to properties to
user settings seems like a useful feature though.
Hi Srinivas/Maxime,
The nvmem drivers don't seem to support row unlocking of OTP. Having
raw write access to the OTP is not a desirable feature. Are there plans
in place to add any additional functionality to the nvm driver model
right now?
>
> Arnd
>
Regards,
Scott