Adding OTP-only device to MTD or CHAR subsystem?
Scott Branden
sbranden at broadcom.com
Mon Dec 28 16:32:48 PST 2015
+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
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