Re: Adding OTP-only device to MTD or CHAR subsystem?

From	Scott Branden <sbranden@broadcom.com>
Newsgroups	linux.kernel
Subject	Re: Adding OTP-only device to MTD or CHAR subsystem?
Date	2015-12-29 01:40 +0100
Message-ID	<qKQut-1c8-9@gated-at.bofh.it> (permalink)
References	<qKPoK-vG-11@gated-at.bofh.it> <qKPyq-zX-19@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

+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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

Adding OTP-only device to MTD or CHAR subsystem? Scott Branden <sbranden@broadcom.com> - 2015-12-29 00:30 +0100
  Re: Adding OTP-only device to MTD or CHAR subsystem? Arnd Bergmann <arnd@arndb.de> - 2015-12-29 00:40 +0100
    Re: Adding OTP-only device to MTD or CHAR subsystem? Scott Branden <sbranden@broadcom.com> - 2015-12-29 01:40 +0100

csiph-web