[meta-freescale] [PATCH 0/1] arm: imx: fsl_otp: make fuses (OTP memory) read-only

[Otavio Salvador]

Hello Alexander,

On Fri, Nov 7, 2014 at 1:23 PM, Alexander Holler <holler at ahsoftware.de> wrote:
> Am 07.11.2014 16:07, schrieb Otavio Salvador:
>>
>> On Fri, Nov 7, 2014 at 1:04 PM, Eric Bénard <eric at eukrea.com> wrote:
>>>
>>> Hi Jon,
>>>
>>> Le Fri, 7 Nov 2014 15:31:15 +0100,
>>> Jon Nettleton <jon.nettleton at gmail.com> a écrit :
>>>>
>>>> Fair enough.  Can we all agree that it should default to disabled?
>>>
>>>
>>> On your product sure, on the evaluation board that's more questionable.
>>>
>>> When an evaluation board's user reach this sysfs entries to do a write
>>> to it I believe that's not a random choice but a user's choice.
>>>
>>> Maybe adding a otp_unlock entry to the sysfs before allowing write could
>>> secure more the feature when running on the evaluation boards so that
>>> the user can think twice before writing to the fuses.
>>
>>
>> I like Eric's idea of the unlock sysfs entry for this purpose.
>
>
> Maybe I should mention that this extremly dangerous driver already was
> posted for submission into the (production) kernel and nobody had a problem
> with it's write functionality, just with some other stuff.
>
> And even if it's ok for FSL to promote this feature with their BSP, I have
> absolutely no love for the way it was done. It now is likely part of many
> production kernels, something never should have happened.
>
> And I still see absolutely no need to have some one time functionality as
> part of the kernel, regardless how usefull it might be for some developers.
> It's a waste of time and resources to include that write functionality in
> something meant for the greater public. Especially something that dangerous.

We have two different things here.

 * Linux support: the driver is perfectly capable of handling the
reading and writing
 * Driver settings: We should, indeed, have it to be explicitly
enabled on the kernel config to allow writing

This is done in other areas of kernel (one which comes to my mind is
NTFS Writing support) and what I proposed was you to make:

CONFIG_FSL_OTP -> read-only
CONFIG_FSL_OTP_WRITE -> write support

The write support needs to be enabled on mfgtools defconfig and
disabled on regular kernels (this is what I think it should be but it
is up to the board maintainer).

-- 
Otavio Salvador                             O.S. Systems
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