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

Alexander Holler holler at ahsoftware.de
Sun Nov 9 10:09:22 PST 2014

Am 09.11.2014 13:34, schrieb Nikolay Dimitrov:
> Hi Alexander,
> The eFuses are lockable. If you don't intend to further modify their
> value after proper programming, you should lock them. If you don't do
> so, you shouldn't blame the Linux driver for the consequences.
> Crippling the IMX OTP driver doesn't solve the system security issues.
> I can write to the IMX physical memory (e.g. to program OCOTP
> registers) without this Linux driver at all, I just need proper
> privileges and the devregs tool (thanks Eric & Troy!).
> I have just like you some imx6 hobby boards. If one of them is bricked,
> it's totally my fault. And yet we have hundreds of thousands of imx6
> boards on the road, which we locked during manufacturing, and disabled
> the OTP driver, so it's impossible to brick them via OTP.

First let me quote again the sentence from the reference manual you 
missed to quote:

"In order to avoid "rogue" code performing erroneous writes to OTP, a 
special unlocking sequence is required for writes to the fuse banks."

To conclude, you are saying:

- The (easy) write functionalty of the driver should be kept because
   it's of no use on locked devices anyway.

- Unlocked devices ("hobby boards", whatever that is) are second class
   devices where it's the owners fault if some malware, wrong script,
   typo or similiar writes to some file in the sysfs.

- The way to write to the OTP offered by the driver is the same as the
   way offered by the HW, which means the more complicated way
   implemented in the HW (which, by the way, is still in effect when
   using devregs) is senseless.


 > To me it seems that the current state of affairs is already perfectly
 > OK and there's no need to panic.

So revealing and trying to fix bugs nowadays means panicking?

I thought it's still part of the normal software development process.
Maybe I really have become oldschool and better get a towel.

Anyway, as I'm running out of hope and polite arguments (at least in
regard to this topic) and getting near to the point of using sentences
Linus has unfortunately become famous for, I better stop to comment

Alexander Holler

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