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How to store a 256 bit key in /sys/fsl_otp/HW_OCOTP_HDCP_KEY*

Question asked by Davis Roman on Dec 2, 2014
Latest reply on Dec 3, 2014 by Yuri Muhin



Our product currently uses a i.mx6solo and I have been asked to store a 256 bit key in the i.mx6 fuses.


In userspace, i see that there is an interface for accessing these fuses via /sys/fsl_otp,


More important, I see that there are a bunch of fields ( HW_OCOTP_HDCP_KEY* ) available.


I was reading about these fuses in the reference manual and they seems to be related to digital rights management.


Since we’re not using this feature in our product, my belief is that we should be able to store our key in these fuses.


( Even if we have to split up this 256 bit key into multiple fields would be ok too )


However, if I echo a value into one of these fuses, the value doesn't persist across reboot.


In fact, I'm not able to cat any of the values from any fuses. (Perhaps this occurs because I'm performing an illegal write, I'm not sure.)

Any suggestions?


P.S. burning the fuses via u-boot or the freescale manufacturing tool is not an option. It would have to be via the userspace /sys/fsl_otp interface.