eeprom: Add support for get/set of vendor version

[wlindauer]

Bytes 158-159 are spec'd for customer overwritable version. Allow
getting and setting this version so it can be used in the future for
things like custom carrier board versions and revisions.

[madisongh]

Is that field really meant for a customer-specified version number? The couple of NVIDIA documents I've looked at just call the field "Version" and specify all-zeroes as a value, which is why I assumed it represented a version of the layout. Do you have a reference for this somewhere?

[wlindauer]

I was going off of this link:
https://docs.nvidia.com/jetson/archives/l4t-archived/l4t-3231/index.html#page/Tegra%20Linux%20Driver%20Package%20Development%20Guide/jetson_eeprom_layout.html

Where it lists this version under the heading: "Customer Overwritable Section" along with the vendor MAC address.

The cboot source code also seems to reference this field with the name "cust_ver" which I assumed to be customer version.

[Lexmark-chad]

@wlindauer, I think @madisongh is correct. I would have interpreted it the same way in that the version represents the layout of the "Customer Overwritable Section".

[wlindauer]

Even if this field is for some kind of layout version (which I think the first version field in the eeprom is for and not this one), shouldn't this field still be writable by the end user? Am I not allowed to specify what version my layout is? If Nvidia didn't intend for it to be writable by the end user, then why is it in the customer over-writable section?

[Lexmark-chad]

I don't think they intended the "customer overwritable" to be "customer writable" in the sense that the vendor could write anything they wanted to in that region. I'm guessing they allow selected over-rides of certain values (like MAC addresses) and NVIDIA controls exactly what those will be. That's my interpretation anyway... But, good point about the eeprom version. Seems redundant to have another version for just that section. You can post into their forums to get a definitive answer on intent.