[U-Boot] Read-only env variables

[Joe Hershberger]

Hi u-boot,

I see u-boot supports readonly serial# and ethaddr, but I have a few
other variables that I need to be read-only.  I'm planning to
implement a generic list of variables that cannot be changed or
deleted.

I'm interested to know what sort of specification people would find
most appropriate.  My current thought is to follow the same delimiter
as the env itself, i.e. null separated list with double null
terminator.  This list would then be defined in the board config
header.  It also seems that you should be able to specify simple
access rules for each variable name perhaps using "=<val>" after each
var name where <val> could have constants (probably numbers for
performance, but could be string literals) to define modes.  Right now
I'm thinking read-only, create-only, change-default, and change-only
(i.e no delete) are the modes that make sense.

I'm also interested if anyone would be opposed to simply using this
new specification of readonly vars to implement the serial# and
ethaddr protection.  The CONFIG_HAS_UID is a bit odd... should that be
available in general for read-only vars?

Comments?

Thanks,
-Joe