[U-Boot] a few questions about saving bootcount in the environment

[Tom Rini]

On Mon, Jul 25, 2016 at 06:57:21AM +0200, Wolfgang Denk wrote:
> Dear Robert,
> 
> In message <alpine.LFD.2.20.1607231318540.16761 at localhost.localdomain> you wrote:
> > 
> > so this tells me that there's not a whole lot of that feature being
> > used, so i won't spend much time on it.
> 
> Right, it is only a last resort when you cannot find any better place
> to storeit (in a hardware register that survives resets).

That's not strictly true.  One of the things I noticed recently is that
Mender uses bootcount, in environment, as a least common denominator.
And thrown in a file in a filesystem, in so far as you trust the
underlying black box to be good about reads/writes and wear levelling,
it's robust enough (for certain values of robust and enough).  We're
dipping into one of those areas where experts have varying opinions on
what's good enough, hence all the qualifiers.  But it is a useful
option.  And neatly circumvents the need for a "driver" to clear the
count too.

[snip]
> > now, i can see where one wants to reset "bootcount" to zero once you
> > boot successfully, but why would you also set "upgrade_available" to
> > zero? don't you want to keep using that feature when you boot in the
> > future?
> 
> --> Heiko ?

Heiko wrote a kernel driver, for the non-env side of things at least at
one point, and the DT bindings didn't get approved.  I picked it up
years ago, tried, and had different DT binding approval problems and
never cycled back to it while I was at TI playing with that kind of
stuff.  Which is why the bootcount in env side of things is so
attractive, it's just fw_setenv/printenv once you're happy with your
system boot.

-- 
Tom
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