[U-Boot] [PATCH] wandboard: add pxe support, set default boot command like highbank

[Wolfgang Denk]

Dear Tom,

In message <20130804214743.GJ5164 at bill-the-cat> you wrote:
> 
> > I am not that pessimistic.  The tools are all available and in place.
> > "env import" (and other capabilities of the "env" command) allow to
> > import any set of environment from any storage location U-Boot can
> > handle.  This allows to implement all kind of fancy features, like
> > "user profiles", "reset to factory defaults", etc. etc.  Of course it
> > also allows to implement settings needed to support booting of a
> > standard distribution.
> 
> How far back do we have an env import command available to all, is one
> the questions. ...

The support for this was added with commit ea882ba "New implementation
for internal handling of environment variables." on Sun Jun 20, 2010,
i. e. more than 2 years ago.

That's a long time, actually.

>            ...  I hadn't thought about saying part of the solution is
> that distros should provide an environment file to import (and if
> applicable, saveenv'ing after).  But what I mean is that we have a half
> dozen (it feels like) semi-flexible environments different boards/socs
> compile in, and it's not easy to share those.  One of the requests is a
> "sane" default boot command, and we do have a number of boards out there
> without a savable environment.

Requests for a "sane" environment are comprehensible.  However, it
will be difficult to reach an agreement what exactly "sane" means
here.  For example, I have never been able to get accustomed to all
the uEnv.txt, user.txt etc. scripts used with a number of boards; for
me, all this seems way too complicated and inflexible, and I always
try to get rid of this stuff.  I'm aware that other people like the
approach.  OK - I see no problems with that: TIMTOWTDI.

I would only have a problem (and a serious one) if such an approach
became standard, or even mandatory.  Not to mention a large number of
projects I know of.

> > You mean, as an external tool, to translate extlinux.conf into a set
> > of U-Boot commands?
> 
> No, I mean as a run-time command in u-boot to, given a pointer to
> extlinux.conf in memory, translate to a set of boot commands.  The use
> case here is that user installs (via package manager) a new kernel and
> just like on your desktop you can chose to boot it, easily enough.

Can we not rather do the translation on the host side, so we don;t
have to add both the code and the runtime overhead for each boot
process?

> > Define "reference platform"?   Do you think, for example, systems in
> > the class of TI's AM1808 or Freescale's i.MX28 are adequate targets to
> > run Fedora?  Does Fedora actually support any targets below ARMv7 ?
> 
> Fedora (and Ubuntu) don't officialy support sub-v7 platforms but that
> hasn't deterred the RPi community from making it happen all the same.
> But yes, AM1808 and i.MX28 and anything else with community support, IOs
> and upstream support is quite useful for maker folks (again, see RPi).
> Debian, iirc, still supports ARMv5 out of the box, and I'm sure anything
> that makes "Just Working" out of the box would be welcome in
> OpenEmbedded/Yocto-land.

Well, OE and Yocto allow to build fine-tuned target environments; they
really don't have any new requirements as "standard" distros like
Fedroa do.

> I'm going to (in a while) hop on the other thread Dennis started and
> cross-posted to the cross-distro list, but I firmly believe an opt-in
> set of defaults that let distros have to care less about board specifics
> is important.

Of course, I agree here.  But as I meantioned before, we should not
try to solve all problems inside U-Boot only.  The ARM kernel itself
is still undergoing a lot of changes, and a number of issus could be
solved in this environment, too.  It's a real pity that distro makes
appear to have much more influence there than any of the many embedded
vendors.

Best regards,

Wolfgang Denk

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