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

[Stephen Warren <swarren@wwwdotorg.org>]

On 08/06/2013 10:18 AM, Otavio Salvador wrote:
> On Tue, Aug 6, 2013 at 12:50 PM, Stephen Warren <swarren@wwwdotorg.org> wrote:
>> On 08/06/2013 05:37 AM, Wolfgang Denk wrote:
>>> Dear Rob Herring,
>>>
>>> In message <CAL_JsqJTg4CVfk0o9hLd4ZVksj+DNEsKLjcv6T7-6F-=BR+J+Q@mail.gmail.com> you wrote:
>>>>
>>>>> Why would you ever want to compile this into U-Boot at all?  Then any
>>>>> changes you need to make mean compiling and installing a new U-Boot,
>>>>> which is something you normally don't want to do.
>>>>
>>>> You may want to have factory default and "user" settings. Building in
>>>> the factory settings would be one way to accomplish that.
>>>
>>> No. Handling these independently, outside of the compiled U-Boot image
>>> is as easy, and much more flexible.
>>>
>>>>> U-Boot is perfectly able to import such settings from text files (or
>>>>> text blobs stored somewhere, even attached to the U-Boot image, if you
>>>>> want), so just use the text files separately, instead of hard
>>>>> compiling them into the code.
>>>>
>>>> In my case, I don't want to compile the environment into u-boot. But
>>>> some people do as I copied my scripts from Tegra which has them
>>>> built-in.
>>
>> We have the *default* environment built-in, which is used when no valid
>> environment is found in flash. If there's an environment in flash, it
>> gets used rather than the built-in default.
> 
> How can someone 'overwrite' the default environment from system or
> when generating a FIT image?

If U-Boot is running, you can get back to the default environment by
running exactly the commands you wrote below.

If you're flashing U-Boot, you could force it to use the default
environment when it boots by erasing/corrupting the copy of the
environment that's stored in flash (or wherever ENV_IS points) at the
same time that you flash the new U-Boot binary.

The question of how to get the default environment when generating a FIT
image doesn't make sense; generating a FIT image of something (kernel,
initrd, DTB?) is entirely unrelated to the environment content that
U-Boot uses when running.

> I am interested in let my customers to revert back to a sane default running:
> 
> env -f -d -a
> saveenv