[U-Boot] [RFC] skip area in flash/memory commands (cp, cmp, ...)

[Albert ARIBAUD]

Le 11/04/2011 20:52, Andreas Pretzsch a écrit :
> Objective: Skip an area in memory commands
>
> Example use case: Skip over embedded environment when updating U-Boot
>
> In case of an embedded environment, a complete U-Boot binary consists of
> two code sections and an environment block in between. In an update flow
> tftp/erase/cp/cmp conveniently using the complete image, the environment
> is also overwritten. As the env might contain device specific data, this
> is not always desirable.
> Of course, one could overcome this with several approaches, e.g.
>    - provide two distinct U-Boot parts on the tftp server
>    - load the complete image and erase/cp/cmp only the desired parts,
>      either via hardcoded addresses and sizes or via some setexpr magic
>    - other ways I simply missed
>
> While this is sufficent, I'd find it handy to be able to skip an area in
> the above commands.
> Possible approaches:
>    - explicit via additional parameters to cp, cmp, etc.
>    - implicit for the embedded environment (confusing and less generic)
>    - based on e.g. some skip_addr, skip_len environment variables or
>      even sets (addr1,addr2 + len1,len2)
>
> There might be other use cases I didn't thought of by now. Also, the
> command list is probably not complete.
>
> What do you think, worth the effort, acceptable in mainline or
> over-engineering ?

Over-engineering IMO.

There is a reason why a board defines its environment as embedded, and 
it is because it wants it applied when flashing a new U-Boot.

But if you really want to keep the existing embedded environment when 
flashing a new U-Boot, then after you have loaded the new U-Boot in RAM 
as usual, all you need is to overwrite its environment with the one 
already in Flash with a single, standard, cp.b instruction. After that 
you can erase Flash and copy from RAM to Flash as usual.

Amicalement,
-- 
Albert.