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

[Andreas Pretzsch]

Am Montag, den 11.04.2011, 21:31 +0200 schrieb 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.

Or simply not to waste flash when having a few small sectors.

> 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.

ACK. The most obvious and simple approach for this scenario. And
rewriting the environment during an U-Boot update doesn't hurt that much
either, the possible window of data loss is reasonably small.


-- 

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