[U-Boot] Extract data file from U-Boot image

[Guilherme Maciel Ferreira]

Dear Wolfgang,

2013/7/25 Wolfgang Denk <wd at denx.de>:
> Dear Guilherme Maciel Ferreira,
>
> In message <CAF=5bWftE3UwPrOH+q+JPm-ag0igmAr_G4s=kLzhSObNhN=YyA at mail.gmail.com> you wrote:
>>
>> I made a patch to allow mkimage to extract files from images, which
>> just works for multi-file image. But, the fact that nobody has ever
>> done this means that this feature is not desired in the tool?
>
> Speaking just for myself: I needed such features only in very rare
> occasions, where it was way faster to use a one-liner on the command
> line than to write any actual code.
>
> YMMV...
>
> But I fear that mkimage explodes from creaping featurism, so if you
> go and implement something like this, please do not add it to kmimage,
> but rather create a separate, new tool, say "dumpimage" or so.

How does 'unimage' sound to you? =) Following the example of
unsquashfs and unubi?

I mean, if people really consider this tool of some use.

>
>> IMHO, it is very convenient to have a C code to do that, specially for
>> embedded systems where scripting is noticeably slower than binary
>> code. Besides it requires 'dd' to extract and another tool to parse
>> file's offsets inside the image.
>
> Well, when I was doing such things, I never did this on the embedded
> targets, nor did I ever have to care about performance because I
> always needed it just once or twice.
>
> Could you please be so kind and feed my curiousity a bit: what exactly
> are you doing that you need such a feature on the target?  I can't
> think of useful applications at the moment...

Well, I'm not allowed to say much, but broadly speaking it's intended
for a less intrusive firmware upgrade.

Today, in order to upgrade the firmware, the device receives a
Multifile image composed by a new kernel and a new root file system
and overwrite both of them. Which requires the device to hang for a
moment.

However, now we want a selective upgrade, where we can pick a few
directories from within the new root file system without the need to
write the whole new file system and kernel.

Best regards,

-- 
Guilherme Maciel Ferreira
Mobile Brazil: +55 48 9904 3728 e +55 48 9134 4651
Site: http://guilhermemacielferreira.com/
Skype: guilherme.maciel.ferreira