[U-Boot] zImage on ARM

["Loïc Minier" <lool@dooz.org>]

On Wed, Sep 08, 2010, Wolfgang Denk wrote:
> zImage does not contain any visible information about what it is,
> when it was build, etc. It is not checksum protected so you cannot
> verify if the image you just downloaded is good enough to erase what
> you have in flash, etc. etc.

 These are indeed nice features of uImages (checksums +
 build date information); but they are not needed in all use cases for
 U-Boot.  Distributions are shipping zImage for ARM nowadays and when
 shipping zImage files withing packages (.deb for instance), there are
 already checksums, file timestamps, public build logs etc. as part of
 the distro toolkit.
   Also, this means end-user systems need mkimage installed (because
 uImage differ slightly across boards).  Not a problem for an embedded
 developer obviously, but would prefer avoiding this need on an end-user
 system.

 (Nitpick: if you want an accurate time for the kernel build, them this
 should rather be recorded during the upstream linux kernel build rather
 than at the time the uImage is created, which could be quite some time
 later!)

> >  Seems zImage is quite widespread now; would it make sense to allow
> >  builing u-boot without that code and rely on the kernel code to unpack?
> Why duplicating the stuff again and again and again?

 Well, I'm proposing skipping one copy   ;-)   the U-Boot one

> >  Or should u-boot just gain a new image type for zImage?
> Why not use uImage like we do with other architectures? 
> Why is it that ARM always has to try to reinvent the wheels?

 Eh, zImage has been around for a while!

 I guess it's just that we don't /need/ the couple extra uImage
 features, and would rather ship zImage directly.

 It would also remove the need for maintaining the table of magic values
 for uImage / uInitrd generation; a problem I described recently on
 another list:
 http://lists.linaro.org/pipermail/linaro-dev/2010-August/000493.html

 So we'd be happy if you'd take patches to have U-Boot accept this
 "dumber" format.

   Cheers,
-- 
Lo?c Minier