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Re: Providing (armhf) u-boot images together with d-i images?

On Wed, Dec 03, 2014 at 03:10:37PM -0800, Vagrant Cascadian wrote:

[providing u-boot images for armhf platforms that do not have
 u-boot in non-volatile storage]

> Simply extracting the relevent u-boot files doesn't seem like enough to
> me. They still need to be installed at particular offsets to the raw SD
> card, or in some cases, to a fat partition on the SD card, though may be
> fussy about exactly where on the fat partition it resides in a rather
> hair-pulling way... so providing just the binaries makes it a little
> easier, but not a whole lot.

I guess it would make sense to provide both the "naked" u-boot
binaries for people who want to manually write them to an SD card
that already contains a partition table without destroying it,
and an additional tiny disk image (<1MB) that contains u-boot at
the proper place (but nothing else, i.e. no partition table if
not needed for u-boot), which can be written with common disk
image handling tools.  The latter would make life a lot easier
for people setting up the installer from Windows for example.

> Providing complete u-boot images for each platform would be 19 images
> for jessie, though each one is fairly small (each between
> 0.5-1M). Though I don't think we've consolidated all documentation
> needed to generate all those platforms with the correct offsets (though
> many are all the same, such as sunxi).

I only know those for sunxi and i.MX6:

- sunxi:
  combined image (SPL + main image) at offset 8kB

- i.MX6:
  SPL at offet 1kB
  main image at offset 42kB

@debian-arm: Could somebody provide this information for i.MX53
and OMAP?

I am unsure about the Exynos platform - IIRC I read somewhere
that one needs a signed non-free first-stage loader to load
u-boot there, which would make it impossible for us to provide
ready-to-boot images, but my memory is shady on that issue and it
might only have been the case for particular SoCs/systems. Ian,
can you provide some information regarding this?

> For images such as hd-media, we'd ideally want to provide complete
> u-boot + kernel + initrd ( + gtk initrd) images, which would grow each
> image considerably.

I know of no armhf system that can load its u-boot from a USB
mass storage device, so AFAICS such a full image could only be
written to an SD card.  This setup would therefore only be useful
if the intended installation target is something else than the SD
card, because otherwise one would have to install to the medium
containing the installer and would therefore not be able to use
the space used by the installer and the CD/DVD ISO image for the
installed system.  I think that for most systems the primary
installation target is the SD card, so I think that we should use
the "tiny SD card image with only u-boot on it" + "USB stick with
hd-media tarball and CD/DVD ISO" model instead of building "full"
hd-media images.

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