Nand flash booting.

[Steve Langasek]

On Mon, Nov 14, 2016 at 03:50:52PM +0100, Oliver Grawert wrote:

> On Mo, 2016-11-14 at 01:21 +0000, Daniel Toussaint wrote:
> > I am working on a board similar to Beaglebone Black, however instead
> > of SD/eMMC it is booting from NAND flash directly. As far as I can
> > see in the documentation there is no way yet to boot a Snappy image
> > in this fashion, is support for this planned ? Is there anything I
> > can do to help out with that ?

> > Meanwhile, I am considering using the Yocto version of snapcraft to
> > package the apps, so that we can later migrate to from the current
> > Yocto image to Snappy. 

> > Thanks for your comments.

> currently the boot process relies heavily on filesystem labels for
> finding the various (namely system-boot and writable) partitions. 

> do your NAND devices expose labels you set in /dev/disk/by-label ? 

> if thats the case it might work to use ubuntu-image with the --workdir
> option which keeps the different partition images around in the
> specified dir. you could then just grab them from there and flash then
> to the respective NAND pratitions.

> if the labels are not exposed this will need a bunch of changes in the
> code to allow some overrides (i.e. via kernel cmdline options), for
> this we will need a wishlist bug as the first step :)

It is an explicit element of the ubuntu-image design that a gadget snap
should be able to emit multiple images for a given model, so that these can
be written out separately across e.g. an SD card and a NAND device. 
However, the current implementation only allows for an image containing a
partition table, and filesystems within that.

Barry, Gustavo, do we need to extend gadget.yaml semantics here to support
some sort of 'schema: raw' for a volume, for the NAND case?

-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slangasek at ubuntu.com                                     vorlon at debian.org
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