[U-Boot] [PATCH V2] add README.distro file

[Dennis Gilmore]

On Mon, 12 Jan 2015 20:57:29 +0100
Sjoerd Simons <sjoerd.simons at collabora.co.uk> wrote:

> On Mon, 2015-01-12 at 17:57 +0000, Ian Campbell wrote:
> > On Mon, 2015-01-12 at 10:34 -0700, Stephen Warren wrote:
> 
> > > * boot.scr must be generated (to boot.scr.uimg) using 
> > > bootloader-specific tools, rather than extlinux.conf,
> > > grub.conf, ... all just need the generation of a text file.
> > 
> > Debian already has the tooling (and has for years) to reproduce
> > boot.scr automatically on upgrades of various relevant components,
> > the user never needs to see the mkimage stuff (that tooling also
> > handles various legacy non-config_distro_bootcmd systems, so it's
> > going to have to remain for the time being either way).
> > 
> > Currently the extlinux.conf generating stuff is tied to the x86
> > syslinux packages, it could be reworked and pulled out into arch
> > indep packages, but there doesn't seem to be all that much benefit
> > compared with what we have now which is working fairly well for us
> > (not to imply that it's perfect).
> 
> One big downside of the boot.scr as generated by flash-kernel in
> Debian is that it doesn't have a menu, which extlinux can provide
> currently. Thus with extlinux we could provide a more similar
> experience to what folks get on x86 with e.g. Grub, iotw select
> provide menu options to boot previous kernels or single user mode etc.
> 
> I do hope to get to experimenting a bit with this for the boards, i
> care about soon. My patchset that was in discussion there was
> actually some pre-work for those things ;). It would be nice if, in
> the end, flash-kernel wouldn't be needed for boards with modern
> u-boot and follwing the distro_boot_cmds, but I'm not actually
> involved with Debians u-boot package so not my call :)

I am carrying some patches in Fedora that were written by someone from
debian porting a board to use the generic options, though it was
incomplete and was missing variables for pxe booting to work. while we
get a menu and you can choose older kernels currently there is no way
to edit things dynamically. this is a feature I want to add. make it
easy to append boot arguments etc. there seems to at least be interest
in the debian camp. to what extent that interest goes I am not sure.

I will cover how things are in Fedora.  It is still not perfect but
is getting better every release. grubby updates extlinux.conf on kernel
install/update/removal etc the exact same code is used on x86 and arm.
we have a extlinux-bootloader package on arm that provides the
framework needed that comes with syslinux-extlinux. anaconda writes out
extlinux.conf on install. I have some scripting work to do to update it
and add the fdtdir entry to extlinux.conf on install. the anaconda code
to deal with extlinux.conf is shared between x86 and arm.
appliance-creator which is the tool we use to make disk images writes
out correct extlinux.conf files for both x86 and arm

from a end user perspective the experience is similar but not quite
exactly the same. longer term id like to use u-boots menu code to offer
up a menu to select the kernel and add editing features. But it is much
easier now to support new boards than it ever has been in the past.

Dennis