[U-Boot] [PATCH 2/4] am335x_evm: scan more partitions and use uname_r

From: Vagrant Cascadian <vagrant@debian.org>
To: u-boot@lists.denx.de
Subject: [U-Boot] [PATCH 2/4] am335x_evm: scan more partitions and use uname_r
Date: Sat, 10 Mar 2018 15:13:24 -0800	[thread overview]
Message-ID: <876063r0bv.fsf@aikidev.net> (raw)
In-Reply-To: <CA+T6QP=0SM=Guyy9J9Nq_s9CHH7dY+qcjhMw7BhXJyx28zALfw@mail.gmail.com>

On 2018-03-10, Jason Kridner wrote:
> On Wed, Mar 7, 2018 at 9:27 AM Tom Rini <trini@konsulko.com> wrote:
>> On Wed, Mar 07, 2018 at 05:40:42AM -0500, Jason Kridner wrote:
>> > This enables mainline u-boot to boot the BeagleBoard.org Debian
>> > distribution builds without extensive environment modifications.
>> >
>> > Some boot layouts only have a single partition on the
>> > MMC/eMMC. This will scan those partitions after the second
>> > partition that was already being scanned.
>> >
>> > Some layouts use uname_r to define the kernel being used for the boot to
>> > support multiple kernels stored within the boot file system without
>> > using symlinks.
>> >
>> > See http://elinux.org/Beagleboard:U-boot_partitioning_layout_2.0 for
>> > more details on the BeagleBoard.org Debian image layout.
...
>> Why does this all differ from the usual Debian case?  Thanks!
>>
>
> I believe the distros typically use /boot/extlinux/extlinux.conf.

Debian typically uses a boot script, at least when installing from
debian-installer. There's a package called u-boot-menu which generates
the extlinux.conf file. There are some ideas floating around to try to
use u-boot's EFI emulation to boot grub-efi for platforms that don't
support EFI natively, as well.

But the majority of officially supported platforms in Debian still just
use boot scripts, for better or worse.

> We need some way to specify a number of other environment variables we
> use elsewhere in our u-boot scripts for applying device-tree overlays
> and such.

Could this functionality can't be implemented as a boot script, rather
than hard-coding it into the u-boot binary?

I know the official BeagleBoard.org images have been using a patched
u-boot for quite some time, and so there is something to be said for
pushing that upstream. Though there is a lot of duplication of
functionality supporting distro_bootcmd, legacy boot, and the patchsets
that BeagleBoard.org images use.

live well,
  vagrant
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