Re: [Buildroot] [PATCH v3 3/4] configs/rock5b: use the arm64 rootfs partition-type-uuid

From: Niklas Cassel via buildroot <buildroot@buildroot.org>
To: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Niklas Cassel via buildroot <buildroot@buildroot.org>,
	Niklas Cassel <cassel@kernel.org>,
	Damien Le Moal <dlemoal@kernel.org>,
	Kilian Zinnecker <kilian.zinnecker@mail.de>
Subject: Re: [Buildroot] [PATCH v3 3/4] configs/rock5b: use the arm64 rootfs partition-type-uuid
Date: Wed, 23 Oct 2024 20:07:44 +0000	[thread overview]
Message-ID: <ZxlXj4Ov7K5Zf8Uj@ryzen> (raw)
In-Reply-To: <20241023181918.13ba7a70@windsurf>

Hello Thomas,

On Wed, Oct 23, 2024 at 06:19:18PM +0200, Thomas Petazzoni wrote:
> Hello Niklas,
> 
> On Tue, 22 Oct 2024 21:50:51 +0000
> Niklas Cassel <Niklas.Cassel@wdc.com> wrote:
> 
> > I don't feel comfortable to change it for platforms that I don't have
> > access too.
> 
> Absolutely, but we can evolve what we can consider to be "the best
> practice", documented in the manual.
> 
> > The reason why I saw this was because u-boot has support for searching
> > for a suitable rootfs (if CONFIG_PARTITION_TYPE_GUID).
> > 
> > and then specifying the type using type=
> > in e.g. PARTS_DEFAULT.
> 
> PARTS_DEFAULT is used to assign the "partitions" environment variable,
> but I don't see anything that uses that except the fastboot
> implementation. So I believe this PARTS_DEFAULT is only used in
> conjunction with fastboot, which is irrelevant to our discussion.

I see.

There obviously is code in uboot to automatically detect and use the
uboot-environment based on the u-boot-env partition type GUID being detected.

I didn't know if any u-boot code actually used PARTS_DEFAULT, or the
root-arm64 partition type GUID, so it seemed better not to change the
partition type GUID for any board I do not have access to.

I could imagine some board supported by buildroot perhaps having a custom
uboot script/config/patch that somehow depends on the rootfs GPT partition
type GUID being what they currently have configured in their genimage.cfg.

I tried to do a 'git grep ",type="' in buildroot, but I couldn't find
anything interesting.

I did find some ',type=' matches (related to PARTS_DEFAULT) in u-boot:
https://github.com/u-boot/u-boot/blob/v2024.10/include/configs/starfive-visionfive2.h#L25
https://github.com/u-boot/u-boot/blob/v2024.10/include/configs/sifive-unleashed.h#L38

But perhaps PARTS_DEFAULT is only used by the fastboot support in u-boot,
like you said.

> I must say I'm a bit confused by your reasoning, which I have a hard
> time following. Could you walk me more step by step? Either I'm missing
> something (very possible), or you're missing something (also possible,
> considering how crazy the U-Boot environment and boot flow is...).

I think that it is most likely me who was missing something :)

It is most likely safe to change the GPT partition type GUID for boards
that use u-boot. (I have no idea about edk2 boards though...)

I've already spent way too much time on getting the u-boot environment
to work in a nice way. (I am happy for all the feedback that you gave,
because of that we finally have a nice solution that hopefully will be
emulated/copied by other boards.)

But I have to respectfully decline to clean up the inconsistency with
regards to root-arm64 vs b921b045-1df0-41c3-af44-4c6f280d3fae vs L.

I have too many things on my todo list already (including some important
non-trivial tasks that I wish I had finished already (if they only weren't
so non-trivial :P)).

Kind regards,
Niklas
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