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

From: Thomas Petazzoni via buildroot <buildroot@buildroot.org>
To: Niklas Cassel <Niklas.Cassel@wdc.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 18:19:18 +0200	[thread overview]
Message-ID: <20241023181918.13ba7a70@windsurf> (raw)
In-Reply-To: <ZxgeOudkPEBVJBkz@ryzen>

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.

> However:
> 1) rock5b does not have the uboot CONFIG_PARTITION_TYPE_GUID Kconfig enabled.
> 2) rockchip is incorrectly specifying the arm64 partition type GUID:
> https://github.com/u-boot/u-boot/blob/master/include/configs/rockchip-common.h#L19
> using uuid= and not type=.

Again, this is only used for fastboot I believe, so not relevant.

> So currently a uboot built for rockchip will only automatically find the rootfs
> partition if the rootfs partition (incorrectly) has set the partition UUID to
> the arm64 partition type UUID.

I don't think so, at least based on the evidence that you provide.

> Rock5b in buildroot does not rely on this automatic finding of rootfs anyway,
> so all good.
> 
> However, there might be other uboot configurations in uboot that actually has
> set the type= a specific partition type GUID in PARTS_DEFAULT, and I don't
> want to risk breaking any platform.

See above.

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...).

Thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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