Re: [Openembedded-architecture] [RFC PATCH] Add genericarm64 MACHINE using upstream defconfig

From: Paul Barker <paul.barker.ct@bp.renesas.com>
To: Ross Burton <ross.burton@arm.com>, poky@lists.yoctoproject.org
Cc: openembedded-core@lists.openembedded.org,
	openembedded-architecture@lists.openembedded.org
Subject: Re: [Openembedded-architecture] [RFC PATCH] Add genericarm64 MACHINE using upstream defconfig
Date: Wed, 21 Feb 2024 15:06:27 +0000	[thread overview]
Message-ID: <95d22879-3f51-466c-a544-91db3fff6dcd@bp.renesas.com> (raw)
In-Reply-To: <20240221105723.1501833-1-ross.burton@arm.com>

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On 21/02/2024 10:57, Ross Burton wrote:
> From: Ross Burton <ross.burton@arm.com>
> 
> This is a new 64-bit "generic" Arm machine, that expects the hardware to
> be SystemReady IR compatible. This is slightly forward-leaning as there's
> not a _lot_ of SystemReady hardware in the wild, but most modern boards
> are and the number will only grow.  Also, this is the only way to have a
> 'generic' machine as without standardised bootloaders and firmware it
> would be impossible.
> 
> The base machine configuration isn't that exciting: it's a fully featured
> machine that supports most things, booting via UEFI and an initramfs.
> 
> However, the kernel is more interesting.  This RFC uses the upstream defconfig
> because unlike some other platforms, the arm64 defconfig is actively
> maintained with the goal of being a 'boots on most hardware' configuration.
> My argument is: why would we duplicate that effort?
> 
> The "linux-yocto way" is configuration fragments and after a week of
> hair-pulling I do actually have fragments that boot on a BeaglePlay, but
> to say this was a tiresome and frustrating exercise would be understating it.
> 
> So, a request for comments: is it acceptable to use the upstream defconfig in
> a reference BSP?  Personally I'm torn: the Yocto way is fragments not monolithic
> configs, but repeating the effort to fragmentise the configuration and then
> also have it sufficiently modular that it can be used in pieces - instead of
> just being a large file split up into smaller files - is a lot of effort for
> what might end up being minimal gain.  My fear is we end up with a fragmented
> configuration that can't be easily modified without breaking some platforms,
> and badly copies what the defconfig already does.

I am in favour of this - I think the "genericarm64" machine should use
the in-tree defconfig so that it can support the widest array of
hardware. If someone wants to trim down the kernel for a particular
platform then they should probably create a specific MACHINE anyway.

If we take the other approach of building up the kernel config from
fragments, how would we know that all SystemReady IR capable systems
will be supported? Yocto Project doesn't have the resources to test
every platform.

For the Renesas RZ SoCs I work on these days, the in-tree defconfig is
the configuration we test with the mainline kernel.

Thanks,

-- 
Paul Barker

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