linux-kernel - Re: [PATCH v2 0/2] ARM: decompressor: support AUTO

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Message-ID: <86pl6kamjk.wl-maz@kernel.org>
Date: Wed, 04 Feb 2026 09:24:47 +0000
From: Marc Zyngier <maz@...nel.org>
To: Linus Walleij <linusw@...nel.org>
Cc: "Christian Marangi (Ansuel)" <ansuelsmth@...il.com>,
	"Russell King (Oracle)" <linux@...linux.org.uk>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jonathan Corbet <corbet@....net>,
	"Mike Rapoport (IBM)" <rppt@...nel.org>,
	Eric DeVolder <eric.devolder@...cle.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Kees Cook <keescook@...omium.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...ainline.org>,
	John Crispin <john@...ozen.org>
Subject: Re: [PATCH v2 0/2] ARM: decompressor: support AUTO_ZRELADDR and appended DTB

Linus,

On Wed, 04 Feb 2026 00:36:29 +0000,
Linus Walleij <linusw@...nel.org> wrote:
> 
> On Mon, Feb 2, 2026 at 12:11 PM Marc Zyngier <maz@...nel.org> wrote:
> 
> > If you can boot the kernel, you can also boot a secondary bootloader
> > that will do the right thing by exposing a DT. Fixing the boot flow
> > should be the priority, rather than adding more band-aids to the
> > kernel.
> 
> I have used this approach with some Broadcom machines equipped
> with the CFE thing they are using. I have that boot U-Boot and
> U-boot boots the kernel. Works fine.
> 
> However, I think it is a thick requirement to put on hobbyist
> contributors to go and write entite boot loaders from scratch,
> I think it's a fine requirement to put on Qualcomm or Renesas
> paid maintainers.

It really isn't a large requirement, and you don't have to write a
full bootloader. All you need is a small shim that wraps the kernel
and enters it as it currently expects. You can even have that as a
separate binary that is loaded independently of the kernel.

Yes, this is an extra bit to carry outside of the kernel itself, and
extra stuff to package for generic distros, but appended DTB is
already a blocker for those.

> Another reason would be that appended DTB is in the same
> league as the GPIO sysfs despite we GPIO maintainers hate it:
> a feature users highly desire because it's easy and convenient
> and practical and quick and thus refuse to let us drop. Every time
> we try to deprecate it more we get a good beating.

I don't think appended DTB is ABI. The GPIO sysfs definitely is.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.