linux-kernel - Re: [PATCH 0/2] Fix CMDLINE_EXTEND handling for FDT "bootargs"

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Date:   Mon, 1 Mar 2021 08:19:32 -0600
From:   Rob Herring <robh@...nel.org>
To:     Will Deacon <will@...nel.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Max Uvarov <muvarov@...il.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Marc Zyngier <maz@...nel.org>,
        Doug Anderson <dianders@...omium.org>,
        Tyler Hicks <tyhicks@...ux.microsoft.com>,
        Frank Rowand <frowand.list@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Palmer Dabbelt <palmer@...belt.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Android Kernel Team <kernel-team@...roid.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 0/2] Fix CMDLINE_EXTEND handling for FDT "bootargs"

On Thu, Feb 25, 2021 at 6:59 AM Will Deacon <will@...nel.org> wrote:
>
> Hi folks,
>
> We recently [1] enabled support for CMDLINE_EXTEND on arm64, however
> when I started looking at replacing Android's out-of-tree implementation [2]

Did anyone go read the common, reworked version of all this I
referenced that supports prepend and append. Here it is again[1].
Maybe I should have been more assertive there and said 'extend' is
ambiguous.

> with the upstream version, I noticed that the two behave significantly
> differently: Android follows the Kconfig help text of appending the
> bootloader arguments to the kernel command line, whereas upstream appends
> the kernel command line to the bootloader arguments. That is, except for
> the EFI stub, which follows the documented behaviour.
>
> I think the documented behaviour is more useful, so this patch series
> reworks the FDT code to follow that and updates the very recently merged
> arm64 idreg early command-line parsing as well.

I can just as easily argue that the kernel having the last say makes
sense. Regardless, I'm pretty sure there's someone out there relying
on current behavior. What is the impact of this change to other
arches?

Rob

[1] https://lore.kernel.org/lkml/20190319232448.45964-2-danielwa@cisco.com/