linux-kernel - Re: [PATCH] ARM: Allow DEBUG_UNCOMPRESS on ARCH

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Message-Id: <6d1f3696-c94a-44ac-996c-83233f694cc0@app.fastmail.com>
Date:   Mon, 30 Jan 2023 09:08:10 +0100
From:   "Arnd Bergmann" <arnd@...db.de>
To:     Jonathan Neuschäfer <j.neuschaefer@....net>,
        linux-arm-kernel@...ts.infradead.org
Cc:     "Russell King" <linux@...linux.org.uk>,
        "William Zhang" <william.zhang@...adcom.com>,
        "Michael Walle" <michael@...le.cc>,
        "Florian Fainelli" <f.fainelli@...il.com>,
        "Tony Lindgren" <tony@...mide.com>,
        "Kavyasree Kotagiri" <kavyasree.kotagiri@...rochip.com>,
        "Ard Biesheuvel" <ardb@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: Allow DEBUG_UNCOMPRESS on ARCH_MULTIPLATFORM

On Sun, Jan 29, 2023, at 17:00, Jonathan Neuschäfer wrote:
> A kernel with DEBUG_UNCOMPRESS=y will only work on one platform, but
> that is already the case with DEBUG_LL=y (and documented in its help
> text), and DEBUG_UNCOMPRESS depends on DEBUG_LL. Therefore, I don't
> think users need to be prevented from enabling DEBUG_UNCOMPRESS on
> ARCH_MULTIPLATFORM kernels.
>
> Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@....net>

I think we should instead change the help text for CONFIG_DEBUG_LL.

There is a very significant difference between the requirements
of DEBUG_LL compared to DEBUG_UNCOMPRESS. The former only provides
the platform specific functions but does not call them unless
a user explicitly passes the "earlyprintk" command line argument
or adds explicit function calls to printascii(), while the latter
makes the kernel immediately unbootable.

     Arnd