linux-kernel - Re: [PATCH] of: fdt: Honor CONFIG_CMDLINE* even without /chosen node

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Date:   Tue, 13 Dec 2022 09:51:33 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Alexander Sverdlin <alexander.sverdlin@...il.com>
Cc:     devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...nel.org>,
        Nikita Shubin <nikita.shubin@...uefel.me>,
        Hartley Sweeten <hsweeten@...ionengravers.com>,
        Lukasz Majewski <lukma@...x.de>,
        Linus Walleij <linusw@...nel.org>
Subject: Re: [PATCH] of: fdt: Honor CONFIG_CMDLINE* even without /chosen node

On Mon, Dec 12, 2022 at 7:01 AM Alexander Sverdlin
<alexander.sverdlin@...il.com> wrote:

> I do not read a strict requirement on /chosen node in either ePAPR or in
> Documentation/devicetree. Help text for CONFIG_CMDLINE and
> CONFIG_CMDLINE_EXTEND doesn't make their behavior explicitly dependent on
> the presence of /chosen or the presense of /chosen/bootargs.
>
> However the early check for /chosen and bailing out in
> early_init_dt_scan_chosen() skips CONFIG_CMDLINE handling which is not
> really related to /chosen node or the particular method of passing cmdline
> from bootloader.
>
> This leads to counterintuitive combinations (assuming
> CONFIG_CMDLINE_EXTEND=y):
>
> a) bootargs="foo", CONFIG_CMDLINE="bar" => cmdline=="foo bar"
> b) /chosen missing, CONFIG_CMDLINE="bar" => cmdline==""
> c) bootargs="", CONFIG_CMDLINE="bar" => cmdline==" bar"
>
> Move CONFIG_CMDLINE handling outside of early_init_dt_scan_chosen() so that
> cases b and c above result in the same cmdline.
>
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@...il.com>

Excellent debugging Alexander!
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

I also think this should go to stable.

Yours,
Linus Walleij