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

[Arnd Bergmann]

On Mon, Dec 12, 2022, at 00:58, Alexander Sverdlin 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@xxxxxxxxx>

Thanks for debugging this and coming up with a fix. We probably want
to have an empty /chosen node in most dts files to stay compatible with
existing kernels, but fixing the kernel is a good idea regardless.

Acked-by: Arnd Bergmann <arnd@xxxxxxxx>

and probably 

Cc: stable@xxxxxxxxxxxxxxx