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Subject: Re: [PATCH] powerpc: Support CMDLINE_EXTEND
To:     Chris Packham <chris.packham@alliedtelesis.co.nz>,
        benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au
Cc:     linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
References: <20190724053303.24317-1-chris.packham@alliedtelesis.co.nz>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <59674457-eda5-fe3b-65e0-29c20102fe4d@c-s.fr>
Date:   Tue, 30 Jul 2019 09:02:45 +0200
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Le 24/07/2019 à 07:33, Chris Packham a écrit :
> Device tree aware platforms can make use of CMDLINE_EXTEND to extend the
> kernel command line provided by the bootloader. This is particularly
> useful to set parameters for built-in modules that would otherwise be
> done at module insertion. Add support for this in the powerpc
> architecture.
> 
> Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
> ---
>   arch/powerpc/Kconfig | 12 ++++++++++++

I think you also have to implement some stuff in early_cmdline_parse() 
in arch/powerpc/kernel/prom_init.c

Maybe look at https://patchwork.ozlabs.org/patch/1074126/

Christophe

>   1 file changed, 12 insertions(+)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index d8dcd8820369..cd9b3974aa36 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -851,6 +851,11 @@ config CMDLINE
>   	  some command-line options at build time by entering them here.  In
>   	  most cases you will need to specify the root device here.
>   
> +choice
> +	prompt "Kernel command line type" if CMDLINE != ""
> +	default CMDLINE_FORCE
> +	depends on CMDLINE_BOOL
> +
>   config CMDLINE_FORCE
>   	bool "Always use the default kernel command string"
>   	depends on CMDLINE_BOOL
> @@ -860,6 +865,13 @@ config CMDLINE_FORCE
>   	  This is useful if you cannot or don't want to change the
>   	  command-line options your boot loader passes to the kernel.
>   
> +config CMDLINE_EXTEND
> +	bool "Extend bootloader kernel arguments"
> +	help
> +	  The command-line arguments provided by the boot loader will be
> +	  appended to the default kernel command string.
> +endchoice
> +
>   config EXTRA_TARGETS
>   	string "Additional default image types"
>   	help
>