Re: [PATCH] MIPS: implement a "bootargs-append" DT property

[James Hogan <james.hogan@mips.com>]

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On Sat, Nov 11, 2017 at 09:19:48AM -0800, Daniel Gimpelevich wrote:
> There are two uses for this:
> 
> 1) It may be useful to split a device-specific kernel command line between
> a .dts file and a .dtsi file, with "bootargs" in one and "bootargs-append"
> in the other, such as for variations of a reference board.
> 
> 2) There are kernel configuration options for prepending "bootargs" to the
> kernel command line that the bootloader has passed, but not for appending.
> A new option for this would be a less future-proof solution, since things
> like this should be in the dtb.
> 
> This is tested on MIPS, but it can be useful on other architectures also.
> 
> Signed-off-by: Daniel Gimpelevich <daniel@gimpelevich.san-francisco.ca.us>

The device tree maintainers should be on Cc. Adding them now.

Cheers
James

> ---
>  arch/mips/kernel/setup.c | 3 +++
>  drivers/of/fdt.c         | 4 ++++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
> index fe39397..95e9bf2 100644
> --- a/arch/mips/kernel/setup.c
> +++ b/arch/mips/kernel/setup.c
> @@ -826,7 +826,10 @@ static void __init arch_mem_init(char **cmdline_p)
>  	extern void plat_mem_setup(void);
>  
>  	/* call board setup routine */
> +	strlcpy(boot_command_line, arcs_cmdline, COMMAND_LINE_SIZE);
>  	plat_mem_setup();
> +	if (strncmp(boot_command_line, arcs_cmdline, COMMAND_LINE_SIZE) == 0)
> +		boot_command_line[0] = '\0';
>  
>  	/*
>  	 * Make sure all kernel memory is in the maps.  The "UP" and
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index ce30c9a..65dbda6 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -1127,6 +1127,10 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
>  	p = of_get_flat_dt_prop(node, "bootargs", &l);
>  	if (p != NULL && l > 0)
>  		strlcpy(data, p, min((int)l, COMMAND_LINE_SIZE));
> +	p = of_get_flat_dt_prop(node, "bootargs-append", &l);
> +	if (p != NULL && l > 0)
> +		strlcat(data, p, min_t(int, strlen(data) + l,
> +					COMMAND_LINE_SIZE));
>  
>  	/*
>  	 * CONFIG_CMDLINE is meant to be a default in case nothing else
> -- 
> 1.9.1
> 
> 

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