[PATCH] ARM: Add config option DEBUG_DECOMPRESS_KERNEL

[Nicolas Pitre]

On Mon, 17 Sep 2012, Maximilian Schwerin wrote:

> This change allows preventing the message "Uncompressing Linux..." from
> being sent to serial port. This is necessary if the primary serial port is
> used for something other than kernel debugging (e.g. some external device
> controlled by serial commands).
> 
> Signed-off-by: Maximilian Schwerin <mvs at tigris.de>
> ---
>  arch/arm/Kconfig.debug          |    9 +++++++++
>  arch/arm/boot/compressed/misc.c |    4 ++++
>  2 files changed, 13 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
> index e968a52..96e90dc 100644
> --- a/arch/arm/Kconfig.debug
> +++ b/arch/arm/Kconfig.debug
> @@ -46,6 +46,15 @@ config OLD_MCOUNT
>  	depends on FUNCTION_TRACER && FRAME_POINTER
>  	default y
>  
> +config DEBUG_DECOMPRESS_KERNEL
> +	bool "Using serial port during decompressing kernel"
> +	depends on DEBUG_KERNEL
> +	default n
> +	help
> +	  If you say Y here you will confirm the start and the end of
> +	  decompressing Linux seeing "Uncompressing Linux... " and
> +	  " done, booting the kernel.\n" on console.

First, "default n" is the default already, so you don't need to provide 
it.

Next, this is going to disable the output by default for everyone which 
is an unwelcome change.  You should make sure that the default behavior 
is like before, and that the option allows you to disable the output.

And then the DEBUG_DECOMPRESS_KERNEL option is a rather bad name.  This 
output has not been considered "debugging" before.  What about 
"INHIBIT_DECOMPRESSOR_OUTPUT" instead?

> diff --git a/arch/arm/boot/compressed/misc.c b/arch/arm/boot/compressed/misc.c
> index 8e2a8fc..edf4a35 100644
> --- a/arch/arm/boot/compressed/misc.c
> +++ b/arch/arm/boot/compressed/misc.c
> @@ -144,11 +144,15 @@ decompress_kernel(unsigned long output_start, unsigned long free_mem_ptr_p,
>  
>  	arch_decomp_setup();
>  
> +#ifdef CONFIG_DEBUG_DECOMPRESS_KERNEL
>  	putstr("Uncompressing Linux...");
> +#endif /* CONFIG_DEBUG_DECOMPRESS_KERNEL */
>  	ret = do_decompress(input_data, input_data_end - input_data,
>  			    output_data, error);
>  	if (ret)
>  		error("decompressor returned an error");
> +#ifdef CONFIG_DEBUG_DECOMPRESS_KERNEL
>  	else
>  		putstr(" done, booting the kernel.\n");
> +#endif /* CONFIG_DEBUG_DECOMPRESS_KERNEL */

That would be cleaner if you simply redefined putstr() to an empty stub.  
Similarly for error() which still can output to the same UART.


Nicolas