linux-kernel - Re: [PATCH REBASE] Add option to disable kernel compression

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Date:	Tue, 8 Oct 2013 12:29:40 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Christian Ruppert <christian.ruppert@...lis.com>
Cc:	linux-kernel@...r.kernel.org,
	alexander.stein@...tec-electronic.com,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"David S. Miller" <davem@...emloft.net>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Noam Camus <noamc@...hip.com>,
	pierrick hascoet <pierrick.hascoet@...lis.com>
Subject: Re: [PATCH REBASE] Add option to disable kernel compression

On Tue,  8 Oct 2013 14:33:32 +0200 Christian Ruppert <christian.ruppert@...lis.com> wrote:

> Until now, kernel compression can only be disabled by deselecting
> HAVE_<compression> in the architecture Kconfig.

Scratching my head a bit.  There's no way of deselecting these things. 
I *think* you mean "by editing arch/xxx/Kconfig and removing all the
"select HAVE_KERNEL_<compression>" lines"?

> However, some
> users/platforms within the same architecture might want to use
> compression while others might want to disable it.

Why would anyone want to run an uncompressed kernel, btw?  Boot time?

> This patch is a solution to the dilemma.
> 
> ...
>
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -118,7 +118,6 @@ config HAVE_KERNEL_LZ4
>  choice
>  	prompt "Kernel compression mode"
>  	default KERNEL_GZIP
> -	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
>  	help
>  	  The linux kernel is a kind of self-extracting executable.
>  	  Several compression algorithms are available, which differ
> @@ -137,6 +136,13 @@ choice
>  
>  	  If in doubt, select 'gzip'
>  
> +config KERNEL_UNCOMPRESSED
> +	bool "No compression"
> +	help
> +	  No compression at all. The kernel is huge but the compression and
> +	  decompression times are zero.
> +	  This is usually not what you want.
> +
>  config KERNEL_GZIP
>  	bool "Gzip"
>  	depends on HAVE_KERNEL_GZIP

It's odd to create CONFIG_KERNEL_UNCOMPRESSED and not use it for
anything, but I guess Kconfig's `choice' forces this.


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