linux-kernel - Re: [PATCH] [RFC] arm: Replace "multiple platforms" by "common platform"

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Date:   Fri, 22 Jun 2018 15:08:37 +0200
From:   Simon Horman <horms@...ge.net.au>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Russell King <linux@...linux.org.uk>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Chris Brandt <Chris.Brandt@...esas.com>,
        Nicolas Pitre <nicolas.pitre@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Vladimir Murzin <vladimir.murzin@....com>,
        Magnus Damm <magnus.damm@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [RFC] arm: Replace "multiple platforms" by "common
 platform"

On Thu, Jun 21, 2018 at 05:59:06PM +0200, Geert Uytterhoeven wrote:
> "ARM multiplatform" has actually two meanings:
>   1. It groups platforms that follow the "ARM multiplatform" software
>      framework,
>   2. It allows to build a single kernel that can be booted on multiple
>      platforms.
> 
> Currently support for XIP and/or NOMMU cannot be enabled on platforms
> that follow the "ARM multiplatform" framework, without duplicating their
> machine selection logic under a new Kconfig symbol.  As (in theory) all
> platforms can be used with XIP and/or NOMMU, this is not sustainable.
> 
> Hence clarify the meaning of ARCH_MULTIPLATFORM:
>   1. Replace "multiple platforms" by "common platform", as it allows to
>      select one or more platforms adhering to the common framework,
>   2. Note that a single kernel may not boot on all platforms if XIP or
>      NOMMU is enabled.
> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> ---
> References:
>   - "[PATCHv4 0/4] arm/versatile: no-MMU support"
>     (http://lists.infradead.org/pipermail/linux-arm-kernel/2018-June/584555.html)
> 
>   - "[PATCH 0/2] ARM: ARMv7 (with MMU) XIP without ARCH_MULTIPLATFORM"
>     (http://lists.infradead.org/pipermail/linux-arm-kernel/2017-February/486835.html)
> 
>  arch/arm/Kconfig | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 54eeb8d00bc62a9f..6b286c018cf748c7 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -329,7 +329,7 @@ choice
>  	default ARCH_MULTIPLATFORM if MMU
>  
>  config ARCH_MULTIPLATFORM
> -	bool "Allow multiple platforms to be selected"
> +	bool "Common platforms (\"multiplatform\")"
>  	depends on MMU
>  	select ARM_HAS_SG_CHAIN
>  	select ARM_PATCH_PHYS_VIRT
> @@ -342,6 +342,13 @@ config ARCH_MULTIPLATFORM
>  	select PCI_DOMAINS if PCI
>  	select SPARSE_IRQ
>  	select USE_OF
> +	help
> +	  Support for systems implemented using the common "multiplatform"
> +	  framework.
> +
> +	  Unless specialized options depending on intimate platform
> +	  details, like XIP or NOMMU, are enabled, this allows to build a
> +	  single kernel that boots on multiple platforms.

Hi Geert,

I wonder if this might be slightly clearer:

	  Unless specialized options that depend on intimate platform
	  details, such as XIP and NOMMU, are enabled, this allows building
	  a single kernel that boots on multiple platforms.

>  
>  config ARM_SINGLE_ARMV7M
>  	bool "ARMv7-M based platforms (Cortex-M0/M3/M4)"
> -- 
> 2.17.1
>