linux-kernel - Re: [PATCH] ARM64: dts: vexpress: Use a symlink to vexpress-v2m-rs1.dtsi from arch=arm

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Date:	Mon, 12 Oct 2015 16:37:50 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Ian Campbell <ian.campbell@...rix.com>
Cc:	linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Kumar Gala <galak@...eaurora.org>,
	Liviu Dudau <liviu.dudau@....com>,
	Sudeep Holla <sudeep.holla@....com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Russell King <linux@....linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Kristina Martsenko <kristina.martsenko@....com>,
	Kevin Hilman <khilman@...aro.org>,
	Frank Rowand <frank.rowand@...ymobile.com>,
	Olof Johansson <olof@...om.net>, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, arm@...nel.org,
	linux-kbuild@...r.kernel.org
Subject: Re: [PATCH] ARM64: dts: vexpress: Use a symlink to
 vexpress-v2m-rs1.dtsi from arch=arm

On Mon, Oct 05, 2015 at 12:53:52PM +0100, Ian Campbell wrote:
> Commit 9ccd608070b6 "arm64: dts: add device tree for ARM SMM-A53x2 on
> LogicTile Express 20MG" added a new dts file to arch/arm64 which
> included "../../../../arm/boot/dts/vexpress-v2m-rs1.dtsi", i.e. a
> .dtsi supplied by arch/arm.
> 
> Unfortunately this causes some issues for the split device tree
> repository[0], since things get moved around there. In that context
> the new .dts ends up at src/arm64/arm/vexpress-v2f-1xv7-ca53x2.dts
> while the include is at src/arm/vexpress-v2m-rs1.dtsi.
> 
> The sharing of the .dtsi is legitimate since the baseboard is the same
> for various vexpress systems whatever processor they use.
> 
> Previously I attempted to resolve this by creating a shared location
> for such things but we have been unable to come to a consensus on
> where that should be.
> 
> Instead this patch simply replaces the use of ../../ in the dts
> /include/ with a symlink in arch/arm64/boot/dts/arm pointing to the
> file arch/arm/boot/dts.
> 
> Since the split device tree repo will shortly be required to flatten
> symlinks for other reasons this will cause the dtsi file to appear in
> both src/arm and src/arm64 in the split repo, which is an improvement
> on not building for arm64 now.
> 
> [0] https://git.kernel.org/cgit/linux/kernel/git/devicetree/devicetree-rebasing.git/
> 
> Signed-off-by: Ian Campbell <ian.campbell@...rix.com>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Pawel Moll <pawel.moll@....com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Kumar Gala <galak@...eaurora.org>
> Cc: Liviu Dudau <liviu.dudau@....com>
> Cc: Sudeep Holla <sudeep.holla@....com>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> Cc: Russell King <linux@....linux.org.uk>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Kristina Martsenko <kristina.martsenko@....com>
> Cc: Kevin Hilman <khilman@...aro.org>
> Cc: Frank Rowand <frank.rowand@...ymobile.com>
> Cc: Olof Johansson <olof@...om.net>
> Cc: devicetree@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: arm@...nel.org
> Cc: linux-kbuild@...r.kernel.org
> ---
> For more on flattening symlinks see
> http://thread.gmane.org/gmane.linux.kernel.input/45646/focus=45742
> ---
>  arch/arm64/boot/dts/arm/vexpress-v2f-1xv7-ca53x2.dts | 2 +-
>  arch/arm64/boot/dts/arm/vexpress-v2m-rs1.dtsi        | 1 +
>  2 files changed, 2 insertions(+), 1 deletion(-)
>  create mode 120000 arch/arm64/boot/dts/arm/vexpress-v2m-rs1.dtsi
> 
> diff --git a/arch/arm64/boot/dts/arm/vexpress-v2f-1xv7-ca53x2.dts b/arch/arm64/boot/dts/arm/vexpress-v2f-1xv7-ca53x2.dts
> index 5b1d018..bb3c26d 100644
> --- a/arch/arm64/boot/dts/arm/vexpress-v2f-1xv7-ca53x2.dts
> +++ b/arch/arm64/boot/dts/arm/vexpress-v2f-1xv7-ca53x2.dts
> @@ -186,6 +186,6 @@
>  				<0 0 41 &gic GIC_SPI 41 IRQ_TYPE_LEVEL_HIGH>,
>  				<0 0 42 &gic GIC_SPI 42 IRQ_TYPE_LEVEL_HIGH>;
>  
> -		/include/ "../../../../arm/boot/dts/vexpress-v2m-rs1.dtsi"
> +		/include/ "vexpress-v2m-rs1.dtsi"
>  	};
>  };
> diff --git a/arch/arm64/boot/dts/arm/vexpress-v2m-rs1.dtsi b/arch/arm64/boot/dts/arm/vexpress-v2m-rs1.dtsi
> new file mode 120000
> index 0000000..68fd0f8
> --- /dev/null
> +++ b/arch/arm64/boot/dts/arm/vexpress-v2m-rs1.dtsi
> @@ -0,0 +1 @@
> +../../../../arm/boot/dts/vexpress-v2m-rs1.dtsi
> \ No newline at end of file

I was under the impression that there was some reason symlinks of this
fashion were discouraged, but I don't know the details, and I don't have
strong feelings either way.

This solves a problem, and we don't seem to have a better solution. So
to that end:

Acked-by: Mark Rutland <mark.rutland@....com>

Thanks,
Mark.
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