Sharing *.dtsi between Linux architectures?

Sharing *.dtsi between Linux architectures?

[Stephen Warren]

Is there a (possibly just proposed) mechanism in place to allow *.dts
from multiple Linux architectures to share common *.dtsi files?

As an example, consider two SoCs that are identical except for the CPU
complex. One uses an ARMv7 CPU (DTs in arch/arm/boot/dts/) and the other
uses some ARMv8 CPU (DTs in arch/am64/boot/dts/). It'd be useful to
define all the SoC components in some common .dtsi file to avoid
duplication, and have both arch/arm/boot/dts/tegraXXX.dtsi and
arch/arm64/boot/dts/tegraYYY.dtsi include that and add the relevant
CPU-related nodes.

I could imagine creating one of the following paths for this purpose:

arch/common/dts/
include/dt-common/
include/dtsi/

... or perhaps re-using the existing:

include/dt-bindings/

... although my original intent for that last location was just to house
header files that define constants that are part of binding definitions,
rather than actual structural content.

Re: Sharing *.dtsi between Linux architectures?

[Rob Herring]

On 07/12/2013 02:58 PM, Stephen Warren wrote:
> Is there a (possibly just proposed) mechanism in place to allow *.dts
> from multiple Linux architectures to share common *.dtsi files?

Nothing proposed yet. There was some discussion at Connect (which I
missed part of). We're certainly going to start to have that issue
between arm and arm64 as well as probably FSL powerpc and arm.

I would like to move all dts files out of arch. I think we should think
about how we construct a separate dts repository and then move the
kernel structure in that direction (it's still believed there is too
much interdependency to have separate repo yet). I don't think cpu
architecture is the right top level structure for dts files. Probably
something by vendor and/or SOC family is more appropriate. Then you have
to figure out how to handle board vs. chip vendors.

> As an example, consider two SoCs that are identical except for the CPU
> complex. One uses an ARMv7 CPU (DTs in arch/arm/boot/dts/) and the other
> uses some ARMv8 CPU (DTs in arch/am64/boot/dts/). It'd be useful to
> define all the SoC components in some common .dtsi file to avoid
> duplication, and have both arch/arm/boot/dts/tegraXXX.dtsi and
> arch/arm64/boot/dts/tegraYYY.dtsi include that and add the relevant
> CPU-related nodes.
> 
> I could imagine creating one of the following paths for this purpose:
> 
> arch/common/dts/
> include/dt-common/
> include/dtsi/
> 
> ... or perhaps re-using the existing:
> 
> include/dt-bindings/
> 
> ... although my original intent for that last location was just to house
> header files that define constants that are part of binding definitions,
> rather than actual structural content.

I think we should stick with defines there.

Rob

Re: Sharing *.dtsi between Linux architectures?

[Jean-Christophe PLAGNIOL-VILLARD]

On Jul 13, 2013, at 4:17 AM, Rob Herring <robherring2@gmail.com> wrote:

> On 07/12/2013 02:58 PM, Stephen Warren wrote:
>> Is there a (possibly just proposed) mechanism in place to allow *.dts
>> from multiple Linux architectures to share common *.dtsi files?
> 
> Nothing proposed yet. There was some discussion at Connect (which I
> missed part of). We're certainly going to start to have that issue
> between arm and arm64 as well as probably FSL powerpc and arm.
> 
> I would like to move all dts files out of arch. I think we should think
> about how we construct a separate dts repository and then move the
> kernel structure in that direction (it's still believed there is too
> much interdependency to have separate repo yet). I don't think cpu
> architecture is the right top level structure for dts files. Probably
> something by vendor and/or SOC family is more appropriate. Then you have
> to figure out how to handle board vs. chip vendors.
> 
>> As an example, consider two SoCs that are identical except for the CPU
>> complex. One uses an ARMv7 CPU (DTs in arch/arm/boot/dts/) and the other
>> uses some ARMv8 CPU (DTs in arch/am64/boot/dts/). It'd be useful to
>> define all the SoC components in some common .dtsi file to avoid
>> duplication, and have both arch/arm/boot/dts/tegraXXX.dtsi and
>> arch/arm64/boot/dts/tegraYYY.dtsi include that and add the relevant
>> CPU-related nodes.
>> 
>> I could imagine creating one of the following paths for this purpose:
>> 
>> arch/common/dts/
>> include/dt-common/
>> include/dtsi/
>> 
>> ... or perhaps re-using the existing:
>> 
>> include/dt-bindings/
>> 
>> ... although my original intent for that last location was just to house
>> header files that define constants that are part of binding definitions,
>> rather than actual structural content.
> 
> I think we should stick with defines there.

I think it's to do it how move the dt simple in dt directory at the root of
the kernel tree

this will simplify the move to out of tree

and include/dt-bindings/ to dt/include/dt-bindings/ and just handle the include
via a -i in the Makefile

Best Regards,
J.
> 
> Rob
> 
> 
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> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: Sharing *.dtsi between Linux architectures?

[Russell King - ARM Linux]

On Fri, Jul 12, 2013 at 01:58:35PM -0600, Stephen Warren wrote:
> Is there a (possibly just proposed) mechanism in place to allow *.dts
> from multiple Linux architectures to share common *.dtsi files?

Don't forget that the long term goal is to move these files out of the
kernel source, which means that they'll be a separately managed project,
possibly with a different file structure.