linux-kernel - RE: [PATCH] arm/dt: tegra devicetree support

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Message-ID: <74CDBE0F657A3D45AFBB94109FB122FF049EBDEF01@HQMAIL01.nvidia.com>
Date:	Wed, 20 Jul 2011 11:40:28 -0700
From:	Stephen Warren <swarren@...dia.com>
To:	Grant Likely <grant.likely@...retlab.ca>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>
CC:	Erik Gilling <konkers@...roid.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Colin Cross <ccross@...roid.com>,
	Olof Johansson <olof@...om.net>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>
Subject: RE: [PATCH] arm/dt: tegra devicetree support

Grant Likely wrote at Wednesday, July 20, 2011 12:32 PM:
> On Wed, Jul 20, 2011 at 05:03:55PM +0100, Mark Brown wrote:
> > On Wed, Jul 20, 2011 at 08:37:19AM -0700, Stephen Warren wrote:
> > > Grant Likely wrote at Tuesday, July 19, 2011 5:43 PM:
> >
> > > > +	sound {
> > > > +		compatible = "nvidia,harmony-sound", "nvidia,tegra-wm8903";
> >
> > > I thought the sound bindings were still somewhat experimental and not
> > > completely agreed upon. One issue I see is that Device Tree is
> > > supposed to represent pure HW, rather than driver-required abstractions,
> > > and at least the compatible name here is pretty Linux-driver-specific.
> >
> > The current decision is that the schematic for embedded audio hardware
> > is sufficiently interesting to be considered hardware in its own right
> > separately to the chips contained within it.
> 
> Correct.  For complex composite devices like audio, it is completely
> appropriate to have a root node that represents the entire complex and
> how it is wired together.

Sure, that makes sense.

> The compatible property here definitely represents the hardware
> because it reflects the sound infrastructure on the harmony board.

I can see that argument for "nvidia,harmony-sound".

But "nvidia,tegra-wm8903" is pretty generic; I can certainly see there
being Tegra 20 systems that use a WM8903 but are so different from either
Harmony or anything supported by sound/soc/tegra/tegra_wm8903.c that the
existing driver isn't applicable. And hence, there may be a different
ASoC driver for such board(s), and hence choosing such a generic name as
"tegra-wm8903" for Harmony/Seaboard's audio layout seems like it might
cause problems in the future.

I'm fine with such a generic name for the platform driver, since that name
can fairly easily be modified just by editing the driver and the board file.
But since *.dts files are at least logically separate from the kernel, such
naming future-proofing is a little more important.

-- 
nvpublic

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