[alsa-devel] [PATCH 1/2] ASoC: rt5677: Add ACPI device probing

[Liam Girdwood]

On Tue, 2014-11-25 at 12:11 +0000, Grant Likely wrote:
> On Sat, Nov 15, 2014 at 6:56 AM, Ben Zhang <benzh at chromium.org> wrote:
> > The rt5677 codec driver looks for ACPI device ID "RT5677CE",
> > which is specified in coreboot. This patch allows platform
> > data to be obtained via ACPI
> >
> > Signed-off-by: Ben Zhang <benzh at chromium.org>
> 
> This looks like an ideal time to talk about shared DT and ACPI driver
> bindings. This driver /already/ has a firmware binding. It is
> documented in the kernel under
> Documentation/bindings/sound/rt5677.txt. We now have a standard method
> for sharing bindings between DT and ACPI in the _DSD method[1].
> Support for DSD is in linux-next and getting merged into v3.19. This
> is exactly the case that _DSD should be used for passing additional
> data to the driver, and it should use the existing binding.
> 
> [1] http://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf
> 
> For a long time we've had the rule on DT that new bindings must be
> documented before we merge a patch. That rule I think has been a good
> one, even if it is a little chaoitc. I think when it comes to ACPI
> drivers that we should be requiring the same: Document the binding,
> either in the kernel as a DT binding, or point to somewhere else that
> has the binding documented.
> 
> Also, since this patch is targeted at v3.19 or later, the
> device-properties API should be used. Don't create something custom.
> 

My sentiments exactly, there would be little point having bespoke device
properties for every single device. Btw, we also need to align here with
Windows too !

Liam