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

Darren Hart
2014-11-25T16:02:38Z

On 11/25/14 06:28, Liam Girdwood wrote:
> On Tue, 2014-11-25 at 12:11 +0000, Grant Likely wrote:
>> On Sat, Nov 15, 2014 at 6:56 AM, Ben Zhang <benzh@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@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 !
>

The Windows folks definitely know about _DSD (and helped define it), so
this is a good opportunity to work through that process. Liam, do you
have a good contact to start that discussion?

--
Darren Hart
Intel Open Source Technology Center