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

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Date:	Tue, 25 Nov 2014 08:01:14 -0800
From:	Darren Hart <dvhart@...ux.intel.com>
To:	Liam Girdwood <liam.r.girdwood@...ux.intel.com>,
	Grant Likely <grant.likely@...retlab.ca>
CC:	Ben Zhang <benzh@...omium.org>,
	Oder Chiou <oder_chiou@...ltek.com>,
	alsa-devel <alsa-devel@...a-project.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Liam Girdwood <lgirdwood@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Mark Brown <broonie@...nel.org>,
	Anatol Pomozov <anatol@...gle.com>,
	Bard Liao <bardliao@...ltek.com>,
	Dylan Reid <dgreid@...omium.org>, flove@...ltek.com
Subject: Re: [alsa-devel] [PATCH 1/2] ASoC: rt5677: Add ACPI device probing



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@...omium.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@...omium.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
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