[alsa-devel] [PATCH] ASoC: rt286: Add API to set supported jack type

[Liam Girdwood]

On Thu, 2014-08-07 at 18:31 +0100, Mark Brown wrote:
> On Thu, Aug 07, 2014 at 01:43:24AM +0000, Bard Liao wrote:
> 
> > > If this is coming from the hardware design I'd expect this to be configured
> > > via platform data or firmware data rather than with an API.
> > > Why do it this way?
> 
> > Actually, this patch is for Intel platform which doesn't support platform data
> > yet. That's why we create an API so they can call the API in machine driver.
> 
> So, this is something that the people wanting to use ACPI in platforms
> with devices like this are going to have to deal with - we need a way of
> getting configuration to devices.  Traditionally small tweaks have been
> done based on DMI information but that's not at all scalable.  I believe
> newer ACPI specs are trying to accomodate this due to the expanding
> range of systems supporting ACPI.  Punting to the machine driver just
> moves the problem around, it doesn't really address it.
> 

Unfortunately this will be needed for some Broadwell based BIOSes since
the timing of the ACPI spec/implementation has meant that some Broadwell
BIOSes will contain the data whilst most others wont atm :( 

> I've CCed in Graeme Gregory who's been writing some guidelines for this
> sort of thing in the context of ARMv8 serviers - the most recent patch
> is:
> 
>    http://thread.gmane.org/gmane.linux.acpi.devel/69757
> 
> The advice there looks good to me - see the "Device Enumeration"
> section.

This is indeed good, just too late for the initial Broadwell BIOSes that
wont have this _DSD field for the codec (it will be hard coded for
Windows anyway).

Liam