[alsa-devel] [PATCH v2 3/8] ASoC: intel: boards: add card for MinnowBoard I2S access

[Pierre-Louis Bossart]

On 1/6/16 11:42 AM, Mark Brown wrote:
> On Tue, Jan 05, 2016 at 08:50:11AM -0600, Pierre-Louis Bossart wrote:
>> On 1/5/16 7:15 AM, Mark Brown wrote:
>
>>> I'm wondering how this is going to get loaded (I don't see what creates
>>> the platform device) and how we handle systems with a CODEC connected on
>>> the expansion headers?
>
>> Good question.
>
>> To solve this audio is disabled by default, and we have an EFI application
>> loaded by the startup.nsh file that sets the relevant codec information in
>> the SSDT table so that you can swap codec cards at will. The EFI application
>> will be open-sourced so that additional codecs can be added as needed with
>> changes in the ASL code. The whole thing was tested with experimental
>> releases in three different setups for now but will be formally released
>> next month.
>
> Sets the relevant codec information by...?

exposing devices and dependencies, setting the _HID, codec I2C address, 
Gpio lines, DSD properties if needed. Nothing new compared to a normal 
DSDT table except that you only add the audio-related information yourself.

>
>> On probe the sst_acpi part checks for the presence of known codecs and
>> registers the platform driver. For the case where no codec is present I just
>> added an entry at the end of the table that always works (checks for an
>> SOC-side HID) and is selected if no other codec was found. I need to add
>> this patch and submit it, forgot to add it in this batch.
>
> Can we punt on this until we've got the rest of the infrastructure to
> look at?  I'd feel safer and it sounds like it's going to need some
> manual hacking to get working anyway until the other bits are lined up.

that's fine, i will provide more documentation to explain the steps 
later this month. The 'infrastructure' isn't that bad really - and since 
the SSDT update application is open-source for once you can't blame the 
BIOS if your audio doesn't work :-)