[alsa-devel] [RFC 00/10] Enable HDA Codec support on Intel Platforms (Series2)

[Pierre-Louis Bossart]

On 12/1/17 8:56 AM, Takashi Iwai wrote:
> On Fri, 01 Dec 2017 10:13:58 +0100,
> Rakesh Ughreja wrote:
>>
>> Many Intel platforms (SKL,KBL) etc. in the market supports enahanced
>> audio capabilities which also includes DSP processing. This patch carry
>> forwads the works that is done in the previous series to enable HD Audio
>> codecs on such platforms.
>>
>> This patch series adds ASoC HDA codec driver for Intel platforms. It is
>> written by reusing the legacy HDA ALSA codec driver. Intention is to
>> maximize the reuse and minimize the changes in the legacy HDA codec driver.
>>
>> I would like to receive feedback before proceeding further on this
>> direction.
> 
> First of all, I appreciate this kind of work finally happening, so
> that ASoC HD-audio can go forward to a wider usage.  However...
> 
> 
>> TODO:
>>
>> - This series is tested on KBL based product (Dell XPS 13).
>> - Basic playback is working with headset and speakers.
>> - Capture operation is not tested.
>> - More platforms and use cases coverage can be added once we have basic
>>    agreement in terms of the overall approach.
> 
> One big thing that is unclear to me is what about the complex I/O
> configuration although we provide only a single machine driver, and
> what happens if the (legacy) codec driver allows the jack retasking.
> I know that nowadays the number of jacks are reduced than before, but
> still there will be desktop boxes with individual front and rear I/O
> jacks.
> 
> 
>> FIXME:
>> - KConfig changes does not look right, but I could not think of any proper
>>    way without making changes into legacy HDA codec driver. So need some
>>    help on this topic.
> 
> And this is another big issue.  As long as you don't allow build both,
> it never flies with distros, and it means no dramatic improvement of
> the situation, either.
> 
> IOW, we have to make the codec driver working on both controller/bus
> implementations, and it essentially means to rewrite the HD-audio
> codec plumbing code.  Currently, it's a kind of half-baked state, and
> we need to cast to unified form.

Before going into codec support, should we first deal with the selection 
of the ASoC/Legacy mode for the controller side of things? Even with 
basic HDMI/iDisp cases, we don't have a clean solution today. When I 
worked on the late Joule platform, there was no fallback mode which 
forced a recompilation depending on BIOS settings.
My understanding is that there is no support for multiple drivers 
registering for the same PCI ID, I believe we'll have to define a 
top-level wrapper which arbitrates internally based on BIOS settings and 
user/distro preferences which mode is selected.

> 
> 
> thanks,
> 
> Takashi
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