[alsa-devel] question on hardware

Harsha, Priya priya.harsha at intel.com
Thu Apr 9 09:36:38 CEST 2009

Hi ,

I need more help here. I tried looking at the .conf file but I have another requirement here. 

Let me put my requirements here. Please suggest me ways to get this done

1. When I get a .prepare call in my driver, I need to know the stream type
2. When I return from that call, I need to send to the user the locally allocated stream id

This is specific to the sound card/ DSP I am developing the driver for. The application is also proprietary.  Is this possible at all? Please suggest me ways to do the same.


>-----Original Message-----
>From: David Dillow [mailto:dave at thedillows.org]
>Sent: Tuesday, December 09, 2008 6:14 PM
>To: Harsha, Priya
>Cc: Clemens Ladisch; alsa-devel at alsa-project.org; Lee Revell
>Subject: Re: [alsa-devel] question on hardware mixing
>On Tue, 2008-12-09 at 14:25 +0530, Harsha, Priya wrote:
>> If I define mixer controls to switch between each substream, I would
>> not be able to handle multiple streams at time....
>Check into the ALSA configuration file syntax -- there are number of
>things you can do there, like define a 'voice' device that uses hooks to
>set a control setting (snd_kcontrol) when you open a PCM. You can use
>that control setting to let your driver know if the PCM channel is being
>used for voice or audio traffic.
>Look at how the EMU10K1 handles surround sound audio
>in /etc/alsa/cards/EMU10K1.conf
>I started to do some similar things for sis7019 surround sound, but
>they've never made it out of my office due to lack of time/testing HW.
>> I had asked this in my earlier follow up email as well - can I use
>> snd_pcm_t->private_data to communicate if it's a voice or audio
>> I understand this private_data gets copied to substream->private data
>> which will reach the driver...
>> Am I right here?
>I can't answer this specifically, but I believe the answer is in the
>name -- 'private'. This is for the ALSA system to use, you can hang your
>own data off a substream using snd_pcm_substream_chip(). Besides, how do
>you plan on setting it in the snd_pcm_t type?
>I think that if you set up some controls, use the config file language,
>and have your audio apps open a 'voice' device, you can get where you

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