pcm prepare

pcm prepare

[Andy Ng]

Hi,

I am quite surprised that by sending hardware params with alsa-lib the
prepare function is called automatically in the driver.

In my case, I would like to open and configure pcmNp and pcmNc and
then call prepare for pcmNp and pcmPc channels.

It is quite imperative to execute specific configuration steps after
both channels are opened and configured.

I was wondering if there is any ioctl interface that can be hooked in
alsa-lib to pass extra configuration info before start the streams.

Any ideas?

Andy

Re: pcm prepare

[Clemens Ladisch]

Andy Ng wrote:
> I am quite surprised that by sending hardware params with alsa-lib the
> prepare function is called automatically in the driver.
>
> In my case, I would like to open and configure pcmNp and pcmNc and
> then call prepare for pcmNp and pcmPc channels.
>
> It is quite imperative to execute specific configuration steps after
> both channels are opened and configured.

What configuration steps?  Is there some dependency or shared resource
between the two streams?  In that case, you have to set the
SNDRV_PCM_INFO_JOINT_DUPLEX flag, and do whatever is necessary in the
first hw_params call, and just check for correctness in the later
hw_params call of the other stream.

> I was wondering if there is any ioctl interface that can be hooked in
> alsa-lib to pass extra configuration info before start the streams.

No.


Regards,
Clemens