Re: pcm prepare

[Clemens Ladisch <clemens@ladisch.de>]

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