snd_pcm_plugin_prepare()

Signal the driver to ready the specified channel (plugin-aware)

Synopsis:

#include <sys/asoundlib.h>

int snd_pcm_plugin_prepare( snd_pcm_t *handle,
                            int channel );

Arguments:

handle: The handle for the PCM device, which you must have opened by calling snd_pcm_open() or snd_pcm_open_preferred().
channel: The channel; SND_PCM_CHANNEL_CAPTURE or SND_PCM_CHANNEL_PLAYBACK.

The snd_pcm_plugin_prepare() function prepares hardware to operate in a specified transfer direction. This call is responsible for all parts of the hardware's startup sequence that require additional initialization time, allowing the final “GO” (usually from writes into the buffers) to execute more quickly.

This function may be called in all states except SND_PCM_STATUS_NOTREADY (returns -EBADFD) and SND_PCM_STATUS_RUNNING (returns -EBUSY). If the operation is successful (zero is returned), the driver state is changed to SND_PCM_STATUS_PREPARED.

If your channel has underrun (during playback) or overrun (during capture), you have to reprepare it before continuing. For an example, see wave.c and waverec.c in the appendix.

Returns:

Zero, or a negative error code.

Errors:

-EBUSY: The subchannel is in the running state.
-EINVAL: Invalid handle.

Examples:

See the wave.c example in the appendix.

Classification:

QNX Neutrino

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Yes
Thread	Yes

Caveats:

This function is the plugin-aware version of snd_pcm_channel_prepare(). It functions exactly the same way. However, make sure that you don't mix and match plugin- and nonplugin-aware functions in your application, or you may get undefined behavior and misleading results.