snd_ctl_file_descriptor()

Get the control file descriptor

Synopsis:

#include <sys/asoundlib.h>

int snd_ctl_file_descriptor( snd_ctl_t *handle );

Arguments:

handle: The handle for the control connection to the card. This must be a handle created by snd_ctl_open().

Library:

libasound.so

Use the -l asound option to qcc to link against this library.

Description:

The snd_ctl_file_descriptor() function returns the file descriptor of the connection to the control interface.

You can use the file descriptor for the select() function (see the QNX Neutrino C Library Reference) for determining if something can be read or written. Your application should then call snd_ctl_read() if data is waiting to be read.

Note: Don't close() the file descriptor. If PLUGIN_ROUTING is enabled (it's disabled by default) and you're dynamically routing devices, then you should consider this file descriptor to be transitory and get it again before each use with select().

Returns:

The file descriptor of the connection to the control interface, or a negative value if an error occurs.

Errors:

-EINVAL: Invalid handle argument.

Classification:

QNX Neutrino

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