snd_ctl_mixer_switch

Get the number and names of control switches for the mixer

Synopsis:

#include <sys/asoundlib.h >
int snd_ctl_mixer_switch_list( snd_ctl_t *handle,
                     int dev, snd_switch_list_t *list );

Arguments:

handle: The handle for the control device. This must have been created by snd_ctl_open().
dev: The mixer device the switches apply to.
list: A pointer to a snd_switch_list_t structure that snd_ctl_mixer_switch_list() fills with information about the switch.

Library:

libasound.so

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

Description:

The snd_ctl_mixer_switch_list() function uses the control device handle to fill the given snd_switch_list_t structure with the number of switches for the mixer specified. It also fills in the array of switches pointed to by pswitches to a limit of switches_size. Before calling snd_mixer_groups(), set the members of the snd_switch_list_t as follows:

pswitches: This pointer must be NULL or point to a valid storage location for the switches (i.e., an array of snd_switch_list_item_t structures).
switches_size: The size of the pswitches storage location in sizeof( snd_switch_list_item_t ) units (i.e., the number of entries in the array).

On a successful return, the snd_ctl_mixer_switch_list() function will fill in these members:

switches: The number of switches retrieved into the pswitch local storage. Read only.
switches_over: The number of switches that could not be retrieved due to the size constraints of the pswitches local storage. Read only.

Returns:

Zero on success, or a negative value if an error occurs.

Errors:

-EINVAL: Invalid handle argument.

Classification:

QNX Neutrino

Safety:
Cancellation point	No
Signal handler	Yes
Thread	Yes

Caveats:

The switch struct must be initialized to a known state before making the call; use memset() to set the struct to zero, and then set the name member to specify which switch to read.