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Get the number and names of control switches for the mixer
#include <sys/asoundlib.h >
int snd_ctl_mixer_switch_list( snd_ctl_t *handle,
int dev, snd_switch_list_t *list );
- 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.
libasound.so
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 total switches in this mixer device.
- switches_over
- The number of switches that couldn't be copied to the storage location.
Zero on success, or a negative value if an error occurs.
- -EINVAL
- Invalid handle argument.
QNX Neutrino
Safety: | |
Cancellation point |
No |
Interrupt handler |
No |
Signal handler |
Yes |
Thread |
Yes |
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.
snd_mixer_group_read(),
mix_ctl.c application example
source code
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