Get the number of elements in the mixer and their element IDs
Synopsis:
#include <sys/asoundlib.h>
int snd_mixer_elements(
snd_mixer_t *handle,
snd_mixer_elements_t *elements );
Arguments:
- handle
- The handle for the mixer device.
This must have been created by
snd_mixer_open().
- elements
- A pointer to a
snd_mixer_elements_t
structure in which snd_mixer_elements() stores the information
about the elements.
Library:
libasound.so
Use the -l asound option with
qcc
to link against this library.
Description:
The snd_mixer_elements() function
fills the given snd_mixer_elements_t structure with the number
of elements in the mixer that the handle was opened on.
It also fills in the array of element IDs pointed to by pelements
to a limit of elements_size.
Note:
We recommend that you work with mixer groups instead of manipulating the elements directly.
Before calling snd_mixer_elements(), set the
snd_mixer_elements_t structure as follows:
- pelements
- This pointer be NULL, or point to a valid storage location
for the elements (i.e., an array of
snd_mixer_eid_t
structures).
- elements_size
- This must reflect the size of the pelements storage location,
in sizeof( snd_mixer_eid_t ) units
(i.e., elements_size must be the number of entries in the
pelements array).
On a successful return, snd_mixer_elements() sets these members:
- elements
The number of elements that are currently valid in the pelements
array. Read only.
- elements_over
- The number of elements that could not be retrieved due to size constraints of the
pelements local storage. Read only.
Returns:
Zero on success, or a negative value on error.
Errors:
- -EINVAL
- Invalid handle.
Classification:
QNX Neutrino
| Safety: |
|
|---|
| Cancellation point |
No |
| Interrupt handler |
No |
| Signal handler |
Yes |
| Thread |
Yes |