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Control callback functions
typedef struct snd_ctl_callbacks {
void *private_data; /* should be used by an application */
void (*rebuild) (void *private_data);
void (*xswitch) (void *private_data, int cmd,
int iface, snd_switch_list_item_t *item);
void *reserved[29]; /* reserved for the future use - must be NULL!!! */
} snd_ctl_callbacks_t;
Use the snd_ctl_callbacks_t structure to define the callback
functions that you need to handle control events.
Pass a pointer to an instance of this structure to
snd_ctl_read().
The members of the snd_ctl_callbacks_t structure include:
- private_data, a pointer to arbitrary data that
you want to pass to the callbacks
- pointers to the callbacks, which are described below.
|
Make sure that you zero-fill any members that you aren't interested in.
You can zero-fill the entire snd_ctl_callbacks_t structure
if you aren't interested in tracking any of these events. |
The rebuild callback is called whenever the control device
is rebuilt.
Its only argument is the private_data that you specified in
this structure.
The xswitch callback is called whenever a switch changes.
Its arguments are:
- private_data
- A pointer to the arbitrary data that you specified in this structure.
- cmd
- One of:
- SND_CTL_READ_SWITCH_VALUE
- SND_CTL_READ_SWITCH_CHANGE
- SND_CTL_READ_SWITCH_ADD
- SND_CTL_READ_SWITCH_REMOVE
- iface
- The device interface the switch is natively associated with.
The possible values are (from <sys/asound.h>):
- SND_CTL_IFACE_CONTROL
- SND_CTL_IFACE_MIXER
- SND_CTL_IFACE_PCM_PLAYBACK
- SND_CTL_IFACE_PCM_CAPTURE
- item
- A pointer to a snd_switch_list_item_t structure that
identifies the specific switch that's been changed.
This structure has only a name member.
QNX Neutrino
snd_ctl_read().
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