# /builddir/build/BUILD/alsa-lib-1.1.0/src/control/hcontrol.c File Reference

HCTL Interface - High Level CTL. More...

## Functions

int | snd_hctl_open (snd_hctl_t **hctlp, const char *name, int mode)
| Opens an HCTL.
int | snd_hctl_open_ctl (snd_hctl_t **hctlp, snd_ctl_t *ctl)
| Opens an HCTL.
int | snd_hctl_close (snd_hctl_t *hctl)
| close HCTL handle
const char * | snd_hctl_name (snd_hctl_t *hctl)
| get identifier of HCTL handle
int | snd_hctl_nonblock (snd_hctl_t *hctl, int nonblock)
| set nonblock mode
int | snd_hctl_async (snd_hctl_t *hctl, int sig, pid_t pid)
| set async mode
int | snd_hctl_poll_descriptors_count (snd_hctl_t *hctl)
| get count of poll descriptors for HCTL handle
int | snd_hctl_poll_descriptors (snd_hctl_t *hctl, struct pollfd *pfds, unsigned int space)
| get poll descriptors
int | snd_hctl_poll_descriptors_revents (snd_hctl_t *hctl, struct pollfd *pfds, unsigned int nfds, unsigned short *revents)
| get returned events from poll descriptors
int | snd_hctl_free (snd_hctl_t *hctl)
| free HCTL loaded elements
int | snd_hctl_set_compare (snd_hctl_t *hctl, snd_hctl_compare_t compare)
| Change HCTL compare function and reorder elements.
int | snd_hctl_compare_fast (const snd_hctl_elem_t *c1, const snd_hctl_elem_t *c2)
| A "don't care" fast compare functions that may be used with snd_hctl_set_compare.
snd_hctl_elem_t * | snd_hctl_first_elem (snd_hctl_t *hctl)
| get first element for an HCTL
snd_hctl_elem_t * | snd_hctl_last_elem (snd_hctl_t *hctl)
| get last element for an HCTL
snd_hctl_elem_t * | snd_hctl_elem_next (snd_hctl_elem_t *elem)
| get next HCTL element
snd_hctl_elem_t * | snd_hctl_elem_prev (snd_hctl_elem_t *elem)
| get previous HCTL element
snd_hctl_elem_t * | snd_hctl_find_elem (snd_hctl_t *hctl, const snd_ctl_elem_id_t *id)
| Search an HCTL element.
int | snd_hctl_load (snd_hctl_t *hctl)
| Load an HCTL with all elements and sort them.
void | snd_hctl_set_callback (snd_hctl_t *hctl, snd_hctl_callback_t callback)
| Set callback function for an HCTL.
void | snd_hctl_set_callback_private (snd_hctl_t *hctl, void *callback_private)
| Set callback private value for an HCTL.
void * | snd_hctl_get_callback_private (snd_hctl_t *hctl)
| Get callback private value for an HCTL.
unsigned int | snd_hctl_get_count (snd_hctl_t *hctl)
| Get number of loaded elements for an HCTL.
int | snd_hctl_wait (snd_hctl_t *hctl, int timeout)
| Wait for a HCTL to become ready (i.e. at least one event pending).
snd_ctl_t * | snd_hctl_ctl (snd_hctl_t *hctl)
| Get a ctl handle associated to the given hctl handle.
int | snd_hctl_handle_events (snd_hctl_t *hctl)
| Handle pending HCTL events invoking callbacks.
int | snd_hctl_elem_info (snd_hctl_elem_t *elem, snd_ctl_elem_info_t *info)
| Get information for an HCTL element.
int | snd_hctl_elem_read (snd_hctl_elem_t *elem, snd_ctl_elem_value_t *value)
| Get value for an HCTL element.
int | snd_hctl_elem_write (snd_hctl_elem_t *elem, snd_ctl_elem_value_t *value)
| Set value for an HCTL element.
int | snd_hctl_elem_tlv_read (snd_hctl_elem_t *elem, unsigned int *tlv, unsigned int tlv_size)
| Get TLV value for an HCTL element.
int | snd_hctl_elem_tlv_write (snd_hctl_elem_t *elem, const unsigned int *tlv)
| Set TLV value for an HCTL element.
int | snd_hctl_elem_tlv_command (snd_hctl_elem_t *elem, const unsigned int *tlv)
| Set TLV value for an HCTL element.
snd_hctl_t * | snd_hctl_elem_get_hctl (snd_hctl_elem_t *elem)
| Get HCTL handle for an HCTL element.
void | snd_hctl_elem_get_id (const snd_hctl_elem_t *obj, snd_ctl_elem_id_t *ptr)
| Get CTL element identifier of a CTL element id/value.
unsigned int | snd_hctl_elem_get_numid (const snd_hctl_elem_t *obj)
| Get element numeric identifier of a CTL element id/value.
snd_ctl_elem_iface_t | snd_hctl_elem_get_interface (const snd_hctl_elem_t *obj)
| Get interface part of CTL element identifier of a CTL element id/value.
unsigned int | snd_hctl_elem_get_device (const snd_hctl_elem_t *obj)
| Get device part of CTL element identifier of a CTL element id/value.
unsigned int | snd_hctl_elem_get_subdevice (const snd_hctl_elem_t *obj)
| Get subdevice part of CTL element identifier of a CTL element id/value.
const char * | snd_hctl_elem_get_name (const snd_hctl_elem_t *obj)
| Get name part of CTL element identifier of a CTL element id/value.
unsigned int | snd_hctl_elem_get_index (const snd_hctl_elem_t *obj)
| Get index part of CTL element identifier of a CTL element id/value.
void | snd_hctl_elem_set_callback (snd_hctl_elem_t *obj, snd_hctl_elem_callback_t val)
| Set callback function for an HCTL element.
void | snd_hctl_elem_set_callback_private (snd_hctl_elem_t *obj, void *val)
| Set callback private value for an HCTL element.
void * | snd_hctl_elem_get_callback_private (const snd_hctl_elem_t *obj)
| Get callback private value for an HCTL element.

## Detailed Description

HCTL Interface - High Level CTL.

Author:
  Jaroslav Kysela <perex@perex.cz>
  Abramo Bagnara <abramo@alsa-project.org>

Date:
  2000

HCTL interface is designed to access preloaded and sorted primitive controls. Callbacks may be used for event handling. See High level control interface page for more details.

## Function Documentation

int snd_hctl_async | ( | snd_hctl_t * | hctl,
|  | int | sig,
|  | pid_t | pid |
| ) |  |  |

set async mode

Parameters:

  | hctl | HCTL handle
  | sig | Signal to raise: < 0 disable, 0 default (SIGIO)
  | pid | Process ID to signal: 0 current

Returns:
  0 on success otherwise a negative error code

A signal is raised when a change happens.

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