---

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_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_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).
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.
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@suse.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.

int snd_hctl_close (  snd_hctl_t *    hctl )

close HCTL handle Parameters: hctl  HCTL handle Returns: 0 on success otherwise a negative error code Closes the specified HCTL handle and frees all associated resources.

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. Parameters: c1  First HCTL element c2  Second HCTL element Returns: -1 if c1 < c2, 0 if c1 == c2, 1 if c1 > c2

void* snd_hctl_elem_get_callback_private (  const snd_hctl_elem_t *    obj )

Get callback private value for an HCTL element. Parameters: obj  HCTL element Returns: callback private 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. Parameters: obj  CTL element id/value Returns: device part of element identifier

snd_hctl_t* snd_hctl_elem_get_hctl (  snd_hctl_elem_t *    elem )

Get HCTL handle for an HCTL element. Parameters: elem  HCTL element Returns: HCTL handle

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. Parameters: obj  CTL element id/value ptr  Pointer to returned CTL element identifier

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. Parameters: obj  CTL element id/value Returns: index part of element identifier

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. Parameters: obj  CTL element id/value Returns: interface part of element identifier

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. Parameters: obj  CTL element id/value Returns: name part of element identifier

unsigned int snd_hctl_elem_get_numid (  const snd_hctl_elem_t *    obj )

Get element numeric identifier of a CTL element id/value. Parameters: obj  CTL element id/value Returns: element numeric identifier

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. Parameters: obj  CTL element id/value Returns: subdevice part of element identifier

int snd_hctl_elem_info (  snd_hctl_elem_t *    elem, snd_ctl_elem_info_t *    info )

Get information for an HCTL element. Parameters: elem  HCTL element info  HCTL element information Returns: 0 otherwise a negative error code on failure

snd_hctl_elem_t* snd_hctl_elem_next (  snd_hctl_elem_t *    elem )

get next HCTL element Parameters: elem  HCTL element Returns: pointer to next element

snd_hctl_elem_t* snd_hctl_elem_prev (  snd_hctl_elem_t *    elem )

get previous HCTL element Parameters: elem  HCTL element Returns: pointer to previous element

int snd_hctl_elem_read (  snd_hctl_elem_t *    elem, snd_ctl_elem_value_t *    value )

Get value for an HCTL element. Parameters: elem  HCTL element value  HCTL element value Returns: 0 otherwise a negative error code on failure

void snd_hctl_elem_set_callback (  snd_hctl_elem_t *    obj, snd_hctl_elem_callback_t    val )

Set callback function for an HCTL element. Parameters: obj  HCTL element val  callback function

void snd_hctl_elem_set_callback_private (  snd_hctl_elem_t *    obj, void *    val )

Set callback private value for an HCTL element. Parameters: obj  HCTL element val  callback private value

int snd_hctl_elem_write (  snd_hctl_elem_t *    elem, snd_ctl_elem_value_t *    value )

Set value for an HCTL element. Parameters: elem  HCTL element value  HCTL element value Returns: 0 otherwise a negative error code on failure

snd_hctl_elem_t* snd_hctl_find_elem (  snd_hctl_t *    hctl, const snd_ctl_elem_id_t *    id )

Search an HCTL element. Parameters: hctl  HCTL handle id  Element identifier Returns: pointer to found HCTL element or NULL if it does not exists

snd_hctl_elem_t* snd_hctl_first_elem (  snd_hctl_t *    hctl )

get first element for an HCTL Parameters: hctl  HCTL handle Returns: pointer to first element

int snd_hctl_free (  snd_hctl_t *    hctl )

free HCTL loaded elements Parameters: hctl  HCTL handle Returns: 0 on success otherwise a negative error code

void* snd_hctl_get_callback_private (  snd_hctl_t *    hctl )

Get callback private value for an HCTL. Parameters: hctl  HCTL handle Returns: callback private value

unsigned int snd_hctl_get_count (  snd_hctl_t *    hctl )

Get number of loaded elements for an HCTL. Parameters: hctl  HCTL handle Returns: elements count

int snd_hctl_handle_events (  snd_hctl_t *    hctl )

Handle pending HCTL events invoking callbacks. Parameters: hctl  HCTL handle Returns: 0 otherwise a negative error code on failure

snd_hctl_elem_t* snd_hctl_last_elem (  snd_hctl_t *    hctl )

get last element for an HCTL Parameters: hctl  HCTL handle Returns: pointer to last element

int snd_hctl_load (  snd_hctl_t *    hctl )

Load an HCTL with all elements and sort them. Parameters: hctl  HCTL handle Returns: 0 on success otherwise a negative error code

const char* snd_hctl_name (  snd_hctl_t *    hctl )

get identifier of HCTL handle Parameters: hctl  HCTL handle Returns: ascii identifier of HCTL handle Returns the ASCII identifier of given HCTL handle. It's the same identifier specified in snd_hctl_open().

int snd_hctl_nonblock (  snd_hctl_t *    hctl, int    nonblock )

set nonblock mode Parameters: hctl  HCTL handle nonblock  0 = block, 1 = nonblock mode Returns: 0 on success otherwise a negative error code

int snd_hctl_open (  snd_hctl_t **    hctlp, const char *    name, int    mode )

Opens an HCTL. Parameters: hctlp  Returned HCTL handle name  ASCII identifier of the underlying CTL handle mode  Open mode (see SND_CTL_NONBLOCK, SND_CTL_ASYNC) Returns: 0 on success otherwise a negative error code

int snd_hctl_poll_descriptors (  snd_hctl_t *    hctl, struct pollfd *    pfds, unsigned int    space )

get poll descriptors Parameters: hctl  HCTL handle pfds  array of poll descriptors space  space in the poll descriptor array Returns: count of filled descriptors

int snd_hctl_poll_descriptors_count (  snd_hctl_t *    hctl )

get count of poll descriptors for HCTL handle Parameters: hctl  HCTL handle Returns: count of poll descriptors

void snd_hctl_set_callback (  snd_hctl_t *    hctl, snd_hctl_callback_t    callback )

Set callback function for an HCTL. Parameters: hctl  HCTL handle callback  callback function

void snd_hctl_set_callback_private (  snd_hctl_t *    hctl, void *    callback_private )

Set callback private value for an HCTL. Parameters: hctl  HCTL handle callback_private  callback private value

int snd_hctl_set_compare (  snd_hctl_t *    hctl, snd_hctl_compare_t    compare )

Change HCTL compare function and reorder elements. Parameters: hctl  HCTL handle compare  Element compare function Returns: 0 on success otherwise a negative error code

int snd_hctl_wait (  snd_hctl_t *    hctl, int    timeout )

Wait for a HCTL to become ready (i.e. at least one event pending). Parameters: hctl  HCTL handle timeout  maximum time in milliseconds to wait Returns: 0 otherwise a negative error code on failure

---