3 * \brief Mixer Interface
4 * \author Jaroslav Kysela <perex@perex.cz>
5 * \author Abramo Bagnara <abramo@alsa-project.org>
8 * Mixer interface is designed to access mixer elements.
9 * Callbacks may be used for event handling.
12 * Mixer Interface - main file
13 * Copyright (c) 1998/1999/2000 by Jaroslav Kysela <perex@perex.cz>
14 * Copyright (c) 2001 by Abramo Bagnara <abramo@alsa-project.org>
17 * This library is free software; you can redistribute it and/or modify
18 * it under the terms of the GNU Lesser General Public License as
19 * published by the Free Software Foundation; either version 2.1 of
20 * the License, or (at your option) any later version.
22 * This program is distributed in the hope that it will be useful,
23 * but WITHOUT ANY WARRANTY; without even the implied warranty of
24 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
25 * GNU Lesser General Public License for more details.
27 * You should have received a copy of the GNU Lesser General Public
28 * License along with this library; if not, write to the Free Software
29 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
33 /*! \page mixer Mixer interface
35 <P>Mixer interface is designed to access the abstracted mixer controls.
36 This is an abstraction layer over the hcontrol layer.
38 \section mixer_general_overview General overview
47 #include <sys/ioctl.h>
48 #include "mixer_local.h"
51 typedef struct _snd_mixer_slave {
53 struct list_head list;
58 static int snd_mixer_compare_default(const snd_mixer_elem_t *c1,
59 const snd_mixer_elem_t *c2);
63 * \brief Opens an empty mixer
64 * \param mixerp Returned mixer handle
65 * \param mode Open mode
66 * \return 0 on success otherwise a negative error code
68 int snd_mixer_open(snd_mixer_t **mixerp, int mode ATTRIBUTE_UNUSED)
72 mixer = calloc(1, sizeof(*mixer));
75 INIT_LIST_HEAD(&mixer->slaves);
76 INIT_LIST_HEAD(&mixer->classes);
77 INIT_LIST_HEAD(&mixer->elems);
78 mixer->compare = snd_mixer_compare_default;
84 * \brief Attach an HCTL element to a mixer element
85 * \param melem Mixer element
86 * \param helem HCTL element
87 * \return 0 on success otherwise a negative error code
89 * For use by mixer element class specific code.
91 int snd_mixer_elem_attach(snd_mixer_elem_t *melem,
92 snd_hctl_elem_t *helem)
94 bag_t *bag = snd_hctl_elem_get_callback_private(helem);
96 err = bag_add(bag, melem);
99 return bag_add(&melem->helems, helem);
103 * \brief Detach an HCTL element from a mixer element
104 * \param melem Mixer element
105 * \param helem HCTL element
106 * \return 0 on success otherwise a negative error code
108 * For use by mixer element class specific code.
110 int snd_mixer_elem_detach(snd_mixer_elem_t *melem,
111 snd_hctl_elem_t *helem)
113 bag_t *bag = snd_hctl_elem_get_callback_private(helem);
115 err = bag_del(bag, melem);
117 err = bag_del(&melem->helems, helem);
123 * \brief Return true if a mixer element does not contain any HCTL elements
124 * \param melem Mixer element
125 * \return 0 if not empty, 1 if empty
127 * For use by mixer element class specific code.
129 int snd_mixer_elem_empty(snd_mixer_elem_t *melem)
131 return bag_empty(&melem->helems);
134 static int hctl_elem_event_handler(snd_hctl_elem_t *helem,
137 bag_t *bag = snd_hctl_elem_get_callback_private(helem);
138 if (mask == SND_CTL_EVENT_MASK_REMOVE) {
142 bag_for_each_safe(i, n, bag) {
143 snd_mixer_elem_t *melem = bag_iterator_entry(i);
144 snd_mixer_class_t *class = melem->class;
145 err = class->event(class, mask, helem, melem);
149 assert(bag_empty(bag));
153 if (mask & (SND_CTL_EVENT_MASK_VALUE | SND_CTL_EVENT_MASK_INFO)) {
156 bag_for_each_safe(i, n, bag) {
157 snd_mixer_elem_t *melem = bag_iterator_entry(i);
158 snd_mixer_class_t *class = melem->class;
159 err = class->event(class, mask, helem, melem);
167 static int hctl_event_handler(snd_hctl_t *hctl, unsigned int mask,
168 snd_hctl_elem_t *elem)
170 snd_mixer_t *mixer = snd_hctl_get_callback_private(hctl);
172 if (mask & SND_CTL_EVENT_MASK_ADD) {
173 struct list_head *pos;
175 int err = bag_new(&bag);
178 snd_hctl_elem_set_callback(elem, hctl_elem_event_handler);
179 snd_hctl_elem_set_callback_private(elem, bag);
180 list_for_each(pos, &mixer->classes) {
181 snd_mixer_class_t *c;
182 c = list_entry(pos, snd_mixer_class_t, list);
183 err = c->event(c, mask, elem, NULL);
193 * \brief Attach an HCTL specified with the CTL device name to an opened mixer
194 * \param mixer Mixer handle
195 * \param name HCTL name (see #snd_hctl_open)
196 * \return 0 on success otherwise a negative error code
198 int snd_mixer_attach(snd_mixer_t *mixer, const char *name)
203 err = snd_hctl_open(&hctl, name, 0);
206 err = snd_mixer_attach_hctl(mixer, hctl);
213 * \brief Attach an HCTL to an opened mixer
214 * \param mixer Mixer handle
215 * \param hctl the HCTL to be attached
216 * \return 0 on success otherwise a negative error code
218 * Upon error, this function closes the given hctl handle automatically.
220 int snd_mixer_attach_hctl(snd_mixer_t *mixer, snd_hctl_t *hctl)
222 snd_mixer_slave_t *slave;
226 slave = calloc(1, sizeof(*slave));
228 snd_hctl_close(hctl);
231 err = snd_hctl_nonblock(hctl, 1);
233 snd_hctl_close(hctl);
237 snd_hctl_set_callback(hctl, hctl_event_handler);
238 snd_hctl_set_callback_private(hctl, mixer);
240 list_add_tail(&slave->list, &mixer->slaves);
245 * \brief Detach a previously attached HCTL to an opened mixer freeing all related resources
246 * \param mixer Mixer handle
247 * \param name HCTL previously attached
248 * \return 0 on success otherwise a negative error code
250 int snd_mixer_detach(snd_mixer_t *mixer, const char *name)
252 struct list_head *pos;
253 list_for_each(pos, &mixer->slaves) {
254 snd_mixer_slave_t *s;
255 s = list_entry(pos, snd_mixer_slave_t, list);
256 if (strcmp(name, snd_hctl_name(s->hctl)) == 0) {
257 snd_hctl_close(s->hctl);
267 * \brief Detach a previously attached HCTL to an opened mixer freeing all related resources
268 * \param mixer Mixer handle
269 * \param hctl HCTL previously attached
270 * \return 0 on success otherwise a negative error code
272 * Note: The hctl handle is not closed!
274 int snd_mixer_detach_hctl(snd_mixer_t *mixer, snd_hctl_t *hctl)
276 struct list_head *pos;
277 list_for_each(pos, &mixer->slaves) {
278 snd_mixer_slave_t *s;
279 s = list_entry(pos, snd_mixer_slave_t, list);
280 if (hctl == s->hctl) {
290 * \brief Obtain a HCTL pointer associated to given name
291 * \param mixer Mixer handle
292 * \param name HCTL previously attached
293 * \param hctl HCTL pointer
294 * \return 0 on success otherwise a negative error code
296 int snd_mixer_get_hctl(snd_mixer_t *mixer, const char *name, snd_hctl_t **hctl)
298 struct list_head *pos;
299 list_for_each(pos, &mixer->slaves) {
300 snd_mixer_slave_t *s;
301 s = list_entry(pos, snd_mixer_slave_t, list);
302 if (strcmp(name, snd_hctl_name(s->hctl)) == 0) {
310 static int snd_mixer_throw_event(snd_mixer_t *mixer, unsigned int mask,
311 snd_mixer_elem_t *elem)
315 return mixer->callback(mixer, mask, elem);
319 static int snd_mixer_elem_throw_event(snd_mixer_elem_t *elem, unsigned int mask)
321 elem->class->mixer->events++;
323 return elem->callback(elem, mask);
327 static int _snd_mixer_find_elem(snd_mixer_t *mixer, snd_mixer_elem_t *elem, int *dir)
332 assert(mixer && elem);
333 assert(mixer->compare);
338 c = mixer->compare(elem, mixer->pelems[idx]);
351 * \brief Get private data associated to give mixer element
352 * \param elem Mixer element
353 * \return private data
355 * For use by mixer element class specific code.
357 void *snd_mixer_elem_get_private(const snd_mixer_elem_t *elem)
359 return elem->private_data;
363 * \brief Allocate a new mixer element
364 * \param elem Returned mixer element
365 * \param type Mixer element type
366 * \param compare_weight Mixer element compare weight
367 * \param private_data Private data
368 * \param private_free Private data free callback
369 * \return 0 on success otherwise a negative error code
371 * For use by mixer element class specific code.
373 int snd_mixer_elem_new(snd_mixer_elem_t **elem,
374 snd_mixer_elem_type_t type,
377 void (*private_free)(snd_mixer_elem_t *elem))
379 snd_mixer_elem_t *melem = calloc(1, sizeof(*melem));
383 melem->compare_weight = compare_weight;
384 melem->private_data = private_data;
385 melem->private_free = private_free;
386 INIT_LIST_HEAD(&melem->helems);
392 * \brief Add an element for a registered mixer element class
393 * \param elem Mixer element
394 * \param class Mixer element class
395 * \return 0 on success otherwise a negative error code
397 * For use by mixer element class specific code.
399 int snd_mixer_elem_add(snd_mixer_elem_t *elem, snd_mixer_class_t *class)
402 snd_mixer_t *mixer = class->mixer;
405 if (mixer->count == mixer->alloc) {
406 snd_mixer_elem_t **m;
408 m = realloc(mixer->pelems, sizeof(*m) * mixer->alloc);
415 if (mixer->count == 0) {
416 list_add_tail(&elem->list, &mixer->elems);
417 mixer->pelems[0] = elem;
419 idx = _snd_mixer_find_elem(mixer, elem, &dir);
422 list_add(&elem->list, &mixer->pelems[idx]->list);
425 list_add_tail(&elem->list, &mixer->pelems[idx]->list);
427 memmove(mixer->pelems + idx + 1,
429 (mixer->count - idx) * sizeof(snd_mixer_elem_t *));
430 mixer->pelems[idx] = elem;
433 return snd_mixer_throw_event(mixer, SND_CTL_EVENT_MASK_ADD, elem);
437 * \brief Remove a mixer element
438 * \param elem Mixer element
439 * \return 0 on success otherwise a negative error code
441 * For use by mixer element class specific code.
443 int snd_mixer_elem_remove(snd_mixer_elem_t *elem)
445 snd_mixer_t *mixer = elem->class->mixer;
450 assert(mixer->count);
451 idx = _snd_mixer_find_elem(mixer, elem, &dir);
454 bag_for_each_safe(i, n, &elem->helems) {
455 snd_hctl_elem_t *helem = bag_iterator_entry(i);
456 snd_mixer_elem_detach(elem, helem);
458 err = snd_mixer_elem_throw_event(elem, SND_CTL_EVENT_MASK_REMOVE);
459 list_del(&elem->list);
460 snd_mixer_elem_free(elem);
462 m = mixer->count - idx;
464 memmove(mixer->pelems + idx,
465 mixer->pelems + idx + 1,
466 m * sizeof(snd_mixer_elem_t *));
471 * \brief Free a mixer element
472 * \param elem Mixer element
473 * \return 0 on success otherwise a negative error code
475 * For use by mixer element class specific code.
477 void snd_mixer_elem_free(snd_mixer_elem_t *elem)
479 if (elem->private_free)
480 elem->private_free(elem);
485 * \brief Mixer element informations are changed
486 * \param elem Mixer element
487 * \return 0 on success otherwise a negative error code
489 * For use by mixer element class specific code.
491 int snd_mixer_elem_info(snd_mixer_elem_t *elem)
493 return snd_mixer_elem_throw_event(elem, SND_CTL_EVENT_MASK_INFO);
497 * \brief Mixer element values is changed
498 * \param elem Mixer element
499 * \return 0 on success otherwise a negative error code
501 * For use by mixer element class specific code.
503 int snd_mixer_elem_value(snd_mixer_elem_t *elem)
505 return snd_mixer_elem_throw_event(elem, SND_CTL_EVENT_MASK_VALUE);
509 * \brief Register mixer element class
510 * \param class Mixer element class
511 * \param mixer Mixer handle
512 * \return 0 on success otherwise a negative error code
514 * For use by mixer element class specific code.
516 int snd_mixer_class_register(snd_mixer_class_t *class, snd_mixer_t *mixer)
518 struct list_head *pos;
519 class->mixer = mixer;
520 list_add_tail(&class->list, &mixer->classes);
523 list_for_each(pos, &mixer->slaves) {
525 snd_mixer_slave_t *slave;
526 snd_hctl_elem_t *elem;
527 slave = list_entry(pos, snd_mixer_slave_t, list);
528 elem = snd_hctl_first_elem(slave->hctl);
530 err = class->event(class, SND_CTL_EVENT_MASK_ADD, elem, NULL);
533 elem = snd_hctl_elem_next(elem);
540 * \brief Unregister mixer element class and remove all its elements
541 * \param class Mixer element class
542 * \return 0 on success otherwise a negative error code
544 * Note that the class structure is also deallocated!
546 int snd_mixer_class_unregister(snd_mixer_class_t *class)
550 snd_mixer_t *mixer = class->mixer;
551 for (k = mixer->count; k > 0; k--) {
552 e = mixer->pelems[k-1];
553 if (e->class == class)
554 snd_mixer_elem_remove(e);
556 if (class->private_free)
557 class->private_free(class);
558 list_del(&class->list);
564 * \brief Load a mixer elements
565 * \param mixer Mixer handle
566 * \return 0 on success otherwise a negative error code
568 int snd_mixer_load(snd_mixer_t *mixer)
570 struct list_head *pos;
571 list_for_each(pos, &mixer->slaves) {
573 snd_mixer_slave_t *s;
574 s = list_entry(pos, snd_mixer_slave_t, list);
575 err = snd_hctl_load(s->hctl);
583 * \brief Unload all mixer elements and free all related resources
584 * \param mixer Mixer handle
586 void snd_mixer_free(snd_mixer_t *mixer)
588 struct list_head *pos;
589 list_for_each(pos, &mixer->slaves) {
590 snd_mixer_slave_t *s;
591 s = list_entry(pos, snd_mixer_slave_t, list);
592 snd_hctl_free(s->hctl);
597 * \brief Close a mixer and free all related resources
598 * \param mixer Mixer handle
599 * \return 0 on success otherwise a negative error code
601 int snd_mixer_close(snd_mixer_t *mixer)
605 while (!list_empty(&mixer->classes)) {
606 snd_mixer_class_t *c;
607 c = list_entry(mixer->classes.next, snd_mixer_class_t, list);
608 snd_mixer_class_unregister(c);
610 assert(list_empty(&mixer->elems));
611 assert(mixer->count == 0);
613 mixer->pelems = NULL;
614 while (!list_empty(&mixer->slaves)) {
616 snd_mixer_slave_t *s;
617 s = list_entry(mixer->slaves.next, snd_mixer_slave_t, list);
618 err = snd_hctl_close(s->hctl);
628 static int snd_mixer_compare_default(const snd_mixer_elem_t *c1,
629 const snd_mixer_elem_t *c2)
631 int d = c1->compare_weight - c2->compare_weight;
634 assert(c1->class && c1->class->compare);
635 assert(c2->class && c2->class->compare);
636 assert(c1->class == c2->class);
637 return c1->class->compare(c1, c2);
640 static int mixer_compare(const void *a, const void *b)
644 mixer = (*((const snd_mixer_elem_t * const *)a))->class->mixer;
645 return mixer->compare(*(const snd_mixer_elem_t * const *)a, *(const snd_mixer_elem_t * const *)b);
648 static int snd_mixer_sort(snd_mixer_t *mixer)
652 assert(mixer->compare);
653 INIT_LIST_HEAD(&mixer->elems);
654 qsort(mixer->pelems, mixer->count, sizeof(snd_mixer_elem_t *), mixer_compare);
655 for (k = 0; k < mixer->count; k++)
656 list_add_tail(&mixer->pelems[k]->list, &mixer->elems);
661 * \brief Change mixer compare function and reorder elements
662 * \param mixer Mixer handle
663 * \param compare Element compare function
664 * \return 0 on success otherwise a negative error code
666 int snd_mixer_set_compare(snd_mixer_t *mixer, snd_mixer_compare_t compare)
668 snd_mixer_compare_t compare_old;
672 compare_old = mixer->compare;
673 mixer->compare = compare == NULL ? snd_mixer_compare_default : compare;
674 if ((err = snd_mixer_sort(mixer)) < 0) {
675 mixer->compare = compare_old;
682 * \brief get count of poll descriptors for mixer handle
683 * \param mixer Mixer handle
684 * \return count of poll descriptors
686 int snd_mixer_poll_descriptors_count(snd_mixer_t *mixer)
688 struct list_head *pos;
691 list_for_each(pos, &mixer->slaves) {
692 snd_mixer_slave_t *s;
694 s = list_entry(pos, snd_mixer_slave_t, list);
695 n = snd_hctl_poll_descriptors_count(s->hctl);
704 * \brief get poll descriptors
705 * \param mixer Mixer handle
706 * \param pfds array of poll descriptors
707 * \param space space in the poll descriptor array
708 * \return count of filled descriptors
710 int snd_mixer_poll_descriptors(snd_mixer_t *mixer, struct pollfd *pfds, unsigned int space)
712 struct list_head *pos;
713 unsigned int count = 0;
715 list_for_each(pos, &mixer->slaves) {
716 snd_mixer_slave_t *s;
718 s = list_entry(pos, snd_mixer_slave_t, list);
719 n = snd_hctl_poll_descriptors(s->hctl, pfds, space);
722 if (space >= (unsigned int) n) {
733 * \brief get returned events from poll descriptors
734 * \param mixer Mixer handle
735 * \param pfds array of poll descriptors
736 * \param nfds count of poll descriptors
737 * \param revents returned events
738 * \return zero if success, otherwise a negative error code
740 int snd_mixer_poll_descriptors_revents(snd_mixer_t *mixer, struct pollfd *pfds, unsigned int nfds, unsigned short *revents)
744 assert(mixer && pfds && revents);
748 for (idx = 0; idx < nfds; idx++, pfds++)
749 res |= pfds->revents & (POLLIN|POLLERR|POLLNVAL);
755 * \brief Wait for a mixer to become ready (i.e. at least one event pending)
756 * \param mixer Mixer handle
757 * \param timeout maximum time in milliseconds to wait
758 * \return 0 otherwise a negative error code on failure
760 int snd_mixer_wait(snd_mixer_t *mixer, int timeout)
762 struct pollfd spfds[16];
763 struct pollfd *pfds = spfds;
766 count = snd_mixer_poll_descriptors(mixer, pfds, sizeof(spfds) / sizeof(spfds[0]));
769 if ((unsigned int) count > sizeof(spfds) / sizeof(spfds[0])) {
770 pfds = malloc(count * sizeof(*pfds));
773 err = snd_mixer_poll_descriptors(mixer, pfds,
774 (unsigned int) count);
775 assert(err == count);
777 err = poll(pfds, (unsigned int) count, timeout);
784 * \brief get first element for a mixer
785 * \param mixer Mixer handle
786 * \return pointer to first element
788 snd_mixer_elem_t *snd_mixer_first_elem(snd_mixer_t *mixer)
791 if (list_empty(&mixer->elems))
793 return list_entry(mixer->elems.next, snd_mixer_elem_t, list);
797 * \brief get last element for a mixer
798 * \param mixer Mixer handle
799 * \return pointer to last element
801 snd_mixer_elem_t *snd_mixer_last_elem(snd_mixer_t *mixer)
804 if (list_empty(&mixer->elems))
806 return list_entry(mixer->elems.prev, snd_mixer_elem_t, list);
810 * \brief get next mixer element
811 * \param elem mixer element
812 * \return pointer to next element
814 snd_mixer_elem_t *snd_mixer_elem_next(snd_mixer_elem_t *elem)
817 if (elem->list.next == &elem->class->mixer->elems)
819 return list_entry(elem->list.next, snd_mixer_elem_t, list);
823 * \brief get previous mixer element
824 * \param elem mixer element
825 * \return pointer to previous element
827 snd_mixer_elem_t *snd_mixer_elem_prev(snd_mixer_elem_t *elem)
830 if (elem->list.prev == &elem->class->mixer->elems)
832 return list_entry(elem->list.prev, snd_mixer_elem_t, list);
836 * \brief Handle pending mixer events invoking callbacks
837 * \param mixer Mixer handle
838 * \return Number of events that occured on success, otherwise a negative error code on failure
840 int snd_mixer_handle_events(snd_mixer_t *mixer)
842 struct list_head *pos;
845 list_for_each(pos, &mixer->slaves) {
847 snd_mixer_slave_t *s;
848 s = list_entry(pos, snd_mixer_slave_t, list);
849 err = snd_hctl_handle_events(s->hctl);
853 return mixer->events;
857 * \brief Set callback function for a mixer
858 * \param obj mixer handle
859 * \param val callback function
861 void snd_mixer_set_callback(snd_mixer_t *obj, snd_mixer_callback_t val)
868 * \brief Set callback private value for a mixer
869 * \param mixer mixer handle
870 * \param val callback private value
872 void snd_mixer_set_callback_private(snd_mixer_t *mixer, void * val)
875 mixer->callback_private = val;
879 * \brief Get callback private value for a mixer
880 * \param mixer mixer handle
881 * \return callback private value
883 void * snd_mixer_get_callback_private(const snd_mixer_t *mixer)
886 return mixer->callback_private;
890 * \brief Get elements count for a mixer
891 * \param mixer mixer handle
892 * \return elements count
894 unsigned int snd_mixer_get_count(const snd_mixer_t *mixer)
901 * \brief Set callback function for a mixer element
902 * \param mixer mixer element
903 * \param val callback function
905 void snd_mixer_elem_set_callback(snd_mixer_elem_t *mixer, snd_mixer_elem_callback_t val)
908 mixer->callback = val;
912 * \brief Set callback private value for a mixer element
913 * \param mixer mixer element
914 * \param val callback private value
916 void snd_mixer_elem_set_callback_private(snd_mixer_elem_t *mixer, void * val)
919 mixer->callback_private = val;
923 * \brief Get callback private value for a mixer element
924 * \param mixer mixer element
925 * \return callback private value
927 void * snd_mixer_elem_get_callback_private(const snd_mixer_elem_t *mixer)
930 return mixer->callback_private;
934 * \brief Get type for a mixer element
935 * \param mixer mixer element
936 * \return mixer element type
938 snd_mixer_elem_type_t snd_mixer_elem_get_type(const snd_mixer_elem_t *mixer)
946 * \brief get size of #snd_mixer_class_t
947 * \return size in bytes
949 size_t snd_mixer_class_sizeof()
951 return sizeof(snd_mixer_class_t);
955 * \brief allocate an invalid #snd_mixer_class_t using standard malloc
956 * \param ptr returned pointer
957 * \return 0 on success otherwise negative error code
959 int snd_mixer_class_malloc(snd_mixer_class_t **ptr)
962 *ptr = calloc(1, sizeof(snd_mixer_class_t));
969 * \brief frees a previously allocated #snd_mixer_class_t
970 * \param obj pointer to object to free
972 void snd_mixer_class_free(snd_mixer_class_t *obj)
974 if (obj->private_free)
975 obj->private_free(obj);
980 * \brief copy one #snd_mixer_class_t to another
981 * \param dst pointer to destination
982 * \param src pointer to source
984 void snd_mixer_class_copy(snd_mixer_class_t *dst, const snd_mixer_class_t *src)
991 * \brief Get a mixer associated to given mixer class
992 * \param obj Mixer simple class identifier
993 * \return mixer pointer
995 snd_mixer_t *snd_mixer_class_get_mixer(const snd_mixer_class_t *obj)
1002 * \brief Get mixer event callback associated to given mixer class
1003 * \param obj Mixer simple class identifier
1004 * \return event callback pointer
1006 snd_mixer_event_t snd_mixer_class_get_event(const snd_mixer_class_t *obj)
1013 * \brief Get mixer private data associated to given mixer class
1014 * \param obj Mixer simple class identifier
1015 * \return event callback pointer
1017 void *snd_mixer_class_get_private(const snd_mixer_class_t *obj)
1020 return obj->private_data;
1025 * \brief Get mixer compare callback associated to given mixer class
1026 * \param obj Mixer simple class identifier
1027 * \return event callback pointer
1029 snd_mixer_compare_t snd_mixer_class_get_compare(const snd_mixer_class_t *obj)
1032 return obj->compare;
1036 * \brief Set mixer event callback to given mixer class
1037 * \param obj Mixer simple class identifier
1038 * \param event Event callback
1039 * \return zero if success, otherwise a negative error code
1041 int snd_mixer_class_set_event(snd_mixer_class_t *obj, snd_mixer_event_t event)
1049 * \brief Set mixer private data to given mixer class
1050 * \param obj Mixer simple class identifier
1051 * \param private_data class private data
1052 * \return zero if success, otherwise a negative error code
1054 int snd_mixer_class_set_private(snd_mixer_class_t *obj, void *private_data)
1057 obj->private_data = private_data;
1062 * \brief Set mixer private data free callback to given mixer class
1063 * \param obj Mixer simple class identifier
1064 * \param private_free Mixer class private data free callback
1065 * \return zero if success, otherwise a negative error code
1067 int snd_mixer_class_set_private_free(snd_mixer_class_t *obj, void (*private_free)(snd_mixer_class_t *))
1070 obj->private_free = private_free;
1075 * \brief Set mixer compare callback to given mixer class
1076 * \param obj Mixer simple class identifier
1077 * \param compare the compare callback to be used
1078 * \return zero if success, otherwise a negative error code
1080 int snd_mixer_class_set_compare(snd_mixer_class_t *obj, snd_mixer_compare_t compare)
1083 obj->compare = compare;