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/**
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* \file async.c
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* \brief Async notification helpers
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* \author Abramo Bagnara <abramo@alsa-project.org>
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* \date 2001
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*/
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/*
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* Async notification helpers
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* Copyright (c) 2001 by Abramo Bagnara <abramo@alsa-project.org>
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*
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* This library is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as
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* published by the Free Software Foundation; either version 2.1 of
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* the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*
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*/
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#include "pcm/pcm_local.h"
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#include "control/control_local.h"
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#include <signal.h>
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static struct sigaction previous_action;
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#define MAX_SIG_FUNCTION_CODE 10 /* i.e. SIG_DFL SIG_IGN SIG_HOLD et al */
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#ifdef SND_ASYNC_RT_SIGNAL
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/** async signal number */
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static int snd_async_signo;
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void snd_async_init(void) __attribute__ ((constructor));
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void snd_async_init(void)
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{
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snd_async_signo = __libc_allocate_rtsig(0);
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if (snd_async_signo < 0) {
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SNDERR("Unable to find a RT signal to use for snd_async");
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exit(1);
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}
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}
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#else
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/** async signal number */
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static const int snd_async_signo = SIGIO;
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#endif
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static LIST_HEAD(snd_async_handlers);
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static void snd_async_handler(int signo ATTRIBUTE_UNUSED, siginfo_t *siginfo, void *context ATTRIBUTE_UNUSED)
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{
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int fd;
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struct list_head *i;
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//assert(siginfo->si_code == SI_SIGIO);
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if (signo == SIGIO
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&& (unsigned long)(previous_action.sa_sigaction) > MAX_SIG_FUNCTION_CODE)
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previous_action.sa_sigaction(signo, siginfo, context);
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fd = siginfo->si_fd;
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list_for_each(i, &snd_async_handlers) {
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snd_async_handler_t *h = list_entry(i, snd_async_handler_t, glist);
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if (h->fd == fd && h->callback)
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h->callback(h);
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}
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}
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/**
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* \brief Registers an async handler.
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* \param handler The function puts the pointer to the new async handler
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* object at the address specified by \p handler.
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* \param fd The file descriptor to be associated with the callback.
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* \param callback The async callback function.
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* \param private_data Private data for the async callback function.
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* \result Zero if successful, otherwise a negative error code.
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*
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* This function associates the callback function with the given file,
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* and saves this association in a \c snd_async_handler_t object.
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*
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* Whenever the \c SIGIO signal is raised for the file \p fd, the callback
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* function will be called with its parameter pointing to the async handler
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* object returned by this function.
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*
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* The ALSA \c sigaction handler for the \c SIGIO signal automatically
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* multiplexes the notifications to the registered async callbacks.
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* However, the application is responsible for instructing the device driver
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* to generate the \c SIGIO signal.
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*
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* The \c SIGIO signal may have been replaced with another signal,
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* see #snd_async_handler_get_signo.
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*
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* When the async handler isn't needed anymore, you must delete it with
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* #snd_async_del_handler.
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*
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* \see snd_async_add_pcm_handler, snd_async_add_ctl_handler
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*/
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int snd_async_add_handler(snd_async_handler_t **handler, int fd,
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snd_async_callback_t callback, void *private_data)
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{
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snd_async_handler_t *h;
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int was_empty;
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assert(handler);
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h = malloc(sizeof(*h));
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if (!h)
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return -ENOMEM;
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h->fd = fd;
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h->callback = callback;
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h->private_data = private_data;
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was_empty = list_empty(&snd_async_handlers);
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list_add_tail(&h->glist, &snd_async_handlers);
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INIT_LIST_HEAD(&h->hlist);
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*handler = h;
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if (was_empty) {
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int err;
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struct sigaction act;
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memset(&act, 0, sizeof(act));
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act.sa_flags = SA_RESTART | SA_SIGINFO;
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act.sa_sigaction = snd_async_handler;
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sigemptyset(&act.sa_mask);
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assert(!previous_action.sa_sigaction);
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err = sigaction(snd_async_signo, &act, &previous_action);
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if (err < 0) {
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SYSERR("sigaction");
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return -errno;
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}
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}
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return 0;
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}
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/**
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* \brief Deletes an async handler.
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* \param handler Handle of the async handler to delete.
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* \result Zero if successful, otherwise a negative error code.
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*/
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int snd_async_del_handler(snd_async_handler_t *handler)
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{
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int err = 0;
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int was_empty = list_empty(&snd_async_handlers);
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assert(handler);
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list_del(&handler->glist);
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if (!was_empty
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&& list_empty(&snd_async_handlers)) {
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err = sigaction(snd_async_signo, &previous_action, NULL);
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if (err < 0) {
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SYSERR("sigaction");
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return -errno;
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}
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memset(&previous_action, 0, sizeof(previous_action));
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}
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if (handler->type == SND_ASYNC_HANDLER_GENERIC)
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goto _end;
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if (!list_empty(&handler->hlist))
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list_del(&handler->hlist);
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if (!list_empty(&handler->hlist))
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goto _end;
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switch (handler->type) {
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#ifdef BUILD_PCM
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case SND_ASYNC_HANDLER_PCM:
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err = snd_pcm_async(handler->u.pcm, -1, 1);
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break;
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#endif
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case SND_ASYNC_HANDLER_CTL:
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err = snd_ctl_async(handler->u.ctl, -1, 1);
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break;
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default:
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assert(0);
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}
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_end:
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free(handler);
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return err;
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}
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/**
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* \brief Returns the signal number assigned to an async handler.
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* \param handler Handle to an async handler.
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* \result The signal number if successful, otherwise a negative error code.
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*
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* The signal number for async handlers usually is \c SIGIO,
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* but wizards can redefine it to a realtime signal
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* when compiling the ALSA library.
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*/
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int snd_async_handler_get_signo(snd_async_handler_t *handler)
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{
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assert(handler);
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return snd_async_signo;
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}
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/**
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* \brief Returns the file descriptor assigned to an async handler.
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* \param handler Handle to an async handler.
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* \result The file descriptor if successful, otherwise a negative error code.
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*/
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int snd_async_handler_get_fd(snd_async_handler_t *handler)
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{
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assert(handler);
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return handler->fd;
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}
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/**
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* \brief Returns the private data assigned to an async handler.
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* \param handler Handle to an async handler.
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* \result The \c private_data value registered with the async handler.
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*/
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void *snd_async_handler_get_callback_private(snd_async_handler_t *handler)
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{
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assert(handler);
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return handler->private_data;
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}
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