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