alsa-lib/src/pcm/pcm_direct.c

/*
 *  PCM - Direct Stream Mixing
 *  Copyright (c) 2003 by Jaroslav Kysela <perex@suse.cz>
 *
 *
 *   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., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 */
  
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/poll.h>
#include <sys/shm.h>
#include <sys/sem.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <sys/mman.h>
#include "pcm_direct.h"

/*
 *
 */
 
 
/*
 * FIXME:
 *  add possibility to use futexes here
 */

int snd_pcm_direct_semaphore_create_or_connect(snd_pcm_direct_t *dmix)
{
	struct semid_ds buf;
	int i;

	dmix->semid = semget(dmix->ipc_key, DIRECT_IPC_SEMS,
			     IPC_CREAT | dmix->ipc_perm);
	if (dmix->semid < 0)
		return -errno;
	if (dmix->ipc_gid < 0)
		return 0;
	for (i = 0; i < DIRECT_IPC_SEMS; i++) {
		if (semctl(dmix->semid, i, IPC_STAT, &buf) < 0) {
			int err = -errno;
			snd_pcm_direct_semaphore_discard(dmix);
			return err;
		}
		buf.sem_perm.gid = dmix->ipc_gid;
		semctl(dmix->semid, i, IPC_SET, &buf);
	}
	return 0;
}

int snd_pcm_direct_semaphore_discard(snd_pcm_direct_t *dmix)
{
	int i;

	if (dmix->semid < 0)
		return -EINVAL;
	for (i = 0; i < DIRECT_IPC_SEMS; i++) {
		if (semctl(dmix->semid, i, IPC_RMID, NULL) < 0)
			return -errno;
	}
	dmix->semid = -1;
	return 0;
}

int snd_pcm_direct_semaphore_down(snd_pcm_direct_t *dmix, int sem_num)
{
	struct sembuf op[2] = { { sem_num, 0, 0 }, { sem_num, 1, SEM_UNDO } };
	assert(dmix->semid >= 0);
	if (semop(dmix->semid, op, 2) < 0)
		return -errno;
	return 0;
}

int snd_pcm_direct_semaphore_up(snd_pcm_direct_t *dmix, int sem_num)
{
	struct sembuf op = { sem_num, -1, SEM_UNDO | IPC_NOWAIT };
	assert(dmix->semid >= 0);
	if (semop(dmix->semid, &op, 1) < 0)
		return -errno;
	return 0;
}

/*
 *  global shared memory area 
 */

int snd_pcm_direct_shm_create_or_connect(snd_pcm_direct_t *dmix)
{
	struct shmid_ds buf;
	int tmpid, err;
	
retryget:
	dmix->shmid = shmget(dmix->ipc_key, sizeof(snd_pcm_direct_share_t),
			     IPC_CREAT | dmix->ipc_perm);
	err = -errno;
	if (dmix->shmid < 0){
		if (errno == EINVAL)
		if ((tmpid = shmget(dmix->ipc_key, 0, dmix->ipc_perm)) != -1)
		if (!shmctl(tmpid, IPC_STAT, &buf))
		if (!buf.shm_nattch)
	    	/* no users so destroy the segment */
		if (!shmctl(tmpid, IPC_RMID, NULL))
		    goto retryget;
		return err;
	}
	dmix->shmptr = shmat(dmix->shmid, 0, 0);
	if (dmix->shmptr == (void *) -1) {
		snd_pcm_direct_shm_discard(dmix);
		return -errno;
	}
	mlock(dmix->shmptr, sizeof(snd_pcm_direct_share_t));
	if (shmctl(dmix->shmid, IPC_STAT, &buf) < 0) {
		snd_pcm_direct_shm_discard(dmix);
		return -errno;
	}
	if (buf.shm_nattch == 1) {	/* we're the first user, clear the segment */
		memset(dmix->shmptr, 0, sizeof(snd_pcm_direct_share_t));
		if (dmix->ipc_gid >= 0) {
			buf.shm_perm.gid = dmix->ipc_gid;
			shmctl(dmix->shmid, IPC_SET, &buf);
		}
		return 1;
	}
	return 0;
}

int snd_pcm_direct_shm_discard(snd_pcm_direct_t *dmix)
{
	struct shmid_ds buf;
	int ret = 0;

	if (dmix->shmid < 0)
		return -EINVAL;
	if (dmix->shmptr != (void *) -1 && shmdt(dmix->shmptr) < 0)
		return -errno;
	dmix->shmptr = (void *) -1;
	if (shmctl(dmix->shmid, IPC_STAT, &buf) < 0)
		return -errno;
	if (buf.shm_nattch == 0) {	/* we're the last user, destroy the segment */
		if (shmctl(dmix->shmid, IPC_RMID, NULL) < 0)
			return -errno;
		ret = 1;
	}
	dmix->shmid = -1;
	return ret;
}

/*
 *  server side
 */

static int get_tmp_name(char *filename, size_t size)
{
	struct timeval tv;

	gettimeofday(&tv, NULL);
	snprintf(filename, size, TMPDIR "/alsa-dmix-%i-%li-%li", (int)getpid(), (long)tv.tv_sec, (long)tv.tv_usec);
	filename[size-1] = '\0';
	return 0;
}

static int make_local_socket(const char *filename, int server, mode_t ipc_perm)
{
	size_t l = strlen(filename);
	size_t size = offsetof(struct sockaddr_un, sun_path) + l;
	struct sockaddr_un *addr = alloca(size);
	int sock;

	sock = socket(PF_LOCAL, SOCK_STREAM, 0);
	if (sock < 0) {
		int result = -errno;
		SYSERR("socket failed");
		return result;
	}

	if (server)
		unlink(filename);
	memset(addr, 0, size); /* make valgrind happy */
	addr->sun_family = AF_LOCAL;
	memcpy(addr->sun_path, filename, l);
	
	if (server) {
		if (bind(sock, (struct sockaddr *) addr, size) < 0) {
			int result = -errno;
			SYSERR("bind failed: %s", filename);
			close(sock);
			return result;
		} else {
			if (chmod(filename, ipc_perm) < 0) {
				int result = -errno;
				SYSERR("chmod failed: %s", filename);
				close(sock);
				return result;
			}
		}
	} else {
		if (connect(sock, (struct sockaddr *) addr, size) < 0) {
			int result = -errno;
			SYSERR("connect failed: %s", filename);
			close(sock);
			return result;
		}
	}
	return sock;
}

#if 0
#define SERVER_JOB_DEBUG
#define server_printf(fmt, args...) printf(fmt, ##args)
#else
#undef SERVER_JOB_DEBUG
#define server_printf(fmt, args...) /* nothing */
#endif

static snd_pcm_direct_t *server_job_dmix;

static void server_cleanup(snd_pcm_direct_t *dmix)
{
	close(dmix->server_fd);
	close(dmix->hw_fd);
	if (dmix->server_free)
		dmix->server_free(dmix);
	unlink(dmix->shmptr->socket_name);
	snd_pcm_direct_shm_discard(dmix);
	snd_pcm_direct_semaphore_discard(dmix);
}

static void server_job_signal(int sig ATTRIBUTE_UNUSED)
{
	snd_pcm_direct_semaphore_down(server_job_dmix, DIRECT_IPC_SEM_CLIENT);
	server_cleanup(server_job_dmix);
	server_printf("DIRECT SERVER EXIT - SIGNAL\n");
	_exit(EXIT_SUCCESS);
}

static void server_job(snd_pcm_direct_t *dmix)
{
	int ret, sck, i;
	int max = 128, current = 0;
	struct pollfd pfds[max + 1];

	server_job_dmix = dmix;
	/* don't allow to be killed */
	signal(SIGHUP, server_job_signal);
	signal(SIGQUIT, server_job_signal);
	signal(SIGTERM, server_job_signal);
	signal(SIGKILL, server_job_signal);
	/* close all files to free resources */
	i = sysconf(_SC_OPEN_MAX);
#ifdef SERVER_JOB_DEBUG
	while (--i >= 3) {
#else
	while (--i >= 0) {
#endif
		if (i != dmix->server_fd && i != dmix->hw_fd)
			close(i);
	}
	
	/* detach from parent */
	setsid();

	pfds[0].fd = dmix->server_fd;
	pfds[0].events = POLLIN | POLLERR | POLLHUP;

	server_printf("DIRECT SERVER STARTED\n");
	while (1) {
		ret = poll(pfds, current + 1, 500);
		server_printf("DIRECT SERVER: poll ret = %i, revents[0] = 0x%x, errno = %i\n", ret, pfds[0].revents, errno);
		if (ret < 0) {
			if (errno == EINTR)
				continue;
			/* some error */
			break;
		}
		if (ret == 0 || (pfds[0].revents & (POLLERR | POLLHUP))) {	/* timeout or error? */
			struct shmid_ds buf;
			snd_pcm_direct_semaphore_down(dmix, DIRECT_IPC_SEM_CLIENT);
			if (shmctl(dmix->shmid, IPC_STAT, &buf) < 0) {
				snd_pcm_direct_shm_discard(dmix);
				snd_pcm_direct_semaphore_up(dmix, DIRECT_IPC_SEM_CLIENT);
				continue;
			}
			server_printf("DIRECT SERVER: nattch = %i\n", (int)buf.shm_nattch);
			if (buf.shm_nattch == 1)	/* server is the last user, exit */
				break;
			snd_pcm_direct_semaphore_up(dmix, DIRECT_IPC_SEM_CLIENT);
			continue;
		}
		if (pfds[0].revents & POLLIN) {
			ret--;
			sck = accept(dmix->server_fd, 0, 0);
			if (sck >= 0) {
				server_printf("DIRECT SERVER: new connection %i\n", sck);
				if (current == max) {
					close(sck);
				} else {
					unsigned char buf = 'A';
					pfds[current+1].fd = sck;
					pfds[current+1].events = POLLIN | POLLERR | POLLHUP;
					snd_send_fd(sck, &buf, 1, dmix->hw_fd);
					server_printf("DIRECT SERVER: fd sent ok\n");
					current++;
				}
			}
		}
		for (i = 0; i < current && ret > 0; i++) {
			struct pollfd *pfd = &pfds[i+1];
			unsigned char cmd;
			server_printf("client %i revents = 0x%x\n", pfd->fd, pfd->revents);
			if (pfd->revents & (POLLERR | POLLHUP)) {
				ret--;
				close(pfd->fd);
				pfd->fd = -1;
				continue;
			}
			if (!(pfd->revents & POLLIN))
				continue;
			ret--;
			if (read(pfd->fd, &cmd, 1) == 1)
				cmd = 0 /*process command */;
		}
		for (i = 0; i < current; i++) {
			if (pfds[i+1].fd < 0) {
				if (i + 1 != max)
					memcpy(&pfds[i+1], &pfds[i+2], sizeof(struct pollfd) * (max - i - 1));
				current--;
			}
		}
	}
	server_cleanup(dmix);
	server_printf("DIRECT SERVER EXIT\n");
#ifdef SERVER_JOB_DEBUG
	close(0); close(1); close(2);
#endif
	_exit(EXIT_SUCCESS);
}

int snd_pcm_direct_server_create(snd_pcm_direct_t *dmix)
{
	int ret;

	dmix->server_fd = -1;

	ret = get_tmp_name(dmix->shmptr->socket_name, sizeof(dmix->shmptr->socket_name));
	if (ret < 0)
		return ret;
	
	ret = make_local_socket(dmix->shmptr->socket_name, 1, dmix->ipc_perm);
	if (ret < 0)
		return ret;
	dmix->server_fd = ret;

	ret = listen(dmix->server_fd, 4);
	if (ret < 0) {
		close(dmix->server_fd);
		return ret;
	}
	
	ret = fork();
	if (ret < 0) {
		close(dmix->server_fd);
		return ret;
	} else if (ret == 0) {
		ret = fork();
		if (ret == 0)
			server_job(dmix);
		_exit(EXIT_SUCCESS);
	} else {
		waitpid(ret, NULL, 0);
	}
	dmix->server_pid = ret;
	dmix->server = 1;
	return 0;
}

int snd_pcm_direct_server_discard(snd_pcm_direct_t *dmix)
{
	if (dmix->server) {
		//kill(dmix->server_pid, SIGTERM);
		//waitpid(dmix->server_pid, NULL, 0);
		dmix->server_pid = (pid_t)-1;
	}
	if (dmix->server_fd > 0) {
		close(dmix->server_fd);
		dmix->server_fd = -1;
	}
	dmix->server = 0;
	return 0;
}

/*
 *  client side
 */

int snd_pcm_direct_client_connect(snd_pcm_direct_t *dmix)
{
	int ret;
	unsigned char buf;

	ret = make_local_socket(dmix->shmptr->socket_name, 0, dmix->ipc_perm);
	if (ret < 0)
		return ret;
	dmix->comm_fd = ret;

	ret = snd_receive_fd(dmix->comm_fd, &buf, 1, &dmix->hw_fd);
	if (ret < 1 || buf != 'A') {
		close(dmix->comm_fd);
		dmix->comm_fd = -1;
		return ret;
	}

	dmix->client = 1;
	return 0;
}

int snd_pcm_direct_client_discard(snd_pcm_direct_t *dmix)
{
	if (dmix->client) {
		close(dmix->comm_fd);
		dmix->comm_fd = -1;
	}
	return 0;
}

/*
 *  plugin helpers
 */

int snd_pcm_direct_nonblock(snd_pcm_t *pcm ATTRIBUTE_UNUSED, int nonblock ATTRIBUTE_UNUSED)
{
	/* value is cached for us in pcm->mode (SND_PCM_NONBLOCK flag) */
	return 0;
}

int snd_pcm_direct_async(snd_pcm_t *pcm, int sig, pid_t pid)
{
	snd_pcm_direct_t *dmix = pcm->private_data;
	return snd_timer_async(dmix->timer, sig, pid);
}

static inline void process_timer_event(snd_pcm_direct_t *dmix ATTRIBUTE_UNUSED,
				       snd_timer_tread_t *te ATTRIBUTE_UNUSED)
{
#if 0
	printf("te->event = %i\n", te->event);
#endif
}

/* empty the timer read queue */
void snd_pcm_direct_clear_timer_queue(snd_pcm_direct_t *dmix)
{
	if (dmix->timer_need_poll) {
		while (poll(&dmix->timer_fd, 1, 0) > 0) {
			/* we don't need the value */
			if (dmix->tread) {
				snd_timer_tread_t rbuf;
				snd_timer_read(dmix->timer, &rbuf, sizeof(rbuf));
				process_timer_event(dmix, &rbuf);
			} else {
				snd_timer_read_t rbuf;
				snd_timer_read(dmix->timer, &rbuf, sizeof(rbuf));
			}
		}
	} else {
		if (dmix->tread) {
			snd_timer_tread_t rbuf;
			while (snd_timer_read(dmix->timer, &rbuf, sizeof(rbuf)) > 0)
				process_timer_event(dmix, &rbuf);
		} else {
			snd_timer_read_t rbuf;
			while (snd_timer_read(dmix->timer, &rbuf, sizeof(rbuf)) > 0)
				;
		}
	}
}

int snd_pcm_direct_timer_stop(snd_pcm_direct_t *dmix)
{
	snd_timer_stop(dmix->timer);
	snd_pcm_direct_clear_timer_queue(dmix);
	return 0;
}

int snd_pcm_direct_poll_revents(snd_pcm_t *pcm, struct pollfd *pfds, unsigned int nfds, unsigned short *revents)
{
	snd_pcm_direct_t *dmix = pcm->private_data;
	unsigned short events;
	int empty = 0;

	assert(pfds && nfds == 1 && revents);
	events = pfds[0].revents;
	if (events & POLLIN) {
		snd_pcm_uframes_t avail;
		snd_pcm_avail_update(pcm);
		if (pcm->stream == SND_PCM_STREAM_PLAYBACK) {
			events |= POLLOUT;
			events &= ~POLLIN;
			avail = snd_pcm_mmap_playback_avail(pcm);
		} else {
			avail = snd_pcm_mmap_capture_avail(pcm);
		}
		empty = avail < pcm->avail_min;
	}
	switch (snd_pcm_state(dmix->spcm)) {
	case SND_PCM_STATE_XRUN:
	case SND_PCM_STATE_SUSPENDED:
		events |= POLLERR;
		break;
	default:
		if (empty) {
			snd_pcm_direct_clear_timer_queue(dmix);
			events &= ~(POLLOUT|POLLIN);
		}
		break;
	}
	*revents = events;
	return 0;
}

int snd_pcm_direct_info(snd_pcm_t *pcm, snd_pcm_info_t * info)
{
	// snd_pcm_direct_t *dmix = pcm->private_data;

	memset(info, 0, sizeof(*info));
	info->stream = pcm->stream;
	info->card = -1;
	/* FIXME: fill this with something more useful: we know the hardware name */
	if (pcm->name) {
		strncpy((char *)info->id, pcm->name, sizeof(info->id));
		strncpy((char *)info->name, pcm->name, sizeof(info->name));
		strncpy((char *)info->subname, pcm->name, sizeof(info->subname));
	}
	info->subdevices_count = 1;
	return 0;
}

static inline snd_mask_t *hw_param_mask(snd_pcm_hw_params_t *params,
					snd_pcm_hw_param_t var)
{
	return &params->masks[var - SND_PCM_HW_PARAM_FIRST_MASK];
}

static inline snd_interval_t *hw_param_interval(snd_pcm_hw_params_t *params,
						snd_pcm_hw_param_t var)
{
	return &params->intervals[var - SND_PCM_HW_PARAM_FIRST_INTERVAL];
}

static int hw_param_interval_refine_one(snd_pcm_hw_params_t *params,
					snd_pcm_hw_param_t var,
					snd_interval_t *src)
{
	snd_interval_t *i;

	if (!(params->rmask & (1<<var)))	/* nothing to do? */
		return 0;
	i = hw_param_interval(params, var);
	if (snd_interval_empty(i)) {
		SNDERR("dshare interval %i empty?", (int)var);
		return -EINVAL;
	}
	if (snd_interval_refine(i, src))
		params->cmask |= 1<<var;
	return 0;
}

#undef REFINE_DEBUG

int snd_pcm_direct_hw_refine(snd_pcm_t *pcm, snd_pcm_hw_params_t *params)
{
	snd_pcm_direct_t *dshare = pcm->private_data;
	static snd_mask_t access = { .bits = { 
					(1<<SNDRV_PCM_ACCESS_MMAP_INTERLEAVED) |
					(1<<SNDRV_PCM_ACCESS_MMAP_NONINTERLEAVED) |
					(1<<SNDRV_PCM_ACCESS_RW_INTERLEAVED) |
					(1<<SNDRV_PCM_ACCESS_RW_NONINTERLEAVED),
					0, 0, 0 } };
	int err;

#ifdef REFINE_DEBUG
	snd_output_t *log;
	snd_output_stdio_attach(&log, stderr, 0);
	snd_output_puts(log, "DMIX REFINE (begin):\n");
	snd_pcm_hw_params_dump(params, log);
#endif
	if (params->rmask & (1<<SND_PCM_HW_PARAM_ACCESS)) {
		if (snd_mask_empty(hw_param_mask(params, SND_PCM_HW_PARAM_ACCESS))) {
			SNDERR("dshare access mask empty?");
			return -EINVAL;
		}
		if (snd_mask_refine(hw_param_mask(params, SND_PCM_HW_PARAM_ACCESS), &access))
			params->cmask |= 1<<SND_PCM_HW_PARAM_ACCESS;
	}
	if (params->rmask & (1<<SND_PCM_HW_PARAM_FORMAT)) {
		if (snd_mask_empty(hw_param_mask(params, SND_PCM_HW_PARAM_FORMAT))) {
			SNDERR("dshare format mask empty?");
			return -EINVAL;
		}
		if (snd_mask_refine_set(hw_param_mask(params, SND_PCM_HW_PARAM_FORMAT),
					dshare->shmptr->hw.format))
			params->cmask |= 1<<SND_PCM_HW_PARAM_FORMAT;
	}
	//snd_mask_none(hw_param_mask(params, SND_PCM_HW_PARAM_SUBFORMAT));
	if (params->rmask & (1<<SND_PCM_HW_PARAM_CHANNELS)) {
		if (snd_interval_empty(hw_param_interval(params, SND_PCM_HW_PARAM_CHANNELS))) {
			SNDERR("dshare channels mask empty?");
			return -EINVAL;
		}
		err = snd_interval_refine_set(hw_param_interval(params, SND_PCM_HW_PARAM_CHANNELS), dshare->channels);
		if (err < 0)
			return err;
	}
	err = hw_param_interval_refine_one(params, SND_PCM_HW_PARAM_RATE,
					   &dshare->shmptr->hw.rate);
	if (err < 0)
		return err;
	err = hw_param_interval_refine_one(params, SND_PCM_HW_PARAM_BUFFER_SIZE,
					   &dshare->shmptr->hw.buffer_size);
	if (err < 0)
		return err;
	err = hw_param_interval_refine_one(params, SND_PCM_HW_PARAM_BUFFER_TIME,
					   &dshare->shmptr->hw.buffer_time);
	if (err < 0)
		return err;
	err = hw_param_interval_refine_one(params, SND_PCM_HW_PARAM_PERIOD_SIZE,
					   &dshare->shmptr->hw.period_size);
	if (err < 0)
		return err;
	err = hw_param_interval_refine_one(params, SND_PCM_HW_PARAM_PERIOD_TIME,
					   &dshare->shmptr->hw.period_time);
	if (err < 0)
		return err;
	err = hw_param_interval_refine_one(params, SND_PCM_HW_PARAM_PERIODS,
					   &dshare->shmptr->hw.periods);
	if (err < 0)
		return err;
	params->info = dshare->shmptr->s.info;
#ifdef REFINE_DEBUG
	snd_output_puts(log, "DMIX REFINE (end):\n");
	snd_pcm_hw_params_dump(params, log);
	snd_output_close(log);
#endif
	return 0;
}

int snd_pcm_direct_hw_params(snd_pcm_t *pcm, snd_pcm_hw_params_t * params)
{
	snd_pcm_direct_t *dmix = pcm->private_data;

	params->info = dmix->shmptr->s.info;
	params->rate_num = dmix->shmptr->s.rate;
	params->rate_den = 1;
	params->fifo_size = 0;
	params->msbits = dmix->shmptr->s.msbits;
	return 0;
}

int snd_pcm_direct_hw_free(snd_pcm_t *pcm ATTRIBUTE_UNUSED)
{
	/* values are cached in the pcm structure */
	return 0;
}

int snd_pcm_direct_sw_params(snd_pcm_t *pcm ATTRIBUTE_UNUSED, snd_pcm_sw_params_t * params ATTRIBUTE_UNUSED)
{
	/* values are cached in the pcm structure */
	return 0;
}

int snd_pcm_direct_channel_info(snd_pcm_t *pcm, snd_pcm_channel_info_t * info)
{
        return snd_pcm_channel_info_shm(pcm, info, -1);
}

int snd_pcm_direct_mmap(snd_pcm_t *pcm ATTRIBUTE_UNUSED)
{
	return 0;
}
        
int snd_pcm_direct_munmap(snd_pcm_t *pcm ATTRIBUTE_UNUSED)
{
	return 0;
}

int snd_pcm_direct_resume(snd_pcm_t *pcm)
{
	snd_pcm_direct_t *dmix = pcm->private_data;
	int err;
	
	snd_pcm_direct_semaphore_down(dmix, DIRECT_IPC_SEM_CLIENT);
	err = snd_pcm_resume(dmix->spcm);
	if (err == -ENOSYS) {
		/* FIXME: error handling? */
		snd_pcm_prepare(dmix->spcm);
		snd_pcm_start(dmix->spcm);
		err = 0;
	}
	snd_pcm_direct_semaphore_up(dmix, DIRECT_IPC_SEM_CLIENT);
	return err;
}

/*
 * this function initializes hardware and starts playback operation with
 * no stop threshold (it operates all time without xrun checking)
 * also, the driver silences the unused ring buffer areas for us
 */
int snd_pcm_direct_initialize_slave(snd_pcm_direct_t *dmix, snd_pcm_t *spcm, struct slave_params *params)
{
	snd_pcm_hw_params_t *hw_params;
	snd_pcm_sw_params_t *sw_params;
	int ret, buffer_is_not_initialized;
	snd_pcm_uframes_t boundary;
	struct pollfd fd;
	int loops = 10;

	snd_pcm_hw_params_alloca(&hw_params);
	snd_pcm_sw_params_alloca(&sw_params);

      __again:
      	if (loops-- <= 0) {
      		SNDERR("unable to find a valid configuration for slave");
      		return -EINVAL;
      	}
	ret = snd_pcm_hw_params_any(spcm, hw_params);
	if (ret < 0) {
		SNDERR("snd_pcm_hw_params_any failed");
		return ret;
	}
	ret = snd_pcm_hw_params_set_access(spcm, hw_params, SND_PCM_ACCESS_MMAP_INTERLEAVED);
	if (ret < 0) {
		ret = snd_pcm_hw_params_set_access(spcm, hw_params, SND_PCM_ACCESS_MMAP_NONINTERLEAVED);
		if (ret < 0) {
			SNDERR("slave plugin does not support mmap interleaved or mmap noninterleaved access");
			return ret;
		}
	}
	ret = snd_pcm_hw_params_set_format(spcm, hw_params, params->format);
	if (ret < 0) {
		snd_pcm_format_t format;
		switch (params->format) {
		case SND_PCM_FORMAT_S32: format = SND_PCM_FORMAT_S16; break;
		case SND_PCM_FORMAT_S16: format = SND_PCM_FORMAT_S32; break;
		default:
			SNDERR("invalid format");
			return -EINVAL;
		}
		ret = snd_pcm_hw_params_set_format(spcm, hw_params, format);
		if (ret < 0) {
			SNDERR("requested or auto-format is not available");
			return ret;
		}
		params->format = format;
	}
	ret = snd_pcm_hw_params_set_channels(spcm, hw_params, params->channels);
	if (ret < 0) {
		unsigned int min, max;
		ret = INTERNAL(snd_pcm_hw_params_get_channels_min)(hw_params, &min);
		if (ret < 0) {
			SNDERR("cannot obtain minimal count of channels");
			return ret;
		}
		ret = INTERNAL(snd_pcm_hw_params_get_channels_min)(hw_params, &max);
		if (ret < 0) {
			SNDERR("cannot obtain maximal count of channels");
			return ret;
		}
		if (min == max) {
			ret = snd_pcm_hw_params_set_channels(spcm, hw_params, min);
			if (ret >= 0)
				params->channels = min;
		}
		if (ret < 0) {
			SNDERR("requested count of channels is not available");
			return ret;
		}
	}
	ret = INTERNAL(snd_pcm_hw_params_set_rate_near)(spcm, hw_params, (unsigned int *)&params->rate, 0);
	if (ret < 0) {
		SNDERR("requested rate is not available");
		return ret;
	}

	buffer_is_not_initialized = 0;
	if (params->buffer_time > 0) {
		ret = INTERNAL(snd_pcm_hw_params_set_buffer_time_near)(spcm, hw_params, (unsigned int *)&params->buffer_time, 0);
		if (ret < 0) {
			SNDERR("unable to set buffer time");
			return ret;
		}
	} else if (params->buffer_size > 0) {
		ret = INTERNAL(snd_pcm_hw_params_set_buffer_size_near)(spcm, hw_params, (snd_pcm_uframes_t *)&params->buffer_size);
		if (ret < 0) {
			SNDERR("unable to set buffer size");
			return ret;
		}
	} else {
		buffer_is_not_initialized = 1;
	}

	if (params->period_time > 0) {
		ret = INTERNAL(snd_pcm_hw_params_set_period_time_near)(spcm, hw_params, (unsigned int *)&params->period_time, 0);
		if (ret < 0) {
			SNDERR("unable to set period_time");
			return ret;
		}
	} else if (params->period_size > 0) {
		ret = INTERNAL(snd_pcm_hw_params_set_period_size_near)(spcm, hw_params, (snd_pcm_uframes_t *)&params->period_size, 0);
		if (ret < 0) {
			SNDERR("unable to set period_size");
			return ret;
		}
	}		
	
	if (buffer_is_not_initialized && params->periods > 0) {
		int periods = params->periods;
		ret = INTERNAL(snd_pcm_hw_params_set_periods_near)(spcm, hw_params, &params->periods, 0);
		if (ret < 0) {
			SNDERR("unable to set requested periods");
			return ret;
		}
		if (params->periods == 1) {
			params->periods = periods;
			if (params->period_time > 0) {
				params->period_time /= 2;
				goto __again;
			} else if (params->period_size > 0) {
				params->period_size /= 2;
				goto __again;
			}
			SNDERR("unable to use stream with periods == 1");
			return ret;
		}
	}
	
	ret = snd_pcm_hw_params(spcm, hw_params);
	if (ret < 0) {
		SNDERR("unable to install hw params");
		return ret;
	}

	/* store some hw_params values to shared info */
	dmix->shmptr->hw.format = snd_mask_value(hw_param_mask(hw_params, SND_PCM_HW_PARAM_FORMAT));
	dmix->shmptr->hw.rate = *hw_param_interval(hw_params, SND_PCM_HW_PARAM_RATE);
	dmix->shmptr->hw.buffer_size = *hw_param_interval(hw_params, SND_PCM_HW_PARAM_BUFFER_SIZE);
	dmix->shmptr->hw.buffer_time = *hw_param_interval(hw_params, SND_PCM_HW_PARAM_BUFFER_TIME);
	dmix->shmptr->hw.period_size = *hw_param_interval(hw_params, SND_PCM_HW_PARAM_PERIOD_SIZE);
	dmix->shmptr->hw.period_time = *hw_param_interval(hw_params, SND_PCM_HW_PARAM_PERIOD_TIME);
	dmix->shmptr->hw.periods = *hw_param_interval(hw_params, SND_PCM_HW_PARAM_PERIODS);


	ret = snd_pcm_sw_params_current(spcm, sw_params);
	if (ret < 0) {
		SNDERR("unable to get current sw_params");
		return ret;
	}

	ret = snd_pcm_sw_params_get_boundary(sw_params, &boundary);
	if (ret < 0) {
		SNDERR("unable to get boundary");
		return ret;
	}
	ret = snd_pcm_sw_params_set_stop_threshold(spcm, sw_params, boundary);
	if (ret < 0) {
		SNDERR("unable to set stop threshold");
		return ret;
	}

	if (dmix->type != SND_PCM_TYPE_DMIX)
		goto __skip_silencing;

	ret = snd_pcm_sw_params_set_silence_threshold(spcm, sw_params, 0);
	if (ret < 0) {
		SNDERR("unable to set silence threshold");
		return ret;
	}
	ret = snd_pcm_sw_params_set_silence_size(spcm, sw_params, boundary);
	if (ret < 0) {
		SNDERR("unable to set silence threshold (please upgrade to 0.9.0rc8+ driver)");
		return ret;
	}

      __skip_silencing:

	ret = snd_pcm_sw_params(spcm, sw_params);
	if (ret < 0) {
		SNDERR("unable to install sw params (please upgrade to 0.9.0rc8+ driver)");
		return ret;
	}

	if (dmix->type == SND_PCM_TYPE_DSHARE) {
		const snd_pcm_channel_area_t *dst_areas;
		dst_areas = snd_pcm_mmap_areas(spcm);
		snd_pcm_areas_silence(dst_areas, 0, spcm->channels, spcm->buffer_size, spcm->format);
	}
	
	ret = snd_pcm_start(spcm);
	if (ret < 0) {
		SNDERR("unable to start PCM stream");
		return ret;
	}

	if (snd_pcm_poll_descriptors_count(spcm) != 1) {
		SNDERR("unable to use hardware pcm with fd more than one!!!");
		return ret;
	}
	snd_pcm_poll_descriptors(spcm, &fd, 1);
	dmix->hw_fd = fd.fd;
	
	dmix->shmptr->s.boundary = spcm->boundary;
	dmix->shmptr->s.buffer_size = spcm->buffer_size;
	dmix->shmptr->s.period_size = spcm->period_size;
	dmix->shmptr->s.sample_bits = spcm->sample_bits;
	dmix->shmptr->s.channels = spcm->channels;
	dmix->shmptr->s.rate = spcm->rate;
	dmix->shmptr->s.format = spcm->format;
	dmix->shmptr->s.info = spcm->info & ~SND_PCM_INFO_PAUSE;
	dmix->shmptr->s.msbits = spcm->msbits;

	/* Currently, we assume that each dmix client has the same
	 * hw_params setting.
	 * If the arbitrary hw_parmas is supported in future,
	 * boundary has to be taken from the slave config but
	 * recalculated for the native boundary size (for 32bit
	 * emulation on 64bit arch).
	 */
	dmix->slave_buffer_size = spcm->buffer_size;
	dmix->slave_period_size = spcm->period_size;
	dmix->slave_boundary = spcm->boundary;

	spcm->donot_close = 1;
	return 0;
}

/*
 * the trick is used here; we cannot use effectively the hardware handle because
 * we cannot drive multiple accesses to appl_ptr; so we use slave timer of given
 * PCM hardware handle; it's not this easy and cheap?
 */
int snd_pcm_direct_initialize_poll_fd(snd_pcm_direct_t *dmix)
{
	int ret;
	snd_pcm_info_t *info;
	char name[128];
	int capture = dmix->type == SND_PCM_TYPE_DSNOOP ? 1 : 0;

	dmix->tread = 1;
	dmix->timer_need_poll = 0;
	snd_pcm_info_alloca(&info);
	ret = snd_pcm_info(dmix->spcm, info);
	if (ret < 0) {
		SNDERR("unable to info for slave pcm");
		return ret;
	}
	sprintf(name, "hw:CLASS=%i,SCLASS=0,CARD=%i,DEV=%i,SUBDEV=%i",
				(int)SND_TIMER_CLASS_PCM, 
				snd_pcm_info_get_card(info),
				snd_pcm_info_get_device(info),
				snd_pcm_info_get_subdevice(info) * 2 + capture);
	ret = snd_timer_open(&dmix->timer, name, SND_TIMER_OPEN_NONBLOCK | SND_TIMER_OPEN_TREAD);
	if (ret < 0) {
		dmix->tread = 1;
		ret = snd_timer_open(&dmix->timer, name, SND_TIMER_OPEN_NONBLOCK);
		if (ret < 0) {
			SNDERR("unable to open timer '%s'", name);
			return ret;
		}
	}

	if (snd_timer_poll_descriptors_count(dmix->timer) != 1) {
		SNDERR("unable to use timer with fd more than one!!!", name);
		return ret;
	}
	snd_timer_poll_descriptors(dmix->timer, &dmix->timer_fd, 1);
	dmix->poll_fd = dmix->timer_fd.fd;

	dmix->timer_event_suspend = 1<<SND_TIMER_EVENT_MSUSPEND;
	dmix->timer_event_resume = 1<<SND_TIMER_EVENT_MRESUME;

	/*
	 * Some hacks for older kernel drivers
	 */
	{
		int ver = 0;
		ioctl(dmix->poll_fd, SNDRV_TIMER_IOCTL_PVERSION, &ver);
		/* In older versions, check via poll before read() is needed
		 * because of the confliction between TIMER_START and
		 * FIONBIO ioctls.
		 */
		if (ver < SNDRV_PROTOCOL_VERSION(2, 0, 4))
			dmix->timer_need_poll = 1;
		/*
		 * In older versions, timer uses pause events instead
		 * suspend/resume events.
		 */
		if (ver < SNDRV_PROTOCOL_VERSION(2, 0, 5)) {
			dmix->timer_event_suspend = 1<<SND_TIMER_EVENT_MPAUSE;
			dmix->timer_event_resume = 1<<SND_TIMER_EVENT_MCONTINUE;
		}
	}
	return 0;
}

static snd_pcm_uframes_t recalc_boundary_size(unsigned long long bsize, snd_pcm_uframes_t buffer_size)
{
	if (bsize > LONG_MAX) {
		bsize = buffer_size;
		while (bsize * 2 <= LONG_MAX - buffer_size)
			bsize *= 2;
	}
	return (snd_pcm_uframes_t)bsize;
}

/*
 * open a slave PCM as secondary client (dup'ed fd)
 */
int snd_pcm_direct_open_secondary_client(snd_pcm_t **spcmp, snd_pcm_direct_t *dmix, const char *client_name)
{
	int ret;
	snd_pcm_t *spcm;

	ret = snd_pcm_hw_open_fd(spcmp, client_name, dmix->hw_fd, 0, 0);
	if (ret < 0) {
		SNDERR("unable to open hardware");
		return ret;
	}
		
	spcm = *spcmp;
	spcm->donot_close = 1;
	spcm->setup = 1;
	/* we copy the slave setting */
	spcm->buffer_size = dmix->shmptr->s.buffer_size;
	spcm->sample_bits = dmix->shmptr->s.sample_bits;
	spcm->channels = dmix->shmptr->s.channels;
	spcm->format = dmix->shmptr->s.format;
	spcm->boundary = recalc_boundary_size(dmix->shmptr->s.boundary, spcm->buffer_size);
	spcm->info = dmix->shmptr->s.info;

	/* Use the slave setting as SPCM, so far */
	dmix->slave_buffer_size = spcm->buffer_size;
	dmix->slave_period_size = dmix->shmptr->s.period_size;
	dmix->slave_boundary = spcm->boundary;

	ret = snd_pcm_mmap(spcm);
	if (ret < 0) {
		SNDERR("unable to mmap channels");
		return ret;
	}
	return 0;
}

int snd_pcm_direct_set_timer_params(snd_pcm_direct_t *dmix)
{
	snd_timer_params_t *params;
	unsigned int filter;
	int ret;

	snd_timer_params_alloca(&params);
	snd_timer_params_set_auto_start(params, 1);
	if (dmix->type != SND_PCM_TYPE_DSNOOP)
		snd_timer_params_set_early_event(params, 1);
	snd_timer_params_set_ticks(params, 1);
	if (dmix->tread) {
		filter = (1<<SND_TIMER_EVENT_TICK) |
			 dmix->timer_event_suspend |
			 dmix->timer_event_resume;
		snd_timer_params_set_filter(params, filter);
	}
	ret = snd_timer_params(dmix->timer, params);
	if (ret < 0) {
		SNDERR("unable to set timer parameters");
                return ret;
	}
	return 0;
}

/*
 *  ring buffer operation
 */
int snd_pcm_direct_check_interleave(snd_pcm_direct_t *dmix, snd_pcm_t *pcm)
{
	unsigned int chn, channels;
	int interleaved = 1;
	const snd_pcm_channel_area_t *dst_areas;
	const snd_pcm_channel_area_t *src_areas;

	if ((snd_pcm_format_physical_width(dmix->type) % 8) != 0)
		interleaved = 0;
	channels = dmix->channels;
	dst_areas = snd_pcm_mmap_areas(dmix->spcm);
	src_areas = snd_pcm_mmap_areas(pcm);
	for (chn = 1; chn < channels; chn++) {
		if (dst_areas[chn-1].addr != dst_areas[chn].addr) {
			interleaved = 0;
			break;
		}
		if (src_areas[chn-1].addr != src_areas[chn].addr) {
			interleaved = 0;
			break;
		}
	}
	for (chn = 0; chn < channels; chn++) {
		if (dmix->bindings && dmix->bindings[chn] != chn) {
			interleaved = 0;
			break;
		}
		if (dst_areas[chn].first != sizeof(signed short) * chn * 8 ||
		    dst_areas[chn].step != channels * sizeof(signed short) * 8) {
			interleaved = 0;
			break;
		}
		if (src_areas[chn].first != sizeof(signed short) * chn * 8 ||
		    src_areas[chn].step != channels * sizeof(signed short) * 8) {
			interleaved = 0;
			break;
		}
	}
	return dmix->interleaved = interleaved;
}

/*
 * parse the channel map
 * id == client channel
 * value == slave's channel
 */
int snd_pcm_direct_parse_bindings(snd_pcm_direct_t *dmix, snd_config_t *cfg)
{
	snd_config_iterator_t i, next;
	unsigned int chn, chn1, count = 0;
	int err;

	dmix->channels = UINT_MAX;
	if (cfg == NULL)
		return 0;
	if (snd_config_get_type(cfg) != SND_CONFIG_TYPE_COMPOUND) {
		SNDERR("invalid type for bindings");
		return -EINVAL;
	}
	snd_config_for_each(i, next, cfg) {
		snd_config_t *n = snd_config_iterator_entry(i);
		const char *id;
		long cchannel;
		if (snd_config_get_id(n, &id) < 0)
			continue;
		err = safe_strtol(id, &cchannel);
		if (err < 0 || cchannel < 0) {
			SNDERR("invalid client channel in binding: %s\n", id);
			return -EINVAL;
		}
		if ((unsigned)cchannel >= count)
			count = cchannel + 1;
	}
	if (count == 0)
		return 0;
	if (count > 1024) {
		SNDERR("client channel out of range");
		return -EINVAL;
	}
	dmix->bindings = malloc(count * sizeof(unsigned int));
	if (dmix->bindings == NULL)
		return -ENOMEM;
	for (chn = 0; chn < count; chn++)
		dmix->bindings[chn] = UINT_MAX;		/* don't route */
	snd_config_for_each(i, next, cfg) {
		snd_config_t *n = snd_config_iterator_entry(i);
		const char *id;
		long cchannel, schannel;
		if (snd_config_get_id(n, &id) < 0)
			continue;
		safe_strtol(id, &cchannel);
		if (snd_config_get_integer(n, &schannel) < 0) {
			SNDERR("unable to get slave channel (should be integer type) in binding: %s\n", id);
			return -EINVAL;
		}
		dmix->bindings[cchannel] = schannel;
	}
	if (dmix->type == SND_PCM_TYPE_DSNOOP)
		goto __skip_same_dst;
	for (chn = 0; chn < count; chn++) {
		for (chn1 = 0; chn1 < count; chn1++) {
			if (chn == chn1)
				continue;
			if (dmix->bindings[chn] == dmix->bindings[chn1]) {
				SNDERR("unable to route channels %d,%d to same destination %d", chn, chn1, dmix->bindings[chn]);
				return -EINVAL;
			}
		}
	}
      __skip_same_dst:
	dmix->channels = count;
	return 0;
}