pipewire/spa/plugins/alsa/alsa-utils.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sched.h>
#include <errno.h>
#include <getopt.h>
#include <sys/time.h>
#include <math.h>
#include <limits.h>
#include <sys/timerfd.h>

#include <lib/debug.h>
#include <lib/format.h>

#include "alsa-utils.h"

#define CHECK(s,msg) if ((err = (s)) < 0) { spa_log_error(state->log, msg ": %s", snd_strerror(err)); return err; }

static int spa_alsa_open(struct state *state)
{
	int err;
	struct props *props = &state->props;

	if (state->opened)
		return 0;

	CHECK(snd_output_stdio_attach(&state->output, stderr, 0), "attach failed");

	spa_log_info(state->log, "ALSA device open '%s'", props->device);
	CHECK(snd_pcm_open(&state->hndl,
			   props->device,
			   state->stream,
			   SND_PCM_NONBLOCK |
			   SND_PCM_NO_AUTO_RESAMPLE |
			   SND_PCM_NO_AUTO_CHANNELS | SND_PCM_NO_AUTO_FORMAT), "open failed");

	state->timerfd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK);
	state->opened = true;

	return 0;
}

int spa_alsa_close(struct state *state)
{
	int err = 0;

	if (!state->opened)
		return 0;

	spa_log_info(state->log, "Device closing");
	CHECK(snd_pcm_close(state->hndl), "close failed");

	close(state->timerfd);
	state->opened = false;

	return err;
}

struct format_info {
	off_t format_offset;
	snd_pcm_format_t format;
};

#if __BYTE_ORDER == __BIG_ENDIAN
#define _FORMAT_LE(fmt)  offsetof(struct type, audio_format. fmt ## _OE)
#define _FORMAT_BE(fmt)  offsetof(struct type, audio_format. fmt)
#elif __BYTE_ORDER == __LITTLE_ENDIAN
#define _FORMAT_LE(fmt)  offsetof(struct type, audio_format. fmt)
#define _FORMAT_BE(fmt)  offsetof(struct type, audio_format. fmt ## _OE)
#endif

static const struct format_info format_info[] = {
	{offsetof(struct type, audio_format.UNKNOWN), SND_PCM_FORMAT_UNKNOWN},
	{offsetof(struct type, audio_format.S8), SND_PCM_FORMAT_S8},
	{offsetof(struct type, audio_format.U8), SND_PCM_FORMAT_U8},
	{_FORMAT_LE(S16), SND_PCM_FORMAT_S16_LE},
	{_FORMAT_BE(S16), SND_PCM_FORMAT_S16_BE},
	{_FORMAT_LE(U16), SND_PCM_FORMAT_U16_LE},
	{_FORMAT_BE(U16), SND_PCM_FORMAT_U16_BE},
	{_FORMAT_LE(S24_32), SND_PCM_FORMAT_S24_LE},
	{_FORMAT_BE(S24_32), SND_PCM_FORMAT_S24_BE},
	{_FORMAT_LE(U24_32), SND_PCM_FORMAT_U24_LE},
	{_FORMAT_BE(U24_32), SND_PCM_FORMAT_U24_BE},
	{_FORMAT_LE(S24), SND_PCM_FORMAT_S24_3LE},
	{_FORMAT_BE(S24), SND_PCM_FORMAT_S24_3BE},
	{_FORMAT_LE(U24), SND_PCM_FORMAT_U24_3LE},
	{_FORMAT_BE(U24), SND_PCM_FORMAT_U24_3BE},
	{_FORMAT_LE(S32), SND_PCM_FORMAT_S32_LE},
	{_FORMAT_BE(S32), SND_PCM_FORMAT_S32_BE},
	{_FORMAT_LE(U32), SND_PCM_FORMAT_U32_LE},
	{_FORMAT_BE(U32), SND_PCM_FORMAT_U32_BE},
	{_FORMAT_LE(F32), SND_PCM_FORMAT_FLOAT_LE},
	{_FORMAT_BE(F32), SND_PCM_FORMAT_FLOAT_BE},
	{_FORMAT_LE(F64), SND_PCM_FORMAT_FLOAT64_LE},
	{_FORMAT_BE(F64), SND_PCM_FORMAT_FLOAT64_BE},
};

static snd_pcm_format_t spa_alsa_format_to_alsa(struct type *map, uint32_t format)
{
	int i;

	for (i = 0; i < SPA_N_ELEMENTS(format_info); i++) {
		uint32_t f = *SPA_MEMBER(map, format_info[i].format_offset, uint32_t);
		if (f == format)
			return format_info[i].format;
	}
	return SND_PCM_FORMAT_UNKNOWN;
}

int
spa_alsa_enum_format(struct state *state, struct spa_format **format, const struct spa_format *filter, uint32_t index)
{
	snd_pcm_t *hndl;
	snd_pcm_hw_params_t *params;
	snd_pcm_format_mask_t *fmask;
	int err, i, j, dir;
	unsigned int min, max;
	uint8_t buffer[4096];
	struct spa_pod_builder b = SPA_POD_BUILDER_INIT(buffer, sizeof(buffer));
	struct spa_pod_frame f[2];
	struct spa_pod_prop *prop;
	struct spa_format *fmt;
	int res;
	bool opened;

	if (index == 1)
		return SPA_RESULT_ENUM_END;

	opened = state->opened;
	if ((err = spa_alsa_open(state)) < 0)
		return SPA_RESULT_ERROR;

	hndl = state->hndl;
	snd_pcm_hw_params_alloca(&params);
	CHECK(snd_pcm_hw_params_any(hndl, params), "Broken configuration: no configurations available");

	spa_pod_builder_push_format(&b, &f[0], state->type.format,
				    state->type.media_type.audio, state->type.media_subtype.raw);

	snd_pcm_format_mask_alloca(&fmask);
	snd_pcm_hw_params_get_format_mask(params, fmask);

	spa_pod_builder_push_prop(&b, &f[1], state->type.format_audio.format, SPA_POD_PROP_RANGE_NONE);
	prop = SPA_POD_BUILDER_DEREF(&b, f[1].ref, struct spa_pod_prop);

	for (i = 1, j = 0; i < SPA_N_ELEMENTS(format_info); i++) {
		const struct format_info *fi = &format_info[i];

		if (snd_pcm_format_mask_test(fmask, fi->format)) {
			uint32_t f = *SPA_MEMBER(&state->type, fi->format_offset, uint32_t);
			if (j++ == 0)
				spa_pod_builder_id(&b, f);
			spa_pod_builder_id(&b, f);
		}
	}
	if (j > 1)
		prop->body.flags |= SPA_POD_PROP_RANGE_ENUM | SPA_POD_PROP_FLAG_UNSET;
	spa_pod_builder_pop(&b, &f[1]);

	CHECK(snd_pcm_hw_params_get_rate_min(params, &min, &dir), "get_rate_min");
	CHECK(snd_pcm_hw_params_get_rate_max(params, &max, &dir), "get_rate_max");

	spa_pod_builder_push_prop(&b, &f[1], state->type.format_audio.rate, SPA_POD_PROP_RANGE_NONE);
	prop = SPA_POD_BUILDER_DEREF(&b, f[1].ref, struct spa_pod_prop);

	spa_pod_builder_int(&b, SPA_CLAMP(44100, min, max));
	if (min != max) {
		spa_pod_builder_int(&b, min);
		spa_pod_builder_int(&b, max);
		prop->body.flags |= SPA_POD_PROP_RANGE_MIN_MAX | SPA_POD_PROP_FLAG_UNSET;
	}
	spa_pod_builder_pop(&b, &f[1]);

	CHECK(snd_pcm_hw_params_get_channels_min(params, &min), "get_channels_min");
	CHECK(snd_pcm_hw_params_get_channels_max(params, &max), "get_channels_max");

	spa_pod_builder_push_prop(&b, &f[1], state->type.format_audio.channels, SPA_POD_PROP_RANGE_NONE);
	prop = SPA_POD_BUILDER_DEREF(&b, f[1].ref, struct spa_pod_prop);

	spa_pod_builder_int(&b, SPA_CLAMP(2, min, max));
	if (min != max) {
		spa_pod_builder_int(&b, min);
		spa_pod_builder_int(&b, max);
		prop->body.flags |= SPA_POD_PROP_RANGE_MIN_MAX | SPA_POD_PROP_FLAG_UNSET;
	}
	spa_pod_builder_pop(&b, &f[1]);
	spa_pod_builder_pop(&b, &f[0]);

	fmt = SPA_POD_BUILDER_DEREF(&b, f[0].ref, struct spa_format);

	spa_pod_builder_init(&b, state->format_buffer, sizeof(state->format_buffer));
	if ((res = spa_format_filter(fmt, filter, &b)) < 0)
		return res;

	*format = SPA_POD_BUILDER_DEREF(&b, 0, struct spa_format);
	if (!opened)
		spa_alsa_close(state);

	return SPA_RESULT_OK;
}

int spa_alsa_set_format(struct state *state, struct spa_audio_info *fmt, uint32_t flags)
{
	unsigned int rrate, rchannels;
	snd_pcm_uframes_t period_size;
	int err, dir;
	snd_pcm_hw_params_t *params;
	snd_pcm_format_t format;
	struct spa_audio_info_raw *info = &fmt->info.raw;
	snd_pcm_t *hndl;
	unsigned int periods;

	if ((err = spa_alsa_open(state)) < 0)
		return err;

	hndl = state->hndl;

	snd_pcm_hw_params_alloca(&params);
	/* choose all parameters */
	CHECK(snd_pcm_hw_params_any(hndl, params), "Broken configuration for playback: no configurations available");
	/* set hardware resampling */
	CHECK(snd_pcm_hw_params_set_rate_resample(hndl, params, 0), "set_rate_resample");
	/* set the interleaved read/write format */
	CHECK(snd_pcm_hw_params_set_access(hndl, params, SND_PCM_ACCESS_MMAP_INTERLEAVED), "set_access");


	/* disable ALSA wakeups, we use a timer */
	if (snd_pcm_hw_params_can_disable_period_wakeup(params))
		CHECK(snd_pcm_hw_params_set_period_wakeup(hndl, params, 0), "set_period_wakeup");

	/* set the sample format */
	format = spa_alsa_format_to_alsa(&state->type, info->format);
	if (format == SND_PCM_FORMAT_UNKNOWN)
		return -EINVAL;

	spa_log_info(state->log, "Stream parameters are %iHz, %s, %i channels", info->rate, snd_pcm_format_name(format),
		     info->channels);
	CHECK(snd_pcm_hw_params_set_format(hndl, params, format), "set_format");

	/* set the count of channels */
	rchannels = info->channels;
	CHECK(snd_pcm_hw_params_set_channels_near(hndl, params, &rchannels), "set_channels");
	if (rchannels != info->channels) {
		spa_log_info(state->log, "Channels doesn't match (requested %u, get %u", info->channels, rchannels);
		if (flags & SPA_PORT_FORMAT_FLAG_NEAREST)
			info->channels = rchannels;
		else
			return -EINVAL;
	}

	/* set the stream rate */
	rrate = info->rate;
	CHECK(snd_pcm_hw_params_set_rate_near(hndl, params, &rrate, 0), "set_rate_near");
	if (rrate != info->rate) {
		spa_log_info(state->log, "Rate doesn't match (requested %iHz, get %iHz)", info->rate, rrate);
		if (flags & SPA_PORT_FORMAT_FLAG_NEAREST)
			info->rate = rrate;
		else
			return -EINVAL;
	}

	state->format = format;
	state->channels = info->channels;
	state->rate = info->rate;
	state->frame_size = info->channels * (snd_pcm_format_physical_width(format) / 8);

	CHECK(snd_pcm_hw_params_get_buffer_size_max(params, &state->buffer_frames), "get_buffer_size_max");

	CHECK(snd_pcm_hw_params_set_buffer_size_near(hndl, params, &state->buffer_frames), "set_buffer_size_near");

	dir = 0;
	period_size = state->buffer_frames;
	CHECK(snd_pcm_hw_params_set_period_size_near(hndl, params, &period_size, &dir), "set_period_size_near");
	state->period_frames = period_size;
	periods = state->buffer_frames / state->period_frames;

	spa_log_info(state->log, "buffer frames %zd, period frames %zd, periods %u, frame_size %zd",
		     state->buffer_frames, state->period_frames, periods, state->frame_size);

	/* write the parameters to device */
	CHECK(snd_pcm_hw_params(hndl, params), "set_hw_params");

	return 0;
}

static int set_swparams(struct state *state)
{
	snd_pcm_t *hndl = state->hndl;
	int err = 0;
	snd_pcm_sw_params_t *params;
	snd_pcm_uframes_t boundary;

	snd_pcm_sw_params_alloca(&params);

	/* get the current params */
	CHECK(snd_pcm_sw_params_current(hndl, params), "sw_params_current");

	CHECK(snd_pcm_sw_params_set_tstamp_mode(hndl, params, SND_PCM_TSTAMP_ENABLE), "sw_params_set_tstamp_mode");

	/* start the transfer */
	CHECK(snd_pcm_sw_params_set_start_threshold(hndl, params, LONG_MAX), "set_start_threshold");
	CHECK(snd_pcm_sw_params_get_boundary(params, &boundary), "get_boundary");

	CHECK(snd_pcm_sw_params_set_stop_threshold(hndl, params, boundary), "set_stop_threshold");

	CHECK(snd_pcm_sw_params_set_period_event(hndl, params, 0), "set_period_event");

	/* write the parameters to the playback device */
	CHECK(snd_pcm_sw_params(hndl, params), "sw_params");

	return 0;
}

static inline snd_pcm_uframes_t
pull_frames(struct state *state,
	    const snd_pcm_channel_area_t *my_areas,
	    snd_pcm_uframes_t offset,
	    snd_pcm_uframes_t frames,
	    bool do_pull)
{
	snd_pcm_uframes_t total_frames = 0, to_write = frames;
	struct spa_port_io *io = state->io;

	if (spa_list_is_empty(&state->ready) && do_pull) {
		io->status = SPA_RESULT_NEED_BUFFER;
		io->range.offset = state->sample_count * state->frame_size;
		io->range.min_size = state->threshold * state->frame_size;
		io->range.max_size = frames * state->frame_size;
		state->callbacks->need_input(&state->node, state->user_data);
	}
	while (!spa_list_is_empty(&state->ready) && to_write > 0) {
		uint8_t *src, *dst;
		size_t n_bytes, n_frames, size;
		off_t offs;
		struct buffer *b;
		bool reuse = false;
		struct spa_data *d;

		b = spa_list_first(&state->ready, struct buffer, link);
		d = b->outbuf->datas;

		dst = SPA_MEMBER(my_areas[0].addr, offset * state->frame_size, uint8_t);

		if (b->rb) {
			struct spa_ringbuffer *ringbuffer = &b->rb->ringbuffer;
			uint32_t index;
			int32_t avail;

			avail = spa_ringbuffer_get_read_index(ringbuffer, &index);

			n_bytes = SPA_MIN(avail, to_write * state->frame_size);
			n_frames = SPA_MIN(to_write, n_bytes / state->frame_size);

			spa_ringbuffer_read_data(ringbuffer, d[0].data, index & ringbuffer->mask, dst, n_bytes);

			spa_ringbuffer_read_update(ringbuffer, index + n_bytes);
			reuse = avail == n_bytes;
		} else {
			offs = SPA_MIN(d[0].chunk->offset + state->ready_offset, d[0].maxsize);
			size = SPA_MIN(d[0].chunk->size, d[0].maxsize) - offs;
			src = SPA_MEMBER(d[0].data, offs, uint8_t);

			n_bytes = SPA_MIN(size, to_write * state->frame_size);
			n_frames = SPA_MIN(to_write, n_bytes / state->frame_size);

			memcpy(dst, src, n_bytes);

			state->ready_offset += n_bytes;
			reuse = (state->ready_offset >= size);
		}
		if (reuse) {
			spa_list_remove(&b->link);
			b->outstanding = true;
			state->io->buffer_id = b->outbuf->id;
			spa_log_trace(state->log, "alsa-util %p: reuse buffer %u", state, b->outbuf->id);
			state->callbacks->reuse_buffer(&state->node,
						       0,
						       b->outbuf->id,
						       state->user_data);
			state->ready_offset = 0;
		}
		total_frames += n_frames;
		to_write -= n_frames;
	}
	if (total_frames == 0 && do_pull) {
		total_frames = SPA_MIN(frames, state->threshold);
		spa_log_trace(state->log, "underrun, want %zd frames", total_frames);
		snd_pcm_areas_silence(my_areas, offset, state->channels, total_frames, state->format);
	}
	return total_frames;
}

static snd_pcm_uframes_t
push_frames(struct state *state,
	    const snd_pcm_channel_area_t *my_areas,
	    snd_pcm_uframes_t offset,
	    snd_pcm_uframes_t frames)
{
	snd_pcm_uframes_t total_frames = 0;
	struct spa_port_io *io = state->io;

	if (spa_list_is_empty(&state->free)) {
		spa_log_trace(state->log, "no more buffers");
	} else {
		uint8_t *src;
		size_t n_bytes;
		struct buffer *b;
		struct spa_data *d;

		b = spa_list_first(&state->free, struct buffer, link);
		spa_list_remove(&b->link);

		if (b->h) {
			b->h->seq = state->sample_count;
			b->h->pts = state->last_monotonic;
			b->h->dts_offset = 0;
		}

		d = b->outbuf->datas;

		total_frames = SPA_MIN(frames, d[0].maxsize / state->frame_size);
		src = SPA_MEMBER(my_areas[0].addr, offset * state->frame_size, uint8_t);
		n_bytes = total_frames * state->frame_size;

		memcpy(d[0].data, src, n_bytes);

		d[0].chunk->offset = 0;
		d[0].chunk->size = n_bytes;
		d[0].chunk->stride = 0;

		{
			b->outstanding = true;
			io->buffer_id = b->outbuf->id;
			io->status = SPA_RESULT_HAVE_BUFFER;
			state->callbacks->have_output(&state->node, state->user_data);
		}
	}
	return total_frames;
}

static int alsa_try_resume(struct state *state)
{
	int res;

	while ((res = snd_pcm_resume(state->hndl)) == -EAGAIN)
		usleep(250000);
	if (res < 0) {
		spa_log_error(state->log, "suspended, failed to resume %s", snd_strerror(res));
		res = snd_pcm_prepare(state->hndl);
		if (res < 0)
			spa_log_error(state->log, "suspended, failed to prepare %s", snd_strerror(res));
	}
	return res;
}

static inline void calc_timeout(size_t target, size_t current,
				size_t rate, snd_htimestamp_t *now,
				struct timespec *ts)
{
	ts->tv_sec = now->tv_sec;
	ts->tv_nsec = now->tv_nsec;
	if (target > current)
		ts->tv_nsec += ((target - current) * SPA_NSEC_PER_SEC) / rate;

	while (ts->tv_nsec >= SPA_NSEC_PER_SEC) {
		ts->tv_sec++;
		ts->tv_nsec -= SPA_NSEC_PER_SEC;
	}
}

static void alsa_on_playback_timeout_event(struct spa_source *source)
{
	uint64_t exp;
	int res;
	struct state *state = source->data;
	snd_pcm_t *hndl = state->hndl;
	snd_pcm_sframes_t avail;
	struct itimerspec ts;
	snd_pcm_uframes_t total_written = 0, filled;
	const snd_pcm_channel_area_t *my_areas;
	snd_pcm_status_t *status;
	snd_htimestamp_t htstamp;

	read(state->timerfd, &exp, sizeof(uint64_t));

	snd_pcm_status_alloca(&status);

	if ((res = snd_pcm_status(hndl, status)) < 0) {
		spa_log_error(state->log, "snd_pcm_status error: %s", snd_strerror(res));
		return;
	}

	avail = snd_pcm_status_get_avail(status);
	snd_pcm_status_get_htstamp(status, &htstamp);

	if (avail > state->buffer_frames)
		avail = state->buffer_frames;

	filled = state->buffer_frames - avail;

	state->last_ticks = state->sample_count - filled;
	state->last_monotonic = (int64_t) htstamp.tv_sec * SPA_NSEC_PER_SEC + (int64_t) htstamp.tv_nsec;

	spa_log_trace(state->log, "timeout %ld %d %ld %ld %ld", filled, state->threshold,
		      state->sample_count, htstamp.tv_sec, htstamp.tv_nsec);

	if (filled > state->threshold) {
		if (snd_pcm_state(hndl) == SND_PCM_STATE_SUSPENDED) {
			spa_log_error(state->log, "suspended: try resume");
			if ((res = alsa_try_resume(state)) < 0)
				return;
		}
	} else {
		snd_pcm_uframes_t to_write = state->buffer_frames - filled;
		bool do_pull = true;

		while (total_written < to_write) {
			snd_pcm_uframes_t written, frames, offset;

			frames = to_write - total_written;
			if ((res = snd_pcm_mmap_begin(hndl, &my_areas, &offset, &frames)) < 0) {
				spa_log_error(state->log, "snd_pcm_mmap_begin error: %s", snd_strerror(res));
				return;
			}
			written = pull_frames(state, my_areas, offset, frames, do_pull);
			if (written < frames)
				to_write = 0;

			if ((res = snd_pcm_mmap_commit(hndl, offset, written)) < 0) {
				spa_log_error(state->log, "snd_pcm_mmap_commit error: %s", snd_strerror(res));
				if (res != -EPIPE && res != -ESTRPIPE)
					return;
			}
			total_written += written;
			do_pull = false;
		}
		state->sample_count += total_written;
	}
	if (!state->alsa_started && total_written > 0) {
		spa_log_debug(state->log, "snd_pcm_start");
		if ((res = snd_pcm_start(state->hndl)) < 0) {
			spa_log_error(state->log, "snd_pcm_start: %s", snd_strerror(res));
			return;
		}
		state->alsa_started = true;
	}

	calc_timeout(total_written + filled, state->threshold, state->rate, &htstamp, &ts.it_value);

	ts.it_interval.tv_sec = 0;
	ts.it_interval.tv_nsec = 0;
	timerfd_settime(state->timerfd, TFD_TIMER_ABSTIME, &ts, NULL);
}


static void alsa_on_capture_timeout_event(struct spa_source *source)
{
	uint64_t exp;
	int res;
	struct state *state = source->data;
	snd_pcm_t *hndl = state->hndl;
	snd_pcm_sframes_t avail;
	snd_pcm_uframes_t total_read = 0;
	struct itimerspec ts;
	const snd_pcm_channel_area_t *my_areas;
	snd_pcm_status_t *status;
	snd_htimestamp_t htstamp;

	read(state->timerfd, &exp, sizeof(uint64_t));

	snd_pcm_status_alloca(&status);

	if ((res = snd_pcm_status(hndl, status)) < 0) {
		spa_log_error(state->log, "snd_pcm_status error: %s", snd_strerror(res));
		return;
	}

	avail = snd_pcm_status_get_avail(status);
	snd_pcm_status_get_htstamp(status, &htstamp);

	state->last_ticks = state->sample_count + avail;
	state->last_monotonic = (int64_t) htstamp.tv_sec * SPA_NSEC_PER_SEC + (int64_t) htstamp.tv_nsec;

	spa_log_trace(state->log, "timeout %ld %d %ld %ld %ld", avail, state->threshold,
		      state->sample_count, htstamp.tv_sec, htstamp.tv_nsec);

	if (avail < state->threshold) {
		if (snd_pcm_state(hndl) == SND_PCM_STATE_SUSPENDED) {
			spa_log_error(state->log, "suspended: try resume");
			if ((res = alsa_try_resume(state)) < 0)
				return;
		}
	} else {
		snd_pcm_uframes_t to_read = avail;

		while (total_read < to_read) {
			snd_pcm_uframes_t read, frames, offset;

			frames = to_read - total_read;
			if ((res = snd_pcm_mmap_begin(hndl, &my_areas, &offset, &frames)) < 0) {
				spa_log_error(state->log, "snd_pcm_mmap_begin error: %s", snd_strerror(res));
				return;
			}

			read = push_frames(state, my_areas, offset, frames);
			if (read < frames)
				to_read = 0;

			if ((res = snd_pcm_mmap_commit(hndl, offset, read)) < 0) {
				spa_log_error(state->log, "snd_pcm_mmap_commit error: %s", snd_strerror(res));
				if (res != -EPIPE && res != -ESTRPIPE)
					return;
			}
			total_read += read;
		}
		state->sample_count += total_read;
	}
	calc_timeout(state->threshold, avail - total_read, state->rate, &htstamp, &ts.it_value);

	ts.it_interval.tv_sec = 0;
	ts.it_interval.tv_nsec = 0;
	timerfd_settime(state->timerfd, TFD_TIMER_ABSTIME, &ts, NULL);
}

int spa_alsa_start(struct state *state, bool xrun_recover)
{
	int err;

	if (state->started)
		return SPA_RESULT_OK;

	spa_log_trace(state->log, "alsa %p: start", state);

	CHECK(set_swparams(state), "swparams");
	if (!xrun_recover)
		snd_pcm_dump(state->hndl, state->output);

	if ((err = snd_pcm_prepare(state->hndl)) < 0) {
		spa_log_error(state->log, "snd_pcm_prepare error: %s", snd_strerror(err));
		return SPA_RESULT_ERROR;
	}

	if (state->stream == SND_PCM_STREAM_PLAYBACK) {
		state->source.func = alsa_on_playback_timeout_event;
	} else {
		state->source.func = alsa_on_capture_timeout_event;
	}
	state->source.data = state;
	state->source.fd = state->timerfd;
	state->source.mask = SPA_IO_IN;
	state->source.rmask = 0;
	spa_loop_add_source(state->data_loop, &state->source);

	state->threshold = state->props.min_latency;

	if (state->stream == SND_PCM_STREAM_PLAYBACK) {
		state->alsa_started = false;
	} else {
		if ((err = snd_pcm_start(state->hndl)) < 0) {
			spa_log_error(state->log, "snd_pcm_start: %s", snd_strerror(err));
			return SPA_RESULT_ERROR;
		}
		state->alsa_started = true;
	}
	state->source.func(&state->source);

	state->started = true;

	return SPA_RESULT_OK;
}

int spa_alsa_pause(struct state *state, bool xrun_recover)
{
	int err;

	if (!state->started)
		return SPA_RESULT_OK;

	spa_log_trace(state->log, "alsa %p: pause", state);

	spa_loop_remove_source(state->data_loop, &state->source);

	if ((err = snd_pcm_drop(state->hndl)) < 0)
		spa_log_error(state->log, "snd_pcm_drop %s", snd_strerror(err));

	state->started = false;

	return SPA_RESULT_OK;
}