[libsigrok.git] / hardware / alsa / alsa.c

/*
 * This file is part of the sigrok project.
 *
 * Copyright (C) 2011 Daniel Ribeiro <drwyrm@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 */

/* Note: This driver doesn't compile, analog support in sigrok is WIP. */

#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <alsa/asoundlib.h>
#include "sigrok.h"
#include "sigrok-internal.h"

#define NUM_PROBES 2
#define SAMPLE_WIDTH 16
#define AUDIO_DEV "plughw:0,0"

struct sr_analog_probe {
	uint8_t att;
	uint8_t res;    /* Needs to be a power of 2, FIXME */
	uint16_t val;   /* Max hardware ADC width is 16bits */
};

struct sr_analog_sample {
	uint8_t num_probes; /* Max hardware probes is 256 */
	struct sr_analog_probe probes[];
};

static int capabilities[] = {
	SR_HWCAP_SAMPLERATE,
	SR_HWCAP_LIMIT_SAMPLES,
	SR_HWCAP_CONTINUOUS,
};

static const char *probe_names[NUM_PROBES + 1] = {
	"0",
	"1",
	NULL,
};

static GSList *device_instances = NULL;

struct alsa {
	uint64_t cur_rate;
	uint64_t limit_samples;
	snd_pcm_t *capture_handle;
	snd_pcm_hw_params_t *hw_params;
	gpointer session_id;
};

static int hw_init(const char *deviceinfo)
{
	struct sr_device_instance *sdi;
	struct alsa *alsa;

	/* Avoid compiler warnings. */
	deviceinfo = deviceinfo;

	if (!(alsa = g_try_malloc0(sizeof(struct alsa)))) {
		sr_err("alsa: %s: alsa malloc failed", __func__);
		return 0;
	}

	sdi = sr_device_instance_new(0, SR_ST_ACTIVE, "alsa", NULL, NULL);
	if (!sdi)
		goto free_alsa;

	sdi->priv = alsa;

	device_instances = g_slist_append(device_instances, sdi);

	return 1;
free_alsa:
	g_free(alsa);
	return 0;
}

static int hw_opendev(int device_index)
{
	struct sr_device_instance *sdi;
	struct alsa *alsa;
	int err;

	if (!(sdi = sr_get_device_instance(device_instances, device_index)))
		return SR_ERR;
	alsa = sdi->priv;

	err = snd_pcm_open(&alsa->capture_handle, AUDIO_DEV,
					SND_PCM_STREAM_CAPTURE, 0);
	if (err < 0) {
		sr_warn("cannot open audio device %s (%s)", AUDIO_DEV,
			snd_strerror(err));
		return SR_ERR;
	}

	err = snd_pcm_hw_params_malloc(&alsa->hw_params);
	if (err < 0) {
		sr_warn("cannot allocate hardware parameter structure (%s)",
			snd_strerror(err));
		return SR_ERR;
	}

	err = snd_pcm_hw_params_any(alsa->capture_handle, alsa->hw_params);
	if (err < 0) {
		sr_warn("cannot initialize hardware parameter structure (%s)",
				snd_strerror(err));
		return SR_ERR;
	}

	return SR_OK;
}

static int hw_closedev(int device_index)
{
	struct sr_device_instance *sdi;
	struct alsa *alsa;

	if (!(sdi = sr_get_device_instance(device_instances, device_index))) {
		sr_err("alsa: %s: sdi was NULL", __func__);
		return SR_ERR; /* TODO: SR_ERR_ARG? */
	}

	if (!(alsa = sdi->priv)) {
		sr_err("alsa: %s: sdi->priv was NULL", __func__);
		return SR_ERR; /* TODO: SR_ERR_ARG? */
	}

	// TODO: Return values of snd_*?
	if (alsa->hw_params)
		snd_pcm_hw_params_free(alsa->hw_params);
	if (alsa->capture_handle)
		snd_pcm_close(alsa->capture_handle);

	return SR_OK;
}

static void hw_cleanup(void)
{
	struct sr_device_instance *sdi;

	if (!(sdi = sr_get_device_instance(device_instances, 0)))
		return;

	free(sdi->priv);
	sr_device_instance_free(sdi);
}

static void *hw_get_device_info(int device_index, int device_info_id)
{
	struct sr_device_instance *sdi;
	struct alsa *alsa;
	void *info = NULL;

	if (!(sdi = sr_get_device_instance(device_instances, device_index)))
		return NULL;
	alsa = sdi->priv;

	switch (device_info_id) {
	case SR_DI_INSTANCE:
		info = sdi;
		break;
	case SR_DI_NUM_PROBES:
		info = GINT_TO_POINTER(NUM_PROBES);
		break;
	case SR_DI_PROBE_NAMES:
		info = probe_names;
		break;
	case SR_DI_CUR_SAMPLERATE:
		info = &alsa->cur_rate;
		break;
	// case SR_DI_PROBE_TYPE:
	// 	info = GINT_TO_POINTER(SR_PROBE_TYPE_ANALOG);
	// 	break;
	}

	return info;
}

static int hw_get_status(int device_index)
{
	/* Avoid compiler warnings. */
	device_index = device_index;

	return SR_ST_ACTIVE;
}

static int *hw_get_capabilities(void)
{
	return capabilities;
}

static int hw_set_configuration(int device_index, int capability, void *value)
{
	struct sr_device_instance *sdi;
	struct alsa *alsa;

	if (!(sdi = sr_get_device_instance(device_instances, device_index)))
		return SR_ERR;
	alsa = sdi->priv;

	switch (capability) {
	case SR_HWCAP_PROBECONFIG:
		return SR_OK;
	case SR_HWCAP_SAMPLERATE:
		alsa->cur_rate = *(uint64_t *) value;
		return SR_OK;
	case SR_HWCAP_LIMIT_SAMPLES:
		alsa->limit_samples = *(uint64_t *) value;
		return SR_OK;
	default:
		return SR_ERR;
	}
}

static int receive_data(int fd, int revents, void *user_data)
{
	struct sr_device_instance *sdi = user_data;
	struct alsa *alsa = sdi->priv;
	struct sr_datafeed_packet packet;
	struct sr_analog_sample *sample;
	unsigned int sample_size = sizeof(struct sr_analog_sample) +
		(NUM_PROBES * sizeof(struct sr_analog_probe));
	char *outb;
	char inb[4096];
	int i, x, count;

	fd = fd;
	revents = revents;

	do {
		memset(inb, 0, sizeof(inb));
		count = snd_pcm_readi(alsa->capture_handle, inb,
			MIN(4096/4, alsa->limit_samples));
		if (count < 1) {
			sr_warn("Failed to read samples");
			return FALSE;
		}

		if (!(outb = g_try_malloc(sample_size * count))) {
			sr_err("alsa: %s: outb malloc failed", __func__);
			return FALSE;
		}

		for (i = 0; i < count; i++) {
			sample = (struct sr_analog_sample *)
						(outb + (i * sample_size));
			sample->num_probes = NUM_PROBES;

			for (x = 0; x < NUM_PROBES; x++) {
				sample->probes[x].val =
					*(uint16_t *) (inb + (i * 4) + (x * 2));
				sample->probes[x].val &= ((1 << 16) - 1);
				sample->probes[x].res = 16;
			}
		}

		packet.type = SR_DF_ANALOG;
		packet.length = count * sample_size;
		packet.unitsize = sample_size;
		packet.payload = outb;
		sr_session_bus(user_data, &packet);
		g_free(outb);
		alsa->limit_samples -= count;

	} while (alsa->limit_samples > 0);

	packet.type = SR_DF_END;
	sr_session_bus(user_data, &packet);

	return TRUE;
}

static int hw_start_acquisition(int device_index, gpointer session_device_id)
{
	struct sr_device_instance *sdi;
	struct alsa *alsa;
	struct sr_datafeed_packet packet;
	struct sr_datafeed_header header;
	struct pollfd *ufds;
	int count;
	int err;

	if (!(sdi = sr_get_device_instance(device_instances, device_index)))
		return SR_ERR;
	alsa = sdi->priv;

	err = snd_pcm_hw_params_set_access(alsa->capture_handle,
			alsa->hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
	if (err < 0) {
		sr_warn("cannot set access type (%s)", snd_strerror(err));
		return SR_ERR;
	}

	/* FIXME: Hardcoded for 16bits */
	err = snd_pcm_hw_params_set_format(alsa->capture_handle,
			alsa->hw_params, SND_PCM_FORMAT_S16_LE);
	if (err < 0) {
		sr_warn("cannot set sample format (%s)", snd_strerror(err));
		return SR_ERR;
	}

	err = snd_pcm_hw_params_set_rate_near(alsa->capture_handle,
			alsa->hw_params, (unsigned int *) &alsa->cur_rate, 0);
	if (err < 0) {
		sr_warn("cannot set sample rate (%s)", snd_strerror(err));
		return SR_ERR;
	}

	err = snd_pcm_hw_params_set_channels(alsa->capture_handle,
			alsa->hw_params, NUM_PROBES);
	if (err < 0) {
		sr_warn("cannot set channel count (%s)", snd_strerror(err));
		return SR_ERR;
	}

	err = snd_pcm_hw_params(alsa->capture_handle, alsa->hw_params);
	if (err < 0) {
		sr_warn("cannot set parameters (%s)", snd_strerror(err));
		return SR_ERR;
	}

	err = snd_pcm_prepare(alsa->capture_handle);
	if (err < 0) {
		sr_warn("cannot prepare audio interface for use (%s)",
				snd_strerror(err));
		return SR_ERR;
	}

	count = snd_pcm_poll_descriptors_count(alsa->capture_handle);
	if (count < 1) {
		sr_warn("Unable to obtain poll descriptors count");
		return SR_ERR;
	}

	if (!(ufds = g_try_malloc(count * sizeof(struct pollfd)))) {
		sr_warn("alsa: %s: ufds malloc failed", __func__);
		return SR_ERR_MALLOC;
	}

	err = snd_pcm_poll_descriptors(alsa->capture_handle, ufds, count);
	if (err < 0) {
		sr_warn("Unable to obtain poll descriptors (%s)",
				snd_strerror(err));
		g_free(ufds);
		return SR_ERR;
	}

	alsa->session_id = session_device_id;
	sr_source_add(ufds[0].fd, ufds[0].events, 10, receive_data, sdi);

	packet.type = SR_DF_HEADER;
	packet.length = sizeof(struct sr_datafeed_header);
	packet.payload = (unsigned char *) &header;
	header.feed_version = 1;
	gettimeofday(&header.starttime, NULL);
	header.samplerate = alsa->cur_rate;
	header.num_analog_probes = NUM_PROBES;
	header.num_logic_probes = 0;
	header.protocol_id = SR_PROTO_RAW;
	sr_session_bus(session_device_id, &packet);
	g_free(ufds);

	return SR_OK;
}

static void hw_stop_acquisition(int device_index, gpointer session_device_id)
{
	/* Avoid compiler warnings. */
	device_index = device_index;
	session_device_id = session_device_id;
}

SR_PRIV struct sr_device_plugin alsa_plugin_info = {
	.name = "alsa",
	.longname = "ALSA driver",
	.api_version = 1,
	.init = hw_init,
	.cleanup = hw_cleanup,
	.opendev = hw_opendev,
	.closedev = hw_closedev,
	.get_device_info = hw_get_device_info,
	.get_status = hw_get_status,
	.get_capabilities = hw_get_capabilities,
	.set_configuration = hw_set_configuration,
	.start_acquisition = hw_start_acquisition,
	.stop_acquisition = hw_stop_acquisition,
};
Commit	Line	Data
	1	/*
	2	* This file is part of the sigrok project.
	3	*
	4	* Copyright (C) 2011 Daniel Ribeiro <drwyrm@gmail.com>
	5	*
	6	* This program is free software; you can redistribute it and/or modify
	7	* it under the terms of the GNU General Public License as published by
	8	* the Free Software Foundation; either version 2 of the License, or
	9	* (at your option) any later version.
	10	*
	11	* This program is distributed in the hope that it will be useful,
	12	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	14	* GNU General Public License for more details.
	15	*
	16	* You should have received a copy of the GNU General Public License
	17	* along with this program; if not, write to the Free Software
	18	* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	19	*/
	20
	21	/* Note: This driver doesn't compile, analog support in sigrok is WIP. */
	22
	23	#include <stdlib.h>
	24	#include <unistd.h>
	25	#include <string.h>
	26	#include <alsa/asoundlib.h>
	27	#include "sigrok.h"
	28	#include "sigrok-internal.h"
	29
	30	#define NUM_PROBES 2
	31	#define SAMPLE_WIDTH 16
	32	#define AUDIO_DEV "plughw:0,0"
	33
	34	struct sr_analog_probe {
	35	uint8_t att;
	36	uint8_t res; /* Needs to be a power of 2, FIXME */
	37	uint16_t val; /* Max hardware ADC width is 16bits */
	38	};
	39
	40	struct sr_analog_sample {
	41	uint8_t num_probes; /* Max hardware probes is 256 */
	42	struct sr_analog_probe probes[];
	43	};
	44
	45	static int capabilities[] = {
	46	SR_HWCAP_SAMPLERATE,
	47	SR_HWCAP_LIMIT_SAMPLES,
	48	SR_HWCAP_CONTINUOUS,
	49	};
	50
	51	static const char *probe_names[NUM_PROBES + 1] = {
	52	"0",
	53	"1",
	54	NULL,
	55	};
	56
	57	static GSList *device_instances = NULL;
	58
	59	struct alsa {
	60	uint64_t cur_rate;
	61	uint64_t limit_samples;
	62	snd_pcm_t *capture_handle;
	63	snd_pcm_hw_params_t *hw_params;
	64	gpointer session_id;
	65	};
	66
	67	static int hw_init(const char *deviceinfo)
	68	{
	69	struct sr_device_instance *sdi;
	70	struct alsa *alsa;
	71
	72	/* Avoid compiler warnings. */
	73	deviceinfo = deviceinfo;
	74
	75	if (!(alsa = g_try_malloc0(sizeof(struct alsa)))) {
	76	sr_err("alsa: %s: alsa malloc failed", __func__);
	77	return 0;
	78	}
	79
	80	sdi = sr_device_instance_new(0, SR_ST_ACTIVE, "alsa", NULL, NULL);
	81	if (!sdi)
	82	goto free_alsa;
	83
	84	sdi->priv = alsa;
	85
	86	device_instances = g_slist_append(device_instances, sdi);
	87
	88	return 1;
	89	free_alsa:
	90	g_free(alsa);
	91	return 0;
	92	}
	93
	94	static int hw_opendev(int device_index)
	95	{
	96	struct sr_device_instance *sdi;
	97	struct alsa *alsa;
	98	int err;
	99
	100	if (!(sdi = sr_get_device_instance(device_instances, device_index)))
	101	return SR_ERR;
	102	alsa = sdi->priv;
	103
	104	err = snd_pcm_open(&alsa->capture_handle, AUDIO_DEV,
	105	SND_PCM_STREAM_CAPTURE, 0);
	106	if (err < 0) {
	107	sr_warn("cannot open audio device %s (%s)", AUDIO_DEV,
	108	snd_strerror(err));
	109	return SR_ERR;
	110	}
	111
	112	err = snd_pcm_hw_params_malloc(&alsa->hw_params);
	113	if (err < 0) {
	114	sr_warn("cannot allocate hardware parameter structure (%s)",
	115	snd_strerror(err));
	116	return SR_ERR;
	117	}
	118
	119	err = snd_pcm_hw_params_any(alsa->capture_handle, alsa->hw_params);
	120	if (err < 0) {
	121	sr_warn("cannot initialize hardware parameter structure (%s)",
	122	snd_strerror(err));
	123	return SR_ERR;
	124	}
	125
	126	return SR_OK;
	127	}
	128
	129	static int hw_closedev(int device_index)
	130	{
	131	struct sr_device_instance *sdi;
	132	struct alsa *alsa;
	133
	134	if (!(sdi = sr_get_device_instance(device_instances, device_index))) {
	135	sr_err("alsa: %s: sdi was NULL", __func__);
	136	return SR_ERR; /* TODO: SR_ERR_ARG? */
	137	}
	138
	139	if (!(alsa = sdi->priv)) {
	140	sr_err("alsa: %s: sdi->priv was NULL", __func__);
	141	return SR_ERR; /* TODO: SR_ERR_ARG? */
	142	}
	143
	144	// TODO: Return values of snd_*?
	145	if (alsa->hw_params)
	146	snd_pcm_hw_params_free(alsa->hw_params);
	147	if (alsa->capture_handle)
	148	snd_pcm_close(alsa->capture_handle);
	149
	150	return SR_OK;
	151	}
	152
	153	static void hw_cleanup(void)
	154	{
	155	struct sr_device_instance *sdi;
	156
	157	if (!(sdi = sr_get_device_instance(device_instances, 0)))
	158	return;
	159
	160	free(sdi->priv);
	161	sr_device_instance_free(sdi);
	162	}
	163
	164	static void *hw_get_device_info(int device_index, int device_info_id)
	165	{
	166	struct sr_device_instance *sdi;
	167	struct alsa *alsa;
	168	void *info = NULL;
	169
	170	if (!(sdi = sr_get_device_instance(device_instances, device_index)))
	171	return NULL;
	172	alsa = sdi->priv;
	173
	174	switch (device_info_id) {
	175	case SR_DI_INSTANCE:
	176	info = sdi;
	177	break;
	178	case SR_DI_NUM_PROBES:
	179	info = GINT_TO_POINTER(NUM_PROBES);
	180	break;
	181	case SR_DI_PROBE_NAMES:
	182	info = probe_names;
	183	break;
	184	case SR_DI_CUR_SAMPLERATE:
	185	info = &alsa->cur_rate;
	186	break;
	187	// case SR_DI_PROBE_TYPE:
	188	// info = GINT_TO_POINTER(SR_PROBE_TYPE_ANALOG);
	189	// break;
	190	}
	191
	192	return info;
	193	}
	194
	195	static int hw_get_status(int device_index)
	196	{
	197	/* Avoid compiler warnings. */
	198	device_index = device_index;
	199
	200	return SR_ST_ACTIVE;
	201	}
	202
	203	static int *hw_get_capabilities(void)
	204	{
	205	return capabilities;
	206	}
	207
	208	static int hw_set_configuration(int device_index, int capability, void *value)
	209	{
	210	struct sr_device_instance *sdi;
	211	struct alsa *alsa;
	212
	213	if (!(sdi = sr_get_device_instance(device_instances, device_index)))
	214	return SR_ERR;
	215	alsa = sdi->priv;
	216
	217	switch (capability) {
	218	case SR_HWCAP_PROBECONFIG:
	219	return SR_OK;
	220	case SR_HWCAP_SAMPLERATE:
	221	alsa->cur_rate = (uint64_t ) value;
	222	return SR_OK;
	223	case SR_HWCAP_LIMIT_SAMPLES:
	224	alsa->limit_samples = (uint64_t ) value;
	225	return SR_OK;
	226	default:
	227	return SR_ERR;
	228	}
	229	}
	230
	231	static int receive_data(int fd, int revents, void *user_data)
	232	{
	233	struct sr_device_instance *sdi = user_data;
	234	struct alsa *alsa = sdi->priv;
	235	struct sr_datafeed_packet packet;
	236	struct sr_analog_sample *sample;
	237	unsigned int sample_size = sizeof(struct sr_analog_sample) +
	238	(NUM_PROBES * sizeof(struct sr_analog_probe));
	239	char *outb;
	240	char inb[4096];
	241	int i, x, count;
	242
	243	fd = fd;
	244	revents = revents;
	245
	246	do {
	247	memset(inb, 0, sizeof(inb));
	248	count = snd_pcm_readi(alsa->capture_handle, inb,
	249	MIN(4096/4, alsa->limit_samples));
	250	if (count < 1) {
	251	sr_warn("Failed to read samples");
	252	return FALSE;
	253	}
	254
	255	if (!(outb = g_try_malloc(sample_size * count))) {
	256	sr_err("alsa: %s: outb malloc failed", __func__);
	257	return FALSE;
	258	}
	259
	260	for (i = 0; i < count; i++) {
	261	sample = (struct sr_analog_sample *)
	262	(outb + (i * sample_size));
	263	sample->num_probes = NUM_PROBES;
	264
	265	for (x = 0; x < NUM_PROBES; x++) {
	266	sample->probes[x].val =
	267	(uint16_t ) (inb + (i * 4) + (x * 2));
	268	sample->probes[x].val &= ((1 << 16) - 1);
	269	sample->probes[x].res = 16;
	270	}
	271	}
	272
	273	packet.type = SR_DF_ANALOG;
	274	packet.length = count * sample_size;
	275	packet.unitsize = sample_size;
	276	packet.payload = outb;
	277	sr_session_bus(user_data, &packet);
	278	g_free(outb);
	279	alsa->limit_samples -= count;
	280
	281	} while (alsa->limit_samples > 0);
	282
	283	packet.type = SR_DF_END;
	284	sr_session_bus(user_data, &packet);
	285
	286	return TRUE;
	287	}
	288
	289	static int hw_start_acquisition(int device_index, gpointer session_device_id)
	290	{
	291	struct sr_device_instance *sdi;
	292	struct alsa *alsa;
	293	struct sr_datafeed_packet packet;
	294	struct sr_datafeed_header header;
	295	struct pollfd *ufds;
	296	int count;
	297	int err;
	298
	299	if (!(sdi = sr_get_device_instance(device_instances, device_index)))
	300	return SR_ERR;
	301	alsa = sdi->priv;
	302
	303	err = snd_pcm_hw_params_set_access(alsa->capture_handle,
	304	alsa->hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
	305	if (err < 0) {
	306	sr_warn("cannot set access type (%s)", snd_strerror(err));
	307	return SR_ERR;
	308	}
	309
	310	/* FIXME: Hardcoded for 16bits */
	311	err = snd_pcm_hw_params_set_format(alsa->capture_handle,
	312	alsa->hw_params, SND_PCM_FORMAT_S16_LE);
	313	if (err < 0) {
	314	sr_warn("cannot set sample format (%s)", snd_strerror(err));
	315	return SR_ERR;
	316	}
	317
	318	err = snd_pcm_hw_params_set_rate_near(alsa->capture_handle,
	319	alsa->hw_params, (unsigned int *) &alsa->cur_rate, 0);
	320	if (err < 0) {
	321	sr_warn("cannot set sample rate (%s)", snd_strerror(err));
	322	return SR_ERR;
	323	}
	324
	325	err = snd_pcm_hw_params_set_channels(alsa->capture_handle,
	326	alsa->hw_params, NUM_PROBES);
	327	if (err < 0) {
	328	sr_warn("cannot set channel count (%s)", snd_strerror(err));
	329	return SR_ERR;
	330	}
	331
	332	err = snd_pcm_hw_params(alsa->capture_handle, alsa->hw_params);
	333	if (err < 0) {
	334	sr_warn("cannot set parameters (%s)", snd_strerror(err));
	335	return SR_ERR;
	336	}
	337
	338	err = snd_pcm_prepare(alsa->capture_handle);
	339	if (err < 0) {
	340	sr_warn("cannot prepare audio interface for use (%s)",
	341	snd_strerror(err));
	342	return SR_ERR;
	343	}
	344
	345	count = snd_pcm_poll_descriptors_count(alsa->capture_handle);
	346	if (count < 1) {
	347	sr_warn("Unable to obtain poll descriptors count");
	348	return SR_ERR;
	349	}
	350
	351	if (!(ufds = g_try_malloc(count * sizeof(struct pollfd)))) {
	352	sr_warn("alsa: %s: ufds malloc failed", __func__);
	353	return SR_ERR_MALLOC;
	354	}
	355
	356	err = snd_pcm_poll_descriptors(alsa->capture_handle, ufds, count);
	357	if (err < 0) {
	358	sr_warn("Unable to obtain poll descriptors (%s)",
	359	snd_strerror(err));
	360	g_free(ufds);
	361	return SR_ERR;
	362	}
	363
	364	alsa->session_id = session_device_id;
	365	sr_source_add(ufds[0].fd, ufds[0].events, 10, receive_data, sdi);
	366
	367	packet.type = SR_DF_HEADER;
	368	packet.length = sizeof(struct sr_datafeed_header);
	369	packet.payload = (unsigned char *) &header;
	370	header.feed_version = 1;
	371	gettimeofday(&header.starttime, NULL);
	372	header.samplerate = alsa->cur_rate;
	373	header.num_analog_probes = NUM_PROBES;
	374	header.num_logic_probes = 0;
	375	header.protocol_id = SR_PROTO_RAW;
	376	sr_session_bus(session_device_id, &packet);
	377	g_free(ufds);
	378
	379	return SR_OK;
	380	}
	381
	382	static void hw_stop_acquisition(int device_index, gpointer session_device_id)
	383	{
	384	/* Avoid compiler warnings. */
	385	device_index = device_index;
	386	session_device_id = session_device_id;
	387	}
	388
	389	SR_PRIV struct sr_device_plugin alsa_plugin_info = {
	390	.name = "alsa",
	391	.longname = "ALSA driver",
	392	.api_version = 1,
	393	.init = hw_init,
	394	.cleanup = hw_cleanup,
	395	.opendev = hw_opendev,
	396	.closedev = hw_closedev,
	397	.get_device_info = hw_get_device_info,
	398	.get_status = hw_get_status,
	399	.get_capabilities = hw_get_capabilities,
	400	.set_configuration = hw_set_configuration,
	401	.start_acquisition = hw_start_acquisition,
	402	.stop_acquisition = hw_stop_acquisition,
	403	};