[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 *dev_insts = 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 *devinfo)
{
	struct sr_dev_inst *sdi;
	struct alsa *alsa;

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

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

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

	sdi->priv = alsa;

	dev_insts = g_slist_append(dev_insts, sdi);

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

static int hw_opendev(int dev_index)
{
	struct sr_dev_inst *sdi;
	struct alsa *alsa;
	int err;

	if (!(sdi = sr_dev_inst_get(dev_insts, dev_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_err("alsa: can't 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_err("alsa: can't 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_err("alsa: can't initialize hardware parameter structure "
		       "(%s)", snd_strerror(err));
		return SR_ERR;
	}

	return SR_OK;
}

static int hw_closedev(int dev_index)
{
	struct sr_dev_inst *sdi;
	struct alsa *alsa;

	if (!(sdi = sr_dev_inst_get(dev_insts, dev_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 int hw_cleanup(void)
{
	struct sr_dev_inst *sdi;

	if (!(sdi = sr_dev_inst_get(dev_insts, 0))) {
		sr_err("alsa: %s: sdi was NULL", __func__);
		return SR_ERR_BUG;
	}

	sr_dev_inst_free(sdi);

	return SR_OK;
}

static void *hw_get_dev_info(int dev_index, int dev_info_id)
{
	struct sr_dev_inst *sdi;
	struct alsa *alsa;
	void *info = NULL;

	if (!(sdi = sr_dev_inst_get(dev_insts, dev_index)))
		return NULL;
	alsa = sdi->priv;

	switch (dev_info_id) {
	case SR_DI_INST:
		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 dev_index)
{
	/* Avoid compiler warnings. */
	dev_index = dev_index;

	return SR_ST_ACTIVE;
}

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

static int hw_set_configuration(int dev_index, int capability, void *value)
{
	struct sr_dev_inst *sdi;
	struct alsa *alsa;

	if (!(sdi = sr_dev_inst_get(dev_insts, dev_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_dev_inst *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_err("alsa: 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 dev_index, gpointer session_dev_id)
{
	struct sr_dev_inst *sdi;
	struct alsa *alsa;
	struct sr_datafeed_packet packet;
	struct sr_datafeed_header header;
	struct pollfd *ufds;
	int count;
	int err;

	if (!(sdi = sr_dev_inst_get(dev_insts, dev_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_err("alsa: can't 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_err("alsa: can't 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_err("alsa: can't 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_err("alsa: can't 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_err("alsa: can't set parameters (%s)", snd_strerror(err));
		return SR_ERR;
	}

	err = snd_pcm_prepare(alsa->capture_handle);
	if (err < 0) {
		sr_err("alsa: can't 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_err("alsa: Unable to obtain poll descriptors count");
		return SR_ERR;
	}

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

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

	alsa->session_id = session_dev_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_dev_id, &packet);
	g_free(ufds);

	return SR_OK;
}

static int hw_stop_acquisition(int dev_index, gpointer session_dev_id)
{
	/* Avoid compiler warnings. */
	dev_index = dev_index;
	session_dev_id = session_dev_id;

	return SR_OK;
}

SR_PRIV struct sr_dev_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_dev_info = hw_get_dev_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 *dev_insts = 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 *devinfo)
	68	{
	69	struct sr_dev_inst *sdi;
	70	struct alsa *alsa;
	71
	72	/* Avoid compiler warnings. */
	73	devinfo = devinfo;
	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_dev_inst_new(0, SR_ST_ACTIVE, "alsa", NULL, NULL);
	81	if (!sdi)
	82	goto free_alsa;
	83
	84	sdi->priv = alsa;
	85
	86	dev_insts = g_slist_append(dev_insts, sdi);
	87
	88	return 1;
	89	free_alsa:
	90	g_free(alsa);
	91	return 0;
	92	}
	93
	94	static int hw_opendev(int dev_index)
	95	{
	96	struct sr_dev_inst *sdi;
	97	struct alsa *alsa;
	98	int err;
	99
	100	if (!(sdi = sr_dev_inst_get(dev_insts, dev_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_err("alsa: can't 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_err("alsa: can't 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_err("alsa: can't initialize hardware parameter structure "
	122	"(%s)", snd_strerror(err));
	123	return SR_ERR;
	124	}
	125
	126	return SR_OK;
	127	}
	128
	129	static int hw_closedev(int dev_index)
	130	{
	131	struct sr_dev_inst *sdi;
	132	struct alsa *alsa;
	133
	134	if (!(sdi = sr_dev_inst_get(dev_insts, dev_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 int hw_cleanup(void)
	154	{
	155	struct sr_dev_inst *sdi;
	156
	157	if (!(sdi = sr_dev_inst_get(dev_insts, 0))) {
	158	sr_err("alsa: %s: sdi was NULL", __func__);
	159	return SR_ERR_BUG;
	160	}
	161
	162	sr_dev_inst_free(sdi);
	163
	164	return SR_OK;
	165	}
	166
	167	static void *hw_get_dev_info(int dev_index, int dev_info_id)
	168	{
	169	struct sr_dev_inst *sdi;
	170	struct alsa *alsa;
	171	void *info = NULL;
	172
	173	if (!(sdi = sr_dev_inst_get(dev_insts, dev_index)))
	174	return NULL;
	175	alsa = sdi->priv;
	176
	177	switch (dev_info_id) {
	178	case SR_DI_INST:
	179	info = sdi;
	180	break;
	181	case SR_DI_NUM_PROBES:
	182	info = GINT_TO_POINTER(NUM_PROBES);
	183	break;
	184	case SR_DI_PROBE_NAMES:
	185	info = probe_names;
	186	break;
	187	case SR_DI_CUR_SAMPLERATE:
	188	info = &alsa->cur_rate;
	189	break;
	190	// case SR_DI_PROBE_TYPE:
	191	// info = GINT_TO_POINTER(SR_PROBE_TYPE_ANALOG);
	192	// break;
	193	}
	194
	195	return info;
	196	}
	197
	198	static int hw_get_status(int dev_index)
	199	{
	200	/* Avoid compiler warnings. */
	201	dev_index = dev_index;
	202
	203	return SR_ST_ACTIVE;
	204	}
	205
	206	static int *hw_get_capabilities(void)
	207	{
	208	return capabilities;
	209	}
	210
	211	static int hw_set_configuration(int dev_index, int capability, void *value)
	212	{
	213	struct sr_dev_inst *sdi;
	214	struct alsa *alsa;
	215
	216	if (!(sdi = sr_dev_inst_get(dev_insts, dev_index)))
	217	return SR_ERR;
	218	alsa = sdi->priv;
	219
	220	switch (capability) {
	221	case SR_HWCAP_PROBECONFIG:
	222	return SR_OK;
	223	case SR_HWCAP_SAMPLERATE:
	224	alsa->cur_rate = (uint64_t ) value;
	225	return SR_OK;
	226	case SR_HWCAP_LIMIT_SAMPLES:
	227	alsa->limit_samples = (uint64_t ) value;
	228	return SR_OK;
	229	default:
	230	return SR_ERR;
	231	}
	232	}
	233
	234	static int receive_data(int fd, int revents, void *user_data)
	235	{
	236	struct sr_dev_inst *sdi = user_data;
	237	struct alsa *alsa = sdi->priv;
	238	struct sr_datafeed_packet packet;
	239	struct sr_analog_sample *sample;
	240	unsigned int sample_size = sizeof(struct sr_analog_sample) +
	241	(NUM_PROBES * sizeof(struct sr_analog_probe));
	242	char *outb;
	243	char inb[4096];
	244	int i, x, count;
	245
	246	fd = fd;
	247	revents = revents;
	248
	249	do {
	250	memset(inb, 0, sizeof(inb));
	251	count = snd_pcm_readi(alsa->capture_handle, inb,
	252	MIN(4096/4, alsa->limit_samples));
	253	if (count < 1) {
	254	sr_err("alsa: Failed to read samples");
	255	return FALSE;
	256	}
	257
	258	if (!(outb = g_try_malloc(sample_size * count))) {
	259	sr_err("alsa: %s: outb malloc failed", __func__);
	260	return FALSE;
	261	}
	262
	263	for (i = 0; i < count; i++) {
	264	sample = (struct sr_analog_sample *)
	265	(outb + (i * sample_size));
	266	sample->num_probes = NUM_PROBES;
	267
	268	for (x = 0; x < NUM_PROBES; x++) {
	269	sample->probes[x].val =
	270	(uint16_t ) (inb + (i * 4) + (x * 2));
	271	sample->probes[x].val &= ((1 << 16) - 1);
	272	sample->probes[x].res = 16;
	273	}
	274	}
	275
	276	packet.type = SR_DF_ANALOG;
	277	packet.length = count * sample_size;
	278	packet.unitsize = sample_size;
	279	packet.payload = outb;
	280	sr_session_bus(user_data, &packet);
	281	g_free(outb);
	282	alsa->limit_samples -= count;
	283
	284	} while (alsa->limit_samples > 0);
	285
	286	packet.type = SR_DF_END;
	287	sr_session_bus(user_data, &packet);
	288
	289	return TRUE;
	290	}
	291
	292	static int hw_start_acquisition(int dev_index, gpointer session_dev_id)
	293	{
	294	struct sr_dev_inst *sdi;
	295	struct alsa *alsa;
	296	struct sr_datafeed_packet packet;
	297	struct sr_datafeed_header header;
	298	struct pollfd *ufds;
	299	int count;
	300	int err;
	301
	302	if (!(sdi = sr_dev_inst_get(dev_insts, dev_index)))
	303	return SR_ERR;
	304	alsa = sdi->priv;
	305
	306	err = snd_pcm_hw_params_set_access(alsa->capture_handle,
	307	alsa->hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
	308	if (err < 0) {
	309	sr_err("alsa: can't set access type (%s)", snd_strerror(err));
	310	return SR_ERR;
	311	}
	312
	313	/* FIXME: Hardcoded for 16bits */
	314	err = snd_pcm_hw_params_set_format(alsa->capture_handle,
	315	alsa->hw_params, SND_PCM_FORMAT_S16_LE);
	316	if (err < 0) {
	317	sr_err("alsa: can't set sample format (%s)", snd_strerror(err));
	318	return SR_ERR;
	319	}
	320
	321	err = snd_pcm_hw_params_set_rate_near(alsa->capture_handle,
	322	alsa->hw_params, (unsigned int *) &alsa->cur_rate, 0);
	323	if (err < 0) {
	324	sr_err("alsa: can't set sample rate (%s)", snd_strerror(err));
	325	return SR_ERR;
	326	}
	327
	328	err = snd_pcm_hw_params_set_channels(alsa->capture_handle,
	329	alsa->hw_params, NUM_PROBES);
	330	if (err < 0) {
	331	sr_err("alsa: can't set channel count (%s)", snd_strerror(err));
	332	return SR_ERR;
	333	}
	334
	335	err = snd_pcm_hw_params(alsa->capture_handle, alsa->hw_params);
	336	if (err < 0) {
	337	sr_err("alsa: can't set parameters (%s)", snd_strerror(err));
	338	return SR_ERR;
	339	}
	340
	341	err = snd_pcm_prepare(alsa->capture_handle);
	342	if (err < 0) {
	343	sr_err("alsa: can't prepare audio interface for use (%s)",
	344	snd_strerror(err));
	345	return SR_ERR;
	346	}
	347
	348	count = snd_pcm_poll_descriptors_count(alsa->capture_handle);
	349	if (count < 1) {
	350	sr_err("alsa: Unable to obtain poll descriptors count");
	351	return SR_ERR;
	352	}
	353
	354	if (!(ufds = g_try_malloc(count * sizeof(struct pollfd)))) {
	355	sr_err("alsa: %s: ufds malloc failed", __func__);
	356	return SR_ERR_MALLOC;
	357	}
	358
	359	err = snd_pcm_poll_descriptors(alsa->capture_handle, ufds, count);
	360	if (err < 0) {
	361	sr_err("alsa: Unable to obtain poll descriptors (%s)",
	362	snd_strerror(err));
	363	g_free(ufds);
	364	return SR_ERR;
	365	}
	366
	367	alsa->session_id = session_dev_id;
	368	sr_source_add(ufds[0].fd, ufds[0].events, 10, receive_data, sdi);
	369
	370	packet.type = SR_DF_HEADER;
	371	packet.length = sizeof(struct sr_datafeed_header);
	372	packet.payload = (unsigned char *) &header;
	373	header.feed_version = 1;
	374	gettimeofday(&header.starttime, NULL);
	375	header.samplerate = alsa->cur_rate;
	376	header.num_analog_probes = NUM_PROBES;
	377	header.num_logic_probes = 0;
	378	header.protocol_id = SR_PROTO_RAW;
	379	sr_session_bus(session_dev_id, &packet);
	380	g_free(ufds);
	381
	382	return SR_OK;
	383	}
	384
	385	static int hw_stop_acquisition(int dev_index, gpointer session_dev_id)
	386	{
	387	/* Avoid compiler warnings. */
	388	dev_index = dev_index;
	389	session_dev_id = session_dev_id;
	390
	391	return SR_OK;
	392	}
	393
	394	SR_PRIV struct sr_dev_plugin alsa_plugin_info = {
	395	.name = "alsa",
	396	.longname = "ALSA driver",
	397	.api_version = 1,
	398	.init = hw_init,
	399	.cleanup = hw_cleanup,
	400	.opendev = hw_opendev,
	401	.closedev = hw_closedev,
	402	.get_dev_info = hw_get_dev_info,
	403	.get_status = hw_get_status,
	404	.get_capabilities = hw_get_capabilities,
	405	.set_configuration = hw_set_configuration,
	406	.start_acquisition = hw_start_acquisition,
	407	.stop_acquisition = hw_stop_acquisition,
	408	};