[libsigrok.git] / 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 "libsigrok.h"
#include "libsigrok-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 const int hwcaps[] = {
	SR_HWCAP_SAMPLERATE,
	SR_HWCAP_LIMIT_SAMPLES,
	SR_HWCAP_CONTINUOUS,
};

/* TODO: Which probe names/numbers to use? */
static const char *probe_names[NUM_PROBES + 1] = {
	"0",
	"1",
	NULL,
};

static GSList *dev_insts = NULL;

/* Private, per-device-instance driver context. */
struct context {
	uint64_t cur_rate;
	uint64_t limit_samples;
	snd_pcm_t *capture_handle;
	snd_pcm_hw_params_t *hw_params;
	void *session_dev_id;
};

static int hw_init(const char *devinfo)
{
	struct sr_dev_inst *sdi;
	struct context *ctx;

	(void)devinfo;

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

	if (!(sdi = sr_dev_inst_new(0, SR_ST_ACTIVE, "alsa", NULL, NULL))) {
		sr_err("alsa: %s: sdi was NULL", __func__);
		goto free_ctx;
	}

	sdi->priv = ctx;

	dev_insts = g_slist_append(dev_insts, sdi);

	return 1;

free_ctx:
	g_free(ctx);
	return 0;
}

static int hw_dev_open(int dev_index)
{
	struct sr_dev_inst *sdi;
	struct context *ctx;
	int ret;

	if (!(sdi = sr_dev_inst_get(dev_insts, dev_index)))
		return SR_ERR;
	ctx = sdi->priv;

	ret = snd_pcm_open(&ctx->capture_handle, AUDIO_DEV,
			   SND_PCM_STREAM_CAPTURE, 0);
	if (ret < 0) {
		sr_err("alsa: can't open audio device %s (%s)", AUDIO_DEV,
		       snd_strerror(ret));
		return SR_ERR;
	}

	ret = snd_pcm_hw_params_malloc(&ctx->hw_params);
	if (ret < 0) {
		sr_err("alsa: can't allocate hardware parameter structure (%s)",
		       snd_strerror(ret));
		return SR_ERR_MALLOC;
	}

	ret = snd_pcm_hw_params_any(ctx->capture_handle, ctx->hw_params);
	if (ret < 0) {
		sr_err("alsa: can't initialize hardware parameter structure "
		       "(%s)", snd_strerror(ret));
		return SR_ERR;
	}

	return SR_OK;
}

static int hw_dev_close(int dev_index)
{
	struct sr_dev_inst *sdi;
	struct context *ctx;

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

	if (!(ctx = sdi->priv)) {
		sr_err("alsa: %s: sdi->priv was NULL", __func__);
		return SR_ERR_BUG;
	}

	// TODO: Return values of snd_*?
	if (ctx->hw_params)
		snd_pcm_hw_params_free(ctx->hw_params);
	if (ctx->capture_handle)
		snd_pcm_close(ctx->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 const void *hw_dev_info_get(int dev_index, int dev_info_id)
{
	struct sr_dev_inst *sdi;
	struct context *ctx;
	void *info = NULL;

	if (!(sdi = sr_dev_inst_get(dev_insts, dev_index)))
		return NULL;
	ctx = 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 = &ctx->cur_rate;
		break;
	// case SR_DI_PROBE_TYPE:
	// 	info = GINT_TO_POINTER(SR_PROBE_TYPE_ANALOG);
	// 	break;
	}

	return info;
}

static int hw_dev_status_get(int dev_index)
{
	/* Avoid compiler warnings. */
	dev_index = dev_index;

	return SR_ST_ACTIVE;
}

static const int *hw_hwcap_get_all(void)
{
	return hwcaps;
}

static int hw_dev_config_set(int dev_index, int hwcap, const void *value)
{
	struct sr_dev_inst *sdi;
	struct context *ctx;

	if (!(sdi = sr_dev_inst_get(dev_insts, dev_index)))
		return SR_ERR;
	ctx = sdi->priv;

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

static int receive_data(int fd, int revents, void *cb_data)
{
	struct sr_dev_inst *sdi = cb_data;
	struct context *ctx = 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(ctx->capture_handle, inb,
			MIN(4096 / 4, ctx->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_send(sdi, &packet);
		g_free(outb);
		ctx->limit_samples -= count;

	} while (ctx->limit_samples > 0);

	packet.type = SR_DF_END;
	sr_session_send(sdi, &packet);

	return TRUE;
}

static int hw_dev_acquisition_start(int dev_index, void *cb_data)
{
	struct sr_dev_inst *sdi;
	struct context *ctx;
	struct sr_datafeed_packet packet;
	struct sr_datafeed_header header;
	struct pollfd *ufds;
	int count;
	int ret;

	if (!(sdi = sr_dev_inst_get(dev_insts, dev_index)))
		return SR_ERR;
	ctx = sdi->priv;

	ret = snd_pcm_hw_params_set_access(ctx->capture_handle,
			ctx->hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
	if (ret < 0) {
		sr_err("alsa: can't set access type (%s)", snd_strerror(ret));
		return SR_ERR;
	}

	/* FIXME: Hardcoded for 16bits */
	ret = snd_pcm_hw_params_set_format(ctx->capture_handle,
			ctx->hw_params, SND_PCM_FORMAT_S16_LE);
	if (ret < 0) {
		sr_err("alsa: can't set sample format (%s)", snd_strerror(ret));
		return SR_ERR;
	}

	ret = snd_pcm_hw_params_set_rate_near(ctx->capture_handle,
			ctx->hw_params, (unsigned int *)&ctx->cur_rate, 0);
	if (ret < 0) {
		sr_err("alsa: can't set sample rate (%s)", snd_strerror(ret));
		return SR_ERR;
	}

	ret = snd_pcm_hw_params_set_channels(ctx->capture_handle,
			ctx->hw_params, NUM_PROBES);
	if (ret < 0) {
		sr_err("alsa: can't set channel count (%s)", snd_strerror(ret));
		return SR_ERR;
	}

	ret = snd_pcm_hw_params(ctx->capture_handle, ctx->hw_params);
	if (ret < 0) {
		sr_err("alsa: can't set parameters (%s)", snd_strerror(ret));
		return SR_ERR;
	}

	ret = snd_pcm_prepare(ctx->capture_handle);
	if (ret < 0) {
		sr_err("alsa: can't prepare audio interface for use (%s)",
		       snd_strerror(ret));
		return SR_ERR;
	}

	count = snd_pcm_poll_descriptors_count(ctx->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;
	}

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

	ctx->session_dev_id = cb_data;
	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 = ctx->cur_rate;
	header.num_analog_probes = NUM_PROBES;
	header.num_logic_probes = 0;
	header.protocol_id = SR_PROTO_RAW;
	sr_session_send(cb_data, &packet);
	g_free(ufds);

	return SR_OK;
}

/* TODO: This stops acquisition on ALL devices, ignoring dev_index. */
static int hw_dev_acquisition_stop(int dev_index, void *cb_data)
{
	(void)dev_index;
	(void)cb_data;

	return SR_OK;
}

SR_PRIV struct sr_dev_driver alsa_driver_info = {
	.name = "alsa",
	.longname = "ALSA driver",
	.api_version = 1,
	.init = hw_init,
	.cleanup = hw_cleanup,
	.dev_open = hw_dev_open,
	.dev_close = hw_dev_close,
	.dev_info_get = hw_dev_info_get,
	.dev_status_get = hw_dev_status_get,
	.hwcap_get_all = hw_hwcap_get_all,
	.dev_config_set = hw_dev_config_set,
	.dev_acquisition_start = hw_dev_acquisition_start,
	.dev_acquisition_stop = hw_dev_acquisition_stop,
};
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 "libsigrok.h"
	28	#include "libsigrok-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 const int hwcaps[] = {
	46	SR_HWCAP_SAMPLERATE,
	47	SR_HWCAP_LIMIT_SAMPLES,
	48	SR_HWCAP_CONTINUOUS,
	49	};
	50
	51	/* TODO: Which probe names/numbers to use? */
	52	static const char *probe_names[NUM_PROBES + 1] = {
	53	"0",
	54	"1",
	55	NULL,
	56	};
	57
	58	static GSList *dev_insts = NULL;
	59
	60	/* Private, per-device-instance driver context. */
	61	struct context {
	62	uint64_t cur_rate;
	63	uint64_t limit_samples;
	64	snd_pcm_t *capture_handle;
	65	snd_pcm_hw_params_t *hw_params;
	66	void *session_dev_id;
	67	};
	68
	69	static int hw_init(const char *devinfo)
	70	{
	71	struct sr_dev_inst *sdi;
	72	struct context *ctx;
	73
	74	(void)devinfo;
	75
	76	if (!(ctx = g_try_malloc0(sizeof(struct context)))) {
	77	sr_err("alsa: %s: ctx malloc failed", __func__);
	78	return SR_ERR_MALLOC;
	79	}
	80
	81	if (!(sdi = sr_dev_inst_new(0, SR_ST_ACTIVE, "alsa", NULL, NULL))) {
	82	sr_err("alsa: %s: sdi was NULL", __func__);
	83	goto free_ctx;
	84	}
	85
	86	sdi->priv = ctx;
	87
	88	dev_insts = g_slist_append(dev_insts, sdi);
	89
	90	return 1;
	91
	92	free_ctx:
	93	g_free(ctx);
	94	return 0;
	95	}
	96
	97	static int hw_dev_open(int dev_index)
	98	{
	99	struct sr_dev_inst *sdi;
	100	struct context *ctx;
	101	int ret;
	102
	103	if (!(sdi = sr_dev_inst_get(dev_insts, dev_index)))
	104	return SR_ERR;
	105	ctx = sdi->priv;
	106
	107	ret = snd_pcm_open(&ctx->capture_handle, AUDIO_DEV,
	108	SND_PCM_STREAM_CAPTURE, 0);
	109	if (ret < 0) {
	110	sr_err("alsa: can't open audio device %s (%s)", AUDIO_DEV,
	111	snd_strerror(ret));
	112	return SR_ERR;
	113	}
	114
	115	ret = snd_pcm_hw_params_malloc(&ctx->hw_params);
	116	if (ret < 0) {
	117	sr_err("alsa: can't allocate hardware parameter structure (%s)",
	118	snd_strerror(ret));
	119	return SR_ERR_MALLOC;
	120	}
	121
	122	ret = snd_pcm_hw_params_any(ctx->capture_handle, ctx->hw_params);
	123	if (ret < 0) {
	124	sr_err("alsa: can't initialize hardware parameter structure "
	125	"(%s)", snd_strerror(ret));
	126	return SR_ERR;
	127	}
	128
	129	return SR_OK;
	130	}
	131
	132	static int hw_dev_close(int dev_index)
	133	{
	134	struct sr_dev_inst *sdi;
	135	struct context *ctx;
	136
	137	if (!(sdi = sr_dev_inst_get(dev_insts, dev_index))) {
	138	sr_err("alsa: %s: sdi was NULL", __func__);
	139	return SR_ERR_BUG;
	140	}
	141
	142	if (!(ctx = sdi->priv)) {
	143	sr_err("alsa: %s: sdi->priv was NULL", __func__);
	144	return SR_ERR_BUG;
	145	}
	146
	147	// TODO: Return values of snd_*?
	148	if (ctx->hw_params)
	149	snd_pcm_hw_params_free(ctx->hw_params);
	150	if (ctx->capture_handle)
	151	snd_pcm_close(ctx->capture_handle);
	152
	153	return SR_OK;
	154	}
	155
	156	static int hw_cleanup(void)
	157	{
	158	struct sr_dev_inst *sdi;
	159
	160	if (!(sdi = sr_dev_inst_get(dev_insts, 0))) {
	161	sr_err("alsa: %s: sdi was NULL", __func__);
	162	return SR_ERR_BUG;
	163	}
	164
	165	sr_dev_inst_free(sdi);
	166
	167	return SR_OK;
	168	}
	169
	170	static const void *hw_dev_info_get(int dev_index, int dev_info_id)
	171	{
	172	struct sr_dev_inst *sdi;
	173	struct context *ctx;
	174	void *info = NULL;
	175
	176	if (!(sdi = sr_dev_inst_get(dev_insts, dev_index)))
	177	return NULL;
	178	ctx = sdi->priv;
	179
	180	switch (dev_info_id) {
	181	case SR_DI_INST:
	182	info = sdi;
	183	break;
	184	case SR_DI_NUM_PROBES:
	185	info = GINT_TO_POINTER(NUM_PROBES);
	186	break;
	187	case SR_DI_PROBE_NAMES:
	188	info = probe_names;
	189	break;
	190	case SR_DI_CUR_SAMPLERATE:
	191	info = &ctx->cur_rate;
	192	break;
	193	// case SR_DI_PROBE_TYPE:
	194	// info = GINT_TO_POINTER(SR_PROBE_TYPE_ANALOG);
	195	// break;
	196	}
	197
	198	return info;
	199	}
	200
	201	static int hw_dev_status_get(int dev_index)
	202	{
	203	/* Avoid compiler warnings. */
	204	dev_index = dev_index;
	205
	206	return SR_ST_ACTIVE;
	207	}
	208
	209	static const int *hw_hwcap_get_all(void)
	210	{
	211	return hwcaps;
	212	}
	213
	214	static int hw_dev_config_set(int dev_index, int hwcap, const void *value)
	215	{
	216	struct sr_dev_inst *sdi;
	217	struct context *ctx;
	218
	219	if (!(sdi = sr_dev_inst_get(dev_insts, dev_index)))
	220	return SR_ERR;
	221	ctx = sdi->priv;
	222
	223	switch (hwcap) {
	224	case SR_HWCAP_PROBECONFIG:
	225	return SR_OK;
	226	case SR_HWCAP_SAMPLERATE:
	227	ctx->cur_rate = (const uint64_t )value;
	228	return SR_OK;
	229	case SR_HWCAP_LIMIT_SAMPLES:
	230	ctx->limit_samples = (const uint64_t )value;
	231	return SR_OK;
	232	default:
	233	return SR_ERR;
	234	}
	235	}
	236
	237	static int receive_data(int fd, int revents, void *cb_data)
	238	{
	239	struct sr_dev_inst *sdi = cb_data;
	240	struct context *ctx = sdi->priv;
	241	struct sr_datafeed_packet packet;
	242	struct sr_analog_sample *sample;
	243	unsigned int sample_size = sizeof(struct sr_analog_sample) +
	244	(NUM_PROBES * sizeof(struct sr_analog_probe));
	245	char *outb;
	246	char inb[4096];
	247	int i, x, count;
	248
	249	fd = fd;
	250	revents = revents;
	251
	252	do {
	253	memset(inb, 0, sizeof(inb));
	254	count = snd_pcm_readi(ctx->capture_handle, inb,
	255	MIN(4096 / 4, ctx->limit_samples));
	256	if (count < 1) {
	257	sr_err("alsa: Failed to read samples");
	258	return FALSE;
	259	}
	260
	261	if (!(outb = g_try_malloc(sample_size * count))) {
	262	sr_err("alsa: %s: outb malloc failed", __func__);
	263	return FALSE;
	264	}
	265
	266	for (i = 0; i < count; i++) {
	267	sample = (struct sr_analog_sample *)
	268	(outb + (i * sample_size));
	269	sample->num_probes = NUM_PROBES;
	270
	271	for (x = 0; x < NUM_PROBES; x++) {
	272	sample->probes[x].val =
	273	(uint16_t )(inb + (i * 4) + (x * 2));
	274	sample->probes[x].val &= ((1 << 16) - 1);
	275	sample->probes[x].res = 16;
	276	}
	277	}
	278
	279	packet.type = SR_DF_ANALOG;
	280	packet.length = count * sample_size;
	281	packet.unitsize = sample_size;
	282	packet.payload = outb;
	283	sr_session_send(sdi, &packet);
	284	g_free(outb);
	285	ctx->limit_samples -= count;
	286
	287	} while (ctx->limit_samples > 0);
	288
	289	packet.type = SR_DF_END;
	290	sr_session_send(sdi, &packet);
	291
	292	return TRUE;
	293	}
	294
	295	static int hw_dev_acquisition_start(int dev_index, void *cb_data)
	296	{
	297	struct sr_dev_inst *sdi;
	298	struct context *ctx;
	299	struct sr_datafeed_packet packet;
	300	struct sr_datafeed_header header;
	301	struct pollfd *ufds;
	302	int count;
	303	int ret;
	304
	305	if (!(sdi = sr_dev_inst_get(dev_insts, dev_index)))
	306	return SR_ERR;
	307	ctx = sdi->priv;
	308
	309	ret = snd_pcm_hw_params_set_access(ctx->capture_handle,
	310	ctx->hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
	311	if (ret < 0) {
	312	sr_err("alsa: can't set access type (%s)", snd_strerror(ret));
	313	return SR_ERR;
	314	}
	315
	316	/* FIXME: Hardcoded for 16bits */
	317	ret = snd_pcm_hw_params_set_format(ctx->capture_handle,
	318	ctx->hw_params, SND_PCM_FORMAT_S16_LE);
	319	if (ret < 0) {
	320	sr_err("alsa: can't set sample format (%s)", snd_strerror(ret));
	321	return SR_ERR;
	322	}
	323
	324	ret = snd_pcm_hw_params_set_rate_near(ctx->capture_handle,
	325	ctx->hw_params, (unsigned int *)&ctx->cur_rate, 0);
	326	if (ret < 0) {
	327	sr_err("alsa: can't set sample rate (%s)", snd_strerror(ret));
	328	return SR_ERR;
	329	}
	330
	331	ret = snd_pcm_hw_params_set_channels(ctx->capture_handle,
	332	ctx->hw_params, NUM_PROBES);
	333	if (ret < 0) {
	334	sr_err("alsa: can't set channel count (%s)", snd_strerror(ret));
	335	return SR_ERR;
	336	}
	337
	338	ret = snd_pcm_hw_params(ctx->capture_handle, ctx->hw_params);
	339	if (ret < 0) {
	340	sr_err("alsa: can't set parameters (%s)", snd_strerror(ret));
	341	return SR_ERR;
	342	}
	343
	344	ret = snd_pcm_prepare(ctx->capture_handle);
	345	if (ret < 0) {
	346	sr_err("alsa: can't prepare audio interface for use (%s)",
	347	snd_strerror(ret));
	348	return SR_ERR;
	349	}
	350
	351	count = snd_pcm_poll_descriptors_count(ctx->capture_handle);
	352	if (count < 1) {
	353	sr_err("alsa: Unable to obtain poll descriptors count");
	354	return SR_ERR;
	355	}
	356
	357	if (!(ufds = g_try_malloc(count * sizeof(struct pollfd)))) {
	358	sr_err("alsa: %s: ufds malloc failed", __func__);
	359	return SR_ERR_MALLOC;
	360	}
	361
	362	ret = snd_pcm_poll_descriptors(ctx->capture_handle, ufds, count);
	363	if (ret < 0) {
	364	sr_err("alsa: Unable to obtain poll descriptors (%s)",
	365	snd_strerror(ret));
	366	g_free(ufds);
	367	return SR_ERR;
	368	}
	369
	370	ctx->session_dev_id = cb_data;
	371	sr_source_add(ufds[0].fd, ufds[0].events, 10, receive_data, sdi);
	372
	373	packet.type = SR_DF_HEADER;
	374	packet.length = sizeof(struct sr_datafeed_header);
	375	packet.payload = (unsigned char *)&header;
	376	header.feed_version = 1;
	377	gettimeofday(&header.starttime, NULL);
	378	header.samplerate = ctx->cur_rate;
	379	header.num_analog_probes = NUM_PROBES;
	380	header.num_logic_probes = 0;
	381	header.protocol_id = SR_PROTO_RAW;
	382	sr_session_send(cb_data, &packet);
	383	g_free(ufds);
	384
	385	return SR_OK;
	386	}
	387
	388	/* TODO: This stops acquisition on ALL devices, ignoring dev_index. */
	389	static int hw_dev_acquisition_stop(int dev_index, void *cb_data)
	390	{
	391	(void)dev_index;
	392	(void)cb_data;
	393
	394	return SR_OK;
	395	}
	396
	397	SR_PRIV struct sr_dev_driver alsa_driver_info = {
	398	.name = "alsa",
	399	.longname = "ALSA driver",
	400	.api_version = 1,
	401	.init = hw_init,
	402	.cleanup = hw_cleanup,
	403	.dev_open = hw_dev_open,
	404	.dev_close = hw_dev_close,
	405	.dev_info_get = hw_dev_info_get,
	406	.dev_status_get = hw_dev_status_get,
	407	.hwcap_get_all = hw_hwcap_get_all,
	408	.dev_config_set = hw_dev_config_set,
	409	.dev_acquisition_start = hw_dev_acquisition_start,
	410	.dev_acquisition_stop = hw_dev_acquisition_stop,
	411	};