session.c - chromium.googlesource.com/chromiumos/third_party/libsigrok - Gitiles

 /*
  * This file is part of the libsigrok project.
  *
  * Copyright (C) 2010-2012 Bert Vermeulen <bert@biot.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 3 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, see <http://www.gnu.org/licenses/>.
  */

 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
 #include <glib.h>
 #include "libsigrok.h"
 #include "libsigrok-internal.h"

 /* Message logging helpers with subsystem-specific prefix string. */
 #define LOG_PREFIX "session: "
 #define sr_log(l, s, args...) sr_log(l, LOG_PREFIX s, ## args)
 #define sr_spew(s, args...) sr_spew(LOG_PREFIX s, ## args)
 #define sr_dbg(s, args...) sr_dbg(LOG_PREFIX s, ## args)
 #define sr_info(s, args...) sr_info(LOG_PREFIX s, ## args)
 #define sr_warn(s, args...) sr_warn(LOG_PREFIX s, ## args)
 #define sr_err(s, args...) sr_err(LOG_PREFIX s, ## args)

 /**
  * @file
  *
  * Creating, using, or destroying libsigrok sessions.
  */

 /**
  * @defgroup grp_session Session handling
  *
  * Creating, using, or destroying libsigrok sessions.
  *
  * @{
  */

 struct source {
 	int timeout;
 	sr_receive_data_callback_t cb;
 	void *cb_data;

 	/* This is used to keep track of the object (fd, pollfd or channel) which is
 	 * being polled and will be used to match the source when removing it again.
 	 */
 	gintptr poll_object;
 };

 struct datafeed_callback {
 	sr_datafeed_callback_t cb;
 	void *cb_data;
 };

 /* There can only be one session at a time. */
 /* 'session' is not static, it's used elsewhere (via 'extern'). */
 struct sr_session *session;

 /**
  * Create a new session.
  *
  * @todo Should it use the file-global "session" variable or take an argument?
  *       The same question applies to all the other session functions.
  *
  * @return A pointer to the newly allocated session, or NULL upon errors.
  */
 SR_API struct sr_session *sr_session_new(void)
 {
 	if (!(session = g_try_malloc0(sizeof(struct sr_session)))) {
 		sr_err("Session malloc failed.");
 		return NULL;
 	}

 	session->source_timeout = -1;
 	session->abort_session = FALSE;
 //	g_mutex_init(&session->stop_mutex);

 	return session;
 }

 /**
  * Destroy the current session.
  *
  * This frees up all memory used by the session.
  *
  * @return SR_OK upon success, SR_ERR_BUG if no session exists.
  */
 SR_API int sr_session_destroy(void)
 {
 	if (!session) {
 		sr_err("%s: session was NULL", __func__);
 		return SR_ERR_BUG;
 	}

 	sr_session_dev_remove_all();

     sr_session_datafeed_callback_remove_all();

     if (session->sources) {
         g_free(session->sources);
         session->sources = NULL;
     }

     if (session->pollfds) {
         g_free(session->pollfds);
         session->pollfds = NULL;
     }

 	/* TODO: Error checks needed? */

 //	g_mutex_clear(&session->stop_mutex);

 	g_free(session);
 	session = NULL;

 	return SR_OK;
 }

 /**
  * Remove all the devices from the current session.
  *
  * The session itself (i.e., the struct sr_session) is not free'd and still
  * exists after this function returns.
  *
  * @return SR_OK upon success, SR_ERR_BUG if no session exists.
  */
 SR_API int sr_session_dev_remove_all(void)
 {
 	if (!session) {
 		sr_err("%s: session was NULL", __func__);
 		return SR_ERR_BUG;
 	}

 	g_slist_free(session->devs);
 	session->devs = NULL;

 	return SR_OK;
 }

 /**
  * Add a device instance to the current session.
  *
  * @param sdi The device instance to add to the current session. Must not
  *            be NULL. Also, sdi->driver and sdi->driver->dev_open must
  *            not be NULL.
  *
  * @return SR_OK upon success, SR_ERR_ARG upon invalid arguments.
  */
 SR_API int sr_session_dev_add(const struct sr_dev_inst *sdi)
 {

 	if (!sdi) {
 		sr_err("%s: sdi was NULL", __func__);
 		return SR_ERR_ARG;
 	}

 	if (!session) {
 		sr_err("%s: session was NULL", __func__);
 		return SR_ERR_BUG;
 	}

 	/* If sdi->driver is NULL, this is a virtual device. */
 	if (!sdi->driver) {
 		sr_dbg("%s: sdi->driver was NULL, this seems to be "
 		       "a virtual device; continuing", __func__);
 		/* Just add the device, don't run dev_open(). */
 		session->devs = g_slist_append(session->devs, (gpointer)sdi);
 		return SR_OK;
 	}

 	/* sdi->driver is non-NULL (i.e. we have a real device). */
 	if (!sdi->driver->dev_open) {
 		sr_err("%s: sdi->driver->dev_open was NULL", __func__);
 		return SR_ERR_BUG;
 	}

 	session->devs = g_slist_append(session->devs, (gpointer)sdi);

 	return SR_OK;
 }

 /**
  * Remove all datafeed callbacks in the current session.
  *
  * @return SR_OK upon success, SR_ERR_BUG if no session exists.
  */
 SR_API int sr_session_datafeed_callback_remove_all(void)
 {
 	if (!session) {
 		sr_err("%s: session was NULL", __func__);
 		return SR_ERR_BUG;
 	}

 	g_slist_free_full(session->datafeed_callbacks, g_free);
 	session->datafeed_callbacks = NULL;

 	return SR_OK;
 }

 /**
  * Add a datafeed callback to the current session.
  *
  * @param cb Function to call when a chunk of data is received.
  *           Must not be NULL.
  * @param cb_data Opaque pointer passed in by the caller.
  *
  * @return SR_OK upon success, SR_ERR_BUG if no session exists.
  */
 SR_API int sr_session_datafeed_callback_add(sr_datafeed_callback_t cb, void *cb_data)
 {
 	struct datafeed_callback *cb_struct;

 	if (!session) {
 		sr_err("%s: session was NULL", __func__);
 		return SR_ERR_BUG;
 	}

 	if (!cb) {
 		sr_err("%s: cb was NULL", __func__);
 		return SR_ERR_ARG;
 	}

 	if (!(cb_struct = g_try_malloc0(sizeof(struct datafeed_callback))))
 		return SR_ERR_MALLOC;

 	cb_struct->cb = cb;
 	cb_struct->cb_data = cb_data;

 	session->datafeed_callbacks =
 	    g_slist_append(session->datafeed_callbacks, cb_struct);

 	return SR_OK;
 }

 static int sr_session_run_poll(void)
 {
 	unsigned int i;
 	int ret;

 	while (session->num_sources > 0) {
 		ret = g_poll(session->pollfds, session->num_sources,
 				session->source_timeout);
 		for (i = 0; i < session->num_sources; i++) {
 			if (session->pollfds[i].revents > 0 || (ret == 0
 				&& session->source_timeout == session->sources[i].timeout)) {
 				/*
 				 * Invoke the source's callback on an event,
 				 * or if the poll timed out and this source
 				 * asked for that timeout.
 				 */
 				if (!session->sources[i].cb(session->pollfds[i].fd,
 						session->pollfds[i].revents,
 						session->sources[i].cb_data))
 					sr_session_source_remove(session->sources[i].poll_object);
 			}
 			/*
 			 * We want to take as little time as possible to stop
 			 * the session if we have been told to do so. Therefore,
 			 * we check the flag after processing every source, not
 			 * just once per main event loop.
 			 */
 //			g_mutex_lock(&session->stop_mutex);
 			if (session->abort_session) {
 				sr_session_stop_sync();
 				/* But once is enough. */
 				session->abort_session = FALSE;
 			}
 //			g_mutex_unlock(&session->stop_mutex);
 		}
 	}

 	return SR_OK;
 }

 /**
  * Start a session.
  *
  * There can only be one session at a time.
  *
  * @return SR_OK upon success, SR_ERR upon errors.
  */
 SR_API int sr_session_start(void)
 {
 	struct sr_dev_inst *sdi;
 	GSList *l;
 	int ret;

 	if (!session) {
 		sr_err("%s: session was NULL; a session must be "
 		       "created before starting it.", __func__);
 		return SR_ERR_BUG;
 	}

 	if (!session->devs) {
 		sr_err("%s: session->devs was NULL; a session "
 		       "cannot be started without devices.", __func__);
 		return SR_ERR_BUG;
 	}

 	sr_info("Starting.");

 	ret = SR_OK;
 	for (l = session->devs; l; l = l->next) {
 		sdi = l->data;
 		if ((ret = sdi->driver->dev_acquisition_start(sdi, sdi)) != SR_OK) {
 			sr_err("%s: could not start an acquisition "
 			       "(%d)", __func__, ret);
 			break;
 		}
 	}

 	/* TODO: What if there are multiple devices? Which return code? */

 	return ret;
 }

 /**
  * Run the session.
  *
  * @return SR_OK upon success, SR_ERR_BUG upon errors.
  */
 SR_API int sr_session_run(void)
 {
 	if (!session) {
 		sr_err("%s: session was NULL; a session must be "
 		       "created first, before running it.", __func__);
 		return SR_ERR_BUG;
 	}

 	if (!session->devs) {
 		/* TODO: Actually the case? */
 		sr_err("%s: session->devs was NULL; a session "
 		       "cannot be run without devices.", __func__);
 		return SR_ERR_BUG;
 	}

 	sr_info("Running.");

 	/* Do we have real sources? */
 	if (session->num_sources == 1 && session->pollfds[0].fd == -1) {
 		/* Dummy source, freewheel over it. */
 		while (session->num_sources)
 			session->sources[0].cb(-1, 0, session->sources[0].cb_data);
 	} else {
 		/* Real sources, use g_poll() main loop. */
 		sr_session_run_poll();
 	}

 	return SR_OK;
 }

 /**
  * Stop the current session.
  *
  * The current session is stopped immediately, with all acquisition sessions
  * being stopped and hardware drivers cleaned up.
  *
  * This must be called from within the session thread, to prevent freeing
  * resources that the session thread will try to use.
  *
  * @return SR_OK upon success, SR_ERR_BUG if no session exists.
  */
 SR_PRIV int sr_session_stop_sync(void)
 {
 	struct sr_dev_inst *sdi;
 	GSList *l;

 	if (!session) {
 		sr_err("%s: session was NULL", __func__);
 		return SR_ERR_BUG;
 	}

 	sr_info("Stopping.");

 	for (l = session->devs; l; l = l->next) {
 		sdi = l->data;
 		if (sdi->driver) {
 			if (sdi->driver->dev_acquisition_stop)
                 sdi->driver->dev_acquisition_stop(sdi, NULL);
 		}
 	}

 	return SR_OK;
 }

 /**
  * Stop the current session.
  *
  * The current session is stopped immediately, with all acquisition sessions
  * being stopped and hardware drivers cleaned up.
  *
  * If the session is run in a separate thread, this function will not block
  * until the session is finished executing. It is the caller's responsibility
  * to wait for the session thread to return before assuming that the session is
  * completely decommissioned.
  *
  * @return SR_OK upon success, SR_ERR_BUG if no session exists.
  */
 SR_API int sr_session_stop(void)
 {
 	if (!session) {
 		sr_err("%s: session was NULL", __func__);
 		return SR_ERR_BUG;
 	}

 //	g_mutex_lock(&session->stop_mutex);
 	session->abort_session = TRUE;
 //	g_mutex_unlock(&session->stop_mutex);

 	return SR_OK;
 }

 /**
  * Debug helper.
  *
  * @param packet The packet to show debugging information for.
  */
 static void datafeed_dump(const struct sr_datafeed_packet *packet)
 {
 	const struct sr_datafeed_logic *logic;
 	const struct sr_datafeed_analog *analog;

 	switch (packet->type) {
 	case SR_DF_HEADER:
 		sr_dbg("bus: Received SR_DF_HEADER packet.");
 		break;
 	case SR_DF_TRIGGER:
 		sr_dbg("bus: Received SR_DF_TRIGGER packet.");
 		break;
 	case SR_DF_META:
 		sr_dbg("bus: Received SR_DF_META packet.");
 		break;
 	case SR_DF_LOGIC:
 		logic = packet->payload;
 		sr_dbg("bus: Received SR_DF_LOGIC packet (%" PRIu64 " bytes).",
 		       logic->length);
 		break;
 	case SR_DF_ANALOG:
 		analog = packet->payload;
 		sr_dbg("bus: Received SR_DF_ANALOG packet (%d samples).",
 		       analog->num_samples);
 		break;
 	case SR_DF_END:
 		sr_dbg("bus: Received SR_DF_END packet.");
 		break;
 	case SR_DF_FRAME_BEGIN:
 		sr_dbg("bus: Received SR_DF_FRAME_BEGIN packet.");
 		break;
 	case SR_DF_FRAME_END:
 		sr_dbg("bus: Received SR_DF_FRAME_END packet.");
 		break;
 	default:
 		sr_dbg("bus: Received unknown packet type: %d.", packet->type);
 		break;
 	}
 }

 /**
  * Send a packet to whatever is listening on the datafeed bus.
  *
  * Hardware drivers use this to send a data packet to the frontend.
  *
  * @param sdi TODO.
  * @param packet The datafeed packet to send to the session bus.
  *
  * @return SR_OK upon success, SR_ERR_ARG upon invalid arguments.
  *
  * @private
  */
 SR_PRIV int sr_session_send(const struct sr_dev_inst *sdi,
 			    const struct sr_datafeed_packet *packet)
 {
 	GSList *l;
 	struct datafeed_callback *cb_struct;

 	if (!sdi) {
 		sr_err("%s: sdi was NULL", __func__);
 		return SR_ERR_ARG;
 	}

 	if (!packet) {
 		sr_err("%s: packet was NULL", __func__);
 		return SR_ERR_ARG;
 	}

 	for (l = session->datafeed_callbacks; l; l = l->next) {
 		if (sr_log_loglevel_get() >= SR_LOG_DBG)
 			datafeed_dump(packet);
 		cb_struct = l->data;
 		cb_struct->cb(sdi, packet, cb_struct->cb_data);
 	}

 	return SR_OK;
 }

 /**
  * Add an event source for a file descriptor.
  *
  * @param pollfd The GPollFD.
  * @param timeout Max time to wait before the callback is called, ignored if 0.
  * @param cb Callback function to add. Must not be NULL.
  * @param cb_data Data for the callback function. Can be NULL.
  * @param poll_object TODO.
  *
  * @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
  *         SR_ERR_MALLOC upon memory allocation errors.
  */
 static int _sr_session_source_add(GPollFD *pollfd, int timeout,
     sr_receive_data_callback_t cb, const struct sr_dev_inst *sdi, gintptr poll_object)
 {
 	struct source *new_sources, *s;
 	GPollFD *new_pollfds;

 	if (!cb) {
 		sr_err("%s: cb was NULL", __func__);
 		return SR_ERR_ARG;
 	}

 	/* Note: cb_data can be NULL, that's not a bug. */

 	new_pollfds = g_try_realloc(session->pollfds,
 			sizeof(GPollFD) * (session->num_sources + 1));
 	if (!new_pollfds) {
 		sr_err("%s: new_pollfds malloc failed", __func__);
 		return SR_ERR_MALLOC;
 	}

 	new_sources = g_try_realloc(session->sources, sizeof(struct source) *
 			(session->num_sources + 1));
 	if (!new_sources) {
 		sr_err("%s: new_sources malloc failed", __func__);
 		return SR_ERR_MALLOC;
 	}

 	new_pollfds[session->num_sources] = *pollfd;
 	s = &new_sources[session->num_sources++];
 	s->timeout = timeout;
 	s->cb = cb;
 	s->cb_data = sdi;
 	s->poll_object = poll_object;
 	session->pollfds = new_pollfds;
 	session->sources = new_sources;

 	if (timeout != session->source_timeout && timeout > 0
 	    && (session->source_timeout == -1 || timeout < session->source_timeout))
 		session->source_timeout = timeout;

 	return SR_OK;
 }

 /**
  * Add an event source for a file descriptor.
  *
  * @param fd The file descriptor.
  * @param events Events to check for.
  * @param timeout Max time to wait before the callback is called, ignored if 0.
  * @param cb Callback function to add. Must not be NULL.
  * @param cb_data Data for the callback function. Can be NULL.
  *
  * @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
  *         SR_ERR_MALLOC upon memory allocation errors.
  */
 SR_API int sr_session_source_add(int fd, int events, int timeout,
 		sr_receive_data_callback_t cb, const struct sr_dev_inst *sdi)
 {
 	GPollFD p;

 	p.fd = fd;
 	p.events = events;

     return _sr_session_source_add(&p, timeout, cb, sdi, (gintptr)fd);
 }

 /**
  * Add an event source for a GPollFD.
  *
  * @param pollfd The GPollFD.
  * @param timeout Max time to wait before the callback is called, ignored if 0.
  * @param cb Callback function to add. Must not be NULL.
  * @param cb_data Data for the callback function. Can be NULL.
  *
  * @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
  *         SR_ERR_MALLOC upon memory allocation errors.
  */
 SR_API int sr_session_source_add_pollfd(GPollFD *pollfd, int timeout,
 		sr_receive_data_callback_t cb, const struct sr_dev_inst *sdi)
 {
     return _sr_session_source_add(pollfd, timeout, cb,
                       sdi, (gintptr)pollfd);
 }

 /**
  * Add an event source for a GIOChannel.
  *
  * @param channel The GIOChannel.
  * @param events Events to poll on.
  * @param timeout Max time to wait before the callback is called, ignored if 0.
  * @param cb Callback function to add. Must not be NULL.
  * @param cb_data Data for the callback function. Can be NULL.
  *
  * @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
  *         SR_ERR_MALLOC upon memory allocation errors.
  */
 SR_API int sr_session_source_add_channel(GIOChannel *channel, int events,
 		int timeout, sr_receive_data_callback_t cb, const struct sr_dev_inst *sdi)
 {
 	GPollFD p;

 #ifdef _WIN32
 	g_io_channel_win32_make_pollfd(channel, events, &p);
 #else
 	p.fd = g_io_channel_unix_get_fd(channel);
 	p.events = events;
 #endif

     return _sr_session_source_add(&p, timeout, cb, sdi, (gintptr)channel);
 }

 /**
  * Remove the source belonging to the specified channel.
  *
  * @todo Add more error checks and logging.
  *
  * @param channel The channel for which the source should be removed.
  *
  * @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
  *         SR_ERR_MALLOC upon memory allocation errors, SR_ERR_BUG upon
  *         internal errors.
  */
 static int _sr_session_source_remove(gintptr poll_object)
 {
 	struct source *new_sources;
 	GPollFD *new_pollfds;
 	unsigned int old;

 	if (!session->sources || !session->num_sources) {
 		sr_err("%s: sources was NULL", __func__);
 		return SR_ERR_BUG;
 	}

 	for (old = 0; old < session->num_sources; old++) {
 		if (session->sources[old].poll_object == poll_object)
 			break;
 	}

 	/* fd not found, nothing to do */
 	if (old == session->num_sources)
 		return SR_OK;

 	session->num_sources -= 1;

 	if (old != session->num_sources) {
 		memmove(&session->pollfds[old], &session->pollfds[old+1],
 			(session->num_sources - old) * sizeof(GPollFD));
 		memmove(&session->sources[old], &session->sources[old+1],
 			(session->num_sources - old) * sizeof(struct source));
 	}

 	new_pollfds = g_try_realloc(session->pollfds, sizeof(GPollFD) * session->num_sources);
 	if (!new_pollfds && session->num_sources > 0) {
 		sr_err("%s: new_pollfds malloc failed", __func__);
 		return SR_ERR_MALLOC;
 	}

 	new_sources = g_try_realloc(session->sources, sizeof(struct source) * session->num_sources);
 	if (!new_sources && session->num_sources > 0) {
 		sr_err("%s: new_sources malloc failed", __func__);
 		return SR_ERR_MALLOC;
 	}

 	session->pollfds = new_pollfds;
 	session->sources = new_sources;

 	return SR_OK;
 }

 /**
  * Remove the source belonging to the specified file descriptor.
  *
  * @param fd The file descriptor for which the source should be removed.
  *
  * @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
  *         SR_ERR_MALLOC upon memory allocation errors, SR_ERR_BUG upon
  *         internal errors.
  */
 SR_API int sr_session_source_remove(int fd)
 {
 	return _sr_session_source_remove((gintptr)fd);
 }

 /**
  * Remove the source belonging to the specified poll descriptor.
  *
  * @param pollfd The poll descriptor for which the source should be removed.
  *
  * @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
  *         SR_ERR_MALLOC upon memory allocation errors, SR_ERR_BUG upon
  *         internal errors.
  */
 SR_API int sr_session_source_remove_pollfd(GPollFD *pollfd)
 {
 	return _sr_session_source_remove((gintptr)pollfd);
 }

 /**
  * Remove the source belonging to the specified channel.
  *
  * @param channel The channel for which the source should be removed.
  *
  * @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
  *         SR_ERR_MALLOC upon memory allocation errors, SR_ERR_BUG upon
  *         internal errors.
  */
 SR_API int sr_session_source_remove_channel(GIOChannel *channel)
 {
 	return _sr_session_source_remove((gintptr)channel);
 }

 /** @} */
	/*
	* This file is part of the libsigrok project.
	*
	* Copyright (C) 2010-2012 Bert Vermeulen <bert@biot.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 3 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, see <http://www.gnu.org/licenses/>.
	*/

	#include <stdio.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <string.h>
	#include <glib.h>
	#include "libsigrok.h"
	#include "libsigrok-internal.h"

	/* Message logging helpers with subsystem-specific prefix string. */
	#define LOG_PREFIX "session: "
	#define sr_log(l, s, args...) sr_log(l, LOG_PREFIX s, ## args)
	#define sr_spew(s, args...) sr_spew(LOG_PREFIX s, ## args)
	#define sr_dbg(s, args...) sr_dbg(LOG_PREFIX s, ## args)
	#define sr_info(s, args...) sr_info(LOG_PREFIX s, ## args)
	#define sr_warn(s, args...) sr_warn(LOG_PREFIX s, ## args)
	#define sr_err(s, args...) sr_err(LOG_PREFIX s, ## args)

	/**
	* @file
	*
	* Creating, using, or destroying libsigrok sessions.
	*/

	/**
	* @defgroup grp_session Session handling
	*
	* Creating, using, or destroying libsigrok sessions.
	*
	* @{
	*/

	struct source {
	int timeout;
	sr_receive_data_callback_t cb;
	void *cb_data;

	/* This is used to keep track of the object (fd, pollfd or channel) which is
	* being polled and will be used to match the source when removing it again.
	*/
	gintptr poll_object;
	};

	struct datafeed_callback {
	sr_datafeed_callback_t cb;
	void *cb_data;
	};

	/* There can only be one session at a time. */
	/* 'session' is not static, it's used elsewhere (via 'extern'). */
	struct sr_session *session;

	/**
	* Create a new session.
	*
	* @todo Should it use the file-global "session" variable or take an argument?
	* The same question applies to all the other session functions.
	*
	* @return A pointer to the newly allocated session, or NULL upon errors.
	*/
	SR_API struct sr_session *sr_session_new(void)
	{
	if (!(session = g_try_malloc0(sizeof(struct sr_session)))) {
	sr_err("Session malloc failed.");
	return NULL;
	}

	session->source_timeout = -1;
	session->abort_session = FALSE;
	// g_mutex_init(&session->stop_mutex);

	return session;
	}

	/**
	* Destroy the current session.
	*
	* This frees up all memory used by the session.
	*
	* @return SR_OK upon success, SR_ERR_BUG if no session exists.
	*/
	SR_API int sr_session_destroy(void)
	{
	if (!session) {
	sr_err("%s: session was NULL", __func__);
	return SR_ERR_BUG;
	}

	sr_session_dev_remove_all();

	sr_session_datafeed_callback_remove_all();

	if (session->sources) {
	g_free(session->sources);
	session->sources = NULL;
	}

	if (session->pollfds) {
	g_free(session->pollfds);
	session->pollfds = NULL;
	}

	/* TODO: Error checks needed? */

	// g_mutex_clear(&session->stop_mutex);

	g_free(session);
	session = NULL;

	return SR_OK;
	}

	/**
	* Remove all the devices from the current session.
	*
	* The session itself (i.e., the struct sr_session) is not free'd and still
	* exists after this function returns.
	*
	* @return SR_OK upon success, SR_ERR_BUG if no session exists.
	*/
	SR_API int sr_session_dev_remove_all(void)
	{
	if (!session) {
	sr_err("%s: session was NULL", __func__);
	return SR_ERR_BUG;
	}

	g_slist_free(session->devs);
	session->devs = NULL;

	return SR_OK;
	}

	/**
	* Add a device instance to the current session.
	*
	* @param sdi The device instance to add to the current session. Must not
	* be NULL. Also, sdi->driver and sdi->driver->dev_open must
	* not be NULL.
	*
	* @return SR_OK upon success, SR_ERR_ARG upon invalid arguments.
	*/
	SR_API int sr_session_dev_add(const struct sr_dev_inst *sdi)
	{

	if (!sdi) {
	sr_err("%s: sdi was NULL", __func__);
	return SR_ERR_ARG;
	}

	if (!session) {
	sr_err("%s: session was NULL", __func__);
	return SR_ERR_BUG;
	}

	/* If sdi->driver is NULL, this is a virtual device. */
	if (!sdi->driver) {
	sr_dbg("%s: sdi->driver was NULL, this seems to be "
	"a virtual device; continuing", __func__);
	/* Just add the device, don't run dev_open(). */
	session->devs = g_slist_append(session->devs, (gpointer)sdi);
	return SR_OK;
	}

	/* sdi->driver is non-NULL (i.e. we have a real device). */
	if (!sdi->driver->dev_open) {
	sr_err("%s: sdi->driver->dev_open was NULL", __func__);
	return SR_ERR_BUG;
	}

	session->devs = g_slist_append(session->devs, (gpointer)sdi);

	return SR_OK;
	}

	/**
	* Remove all datafeed callbacks in the current session.
	*
	* @return SR_OK upon success, SR_ERR_BUG if no session exists.
	*/
	SR_API int sr_session_datafeed_callback_remove_all(void)
	{
	if (!session) {
	sr_err("%s: session was NULL", __func__);
	return SR_ERR_BUG;
	}

	g_slist_free_full(session->datafeed_callbacks, g_free);
	session->datafeed_callbacks = NULL;

	return SR_OK;
	}

	/**
	* Add a datafeed callback to the current session.
	*
	* @param cb Function to call when a chunk of data is received.
	* Must not be NULL.
	* @param cb_data Opaque pointer passed in by the caller.
	*
	* @return SR_OK upon success, SR_ERR_BUG if no session exists.
	*/
	SR_API int sr_session_datafeed_callback_add(sr_datafeed_callback_t cb, void *cb_data)
	{
	struct datafeed_callback *cb_struct;

	if (!session) {
	sr_err("%s: session was NULL", __func__);
	return SR_ERR_BUG;
	}

	if (!cb) {
	sr_err("%s: cb was NULL", __func__);
	return SR_ERR_ARG;
	}

	if (!(cb_struct = g_try_malloc0(sizeof(struct datafeed_callback))))
	return SR_ERR_MALLOC;

	cb_struct->cb = cb;
	cb_struct->cb_data = cb_data;

	session->datafeed_callbacks =
	g_slist_append(session->datafeed_callbacks, cb_struct);

	return SR_OK;
	}

	static int sr_session_run_poll(void)
	{
	unsigned int i;
	int ret;

	while (session->num_sources > 0) {
	ret = g_poll(session->pollfds, session->num_sources,
	session->source_timeout);
	for (i = 0; i < session->num_sources; i++) {
	if (session->pollfds[i].revents > 0 \|\| (ret == 0
	&& session->source_timeout == session->sources[i].timeout)) {
	/*
	* Invoke the source's callback on an event,
	* or if the poll timed out and this source
	* asked for that timeout.
	*/
	if (!session->sources[i].cb(session->pollfds[i].fd,
	session->pollfds[i].revents,
	session->sources[i].cb_data))
	sr_session_source_remove(session->sources[i].poll_object);
	}
	/*
	* We want to take as little time as possible to stop
	* the session if we have been told to do so. Therefore,
	* we check the flag after processing every source, not
	* just once per main event loop.
	*/
	// g_mutex_lock(&session->stop_mutex);
	if (session->abort_session) {
	sr_session_stop_sync();
	/* But once is enough. */
	session->abort_session = FALSE;
	}
	// g_mutex_unlock(&session->stop_mutex);
	}
	}

	return SR_OK;
	}

	/**
	* Start a session.
	*
	* There can only be one session at a time.
	*
	* @return SR_OK upon success, SR_ERR upon errors.
	*/
	SR_API int sr_session_start(void)
	{
	struct sr_dev_inst *sdi;
	GSList *l;
	int ret;

	if (!session) {
	sr_err("%s: session was NULL; a session must be "
	"created before starting it.", __func__);
	return SR_ERR_BUG;
	}

	if (!session->devs) {
	sr_err("%s: session->devs was NULL; a session "
	"cannot be started without devices.", __func__);
	return SR_ERR_BUG;
	}

	sr_info("Starting.");

	ret = SR_OK;
	for (l = session->devs; l; l = l->next) {
	sdi = l->data;
	if ((ret = sdi->driver->dev_acquisition_start(sdi, sdi)) != SR_OK) {
	sr_err("%s: could not start an acquisition "
	"(%d)", __func__, ret);
	break;
	}
	}

	/* TODO: What if there are multiple devices? Which return code? */

	return ret;
	}

	/**
	* Run the session.
	*
	* @return SR_OK upon success, SR_ERR_BUG upon errors.
	*/
	SR_API int sr_session_run(void)
	{
	if (!session) {
	sr_err("%s: session was NULL; a session must be "
	"created first, before running it.", __func__);
	return SR_ERR_BUG;
	}

	if (!session->devs) {
	/* TODO: Actually the case? */
	sr_err("%s: session->devs was NULL; a session "
	"cannot be run without devices.", __func__);
	return SR_ERR_BUG;
	}

	sr_info("Running.");

	/* Do we have real sources? */
	if (session->num_sources == 1 && session->pollfds[0].fd == -1) {
	/* Dummy source, freewheel over it. */
	while (session->num_sources)
	session->sources[0].cb(-1, 0, session->sources[0].cb_data);
	} else {
	/* Real sources, use g_poll() main loop. */
	sr_session_run_poll();
	}

	return SR_OK;
	}

	/**
	* Stop the current session.
	*
	* The current session is stopped immediately, with all acquisition sessions
	* being stopped and hardware drivers cleaned up.
	*
	* This must be called from within the session thread, to prevent freeing
	* resources that the session thread will try to use.
	*
	* @return SR_OK upon success, SR_ERR_BUG if no session exists.
	*/
	SR_PRIV int sr_session_stop_sync(void)
	{
	struct sr_dev_inst *sdi;
	GSList *l;

	if (!session) {
	sr_err("%s: session was NULL", __func__);
	return SR_ERR_BUG;
	}

	sr_info("Stopping.");

	for (l = session->devs; l; l = l->next) {
	sdi = l->data;
	if (sdi->driver) {
	if (sdi->driver->dev_acquisition_stop)
	sdi->driver->dev_acquisition_stop(sdi, NULL);
	}
	}

	return SR_OK;
	}

	/**
	* Stop the current session.
	*
	* The current session is stopped immediately, with all acquisition sessions
	* being stopped and hardware drivers cleaned up.
	*
	* If the session is run in a separate thread, this function will not block
	* until the session is finished executing. It is the caller's responsibility
	* to wait for the session thread to return before assuming that the session is
	* completely decommissioned.
	*
	* @return SR_OK upon success, SR_ERR_BUG if no session exists.
	*/
	SR_API int sr_session_stop(void)
	{
	if (!session) {
	sr_err("%s: session was NULL", __func__);
	return SR_ERR_BUG;
	}

	// g_mutex_lock(&session->stop_mutex);
	session->abort_session = TRUE;
	// g_mutex_unlock(&session->stop_mutex);

	return SR_OK;
	}

	/**
	* Debug helper.
	*
	* @param packet The packet to show debugging information for.
	*/
	static void datafeed_dump(const struct sr_datafeed_packet *packet)
	{
	const struct sr_datafeed_logic *logic;
	const struct sr_datafeed_analog *analog;

	switch (packet->type) {
	case SR_DF_HEADER:
	sr_dbg("bus: Received SR_DF_HEADER packet.");
	break;
	case SR_DF_TRIGGER:
	sr_dbg("bus: Received SR_DF_TRIGGER packet.");
	break;
	case SR_DF_META:
	sr_dbg("bus: Received SR_DF_META packet.");
	break;
	case SR_DF_LOGIC:
	logic = packet->payload;
	sr_dbg("bus: Received SR_DF_LOGIC packet (%" PRIu64 " bytes).",
	logic->length);
	break;
	case SR_DF_ANALOG:
	analog = packet->payload;
	sr_dbg("bus: Received SR_DF_ANALOG packet (%d samples).",
	analog->num_samples);
	break;
	case SR_DF_END:
	sr_dbg("bus: Received SR_DF_END packet.");
	break;
	case SR_DF_FRAME_BEGIN:
	sr_dbg("bus: Received SR_DF_FRAME_BEGIN packet.");
	break;
	case SR_DF_FRAME_END:
	sr_dbg("bus: Received SR_DF_FRAME_END packet.");
	break;
	default:
	sr_dbg("bus: Received unknown packet type: %d.", packet->type);
	break;
	}
	}

	/**
	* Send a packet to whatever is listening on the datafeed bus.
	*
	* Hardware drivers use this to send a data packet to the frontend.
	*
	* @param sdi TODO.
	* @param packet The datafeed packet to send to the session bus.
	*
	* @return SR_OK upon success, SR_ERR_ARG upon invalid arguments.
	*
	* @private
	*/
	SR_PRIV int sr_session_send(const struct sr_dev_inst *sdi,
	const struct sr_datafeed_packet *packet)
	{
	GSList *l;
	struct datafeed_callback *cb_struct;

	if (!sdi) {
	sr_err("%s: sdi was NULL", __func__);
	return SR_ERR_ARG;
	}

	if (!packet) {
	sr_err("%s: packet was NULL", __func__);
	return SR_ERR_ARG;
	}

	for (l = session->datafeed_callbacks; l; l = l->next) {
	if (sr_log_loglevel_get() >= SR_LOG_DBG)
	datafeed_dump(packet);
	cb_struct = l->data;
	cb_struct->cb(sdi, packet, cb_struct->cb_data);
	}

	return SR_OK;
	}

	/**
	* Add an event source for a file descriptor.
	*
	* @param pollfd The GPollFD.
	* @param timeout Max time to wait before the callback is called, ignored if 0.
	* @param cb Callback function to add. Must not be NULL.
	* @param cb_data Data for the callback function. Can be NULL.
	* @param poll_object TODO.
	*
	* @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
	* SR_ERR_MALLOC upon memory allocation errors.
	*/
	static int _sr_session_source_add(GPollFD *pollfd, int timeout,
	sr_receive_data_callback_t cb, const struct sr_dev_inst *sdi, gintptr poll_object)
	{
	struct source new_sources, s;
	GPollFD *new_pollfds;

	if (!cb) {
	sr_err("%s: cb was NULL", __func__);
	return SR_ERR_ARG;
	}

	/* Note: cb_data can be NULL, that's not a bug. */

	new_pollfds = g_try_realloc(session->pollfds,
	sizeof(GPollFD) * (session->num_sources + 1));
	if (!new_pollfds) {
	sr_err("%s: new_pollfds malloc failed", __func__);
	return SR_ERR_MALLOC;
	}

	new_sources = g_try_realloc(session->sources, sizeof(struct source) *
	(session->num_sources + 1));
	if (!new_sources) {
	sr_err("%s: new_sources malloc failed", __func__);
	return SR_ERR_MALLOC;
	}

	new_pollfds[session->num_sources] = *pollfd;
	s = &new_sources[session->num_sources++];
	s->timeout = timeout;
	s->cb = cb;
	s->cb_data = sdi;
	s->poll_object = poll_object;
	session->pollfds = new_pollfds;
	session->sources = new_sources;

	if (timeout != session->source_timeout && timeout > 0
	&& (session->source_timeout == -1 \|\| timeout < session->source_timeout))
	session->source_timeout = timeout;

	return SR_OK;
	}

	/**
	* Add an event source for a file descriptor.
	*
	* @param fd The file descriptor.
	* @param events Events to check for.
	* @param timeout Max time to wait before the callback is called, ignored if 0.
	* @param cb Callback function to add. Must not be NULL.
	* @param cb_data Data for the callback function. Can be NULL.
	*
	* @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
	* SR_ERR_MALLOC upon memory allocation errors.
	*/
	SR_API int sr_session_source_add(int fd, int events, int timeout,
	sr_receive_data_callback_t cb, const struct sr_dev_inst *sdi)
	{
	GPollFD p;

	p.fd = fd;
	p.events = events;

	return _sr_session_source_add(&p, timeout, cb, sdi, (gintptr)fd);
	}

	/**
	* Add an event source for a GPollFD.
	*
	* @param pollfd The GPollFD.
	* @param timeout Max time to wait before the callback is called, ignored if 0.
	* @param cb Callback function to add. Must not be NULL.
	* @param cb_data Data for the callback function. Can be NULL.
	*
	* @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
	* SR_ERR_MALLOC upon memory allocation errors.
	*/
	SR_API int sr_session_source_add_pollfd(GPollFD *pollfd, int timeout,
	sr_receive_data_callback_t cb, const struct sr_dev_inst *sdi)
	{
	return _sr_session_source_add(pollfd, timeout, cb,
	sdi, (gintptr)pollfd);
	}

	/**
	* Add an event source for a GIOChannel.
	*
	* @param channel The GIOChannel.
	* @param events Events to poll on.
	* @param timeout Max time to wait before the callback is called, ignored if 0.
	* @param cb Callback function to add. Must not be NULL.
	* @param cb_data Data for the callback function. Can be NULL.
	*
	* @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
	* SR_ERR_MALLOC upon memory allocation errors.
	*/
	SR_API int sr_session_source_add_channel(GIOChannel *channel, int events,
	int timeout, sr_receive_data_callback_t cb, const struct sr_dev_inst *sdi)
	{
	GPollFD p;

	#ifdef _WIN32
	g_io_channel_win32_make_pollfd(channel, events, &p);
	#else
	p.fd = g_io_channel_unix_get_fd(channel);
	p.events = events;
	#endif

	return _sr_session_source_add(&p, timeout, cb, sdi, (gintptr)channel);
	}

	/**
	* Remove the source belonging to the specified channel.
	*
	* @todo Add more error checks and logging.
	*
	* @param channel The channel for which the source should be removed.
	*
	* @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
	* SR_ERR_MALLOC upon memory allocation errors, SR_ERR_BUG upon
	* internal errors.
	*/
	static int _sr_session_source_remove(gintptr poll_object)
	{
	struct source *new_sources;
	GPollFD *new_pollfds;
	unsigned int old;

	if (!session->sources \|\| !session->num_sources) {
	sr_err("%s: sources was NULL", __func__);
	return SR_ERR_BUG;
	}

	for (old = 0; old < session->num_sources; old++) {
	if (session->sources[old].poll_object == poll_object)
	break;
	}

	/* fd not found, nothing to do */
	if (old == session->num_sources)
	return SR_OK;

	session->num_sources -= 1;

	if (old != session->num_sources) {
	memmove(&session->pollfds[old], &session->pollfds[old+1],
	(session->num_sources - old) * sizeof(GPollFD));
	memmove(&session->sources[old], &session->sources[old+1],
	(session->num_sources - old) * sizeof(struct source));
	}

	new_pollfds = g_try_realloc(session->pollfds, sizeof(GPollFD) * session->num_sources);
	if (!new_pollfds && session->num_sources > 0) {
	sr_err("%s: new_pollfds malloc failed", __func__);
	return SR_ERR_MALLOC;
	}

	new_sources = g_try_realloc(session->sources, sizeof(struct source) * session->num_sources);
	if (!new_sources && session->num_sources > 0) {
	sr_err("%s: new_sources malloc failed", __func__);
	return SR_ERR_MALLOC;
	}

	session->pollfds = new_pollfds;
	session->sources = new_sources;

	return SR_OK;
	}

	/**
	* Remove the source belonging to the specified file descriptor.
	*
	* @param fd The file descriptor for which the source should be removed.
	*
	* @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
	* SR_ERR_MALLOC upon memory allocation errors, SR_ERR_BUG upon
	* internal errors.
	*/
	SR_API int sr_session_source_remove(int fd)
	{
	return _sr_session_source_remove((gintptr)fd);
	}

	/**
	* Remove the source belonging to the specified poll descriptor.
	*
	* @param pollfd The poll descriptor for which the source should be removed.
	*
	* @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
	* SR_ERR_MALLOC upon memory allocation errors, SR_ERR_BUG upon
	* internal errors.
	*/
	SR_API int sr_session_source_remove_pollfd(GPollFD *pollfd)
	{
	return _sr_session_source_remove((gintptr)pollfd);
	}

	/**
	* Remove the source belonging to the specified channel.
	*
	* @param channel The channel for which the source should be removed.
	*
	* @return SR_OK upon success, SR_ERR_ARG upon invalid arguments, or
	* SR_ERR_MALLOC upon memory allocation errors, SR_ERR_BUG upon
	* internal errors.
	*/
	SR_API int sr_session_source_remove_channel(GIOChannel *channel)
	{
	return _sr_session_source_remove((gintptr)channel);
	}

	/** @} */