1/*
2 * Core functions for libusb
3 * Copyright (C) 2007-2008 Daniel Drake <dsd@gentoo.org>
4 * Copyright (c) 2001 Johannes Erdfelt <johannes@erdfelt.com>
5 *
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * This library 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 GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21#include <config.h>
22
23#include <errno.h>
24#include <poll.h>
25#include <stdarg.h>
26#include <stdio.h>
27#include <stdlib.h>
28#include <string.h>
29#include <sys/types.h>
30#include <unistd.h>
31
32#include "libusb.h"
33#include "libusbi.h"
34
35#if defined(OS_LINUX)
36const struct usbi_os_backend * const usbi_backend = &linux_usbfs_backend;
37#elif defined(OS_DARWIN)
38const struct usbi_os_backend * const usbi_backend = &darwin_backend;
39#else
40#error "Unsupported OS"
41#endif
42
43struct libusb_context *usbi_default_context = NULL;
44static pthread_mutex_t default_context_lock = PTHREAD_MUTEX_INITIALIZER;
45
46/**
47 * \mainpage libusb-1.0 API Reference
48 *
49 * \section intro Introduction
50 *
51 * libusb is an open source library that allows you to communicate with USB
52 * devices from userspace. For more info, see the
53 * <a href="http://libusb.sourceforge.net">libusb homepage</a>.
54 *
55 * This documentation is aimed at application developers wishing to
56 * communicate with USB peripherals from their own software. After reviewing
57 * this documentation, feedback and questions can be sent to the
58 * <a href="http://sourceforge.net/mail/?group_id=1674">libusb-devel mailing
59 * list</a>.
60 *
61 * This documentation assumes knowledge of how to operate USB devices from
62 * a software standpoint (descriptors, configurations, interfaces, endpoints,
63 * control/bulk/interrupt/isochronous transfers, etc). Full information
64 * can be found in the <a href="http://www.usb.org/developers/docs/">USB 2.0
65 * Specification</a> which is available for free download. You can probably
66 * find less verbose introductions by searching the web.
67 *
68 * \section features Library features
69 *
70 * - All transfer types supported (control/bulk/interrupt/isochronous)
71 * - 2 transfer interfaces:
72 *    -# Synchronous (simple)
73 *    -# Asynchronous (more complicated, but more powerful)
74 * - Thread safe (although the asynchronous interface means that you
75 *   usually won't need to thread)
76 * - Lightweight with lean API
77 * - Compatible with libusb-0.1 through the libusb-compat-0.1 translation layer
78 *
79 * \section gettingstarted Getting Started
80 *
81 * To begin reading the API documentation, start with the Modules page which
82 * links to the different categories of libusb's functionality.
83 *
84 * One decision you will have to make is whether to use the synchronous
85 * or the asynchronous data transfer interface. The \ref io documentation
86 * provides some insight into this topic.
87 *
88 * Some example programs can be found in the libusb source distribution under
89 * the "examples" subdirectory. The libusb homepage includes a list of
90 * real-life project examples which use libusb.
91 *
92 * \section errorhandling Error handling
93 *
94 * libusb functions typically return 0 on success or a negative error code
95 * on failure. These negative error codes relate to LIBUSB_ERROR constants
96 * which are listed on the \ref misc "miscellaneous" documentation page.
97 *
98 * \section msglog Debug message logging
99 *
100 * libusb does not log any messages by default. Your application is therefore
101 * free to close stdout/stderr and those descriptors may be reused without
102 * worry.
103 *
104 * The libusb_set_debug() function can be used to enable stdout/stderr logging
105 * of certain messages. Under standard configuration, libusb doesn't really
106 * log much at all, so you are advised to use this function to enable all
107 * error/warning/informational messages. It will help you debug problems with
108 * your software.
109 *
110 * The logged messages are unstructured. There is no one-to-one correspondence
111 * between messages being logged and success or failure return codes from
112 * libusb functions. There is no format to the messages, so you should not
113 * try to capture or parse them. They are not and will not be localized.
114 * These messages are not suitable for being passed to your application user;
115 * instead, you should interpret the error codes returned from libusb functions
116 * and provide appropriate notification to the user. The messages are simply
117 * there to aid you as a programmer, and if you're confused because you're
118 * getting a strange error code from a libusb function, enabling message
119 * logging may give you a suitable explanation.
120 *
121 * The LIBUSB_DEBUG environment variable can be used to enable message logging
122 * at run-time. This environment variable should be set to a number, which is
123 * interpreted the same as the libusb_set_debug() parameter. When this
124 * environment variable is set, the message logging verbosity level is fixed
125 * and libusb_set_debug() effectively does nothing.
126 *
127 * libusb can be compiled without any logging functions, useful for embedded
128 * systems. In this case, libusb_set_debug() and the LIBUSB_DEBUG environment
129 * variable have no effects.
130 *
131 * libusb can also be compiled with verbose debugging messages. When the
132 * library is compiled in this way, all messages of all verbosities are always
133 * logged.  libusb_set_debug() and the LIBUSB_DEBUG environment variable have
134 * no effects.
135 *
136 * \section remarks Other remarks
137 *
138 * libusb does have imperfections. The \ref caveats "caveats" page attempts
139 * to document these.
140 */
141
142/**
143 * \page caveats Caveats
144 *
145 * \section devresets Device resets
146 *
147 * The libusb_reset_device() function allows you to reset a device. If your
148 * program has to call such a function, it should obviously be aware that
149 * the reset will cause device state to change (e.g. register values may be
150 * reset).
151 *
152 * The problem is that any other program could reset the device your program
153 * is working with, at any time. libusb does not offer a mechanism to inform
154 * you when this has happened, so if someone else resets your device it will
155 * not be clear to your own program why the device state has changed.
156 *
157 * Ultimately, this is a limitation of writing drivers in userspace.
158 * Separation from the USB stack in the underlying kernel makes it difficult
159 * for the operating system to deliver such notifications to your program.
160 * The Linux kernel USB stack allows such reset notifications to be delivered
161 * to in-kernel USB drivers, but it is not clear how such notifications could
162 * be delivered to second-class drivers that live in userspace.
163 *
164 * \section blockonly Blocking-only functionality
165 *
166 * The functionality listed below is only available through synchronous,
167 * blocking functions. There are no asynchronous/non-blocking alternatives,
168 * and no clear ways of implementing these.
169 *
170 * - Configuration activation (libusb_set_configuration())
171 * - Interface/alternate setting activation (libusb_set_interface_alt_setting())
172 * - Releasing of interfaces (libusb_release_interface())
173 * - Clearing of halt/stall condition (libusb_clear_halt())
174 * - Device resets (libusb_reset_device())
175 *
176 * \section nohotplug No hotplugging
177 *
178 * libusb-1.0 lacks functionality for providing notifications of when devices
179 * are added or removed. This functionality is planned to be implemented
180 * for libusb-1.1.
181 *
182 * That said, there is basic disconnection handling for open device handles:
183 *  - If there are ongoing transfers, libusb's handle_events loop will detect
184 *    disconnections and complete ongoing transfers with the
185 *    LIBUSB_TRANSFER_NO_DEVICE status code.
186 *  - Many functions such as libusb_set_configuration() return the special
187 *    LIBUSB_ERROR_NO_DEVICE error code when the device has been disconnected.
188 *
189 * \section configsel Configuration selection and handling
190 *
191 * When libusb presents a device handle to an application, there is a chance
192 * that the corresponding device may be in unconfigured state. For devices
193 * with multiple configurations, there is also a chance that the configuration
194 * currently selected is not the one that the application wants to use.
195 *
196 * The obvious solution is to add a call to libusb_set_configuration() early
197 * on during your device initialization routines, but there are caveats to
198 * be aware of:
199 * -# If the device is already in the desired configuration, calling
200 *    libusb_set_configuration() using the same configuration value will cause
201 *    a lightweight device reset. This may not be desirable behaviour.
202 * -# libusb will be unable to change configuration if the device is in
203 *    another configuration and other programs or drivers have claimed
204 *    interfaces under that configuration.
205 * -# In the case where the desired configuration is already active, libusb
206 *    may not even be able to perform a lightweight device reset. For example,
207 *    take my USB keyboard with fingerprint reader: I'm interested in driving
208 *    the fingerprint reader interface through libusb, but the kernel's
209 *    USB-HID driver will almost always have claimed the keyboard interface.
210 *    Because the kernel has claimed an interface, it is not even possible to
211 *    perform the lightweight device reset, so libusb_set_configuration() will
212 *    fail. (Luckily the device in question only has a single configuration.)
213 *
214 * One solution to some of the above problems is to consider the currently
215 * active configuration. If the configuration we want is already active, then
216 * we don't have to select any configuration:
217\code
218cfg = libusb_get_configuration(dev);
219if (cfg != desired)
220	libusb_set_configuration(dev, desired);
221\endcode
222 *
223 * This is probably suitable for most scenarios, but is inherently racy:
224 * another application or driver may change the selected configuration
225 * <em>after</em> the libusb_get_configuration() call.
226 *
227 * Even in cases where libusb_set_configuration() succeeds, consider that other
228 * applications or drivers may change configuration after your application
229 * calls libusb_set_configuration().
230 *
231 * One possible way to lock your device into a specific configuration is as
232 * follows:
233 * -# Set the desired configuration (or use the logic above to realise that
234 *    it is already in the desired configuration)
235 * -# Claim the interface that you wish to use
236 * -# Check that the currently active configuration is the one that you want
237 *    to use.
238 *
239 * The above method works because once an interface is claimed, no application
240 * or driver is able to select another configuration.
241 *
242 * \section earlycomp Early transfer completion
243 *
244 * NOTE: This section is currently Linux-centric. I am not sure if any of these
245 * considerations apply to Darwin or other platforms.
246 *
247 * When a transfer completes early (i.e. when less data is received/sent in
248 * any one packet than the transfer buffer allows for) then libusb is designed
249 * to terminate the transfer immediately, not transferring or receiving any
250 * more data unless other transfers have been queued by the user.
251 *
252 * On legacy platforms, libusb is unable to do this in all situations. After
253 * the incomplete packet occurs, "surplus" data may be transferred. Prior to
254 * libusb v1.0.2, this information was lost (and for device-to-host transfers,
255 * the corresponding data was discarded). As of libusb v1.0.3, this information
256 * is kept (the data length of the transfer is updated) and, for device-to-host
257 * transfesr, any surplus data was added to the buffer. Still, this is not
258 * a nice solution because it loses the information about the end of the short
259 * packet, and the user probably wanted that surplus data to arrive in the next
260 * logical transfer.
261 *
262 * A previous workaround was to only ever submit transfers of size 16kb or
263 * less.
264 *
265 * As of libusb v1.0.4 and Linux v2.6.32, this is fixed. A technical
266 * explanation of this issue follows.
267 *
268 * When you ask libusb to submit a bulk transfer larger than 16kb in size,
269 * libusb breaks it up into a number of smaller subtransfers. This is because
270 * the usbfs kernel interface only accepts transfers of up to 16kb in size.
271 * The subtransfers are submitted all at once so that the kernel can queue
272 * them at the hardware level, therefore maximizing bus throughput.
273 *
274 * On legacy platforms, this caused problems when transfers completed early
275 * Upon this event, the kernel would terminate all further packets in that
276 * subtransfer (but not any following ones). libusb would note this event and
277 * immediately cancel any following subtransfers that had been queued,
278 * but often libusb was not fast enough, and the following subtransfers had
279 * started before libusb got around to cancelling them.
280 *
281 * Thanks to an API extension to usbfs, this is fixed with recent kernel and
282 * libusb releases. The solution was to allow libusb to communicate to the
283 * kernel where boundaries occur between logical libusb-level transfers. When
284 * a short transfer (or other error) occurs, the kernel will cancel all the
285 * subtransfers until the boundary without allowing those transfers to start.
286 */
287
288/**
289 * \page contexts Contexts
290 *
291 * It is possible that libusb may be used simultaneously from two independent
292 * libraries linked into the same executable. For example, if your application
293 * has a plugin-like system which allows the user to dynamically load a range
294 * of modules into your program, it is feasible that two independently
295 * developed modules may both use libusb.
296 *
297 * libusb is written to allow for these multiple user scenarios. The two
298 * "instances" of libusb will not interfere: libusb_set_debug() calls
299 * from one user will not affect the same settings for other users, other
300 * users can continue using libusb after one of them calls libusb_exit(), etc.
301 *
302 * This is made possible through libusb's <em>context</em> concept. When you
303 * call libusb_init(), you are (optionally) given a context. You can then pass
304 * this context pointer back into future libusb functions.
305 *
306 * In order to keep things simple for more simplistic applications, it is
307 * legal to pass NULL to all functions requiring a context pointer (as long as
308 * you're sure no other code will attempt to use libusb from the same process).
309 * When you pass NULL, the default context will be used. The default context
310 * is created the first time a process calls libusb_init() when no other
311 * context is alive. Contexts are destroyed during libusb_exit().
312 *
313 * You may be wondering why only a subset of libusb functions require a
314 * context pointer in their function definition. Internally, libusb stores
315 * context pointers in other objects (e.g. libusb_device instances) and hence
316 * can infer the context from those objects.
317 */
318
319/**
320 * @defgroup lib Library initialization/deinitialization
321 * This page details how to initialize and deinitialize libusb. Initialization
322 * must be performed before using any libusb functionality, and similarly you
323 * must not call any libusb functions after deinitialization.
324 */
325
326/**
327 * @defgroup dev Device handling and enumeration
328 * The functionality documented below is designed to help with the following
329 * operations:
330 * - Enumerating the USB devices currently attached to the system
331 * - Choosing a device to operate from your software
332 * - Opening and closing the chosen device
333 *
334 * \section nutshell In a nutshell...
335 *
336 * The description below really makes things sound more complicated than they
337 * actually are. The following sequence of function calls will be suitable
338 * for almost all scenarios and does not require you to have such a deep
339 * understanding of the resource management issues:
340 * \code
341// discover devices
342libusb_device **list;
343libusb_device *found = NULL;
344ssize_t cnt = libusb_get_device_list(NULL, &list);
345ssize_t i = 0;
346int err = 0;
347if (cnt < 0)
348	error();
349
350for (i = 0; i < cnt; i++) {
351	libusb_device *device = list[i];
352	if (is_interesting(device)) {
353		found = device;
354		break;
355	}
356}
357
358if (found) {
359	libusb_device_handle *handle;
360
361	err = libusb_open(found, &handle);
362	if (err)
363		error();
364	// etc
365}
366
367libusb_free_device_list(list, 1);
368\endcode
369 *
370 * The two important points:
371 * - You asked libusb_free_device_list() to unreference the devices (2nd
372 *   parameter)
373 * - You opened the device before freeing the list and unreferencing the
374 *   devices
375 *
376 * If you ended up with a handle, you can now proceed to perform I/O on the
377 * device.
378 *
379 * \section devshandles Devices and device handles
380 * libusb has a concept of a USB device, represented by the
381 * \ref libusb_device opaque type. A device represents a USB device that
382 * is currently or was previously connected to the system. Using a reference
383 * to a device, you can determine certain information about the device (e.g.
384 * you can read the descriptor data).
385 *
386 * The libusb_get_device_list() function can be used to obtain a list of
387 * devices currently connected to the system. This is known as device
388 * discovery.
389 *
390 * Just because you have a reference to a device does not mean it is
391 * necessarily usable. The device may have been unplugged, you may not have
392 * permission to operate such device, or another program or driver may be
393 * using the device.
394 *
395 * When you've found a device that you'd like to operate, you must ask
396 * libusb to open the device using the libusb_open() function. Assuming
397 * success, libusb then returns you a <em>device handle</em>
398 * (a \ref libusb_device_handle pointer). All "real" I/O operations then
399 * operate on the handle rather than the original device pointer.
400 *
401 * \section devref Device discovery and reference counting
402 *
403 * Device discovery (i.e. calling libusb_get_device_list()) returns a
404 * freshly-allocated list of devices. The list itself must be freed when
405 * you are done with it. libusb also needs to know when it is OK to free
406 * the contents of the list - the devices themselves.
407 *
408 * To handle these issues, libusb provides you with two separate items:
409 * - A function to free the list itself
410 * - A reference counting system for the devices inside
411 *
412 * New devices presented by the libusb_get_device_list() function all have a
413 * reference count of 1. You can increase and decrease reference count using
414 * libusb_ref_device() and libusb_unref_device(). A device is destroyed when
415 * its reference count reaches 0.
416 *
417 * With the above information in mind, the process of opening a device can
418 * be viewed as follows:
419 * -# Discover devices using libusb_get_device_list().
420 * -# Choose the device that you want to operate, and call libusb_open().
421 * -# Unref all devices in the discovered device list.
422 * -# Free the discovered device list.
423 *
424 * The order is important - you must not unreference the device before
425 * attempting to open it, because unreferencing it may destroy the device.
426 *
427 * For convenience, the libusb_free_device_list() function includes a
428 * parameter to optionally unreference all the devices in the list before
429 * freeing the list itself. This combines steps 3 and 4 above.
430 *
431 * As an implementation detail, libusb_open() actually adds a reference to
432 * the device in question. This is because the device remains available
433 * through the handle via libusb_get_device(). The reference is deleted during
434 * libusb_close().
435 */
436
437/** @defgroup misc Miscellaneous */
438
439/* we traverse usbfs without knowing how many devices we are going to find.
440 * so we create this discovered_devs model which is similar to a linked-list
441 * which grows when required. it can be freed once discovery has completed,
442 * eliminating the need for a list node in the libusb_device structure
443 * itself. */
444#define DISCOVERED_DEVICES_SIZE_STEP 8
445
446static struct discovered_devs *discovered_devs_alloc(void)
447{
448	struct discovered_devs *ret =
449		malloc(sizeof(*ret) + (sizeof(void *) * DISCOVERED_DEVICES_SIZE_STEP));
450
451	if (ret) {
452		ret->len = 0;
453		ret->capacity = DISCOVERED_DEVICES_SIZE_STEP;
454	}
455	return ret;
456}
457
458/* append a device to the discovered devices collection. may realloc itself,
459 * returning new discdevs. returns NULL on realloc failure. */
460struct discovered_devs *discovered_devs_append(
461	struct discovered_devs *discdevs, struct libusb_device *dev)
462{
463	size_t len = discdevs->len;
464	size_t capacity;
465
466	/* if there is space, just append the device */
467	if (len < discdevs->capacity) {
468		discdevs->devices[len] = libusb_ref_device(dev);
469		discdevs->len++;
470		return discdevs;
471	}
472
473	/* exceeded capacity, need to grow */
474	usbi_dbg("need to increase capacity");
475	capacity = discdevs->capacity + DISCOVERED_DEVICES_SIZE_STEP;
476	discdevs = realloc(discdevs,
477		sizeof(*discdevs) + (sizeof(void *) * capacity));
478	if (discdevs) {
479		discdevs->capacity = capacity;
480		discdevs->devices[len] = libusb_ref_device(dev);
481		discdevs->len++;
482	}
483
484	return discdevs;
485}
486
487static void discovered_devs_free(struct discovered_devs *discdevs)
488{
489	size_t i;
490
491	for (i = 0; i < discdevs->len; i++)
492		libusb_unref_device(discdevs->devices[i]);
493
494	free(discdevs);
495}
496
497/* Allocate a new device with a specific session ID. The returned device has
498 * a reference count of 1. */
499struct libusb_device *usbi_alloc_device(struct libusb_context *ctx,
500	unsigned long session_id)
501{
502	size_t priv_size = usbi_backend->device_priv_size;
503	struct libusb_device *dev = malloc(sizeof(*dev) + priv_size);
504	int r;
505
506	if (!dev)
507		return NULL;
508
509	r = pthread_mutex_init(&dev->lock, NULL);
510	if (r)
511		return NULL;
512
513	dev->ctx = ctx;
514	dev->refcnt = 1;
515	dev->session_data = session_id;
516	memset(&dev->os_priv, 0, priv_size);
517
518	pthread_mutex_lock(&ctx->usb_devs_lock);
519	list_add(&dev->list, &ctx->usb_devs);
520	pthread_mutex_unlock(&ctx->usb_devs_lock);
521	return dev;
522}
523
524/* Perform some final sanity checks on a newly discovered device. If this
525 * function fails (negative return code), the device should not be added
526 * to the discovered device list. */
527int usbi_sanitize_device(struct libusb_device *dev)
528{
529	int r;
530	unsigned char raw_desc[DEVICE_DESC_LENGTH];
531	uint8_t num_configurations;
532	int host_endian;
533
534	r = usbi_backend->get_device_descriptor(dev, raw_desc, &host_endian);
535	if (r < 0)
536		return r;
537
538	num_configurations = raw_desc[DEVICE_DESC_LENGTH - 1];
539	if (num_configurations > USB_MAXCONFIG) {
540		usbi_err(DEVICE_CTX(dev), "too many configurations");
541		return LIBUSB_ERROR_IO;
542	} else if (num_configurations < 1) {
543		usbi_dbg("no configurations?");
544		return LIBUSB_ERROR_IO;
545	}
546
547	dev->num_configurations = num_configurations;
548	return 0;
549}
550
551/* Examine libusb's internal list of known devices, looking for one with
552 * a specific session ID. Returns the matching device if it was found, and
553 * NULL otherwise. */
554struct libusb_device *usbi_get_device_by_session_id(struct libusb_context *ctx,
555	unsigned long session_id)
556{
557	struct libusb_device *dev;
558	struct libusb_device *ret = NULL;
559
560	pthread_mutex_lock(&ctx->usb_devs_lock);
561	list_for_each_entry(dev, &ctx->usb_devs, list)
562		if (dev->session_data == session_id) {
563			ret = dev;
564			break;
565		}
566	pthread_mutex_unlock(&ctx->usb_devs_lock);
567
568	return ret;
569}
570
571/** @ingroup dev
572 * Returns a list of USB devices currently attached to the system. This is
573 * your entry point into finding a USB device to operate.
574 *
575 * You are expected to unreference all the devices when you are done with
576 * them, and then free the list with libusb_free_device_list(). Note that
577 * libusb_free_device_list() can unref all the devices for you. Be careful
578 * not to unreference a device you are about to open until after you have
579 * opened it.
580 *
581 * This return value of this function indicates the number of devices in
582 * the resultant list. The list is actually one element larger, as it is
583 * NULL-terminated.
584 *
585 * \param ctx the context to operate on, or NULL for the default context
586 * \param list output location for a list of devices. Must be later freed with
587 * libusb_free_device_list().
588 * \returns the number of devices in the outputted list, or LIBUSB_ERROR_NO_MEM
589 * on memory allocation failure.
590 */
591API_EXPORTED ssize_t libusb_get_device_list(libusb_context *ctx,
592	libusb_device ***list)
593{
594	struct discovered_devs *discdevs = discovered_devs_alloc();
595	struct libusb_device **ret;
596	int r = 0;
597	size_t i;
598	ssize_t len;
599	USBI_GET_CONTEXT(ctx);
600	usbi_dbg("");
601
602	if (!discdevs)
603		return LIBUSB_ERROR_NO_MEM;
604
605	r = usbi_backend->get_device_list(ctx, &discdevs);
606	if (r < 0) {
607		len = r;
608		goto out;
609	}
610
611	/* convert discovered_devs into a list */
612	len = discdevs->len;
613	ret = malloc(sizeof(void *) * (len + 1));
614	if (!ret) {
615		len = LIBUSB_ERROR_NO_MEM;
616		goto out;
617	}
618
619	ret[len] = NULL;
620	for (i = 0; i < len; i++) {
621		struct libusb_device *dev = discdevs->devices[i];
622		ret[i] = libusb_ref_device(dev);
623	}
624	*list = ret;
625
626out:
627	discovered_devs_free(discdevs);
628	return len;
629}
630
631/** \ingroup dev
632 * Frees a list of devices previously discovered using
633 * libusb_get_device_list(). If the unref_devices parameter is set, the
634 * reference count of each device in the list is decremented by 1.
635 * \param list the list to free
636 * \param unref_devices whether to unref the devices in the list
637 */
638API_EXPORTED void libusb_free_device_list(libusb_device **list,
639	int unref_devices)
640{
641	if (!list)
642		return;
643
644	if (unref_devices) {
645		int i = 0;
646		struct libusb_device *dev;
647
648		while ((dev = list[i++]) != NULL)
649			libusb_unref_device(dev);
650	}
651	free(list);
652}
653
654/** \ingroup dev
655 * Get the number of the bus that a device is connected to.
656 * \param dev a device
657 * \returns the bus number
658 */
659API_EXPORTED uint8_t libusb_get_bus_number(libusb_device *dev)
660{
661	return dev->bus_number;
662}
663
664/** \ingroup dev
665 * Get the address of the device on the bus it is connected to.
666 * \param dev a device
667 * \returns the device address
668 */
669API_EXPORTED uint8_t libusb_get_device_address(libusb_device *dev)
670{
671	return dev->device_address;
672}
673
674static const struct libusb_endpoint_descriptor *find_endpoint(
675	struct libusb_config_descriptor *config, unsigned char endpoint)
676{
677	int iface_idx;
678	for (iface_idx = 0; iface_idx < config->bNumInterfaces; iface_idx++) {
679		const struct libusb_interface *iface = &config->interface[iface_idx];
680		int altsetting_idx;
681
682		for (altsetting_idx = 0; altsetting_idx < iface->num_altsetting;
683				altsetting_idx++) {
684			const struct libusb_interface_descriptor *altsetting
685				= &iface->altsetting[altsetting_idx];
686			int ep_idx;
687
688			for (ep_idx = 0; ep_idx < altsetting->bNumEndpoints; ep_idx++) {
689				const struct libusb_endpoint_descriptor *ep =
690					&altsetting->endpoint[ep_idx];
691				if (ep->bEndpointAddress == endpoint)
692					return ep;
693			}
694		}
695	}
696	return NULL;
697}
698
699/** \ingroup dev
700 * Convenience function to retrieve the wMaxPacketSize value for a particular
701 * endpoint in the active device configuration.
702 *
703 * This function was originally intended to be of assistance when setting up
704 * isochronous transfers, but a design mistake resulted in this function
705 * instead. It simply returns the wMaxPacketSize value without considering
706 * its contents. If you're dealing with isochronous transfers, you probably
707 * want libusb_get_max_iso_packet_size() instead.
708 *
709 * \param dev a device
710 * \param endpoint address of the endpoint in question
711 * \returns the wMaxPacketSize value
712 * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
713 * \returns LIBUSB_ERROR_OTHER on other failure
714 */
715API_EXPORTED int libusb_get_max_packet_size(libusb_device *dev,
716	unsigned char endpoint)
717{
718	struct libusb_config_descriptor *config;
719	const struct libusb_endpoint_descriptor *ep;
720	int r;
721
722	r = libusb_get_active_config_descriptor(dev, &config);
723	if (r < 0) {
724		usbi_err(DEVICE_CTX(dev),
725			"could not retrieve active config descriptor");
726		return LIBUSB_ERROR_OTHER;
727	}
728
729	ep = find_endpoint(config, endpoint);
730	if (!ep)
731		return LIBUSB_ERROR_NOT_FOUND;
732
733	r = ep->wMaxPacketSize;
734	libusb_free_config_descriptor(config);
735	return r;
736}
737
738/** \ingroup dev
739 * Calculate the maximum packet size which a specific endpoint is capable is
740 * sending or receiving in the duration of 1 microframe
741 *
742 * Only the active configution is examined. The calculation is based on the
743 * wMaxPacketSize field in the endpoint descriptor as described in section
744 * 9.6.6 in the USB 2.0 specifications.
745 *
746 * If acting on an isochronous or interrupt endpoint, this function will
747 * multiply the value found in bits 0:10 by the number of transactions per
748 * microframe (determined by bits 11:12). Otherwise, this function just
749 * returns the numeric value found in bits 0:10.
750 *
751 * This function is useful for setting up isochronous transfers, for example
752 * you might pass the return value from this function to
753 * libusb_set_iso_packet_lengths() in order to set the length field of every
754 * isochronous packet in a transfer.
755 *
756 * Since v1.0.3.
757 *
758 * \param dev a device
759 * \param endpoint address of the endpoint in question
760 * \returns the maximum packet size which can be sent/received on this endpoint
761 * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
762 * \returns LIBUSB_ERROR_OTHER on other failure
763 */
764API_EXPORTED int libusb_get_max_iso_packet_size(libusb_device *dev,
765	unsigned char endpoint)
766{
767	struct libusb_config_descriptor *config;
768	const struct libusb_endpoint_descriptor *ep;
769	enum libusb_transfer_type ep_type;
770	uint16_t val;
771	int r;
772
773	r = libusb_get_active_config_descriptor(dev, &config);
774	if (r < 0) {
775		usbi_err(DEVICE_CTX(dev),
776			"could not retrieve active config descriptor");
777		return LIBUSB_ERROR_OTHER;
778	}
779
780	ep = find_endpoint(config, endpoint);
781	if (!ep)
782		return LIBUSB_ERROR_NOT_FOUND;
783
784	val = ep->wMaxPacketSize;
785	ep_type = ep->bmAttributes & 0x3;
786	libusb_free_config_descriptor(config);
787
788	r = val & 0x07ff;
789	if (ep_type == LIBUSB_TRANSFER_TYPE_ISOCHRONOUS
790			|| ep_type == LIBUSB_TRANSFER_TYPE_INTERRUPT)
791		r *= (1 + ((val >> 11) & 3));
792	return r;
793}
794
795/** \ingroup dev
796 * Increment the reference count of a device.
797 * \param dev the device to reference
798 * \returns the same device
799 */
800API_EXPORTED libusb_device *libusb_ref_device(libusb_device *dev)
801{
802	pthread_mutex_lock(&dev->lock);
803	dev->refcnt++;
804	pthread_mutex_unlock(&dev->lock);
805	return dev;
806}
807
808/** \ingroup dev
809 * Decrement the reference count of a device. If the decrement operation
810 * causes the reference count to reach zero, the device shall be destroyed.
811 * \param dev the device to unreference
812 */
813API_EXPORTED void libusb_unref_device(libusb_device *dev)
814{
815	int refcnt;
816
817	if (!dev)
818		return;
819
820	pthread_mutex_lock(&dev->lock);
821	refcnt = --dev->refcnt;
822	pthread_mutex_unlock(&dev->lock);
823
824	if (refcnt == 0) {
825		usbi_dbg("destroy device %d.%d", dev->bus_number, dev->device_address);
826
827		if (usbi_backend->destroy_device)
828			usbi_backend->destroy_device(dev);
829
830		pthread_mutex_lock(&dev->ctx->usb_devs_lock);
831		list_del(&dev->list);
832		pthread_mutex_unlock(&dev->ctx->usb_devs_lock);
833
834		free(dev);
835	}
836}
837
838/** \ingroup dev
839 * Open a device and obtain a device handle. A handle allows you to perform
840 * I/O on the device in question.
841 *
842 * Internally, this function adds a reference to the device and makes it
843 * available to you through libusb_get_device(). This reference is removed
844 * during libusb_close().
845 *
846 * This is a non-blocking function; no requests are sent over the bus.
847 *
848 * \param dev the device to open
849 * \param handle output location for the returned device handle pointer. Only
850 * populated when the return code is 0.
851 * \returns 0 on success
852 * \returns LIBUSB_ERROR_NO_MEM on memory allocation failure
853 * \returns LIBUSB_ERROR_ACCESS if the user has insufficient permissions
854 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
855 * \returns another LIBUSB_ERROR code on other failure
856 */
857API_EXPORTED int libusb_open(libusb_device *dev, libusb_device_handle **handle)
858{
859	struct libusb_context *ctx = DEVICE_CTX(dev);
860	struct libusb_device_handle *_handle;
861	size_t priv_size = usbi_backend->device_handle_priv_size;
862	unsigned char dummy = 1;
863	int r;
864	usbi_dbg("open %d.%d", dev->bus_number, dev->device_address);
865
866	_handle = malloc(sizeof(*_handle) + priv_size);
867	if (!_handle)
868		return LIBUSB_ERROR_NO_MEM;
869
870	r = pthread_mutex_init(&_handle->lock, NULL);
871	if (r)
872		return LIBUSB_ERROR_OTHER;
873
874	_handle->dev = libusb_ref_device(dev);
875	_handle->claimed_interfaces = 0;
876	memset(&_handle->os_priv, 0, priv_size);
877
878	r = usbi_backend->open(_handle);
879	if (r < 0) {
880		libusb_unref_device(dev);
881		free(_handle);
882		return r;
883	}
884
885	pthread_mutex_lock(&ctx->open_devs_lock);
886	list_add(&_handle->list, &ctx->open_devs);
887	pthread_mutex_unlock(&ctx->open_devs_lock);
888	*handle = _handle;
889
890
891	/* At this point, we want to interrupt any existing event handlers so
892	 * that they realise the addition of the new device's poll fd. One
893	 * example when this is desirable is if the user is running a separate
894	 * dedicated libusb events handling thread, which is running with a long
895	 * or infinite timeout. We want to interrupt that iteration of the loop,
896	 * so that it picks up the new fd, and then continues. */
897
898	/* record that we are messing with poll fds */
899	pthread_mutex_lock(&ctx->pollfd_modify_lock);
900	ctx->pollfd_modify++;
901	pthread_mutex_unlock(&ctx->pollfd_modify_lock);
902
903	/* write some data on control pipe to interrupt event handlers */
904	r = write(ctx->ctrl_pipe[1], &dummy, sizeof(dummy));
905	if (r <= 0) {
906		usbi_warn(ctx, "internal signalling write failed");
907		pthread_mutex_lock(&ctx->pollfd_modify_lock);
908		ctx->pollfd_modify--;
909		pthread_mutex_unlock(&ctx->pollfd_modify_lock);
910		return 0;
911	}
912
913	/* take event handling lock */
914	libusb_lock_events(ctx);
915
916	/* read the dummy data */
917	r = read(ctx->ctrl_pipe[0], &dummy, sizeof(dummy));
918	if (r <= 0)
919		usbi_warn(ctx, "internal signalling read failed");
920
921	/* we're done with modifying poll fds */
922	pthread_mutex_lock(&ctx->pollfd_modify_lock);
923	ctx->pollfd_modify--;
924	pthread_mutex_unlock(&ctx->pollfd_modify_lock);
925
926	/* Release event handling lock and wake up event waiters */
927	libusb_unlock_events(ctx);
928
929	return 0;
930}
931
932/** \ingroup dev
933 * Convenience function for finding a device with a particular
934 * <tt>idVendor</tt>/<tt>idProduct</tt> combination. This function is intended
935 * for those scenarios where you are using libusb to knock up a quick test
936 * application - it allows you to avoid calling libusb_get_device_list() and
937 * worrying about traversing/freeing the list.
938 *
939 * This function has limitations and is hence not intended for use in real
940 * applications: if multiple devices have the same IDs it will only
941 * give you the first one, etc.
942 *
943 * \param ctx the context to operate on, or NULL for the default context
944 * \param vendor_id the idVendor value to search for
945 * \param product_id the idProduct value to search for
946 * \returns a handle for the first found device, or NULL on error or if the
947 * device could not be found. */
948API_EXPORTED libusb_device_handle *libusb_open_device_with_vid_pid(
949	libusb_context *ctx, uint16_t vendor_id, uint16_t product_id)
950{
951	struct libusb_device **devs;
952	struct libusb_device *found = NULL;
953	struct libusb_device *dev;
954	struct libusb_device_handle *handle = NULL;
955	size_t i = 0;
956	int r;
957
958	if (libusb_get_device_list(ctx, &devs) < 0)
959		return NULL;
960
961	while ((dev = devs[i++]) != NULL) {
962		struct libusb_device_descriptor desc;
963		r = libusb_get_device_descriptor(dev, &desc);
964		if (r < 0)
965			goto out;
966		if (desc.idVendor == vendor_id && desc.idProduct == product_id) {
967			found = dev;
968			break;
969		}
970	}
971
972	if (found) {
973		r = libusb_open(found, &handle);
974		if (r < 0)
975			handle = NULL;
976	}
977
978out:
979	libusb_free_device_list(devs, 1);
980	return handle;
981}
982
983static void do_close(struct libusb_context *ctx,
984	struct libusb_device_handle *dev_handle)
985{
986	pthread_mutex_lock(&ctx->open_devs_lock);
987	list_del(&dev_handle->list);
988	pthread_mutex_unlock(&ctx->open_devs_lock);
989
990	usbi_backend->close(dev_handle);
991	libusb_unref_device(dev_handle->dev);
992	free(dev_handle);
993}
994
995/** \ingroup dev
996 * Close a device handle. Should be called on all open handles before your
997 * application exits.
998 *
999 * Internally, this function destroys the reference that was added by
1000 * libusb_open() on the given device.
1001 *
1002 * This is a non-blocking function; no requests are sent over the bus.
1003 *
1004 * \param dev_handle the handle to close
1005 */
1006API_EXPORTED void libusb_close(libusb_device_handle *dev_handle)
1007{
1008	struct libusb_context *ctx;
1009	unsigned char dummy = 1;
1010	ssize_t r;
1011
1012	if (!dev_handle)
1013		return;
1014	usbi_dbg("");
1015
1016	ctx = HANDLE_CTX(dev_handle);
1017
1018	/* Similarly to libusb_open(), we want to interrupt all event handlers
1019	 * at this point. More importantly, we want to perform the actual close of
1020	 * the device while holding the event handling lock (preventing any other
1021	 * thread from doing event handling) because we will be removing a file
1022	 * descriptor from the polling loop. */
1023
1024	/* record that we are messing with poll fds */
1025	pthread_mutex_lock(&ctx->pollfd_modify_lock);
1026	ctx->pollfd_modify++;
1027	pthread_mutex_unlock(&ctx->pollfd_modify_lock);
1028
1029	/* write some data on control pipe to interrupt event handlers */
1030	r = write(ctx->ctrl_pipe[1], &dummy, sizeof(dummy));
1031	if (r <= 0) {
1032		usbi_warn(ctx, "internal signalling write failed, closing anyway");
1033		do_close(ctx, dev_handle);
1034		pthread_mutex_lock(&ctx->pollfd_modify_lock);
1035		ctx->pollfd_modify--;
1036		pthread_mutex_unlock(&ctx->pollfd_modify_lock);
1037		return;
1038	}
1039
1040	/* take event handling lock */
1041	libusb_lock_events(ctx);
1042
1043	/* read the dummy data */
1044	r = read(ctx->ctrl_pipe[0], &dummy, sizeof(dummy));
1045	if (r <= 0)
1046		usbi_warn(ctx, "internal signalling read failed, closing anyway");
1047
1048	/* Close the device */
1049	do_close(ctx, dev_handle);
1050
1051	/* we're done with modifying poll fds */
1052	pthread_mutex_lock(&ctx->pollfd_modify_lock);
1053	ctx->pollfd_modify--;
1054	pthread_mutex_unlock(&ctx->pollfd_modify_lock);
1055
1056	/* Release event handling lock and wake up event waiters */
1057	libusb_unlock_events(ctx);
1058}
1059
1060/** \ingroup dev
1061 * Get the underlying device for a handle. This function does not modify
1062 * the reference count of the returned device, so do not feel compelled to
1063 * unreference it when you are done.
1064 * \param dev_handle a device handle
1065 * \returns the underlying device
1066 */
1067API_EXPORTED libusb_device *libusb_get_device(libusb_device_handle *dev_handle)
1068{
1069	return dev_handle->dev;
1070}
1071
1072/** \ingroup dev
1073 * Determine the bConfigurationValue of the currently active configuration.
1074 *
1075 * You could formulate your own control request to obtain this information,
1076 * but this function has the advantage that it may be able to retrieve the
1077 * information from operating system caches (no I/O involved).
1078 *
1079 * If the OS does not cache this information, then this function will block
1080 * while a control transfer is submitted to retrieve the information.
1081 *
1082 * This function will return a value of 0 in the <tt>config</tt> output
1083 * parameter if the device is in unconfigured state.
1084 *
1085 * \param dev a device handle
1086 * \param config output location for the bConfigurationValue of the active
1087 * configuration (only valid for return code 0)
1088 * \returns 0 on success
1089 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1090 * \returns another LIBUSB_ERROR code on other failure
1091 */
1092API_EXPORTED int libusb_get_configuration(libusb_device_handle *dev,
1093	int *config)
1094{
1095	int r = LIBUSB_ERROR_NOT_SUPPORTED;
1096
1097	usbi_dbg("");
1098	if (usbi_backend->get_configuration)
1099		r = usbi_backend->get_configuration(dev, config);
1100
1101	if (r == LIBUSB_ERROR_NOT_SUPPORTED) {
1102		uint8_t tmp = 0;
1103		usbi_dbg("falling back to control message");
1104		r = libusb_control_transfer(dev, LIBUSB_ENDPOINT_IN,
1105			LIBUSB_REQUEST_GET_CONFIGURATION, 0, 0, &tmp, 1, 1000);
1106		if (r == 0) {
1107			usbi_err(HANDLE_CTX(dev), "zero bytes returned in ctrl transfer?");
1108			r = LIBUSB_ERROR_IO;
1109		} else if (r == 1) {
1110			r = 0;
1111			*config = tmp;
1112		} else {
1113			usbi_dbg("control failed, error %d", r);
1114		}
1115	}
1116
1117	if (r == 0)
1118		usbi_dbg("active config %d", *config);
1119
1120	return r;
1121}
1122
1123/** \ingroup dev
1124 * Set the active configuration for a device.
1125 *
1126 * The operating system may or may not have already set an active
1127 * configuration on the device. It is up to your application to ensure the
1128 * correct configuration is selected before you attempt to claim interfaces
1129 * and perform other operations.
1130 *
1131 * If you call this function on a device already configured with the selected
1132 * configuration, then this function will act as a lightweight device reset:
1133 * it will issue a SET_CONFIGURATION request using the current configuration,
1134 * causing most USB-related device state to be reset (altsetting reset to zero,
1135 * endpoint halts cleared, toggles reset).
1136 *
1137 * You cannot change/reset configuration if your application has claimed
1138 * interfaces - you should free them with libusb_release_interface() first.
1139 * You cannot change/reset configuration if other applications or drivers have
1140 * claimed interfaces.
1141 *
1142 * A configuration value of -1 will put the device in unconfigured state.
1143 * The USB specifications state that a configuration value of 0 does this,
1144 * however buggy devices exist which actually have a configuration 0.
1145 *
1146 * You should always use this function rather than formulating your own
1147 * SET_CONFIGURATION control request. This is because the underlying operating
1148 * system needs to know when such changes happen.
1149 *
1150 * This is a blocking function.
1151 *
1152 * \param dev a device handle
1153 * \param configuration the bConfigurationValue of the configuration you
1154 * wish to activate, or -1 if you wish to put the device in unconfigured state
1155 * \returns 0 on success
1156 * \returns LIBUSB_ERROR_NOT_FOUND if the requested configuration does not exist
1157 * \returns LIBUSB_ERROR_BUSY if interfaces are currently claimed
1158 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1159 * \returns another LIBUSB_ERROR code on other failure
1160 */
1161API_EXPORTED int libusb_set_configuration(libusb_device_handle *dev,
1162	int configuration)
1163{
1164	usbi_dbg("configuration %d", configuration);
1165	return usbi_backend->set_configuration(dev, configuration);
1166}
1167
1168/** \ingroup dev
1169 * Claim an interface on a given device handle. You must claim the interface
1170 * you wish to use before you can perform I/O on any of its endpoints.
1171 *
1172 * It is legal to attempt to claim an already-claimed interface, in which
1173 * case libusb just returns 0 without doing anything.
1174 *
1175 * Claiming of interfaces is a purely logical operation; it does not cause
1176 * any requests to be sent over the bus. Interface claiming is used to
1177 * instruct the underlying operating system that your application wishes
1178 * to take ownership of the interface.
1179 *
1180 * This is a non-blocking function.
1181 *
1182 * \param dev a device handle
1183 * \param interface_number the <tt>bInterfaceNumber</tt> of the interface you
1184 * wish to claim
1185 * \returns 0 on success
1186 * \returns LIBUSB_ERROR_NOT_FOUND if the requested interface does not exist
1187 * \returns LIBUSB_ERROR_BUSY if another program or driver has claimed the
1188 * interface
1189 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1190 * \returns a LIBUSB_ERROR code on other failure
1191 */
1192API_EXPORTED int libusb_claim_interface(libusb_device_handle *dev,
1193	int interface_number)
1194{
1195	int r = 0;
1196
1197	usbi_dbg("interface %d", interface_number);
1198	if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
1199		return LIBUSB_ERROR_INVALID_PARAM;
1200
1201	pthread_mutex_lock(&dev->lock);
1202	if (dev->claimed_interfaces & (1 << interface_number))
1203		goto out;
1204
1205	r = usbi_backend->claim_interface(dev, interface_number);
1206	if (r == 0)
1207		dev->claimed_interfaces |= 1 << interface_number;
1208
1209out:
1210	pthread_mutex_unlock(&dev->lock);
1211	return r;
1212}
1213
1214/** \ingroup dev
1215 * Release an interface previously claimed with libusb_claim_interface(). You
1216 * should release all claimed interfaces before closing a device handle.
1217 *
1218 * This is a blocking function. A SET_INTERFACE control request will be sent
1219 * to the device, resetting interface state to the first alternate setting.
1220 *
1221 * \param dev a device handle
1222 * \param interface_number the <tt>bInterfaceNumber</tt> of the
1223 * previously-claimed interface
1224 * \returns 0 on success
1225 * \returns LIBUSB_ERROR_NOT_FOUND if the interface was not claimed
1226 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1227 * \returns another LIBUSB_ERROR code on other failure
1228 */
1229API_EXPORTED int libusb_release_interface(libusb_device_handle *dev,
1230	int interface_number)
1231{
1232	int r;
1233
1234	usbi_dbg("interface %d", interface_number);
1235	if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
1236		return LIBUSB_ERROR_INVALID_PARAM;
1237
1238	pthread_mutex_lock(&dev->lock);
1239	if (!(dev->claimed_interfaces & (1 << interface_number))) {
1240		r = LIBUSB_ERROR_NOT_FOUND;
1241		goto out;
1242	}
1243
1244	r = usbi_backend->release_interface(dev, interface_number);
1245	if (r == 0)
1246		dev->claimed_interfaces &= ~(1 << interface_number);
1247
1248out:
1249	pthread_mutex_unlock(&dev->lock);
1250	return r;
1251}
1252
1253/** \ingroup dev
1254 * Activate an alternate setting for an interface. The interface must have
1255 * been previously claimed with libusb_claim_interface().
1256 *
1257 * You should always use this function rather than formulating your own
1258 * SET_INTERFACE control request. This is because the underlying operating
1259 * system needs to know when such changes happen.
1260 *
1261 * This is a blocking function.
1262 *
1263 * \param dev a device handle
1264 * \param interface_number the <tt>bInterfaceNumber</tt> of the
1265 * previously-claimed interface
1266 * \param alternate_setting the <tt>bAlternateSetting</tt> of the alternate
1267 * setting to activate
1268 * \returns 0 on success
1269 * \returns LIBUSB_ERROR_NOT_FOUND if the interface was not claimed, or the
1270 * requested alternate setting does not exist
1271 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1272 * \returns another LIBUSB_ERROR code on other failure
1273 */
1274API_EXPORTED int libusb_set_interface_alt_setting(libusb_device_handle *dev,
1275	int interface_number, int alternate_setting)
1276{
1277	usbi_dbg("interface %d altsetting %d",
1278		interface_number, alternate_setting);
1279	if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
1280		return LIBUSB_ERROR_INVALID_PARAM;
1281
1282	pthread_mutex_lock(&dev->lock);
1283	if (!(dev->claimed_interfaces & (1 << interface_number))) {
1284		pthread_mutex_unlock(&dev->lock);
1285		return LIBUSB_ERROR_NOT_FOUND;
1286	}
1287	pthread_mutex_unlock(&dev->lock);
1288
1289	return usbi_backend->set_interface_altsetting(dev, interface_number,
1290		alternate_setting);
1291}
1292
1293/** \ingroup dev
1294 * Clear the halt/stall condition for an endpoint. Endpoints with halt status
1295 * are unable to receive or transmit data until the halt condition is stalled.
1296 *
1297 * You should cancel all pending transfers before attempting to clear the halt
1298 * condition.
1299 *
1300 * This is a blocking function.
1301 *
1302 * \param dev a device handle
1303 * \param endpoint the endpoint to clear halt status
1304 * \returns 0 on success
1305 * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
1306 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1307 * \returns another LIBUSB_ERROR code on other failure
1308 */
1309API_EXPORTED int libusb_clear_halt(libusb_device_handle *dev,
1310	unsigned char endpoint)
1311{
1312	usbi_dbg("endpoint %x", endpoint);
1313	return usbi_backend->clear_halt(dev, endpoint);
1314}
1315
1316/** \ingroup dev
1317 * Perform a USB port reset to reinitialize a device. The system will attempt
1318 * to restore the previous configuration and alternate settings after the
1319 * reset has completed.
1320 *
1321 * If the reset fails, the descriptors change, or the previous state cannot be
1322 * restored, the device will appear to be disconnected and reconnected. This
1323 * means that the device handle is no longer valid (you should close it) and
1324 * rediscover the device. A return code of LIBUSB_ERROR_NOT_FOUND indicates
1325 * when this is the case.
1326 *
1327 * This is a blocking function which usually incurs a noticeable delay.
1328 *
1329 * \param dev a handle of the device to reset
1330 * \returns 0 on success
1331 * \returns LIBUSB_ERROR_NOT_FOUND if re-enumeration is required, or if the
1332 * device has been disconnected
1333 * \returns another LIBUSB_ERROR code on other failure
1334 */
1335API_EXPORTED int libusb_reset_device(libusb_device_handle *dev)
1336{
1337	usbi_dbg("");
1338	return usbi_backend->reset_device(dev);
1339}
1340
1341/** \ingroup dev
1342 * Determine if a kernel driver is active on an interface. If a kernel driver
1343 * is active, you cannot claim the interface, and libusb will be unable to
1344 * perform I/O.
1345 *
1346 * \param dev a device handle
1347 * \param interface the interface to check
1348 * \returns 0 if no kernel driver is active
1349 * \returns 1 if a kernel driver is active
1350 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1351 * \returns another LIBUSB_ERROR code on other failure
1352 * \see libusb_detach_kernel_driver()
1353 */
1354API_EXPORTED int libusb_kernel_driver_active(libusb_device_handle *dev,
1355	int interface)
1356{
1357	usbi_dbg("interface %d", interface);
1358	if (usbi_backend->kernel_driver_active)
1359		return usbi_backend->kernel_driver_active(dev, interface);
1360	else
1361		return LIBUSB_ERROR_NOT_SUPPORTED;
1362}
1363
1364/** \ingroup dev
1365 * Detach a kernel driver from an interface. If successful, you will then be
1366 * able to claim the interface and perform I/O.
1367 *
1368 * \param dev a device handle
1369 * \param interface the interface to detach the driver from
1370 * \returns 0 on success
1371 * \returns LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
1372 * \returns LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
1373 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1374 * \returns another LIBUSB_ERROR code on other failure
1375 * \see libusb_kernel_driver_active()
1376 */
1377API_EXPORTED int libusb_detach_kernel_driver(libusb_device_handle *dev,
1378	int interface)
1379{
1380	usbi_dbg("interface %d", interface);
1381	if (usbi_backend->detach_kernel_driver)
1382		return usbi_backend->detach_kernel_driver(dev, interface);
1383	else
1384		return LIBUSB_ERROR_NOT_SUPPORTED;
1385}
1386
1387/** \ingroup dev
1388 * Re-attach an interface's kernel driver, which was previously detached
1389 * using libusb_detach_kernel_driver().
1390 *
1391 * \param dev a device handle
1392 * \param interface the interface to attach the driver from
1393 * \returns 0 on success
1394 * \returns LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
1395 * \returns LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
1396 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1397 * \returns LIBUSB_ERROR_BUSY if the driver cannot be attached because the
1398 * interface is claimed by a program or driver
1399 * \returns another LIBUSB_ERROR code on other failure
1400 * \see libusb_kernel_driver_active()
1401 */
1402API_EXPORTED int libusb_attach_kernel_driver(libusb_device_handle *dev,
1403	int interface)
1404{
1405	usbi_dbg("interface %d", interface);
1406	if (usbi_backend->attach_kernel_driver)
1407		return usbi_backend->attach_kernel_driver(dev, interface);
1408	else
1409		return LIBUSB_ERROR_NOT_SUPPORTED;
1410}
1411
1412/** \ingroup lib
1413 * Set message verbosity.
1414 *  - Level 0: no messages ever printed by the library (default)
1415 *  - Level 1: error messages are printed to stderr
1416 *  - Level 2: warning and error messages are printed to stderr
1417 *  - Level 3: informational messages are printed to stdout, warning and error
1418 *    messages are printed to stderr
1419 *
1420 * The default level is 0, which means no messages are ever printed. If you
1421 * choose to increase the message verbosity level, ensure that your
1422 * application does not close the stdout/stderr file descriptors.
1423 *
1424 * You are advised to set level 3. libusb is conservative with its message
1425 * logging and most of the time, will only log messages that explain error
1426 * conditions and other oddities. This will help you debug your software.
1427 *
1428 * If the LIBUSB_DEBUG environment variable was set when libusb was
1429 * initialized, this function does nothing: the message verbosity is fixed
1430 * to the value in the environment variable.
1431 *
1432 * If libusb was compiled without any message logging, this function does
1433 * nothing: you'll never get any messages.
1434 *
1435 * If libusb was compiled with verbose debug message logging, this function
1436 * does nothing: you'll always get messages from all levels.
1437 *
1438 * \param ctx the context to operate on, or NULL for the default context
1439 * \param level debug level to set
1440 */
1441API_EXPORTED void libusb_set_debug(libusb_context *ctx, int level)
1442{
1443	USBI_GET_CONTEXT(ctx);
1444	if (!ctx->debug_fixed)
1445		ctx->debug = level;
1446}
1447
1448/** \ingroup lib
1449 * Initialize libusb. This function must be called before calling any other
1450 * libusb function.
1451 * \param context Optional output location for context pointer.
1452 * Only valid on return code 0.
1453 * \returns 0 on success, or a LIBUSB_ERROR code on failure
1454 */
1455API_EXPORTED int libusb_init(libusb_context **context)
1456{
1457	char *dbg = getenv("LIBUSB_DEBUG");
1458	struct libusb_context *ctx = malloc(sizeof(*ctx));
1459	int r;
1460
1461	if (!ctx)
1462		return LIBUSB_ERROR_NO_MEM;
1463	memset(ctx, 0, sizeof(*ctx));
1464
1465	if (dbg) {
1466		ctx->debug = atoi(dbg);
1467		if (ctx->debug)
1468			ctx->debug_fixed = 1;
1469	}
1470
1471	usbi_dbg("");
1472
1473	if (usbi_backend->init) {
1474		r = usbi_backend->init(ctx);
1475		if (r)
1476			goto err;
1477	}
1478
1479	pthread_mutex_init(&ctx->usb_devs_lock, NULL);
1480	pthread_mutex_init(&ctx->open_devs_lock, NULL);
1481	list_init(&ctx->usb_devs);
1482	list_init(&ctx->open_devs);
1483
1484	r = usbi_io_init(ctx);
1485	if (r < 0) {
1486		if (usbi_backend->exit)
1487			usbi_backend->exit();
1488		goto err;
1489	}
1490
1491	pthread_mutex_lock(&default_context_lock);
1492	if (!usbi_default_context) {
1493		usbi_dbg("created default context");
1494		usbi_default_context = ctx;
1495	}
1496	pthread_mutex_unlock(&default_context_lock);
1497
1498	if (context)
1499		*context = ctx;
1500	return 0;
1501
1502err:
1503	free(ctx);
1504	return r;
1505}
1506
1507/** \ingroup lib
1508 * Deinitialize libusb. Should be called after closing all open devices and
1509 * before your application terminates.
1510 * \param ctx the context to deinitialize, or NULL for the default context
1511 */
1512API_EXPORTED void libusb_exit(struct libusb_context *ctx)
1513{
1514	USBI_GET_CONTEXT(ctx);
1515	usbi_dbg("");
1516
1517	/* a little sanity check. doesn't bother with open_devs locking because
1518	 * unless there is an application bug, nobody will be accessing this. */
1519	if (!list_empty(&ctx->open_devs))
1520		usbi_warn(ctx, "application left some devices open");
1521
1522	usbi_io_exit(ctx);
1523	if (usbi_backend->exit)
1524		usbi_backend->exit();
1525
1526	pthread_mutex_lock(&default_context_lock);
1527	if (ctx == usbi_default_context) {
1528		usbi_dbg("freeing default context");
1529		usbi_default_context = NULL;
1530	}
1531	pthread_mutex_unlock(&default_context_lock);
1532
1533	free(ctx);
1534}
1535
1536void usbi_log(struct libusb_context *ctx, enum usbi_log_level level,
1537	const char *function, const char *format, ...)
1538{
1539	va_list args;
1540	FILE *stream = stdout;
1541	const char *prefix;
1542
1543#ifndef ENABLE_DEBUG_LOGGING
1544	USBI_GET_CONTEXT(ctx);
1545	if (!ctx->debug)
1546		return;
1547	if (level == LOG_LEVEL_WARNING && ctx->debug < 2)
1548		return;
1549	if (level == LOG_LEVEL_INFO && ctx->debug < 3)
1550		return;
1551#endif
1552
1553	switch (level) {
1554	case LOG_LEVEL_INFO:
1555		prefix = "info";
1556		break;
1557	case LOG_LEVEL_WARNING:
1558		stream = stderr;
1559		prefix = "warning";
1560		break;
1561	case LOG_LEVEL_ERROR:
1562		stream = stderr;
1563		prefix = "error";
1564		break;
1565	case LOG_LEVEL_DEBUG:
1566		stream = stderr;
1567		prefix = "debug";
1568		break;
1569	default:
1570		stream = stderr;
1571		prefix = "unknown";
1572		break;
1573	}
1574
1575	fprintf(stream, "libusb:%s [%s] ", prefix, function);
1576
1577	va_start (args, format);
1578	vfprintf(stream, format, args);
1579	va_end (args);
1580
1581	fprintf(stream, "\n");
1582}
1583
1584