2 * Core functions for libusb
3 * Copyright (C) 2007-2008 Daniel Drake <dsd@gentoo.org>
4 * Copyright (c) 2001 Johannes Erdfelt <johannes@erdfelt.com>
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.
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.
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
29 #include <sys/types.h>
36 const struct usbi_os_backend * const usbi_backend = &linux_usbfs_backend;
37 #elif defined(OS_DARWIN)
38 const struct usbi_os_backend * const usbi_backend = &darwin_backend;
40 #error "Unsupported OS"
43 struct libusb_context *usbi_default_context = NULL;
44 static usbi_mutex_static_t default_context_lock = USBI_MUTEX_INITIALIZER;
47 * \mainpage libusb-1.0 API Reference
49 * \section intro Introduction
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>.
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
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.
68 * \section features Library features
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
79 * \section gettingstarted Getting Started
81 * To begin reading the API documentation, start with the Modules page which
82 * links to the different categories of libusb's functionality.
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.
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.
92 * \section errorhandling Error handling
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.
98 * \section msglog Debug message logging
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
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
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.
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.
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.
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
136 * \section remarks Other remarks
138 * libusb does have imperfections. The \ref caveats "caveats" page attempts
143 * \page caveats Caveats
145 * \section devresets Device resets
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
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.
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.
164 * \section blockonly Blocking-only functionality
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.
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())
176 * \section nohotplug No hotplugging
178 * libusb-1.0 lacks functionality for providing notifications of when devices
179 * are added or removed. This functionality is planned to be implemented
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.
189 * \section configsel Configuration selection and handling
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.
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
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.)
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:
218 cfg = libusb_get_configuration(dev);
220 libusb_set_configuration(dev, desired);
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.
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().
231 * One possible way to lock your device into a specific configuration is as
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
239 * The above method works because once an interface is claimed, no application
240 * or driver is able to select another configuration.
242 * \section earlycomp Early transfer completion
244 * NOTE: This section is currently Linux-centric. I am not sure if any of these
245 * considerations apply to Darwin or other platforms.
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.
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
262 * A previous workaround was to only ever submit transfers of size 16kb or
265 * As of libusb v1.0.4 and Linux v2.6.32, this is fixed. A technical
266 * explanation of this issue follows.
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.
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.
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.
289 * \page contexts Contexts
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.
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.
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.
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().
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.
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.
327 * @defgroup dev Device handling and enumeration
328 * The functionality documented below is designed to help with the following
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
334 * \section nutshell In a nutshell...
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:
342 libusb_device **list;
343 libusb_device *found = NULL;
344 ssize_t cnt = libusb_get_device_list(NULL, &list);
350 for (i = 0; i < cnt; i++) {
351 libusb_device *device = list[i];
352 if (is_interesting(device)) {
359 libusb_device_handle *handle;
361 err = libusb_open(found, &handle);
367 libusb_free_device_list(list, 1);
370 * The two important points:
371 * - You asked libusb_free_device_list() to unreference the devices (2nd
373 * - You opened the device before freeing the list and unreferencing the
376 * If you ended up with a handle, you can now proceed to perform I/O on the
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).
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
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
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.
401 * \section devref Device discovery and reference counting
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.
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
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.
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.
424 * The order is important - you must not unreference the device before
425 * attempting to open it, because unreferencing it may destroy the device.
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.
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
437 /** @defgroup misc Miscellaneous */
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
444 #define DISCOVERED_DEVICES_SIZE_STEP 8
446 static struct discovered_devs *discovered_devs_alloc(void)
448 struct discovered_devs *ret =
449 malloc(sizeof(*ret) + (sizeof(void *) * DISCOVERED_DEVICES_SIZE_STEP));
453 ret->capacity = DISCOVERED_DEVICES_SIZE_STEP;
458 /* append a device to the discovered devices collection. may realloc itself,
459 * returning new discdevs. returns NULL on realloc failure. */
460 struct discovered_devs *discovered_devs_append(
461 struct discovered_devs *discdevs, struct libusb_device *dev)
463 size_t len = discdevs->len;
466 /* if there is space, just append the device */
467 if (len < discdevs->capacity) {
468 discdevs->devices[len] = libusb_ref_device(dev);
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));
479 discdevs->capacity = capacity;
480 discdevs->devices[len] = libusb_ref_device(dev);
487 static void discovered_devs_free(struct discovered_devs *discdevs)
491 for (i = 0; i < discdevs->len; i++)
492 libusb_unref_device(discdevs->devices[i]);
497 /* Allocate a new device with a specific session ID. The returned device has
498 * a reference count of 1. */
499 struct libusb_device *usbi_alloc_device(struct libusb_context *ctx,
500 unsigned long session_id)
502 size_t priv_size = usbi_backend->device_priv_size;
503 struct libusb_device *dev = malloc(sizeof(*dev) + priv_size);
509 r = usbi_mutex_init(&dev->lock, NULL);
517 dev->session_data = session_id;
518 memset(&dev->os_priv, 0, priv_size);
520 usbi_mutex_lock(&ctx->usb_devs_lock);
521 list_add(&dev->list, &ctx->usb_devs);
522 usbi_mutex_unlock(&ctx->usb_devs_lock);
526 /* Perform some final sanity checks on a newly discovered device. If this
527 * function fails (negative return code), the device should not be added
528 * to the discovered device list. */
529 int usbi_sanitize_device(struct libusb_device *dev)
532 unsigned char raw_desc[DEVICE_DESC_LENGTH];
533 uint8_t num_configurations;
536 r = usbi_backend->get_device_descriptor(dev, raw_desc, &host_endian);
540 num_configurations = raw_desc[DEVICE_DESC_LENGTH - 1];
541 if (num_configurations > USB_MAXCONFIG) {
542 usbi_err(DEVICE_CTX(dev), "too many configurations");
543 return LIBUSB_ERROR_IO;
544 } else if (num_configurations < 1) {
545 usbi_dbg("no configurations?");
546 return LIBUSB_ERROR_IO;
549 dev->num_configurations = num_configurations;
553 /* Examine libusb's internal list of known devices, looking for one with
554 * a specific session ID. Returns the matching device if it was found, and
556 struct libusb_device *usbi_get_device_by_session_id(struct libusb_context *ctx,
557 unsigned long session_id)
559 struct libusb_device *dev;
560 struct libusb_device *ret = NULL;
562 usbi_mutex_lock(&ctx->usb_devs_lock);
563 list_for_each_entry(dev, &ctx->usb_devs, list)
564 if (dev->session_data == session_id) {
568 usbi_mutex_unlock(&ctx->usb_devs_lock);
574 * Returns a list of USB devices currently attached to the system. This is
575 * your entry point into finding a USB device to operate.
577 * You are expected to unreference all the devices when you are done with
578 * them, and then free the list with libusb_free_device_list(). Note that
579 * libusb_free_device_list() can unref all the devices for you. Be careful
580 * not to unreference a device you are about to open until after you have
583 * This return value of this function indicates the number of devices in
584 * the resultant list. The list is actually one element larger, as it is
587 * \param ctx the context to operate on, or NULL for the default context
588 * \param list output location for a list of devices. Must be later freed with
589 * libusb_free_device_list().
590 * \returns the number of devices in the outputted list, or LIBUSB_ERROR_NO_MEM
591 * on memory allocation failure.
593 API_EXPORTED ssize_t libusb_get_device_list(libusb_context *ctx,
594 libusb_device ***list)
596 struct discovered_devs *discdevs = discovered_devs_alloc();
597 struct libusb_device **ret;
601 USBI_GET_CONTEXT(ctx);
605 return LIBUSB_ERROR_NO_MEM;
607 r = usbi_backend->get_device_list(ctx, &discdevs);
613 /* convert discovered_devs into a list */
615 ret = malloc(sizeof(void *) * (len + 1));
617 len = LIBUSB_ERROR_NO_MEM;
622 for (i = 0; i < len; i++) {
623 struct libusb_device *dev = discdevs->devices[i];
624 ret[i] = libusb_ref_device(dev);
629 discovered_devs_free(discdevs);
634 * Frees a list of devices previously discovered using
635 * libusb_get_device_list(). If the unref_devices parameter is set, the
636 * reference count of each device in the list is decremented by 1.
637 * \param list the list to free
638 * \param unref_devices whether to unref the devices in the list
640 API_EXPORTED void libusb_free_device_list(libusb_device **list,
648 struct libusb_device *dev;
650 while ((dev = list[i++]) != NULL)
651 libusb_unref_device(dev);
657 * Get the number of the bus that a device is connected to.
658 * \param dev a device
659 * \returns the bus number
661 API_EXPORTED uint8_t libusb_get_bus_number(libusb_device *dev)
663 return dev->bus_number;
667 * Get the address of the device on the bus it is connected to.
668 * \param dev a device
669 * \returns the device address
671 API_EXPORTED uint8_t libusb_get_device_address(libusb_device *dev)
673 return dev->device_address;
676 static const struct libusb_endpoint_descriptor *find_endpoint(
677 struct libusb_config_descriptor *config, unsigned char endpoint)
680 for (iface_idx = 0; iface_idx < config->bNumInterfaces; iface_idx++) {
681 const struct libusb_interface *iface = &config->interface[iface_idx];
684 for (altsetting_idx = 0; altsetting_idx < iface->num_altsetting;
686 const struct libusb_interface_descriptor *altsetting
687 = &iface->altsetting[altsetting_idx];
690 for (ep_idx = 0; ep_idx < altsetting->bNumEndpoints; ep_idx++) {
691 const struct libusb_endpoint_descriptor *ep =
692 &altsetting->endpoint[ep_idx];
693 if (ep->bEndpointAddress == endpoint)
702 * Convenience function to retrieve the wMaxPacketSize value for a particular
703 * endpoint in the active device configuration.
705 * This function was originally intended to be of assistance when setting up
706 * isochronous transfers, but a design mistake resulted in this function
707 * instead. It simply returns the wMaxPacketSize value without considering
708 * its contents. If you're dealing with isochronous transfers, you probably
709 * want libusb_get_max_iso_packet_size() instead.
711 * \param dev a device
712 * \param endpoint address of the endpoint in question
713 * \returns the wMaxPacketSize value
714 * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
715 * \returns LIBUSB_ERROR_OTHER on other failure
717 API_EXPORTED int libusb_get_max_packet_size(libusb_device *dev,
718 unsigned char endpoint)
720 struct libusb_config_descriptor *config;
721 const struct libusb_endpoint_descriptor *ep;
724 r = libusb_get_active_config_descriptor(dev, &config);
726 usbi_err(DEVICE_CTX(dev),
727 "could not retrieve active config descriptor");
728 return LIBUSB_ERROR_OTHER;
731 ep = find_endpoint(config, endpoint);
733 return LIBUSB_ERROR_NOT_FOUND;
735 r = ep->wMaxPacketSize;
736 libusb_free_config_descriptor(config);
741 * Calculate the maximum packet size which a specific endpoint is capable is
742 * sending or receiving in the duration of 1 microframe
744 * Only the active configution is examined. The calculation is based on the
745 * wMaxPacketSize field in the endpoint descriptor as described in section
746 * 9.6.6 in the USB 2.0 specifications.
748 * If acting on an isochronous or interrupt endpoint, this function will
749 * multiply the value found in bits 0:10 by the number of transactions per
750 * microframe (determined by bits 11:12). Otherwise, this function just
751 * returns the numeric value found in bits 0:10.
753 * This function is useful for setting up isochronous transfers, for example
754 * you might pass the return value from this function to
755 * libusb_set_iso_packet_lengths() in order to set the length field of every
756 * isochronous packet in a transfer.
760 * \param dev a device
761 * \param endpoint address of the endpoint in question
762 * \returns the maximum packet size which can be sent/received on this endpoint
763 * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
764 * \returns LIBUSB_ERROR_OTHER on other failure
766 API_EXPORTED int libusb_get_max_iso_packet_size(libusb_device *dev,
767 unsigned char endpoint)
769 struct libusb_config_descriptor *config;
770 const struct libusb_endpoint_descriptor *ep;
771 enum libusb_transfer_type ep_type;
775 r = libusb_get_active_config_descriptor(dev, &config);
777 usbi_err(DEVICE_CTX(dev),
778 "could not retrieve active config descriptor");
779 return LIBUSB_ERROR_OTHER;
782 ep = find_endpoint(config, endpoint);
784 return LIBUSB_ERROR_NOT_FOUND;
786 val = ep->wMaxPacketSize;
787 ep_type = ep->bmAttributes & 0x3;
788 libusb_free_config_descriptor(config);
791 if (ep_type == LIBUSB_TRANSFER_TYPE_ISOCHRONOUS
792 || ep_type == LIBUSB_TRANSFER_TYPE_INTERRUPT)
793 r *= (1 + ((val >> 11) & 3));
798 * Increment the reference count of a device.
799 * \param dev the device to reference
800 * \returns the same device
802 API_EXPORTED libusb_device *libusb_ref_device(libusb_device *dev)
804 usbi_mutex_lock(&dev->lock);
806 usbi_mutex_unlock(&dev->lock);
811 * Decrement the reference count of a device. If the decrement operation
812 * causes the reference count to reach zero, the device shall be destroyed.
813 * \param dev the device to unreference
815 API_EXPORTED void libusb_unref_device(libusb_device *dev)
822 usbi_mutex_lock(&dev->lock);
823 refcnt = --dev->refcnt;
824 usbi_mutex_unlock(&dev->lock);
827 usbi_dbg("destroy device %d.%d", dev->bus_number, dev->device_address);
829 if (usbi_backend->destroy_device)
830 usbi_backend->destroy_device(dev);
832 usbi_mutex_lock(&dev->ctx->usb_devs_lock);
833 list_del(&dev->list);
834 usbi_mutex_unlock(&dev->ctx->usb_devs_lock);
836 usbi_mutex_destroy(&dev->lock);
842 * Open a device and obtain a device handle. A handle allows you to perform
843 * I/O on the device in question.
845 * Internally, this function adds a reference to the device and makes it
846 * available to you through libusb_get_device(). This reference is removed
847 * during libusb_close().
849 * This is a non-blocking function; no requests are sent over the bus.
851 * \param dev the device to open
852 * \param handle output location for the returned device handle pointer. Only
853 * populated when the return code is 0.
854 * \returns 0 on success
855 * \returns LIBUSB_ERROR_NO_MEM on memory allocation failure
856 * \returns LIBUSB_ERROR_ACCESS if the user has insufficient permissions
857 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
858 * \returns another LIBUSB_ERROR code on other failure
860 API_EXPORTED int libusb_open(libusb_device *dev, libusb_device_handle **handle)
862 struct libusb_context *ctx = DEVICE_CTX(dev);
863 struct libusb_device_handle *_handle;
864 size_t priv_size = usbi_backend->device_handle_priv_size;
865 unsigned char dummy = 1;
867 usbi_dbg("open %d.%d", dev->bus_number, dev->device_address);
869 _handle = malloc(sizeof(*_handle) + priv_size);
871 return LIBUSB_ERROR_NO_MEM;
873 r = usbi_mutex_init(&_handle->lock, NULL);
876 return LIBUSB_ERROR_OTHER;
879 _handle->dev = libusb_ref_device(dev);
880 _handle->claimed_interfaces = 0;
881 memset(&_handle->os_priv, 0, priv_size);
883 r = usbi_backend->open(_handle);
885 libusb_unref_device(dev);
886 usbi_mutex_destroy(&_handle->lock);
891 usbi_mutex_lock(&ctx->open_devs_lock);
892 list_add(&_handle->list, &ctx->open_devs);
893 usbi_mutex_unlock(&ctx->open_devs_lock);
897 /* At this point, we want to interrupt any existing event handlers so
898 * that they realise the addition of the new device's poll fd. One
899 * example when this is desirable is if the user is running a separate
900 * dedicated libusb events handling thread, which is running with a long
901 * or infinite timeout. We want to interrupt that iteration of the loop,
902 * so that it picks up the new fd, and then continues. */
904 /* record that we are messing with poll fds */
905 usbi_mutex_lock(&ctx->pollfd_modify_lock);
906 ctx->pollfd_modify++;
907 usbi_mutex_unlock(&ctx->pollfd_modify_lock);
909 /* write some data on control pipe to interrupt event handlers */
910 r = write(ctx->ctrl_pipe[1], &dummy, sizeof(dummy));
912 usbi_warn(ctx, "internal signalling write failed");
913 usbi_mutex_lock(&ctx->pollfd_modify_lock);
914 ctx->pollfd_modify--;
915 usbi_mutex_unlock(&ctx->pollfd_modify_lock);
919 /* take event handling lock */
920 libusb_lock_events(ctx);
922 /* read the dummy data */
923 r = read(ctx->ctrl_pipe[0], &dummy, sizeof(dummy));
925 usbi_warn(ctx, "internal signalling read failed");
927 /* we're done with modifying poll fds */
928 usbi_mutex_lock(&ctx->pollfd_modify_lock);
929 ctx->pollfd_modify--;
930 usbi_mutex_unlock(&ctx->pollfd_modify_lock);
932 /* Release event handling lock and wake up event waiters */
933 libusb_unlock_events(ctx);
939 * Convenience function for finding a device with a particular
940 * <tt>idVendor</tt>/<tt>idProduct</tt> combination. This function is intended
941 * for those scenarios where you are using libusb to knock up a quick test
942 * application - it allows you to avoid calling libusb_get_device_list() and
943 * worrying about traversing/freeing the list.
945 * This function has limitations and is hence not intended for use in real
946 * applications: if multiple devices have the same IDs it will only
947 * give you the first one, etc.
949 * \param ctx the context to operate on, or NULL for the default context
950 * \param vendor_id the idVendor value to search for
951 * \param product_id the idProduct value to search for
952 * \returns a handle for the first found device, or NULL on error or if the
953 * device could not be found. */
954 API_EXPORTED libusb_device_handle *libusb_open_device_with_vid_pid(
955 libusb_context *ctx, uint16_t vendor_id, uint16_t product_id)
957 struct libusb_device **devs;
958 struct libusb_device *found = NULL;
959 struct libusb_device *dev;
960 struct libusb_device_handle *handle = NULL;
964 if (libusb_get_device_list(ctx, &devs) < 0)
967 while ((dev = devs[i++]) != NULL) {
968 struct libusb_device_descriptor desc;
969 r = libusb_get_device_descriptor(dev, &desc);
972 if (desc.idVendor == vendor_id && desc.idProduct == product_id) {
979 r = libusb_open(found, &handle);
985 libusb_free_device_list(devs, 1);
989 static void do_close(struct libusb_context *ctx,
990 struct libusb_device_handle *dev_handle)
992 usbi_mutex_lock(&ctx->open_devs_lock);
993 list_del(&dev_handle->list);
994 usbi_mutex_unlock(&ctx->open_devs_lock);
996 usbi_backend->close(dev_handle);
997 libusb_unref_device(dev_handle->dev);
998 usbi_mutex_destroy(&dev_handle->lock);
1003 * Close a device handle. Should be called on all open handles before your
1004 * application exits.
1006 * Internally, this function destroys the reference that was added by
1007 * libusb_open() on the given device.
1009 * This is a non-blocking function; no requests are sent over the bus.
1011 * \param dev_handle the handle to close
1013 API_EXPORTED void libusb_close(libusb_device_handle *dev_handle)
1015 struct libusb_context *ctx;
1016 unsigned char dummy = 1;
1023 ctx = HANDLE_CTX(dev_handle);
1025 /* Similarly to libusb_open(), we want to interrupt all event handlers
1026 * at this point. More importantly, we want to perform the actual close of
1027 * the device while holding the event handling lock (preventing any other
1028 * thread from doing event handling) because we will be removing a file
1029 * descriptor from the polling loop. */
1031 /* record that we are messing with poll fds */
1032 usbi_mutex_lock(&ctx->pollfd_modify_lock);
1033 ctx->pollfd_modify++;
1034 usbi_mutex_unlock(&ctx->pollfd_modify_lock);
1036 /* write some data on control pipe to interrupt event handlers */
1037 r = write(ctx->ctrl_pipe[1], &dummy, sizeof(dummy));
1039 usbi_warn(ctx, "internal signalling write failed, closing anyway");
1040 do_close(ctx, dev_handle);
1041 usbi_mutex_lock(&ctx->pollfd_modify_lock);
1042 ctx->pollfd_modify--;
1043 usbi_mutex_unlock(&ctx->pollfd_modify_lock);
1047 /* take event handling lock */
1048 libusb_lock_events(ctx);
1050 /* read the dummy data */
1051 r = read(ctx->ctrl_pipe[0], &dummy, sizeof(dummy));
1053 usbi_warn(ctx, "internal signalling read failed, closing anyway");
1055 /* Close the device */
1056 do_close(ctx, dev_handle);
1058 /* we're done with modifying poll fds */
1059 usbi_mutex_lock(&ctx->pollfd_modify_lock);
1060 ctx->pollfd_modify--;
1061 usbi_mutex_unlock(&ctx->pollfd_modify_lock);
1063 /* Release event handling lock and wake up event waiters */
1064 libusb_unlock_events(ctx);
1068 * Get the underlying device for a handle. This function does not modify
1069 * the reference count of the returned device, so do not feel compelled to
1070 * unreference it when you are done.
1071 * \param dev_handle a device handle
1072 * \returns the underlying device
1074 API_EXPORTED libusb_device *libusb_get_device(libusb_device_handle *dev_handle)
1076 return dev_handle->dev;
1080 * Determine the bConfigurationValue of the currently active configuration.
1082 * You could formulate your own control request to obtain this information,
1083 * but this function has the advantage that it may be able to retrieve the
1084 * information from operating system caches (no I/O involved).
1086 * If the OS does not cache this information, then this function will block
1087 * while a control transfer is submitted to retrieve the information.
1089 * This function will return a value of 0 in the <tt>config</tt> output
1090 * parameter if the device is in unconfigured state.
1092 * \param dev a device handle
1093 * \param config output location for the bConfigurationValue of the active
1094 * configuration (only valid for return code 0)
1095 * \returns 0 on success
1096 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1097 * \returns another LIBUSB_ERROR code on other failure
1099 API_EXPORTED int libusb_get_configuration(libusb_device_handle *dev,
1102 int r = LIBUSB_ERROR_NOT_SUPPORTED;
1105 if (usbi_backend->get_configuration)
1106 r = usbi_backend->get_configuration(dev, config);
1108 if (r == LIBUSB_ERROR_NOT_SUPPORTED) {
1110 usbi_dbg("falling back to control message");
1111 r = libusb_control_transfer(dev, LIBUSB_ENDPOINT_IN,
1112 LIBUSB_REQUEST_GET_CONFIGURATION, 0, 0, &tmp, 1, 1000);
1114 usbi_err(HANDLE_CTX(dev), "zero bytes returned in ctrl transfer?");
1115 r = LIBUSB_ERROR_IO;
1116 } else if (r == 1) {
1120 usbi_dbg("control failed, error %d", r);
1125 usbi_dbg("active config %d", *config);
1131 * Set the active configuration for a device.
1133 * The operating system may or may not have already set an active
1134 * configuration on the device. It is up to your application to ensure the
1135 * correct configuration is selected before you attempt to claim interfaces
1136 * and perform other operations.
1138 * If you call this function on a device already configured with the selected
1139 * configuration, then this function will act as a lightweight device reset:
1140 * it will issue a SET_CONFIGURATION request using the current configuration,
1141 * causing most USB-related device state to be reset (altsetting reset to zero,
1142 * endpoint halts cleared, toggles reset).
1144 * You cannot change/reset configuration if your application has claimed
1145 * interfaces - you should free them with libusb_release_interface() first.
1146 * You cannot change/reset configuration if other applications or drivers have
1147 * claimed interfaces.
1149 * A configuration value of -1 will put the device in unconfigured state.
1150 * The USB specifications state that a configuration value of 0 does this,
1151 * however buggy devices exist which actually have a configuration 0.
1153 * You should always use this function rather than formulating your own
1154 * SET_CONFIGURATION control request. This is because the underlying operating
1155 * system needs to know when such changes happen.
1157 * This is a blocking function.
1159 * \param dev a device handle
1160 * \param configuration the bConfigurationValue of the configuration you
1161 * wish to activate, or -1 if you wish to put the device in unconfigured state
1162 * \returns 0 on success
1163 * \returns LIBUSB_ERROR_NOT_FOUND if the requested configuration does not exist
1164 * \returns LIBUSB_ERROR_BUSY if interfaces are currently claimed
1165 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1166 * \returns another LIBUSB_ERROR code on other failure
1168 API_EXPORTED int libusb_set_configuration(libusb_device_handle *dev,
1171 usbi_dbg("configuration %d", configuration);
1172 return usbi_backend->set_configuration(dev, configuration);
1176 * Claim an interface on a given device handle. You must claim the interface
1177 * you wish to use before you can perform I/O on any of its endpoints.
1179 * It is legal to attempt to claim an already-claimed interface, in which
1180 * case libusb just returns 0 without doing anything.
1182 * Claiming of interfaces is a purely logical operation; it does not cause
1183 * any requests to be sent over the bus. Interface claiming is used to
1184 * instruct the underlying operating system that your application wishes
1185 * to take ownership of the interface.
1187 * This is a non-blocking function.
1189 * \param dev a device handle
1190 * \param interface_number the <tt>bInterfaceNumber</tt> of the interface you
1192 * \returns 0 on success
1193 * \returns LIBUSB_ERROR_NOT_FOUND if the requested interface does not exist
1194 * \returns LIBUSB_ERROR_BUSY if another program or driver has claimed the
1196 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1197 * \returns a LIBUSB_ERROR code on other failure
1199 API_EXPORTED int libusb_claim_interface(libusb_device_handle *dev,
1200 int interface_number)
1204 usbi_dbg("interface %d", interface_number);
1205 if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
1206 return LIBUSB_ERROR_INVALID_PARAM;
1208 usbi_mutex_lock(&dev->lock);
1209 if (dev->claimed_interfaces & (1 << interface_number))
1212 r = usbi_backend->claim_interface(dev, interface_number);
1214 dev->claimed_interfaces |= 1 << interface_number;
1217 usbi_mutex_unlock(&dev->lock);
1222 * Release an interface previously claimed with libusb_claim_interface(). You
1223 * should release all claimed interfaces before closing a device handle.
1225 * This is a blocking function. A SET_INTERFACE control request will be sent
1226 * to the device, resetting interface state to the first alternate setting.
1228 * \param dev a device handle
1229 * \param interface_number the <tt>bInterfaceNumber</tt> of the
1230 * previously-claimed interface
1231 * \returns 0 on success
1232 * \returns LIBUSB_ERROR_NOT_FOUND if the interface was not claimed
1233 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1234 * \returns another LIBUSB_ERROR code on other failure
1236 API_EXPORTED int libusb_release_interface(libusb_device_handle *dev,
1237 int interface_number)
1241 usbi_dbg("interface %d", interface_number);
1242 if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
1243 return LIBUSB_ERROR_INVALID_PARAM;
1245 usbi_mutex_lock(&dev->lock);
1246 if (!(dev->claimed_interfaces & (1 << interface_number))) {
1247 r = LIBUSB_ERROR_NOT_FOUND;
1251 r = usbi_backend->release_interface(dev, interface_number);
1253 dev->claimed_interfaces &= ~(1 << interface_number);
1256 usbi_mutex_unlock(&dev->lock);
1261 * Activate an alternate setting for an interface. The interface must have
1262 * been previously claimed with libusb_claim_interface().
1264 * You should always use this function rather than formulating your own
1265 * SET_INTERFACE control request. This is because the underlying operating
1266 * system needs to know when such changes happen.
1268 * This is a blocking function.
1270 * \param dev a device handle
1271 * \param interface_number the <tt>bInterfaceNumber</tt> of the
1272 * previously-claimed interface
1273 * \param alternate_setting the <tt>bAlternateSetting</tt> of the alternate
1274 * setting to activate
1275 * \returns 0 on success
1276 * \returns LIBUSB_ERROR_NOT_FOUND if the interface was not claimed, or the
1277 * requested alternate setting does not exist
1278 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1279 * \returns another LIBUSB_ERROR code on other failure
1281 API_EXPORTED int libusb_set_interface_alt_setting(libusb_device_handle *dev,
1282 int interface_number, int alternate_setting)
1284 usbi_dbg("interface %d altsetting %d",
1285 interface_number, alternate_setting);
1286 if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
1287 return LIBUSB_ERROR_INVALID_PARAM;
1289 usbi_mutex_lock(&dev->lock);
1290 if (!(dev->claimed_interfaces & (1 << interface_number))) {
1291 usbi_mutex_unlock(&dev->lock);
1292 return LIBUSB_ERROR_NOT_FOUND;
1294 usbi_mutex_unlock(&dev->lock);
1296 return usbi_backend->set_interface_altsetting(dev, interface_number,
1301 * Clear the halt/stall condition for an endpoint. Endpoints with halt status
1302 * are unable to receive or transmit data until the halt condition is stalled.
1304 * You should cancel all pending transfers before attempting to clear the halt
1307 * This is a blocking function.
1309 * \param dev a device handle
1310 * \param endpoint the endpoint to clear halt status
1311 * \returns 0 on success
1312 * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
1313 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1314 * \returns another LIBUSB_ERROR code on other failure
1316 API_EXPORTED int libusb_clear_halt(libusb_device_handle *dev,
1317 unsigned char endpoint)
1319 usbi_dbg("endpoint %x", endpoint);
1320 return usbi_backend->clear_halt(dev, endpoint);
1324 * Perform a USB port reset to reinitialize a device. The system will attempt
1325 * to restore the previous configuration and alternate settings after the
1326 * reset has completed.
1328 * If the reset fails, the descriptors change, or the previous state cannot be
1329 * restored, the device will appear to be disconnected and reconnected. This
1330 * means that the device handle is no longer valid (you should close it) and
1331 * rediscover the device. A return code of LIBUSB_ERROR_NOT_FOUND indicates
1332 * when this is the case.
1334 * This is a blocking function which usually incurs a noticeable delay.
1336 * \param dev a handle of the device to reset
1337 * \returns 0 on success
1338 * \returns LIBUSB_ERROR_NOT_FOUND if re-enumeration is required, or if the
1339 * device has been disconnected
1340 * \returns another LIBUSB_ERROR code on other failure
1342 API_EXPORTED int libusb_reset_device(libusb_device_handle *dev)
1345 return usbi_backend->reset_device(dev);
1349 * Determine if a kernel driver is active on an interface. If a kernel driver
1350 * is active, you cannot claim the interface, and libusb will be unable to
1353 * \param dev a device handle
1354 * \param interface the interface to check
1355 * \returns 0 if no kernel driver is active
1356 * \returns 1 if a kernel driver is active
1357 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1358 * \returns another LIBUSB_ERROR code on other failure
1359 * \see libusb_detach_kernel_driver()
1361 API_EXPORTED int libusb_kernel_driver_active(libusb_device_handle *dev,
1364 usbi_dbg("interface %d", interface);
1365 if (usbi_backend->kernel_driver_active)
1366 return usbi_backend->kernel_driver_active(dev, interface);
1368 return LIBUSB_ERROR_NOT_SUPPORTED;
1372 * Detach a kernel driver from an interface. If successful, you will then be
1373 * able to claim the interface and perform I/O.
1375 * \param dev a device handle
1376 * \param interface the interface to detach the driver from
1377 * \returns 0 on success
1378 * \returns LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
1379 * \returns LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
1380 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1381 * \returns another LIBUSB_ERROR code on other failure
1382 * \see libusb_kernel_driver_active()
1384 API_EXPORTED int libusb_detach_kernel_driver(libusb_device_handle *dev,
1387 usbi_dbg("interface %d", interface);
1388 if (usbi_backend->detach_kernel_driver)
1389 return usbi_backend->detach_kernel_driver(dev, interface);
1391 return LIBUSB_ERROR_NOT_SUPPORTED;
1395 * Re-attach an interface's kernel driver, which was previously detached
1396 * using libusb_detach_kernel_driver().
1398 * \param dev a device handle
1399 * \param interface the interface to attach the driver from
1400 * \returns 0 on success
1401 * \returns LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
1402 * \returns LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
1403 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1404 * \returns LIBUSB_ERROR_BUSY if the driver cannot be attached because the
1405 * interface is claimed by a program or driver
1406 * \returns another LIBUSB_ERROR code on other failure
1407 * \see libusb_kernel_driver_active()
1409 API_EXPORTED int libusb_attach_kernel_driver(libusb_device_handle *dev,
1412 usbi_dbg("interface %d", interface);
1413 if (usbi_backend->attach_kernel_driver)
1414 return usbi_backend->attach_kernel_driver(dev, interface);
1416 return LIBUSB_ERROR_NOT_SUPPORTED;
1420 * Set message verbosity.
1421 * - Level 0: no messages ever printed by the library (default)
1422 * - Level 1: error messages are printed to stderr
1423 * - Level 2: warning and error messages are printed to stderr
1424 * - Level 3: informational messages are printed to stdout, warning and error
1425 * messages are printed to stderr
1427 * The default level is 0, which means no messages are ever printed. If you
1428 * choose to increase the message verbosity level, ensure that your
1429 * application does not close the stdout/stderr file descriptors.
1431 * You are advised to set level 3. libusb is conservative with its message
1432 * logging and most of the time, will only log messages that explain error
1433 * conditions and other oddities. This will help you debug your software.
1435 * If the LIBUSB_DEBUG environment variable was set when libusb was
1436 * initialized, this function does nothing: the message verbosity is fixed
1437 * to the value in the environment variable.
1439 * If libusb was compiled without any message logging, this function does
1440 * nothing: you'll never get any messages.
1442 * If libusb was compiled with verbose debug message logging, this function
1443 * does nothing: you'll always get messages from all levels.
1445 * \param ctx the context to operate on, or NULL for the default context
1446 * \param level debug level to set
1448 API_EXPORTED void libusb_set_debug(libusb_context *ctx, int level)
1450 USBI_GET_CONTEXT(ctx);
1451 if (!ctx->debug_fixed)
1456 * Initialize libusb. This function must be called before calling any other
1458 * \param context Optional output location for context pointer.
1459 * Only valid on return code 0.
1460 * \returns 0 on success, or a LIBUSB_ERROR code on failure
1462 API_EXPORTED int libusb_init(libusb_context **context)
1464 char *dbg = getenv("LIBUSB_DEBUG");
1465 struct libusb_context *ctx = malloc(sizeof(*ctx));
1469 return LIBUSB_ERROR_NO_MEM;
1470 memset(ctx, 0, sizeof(*ctx));
1473 ctx->debug = atoi(dbg);
1475 ctx->debug_fixed = 1;
1480 if (usbi_backend->init) {
1481 r = usbi_backend->init(ctx);
1486 usbi_mutex_init(&ctx->usb_devs_lock, NULL);
1487 usbi_mutex_init(&ctx->open_devs_lock, NULL);
1488 list_init(&ctx->usb_devs);
1489 list_init(&ctx->open_devs);
1491 r = usbi_io_init(ctx);
1493 if (usbi_backend->exit)
1494 usbi_backend->exit();
1498 usbi_mutex_static_lock(&default_context_lock);
1499 if (!usbi_default_context) {
1500 usbi_dbg("created default context");
1501 usbi_default_context = ctx;
1503 usbi_mutex_static_unlock(&default_context_lock);
1510 usbi_mutex_destroy(&ctx->open_devs_lock);
1511 usbi_mutex_destroy(&ctx->usb_devs_lock);
1517 * Deinitialize libusb. Should be called after closing all open devices and
1518 * before your application terminates.
1519 * \param ctx the context to deinitialize, or NULL for the default context
1521 API_EXPORTED void libusb_exit(struct libusb_context *ctx)
1523 USBI_GET_CONTEXT(ctx);
1526 /* a little sanity check. doesn't bother with open_devs locking because
1527 * unless there is an application bug, nobody will be accessing this. */
1528 if (!list_empty(&ctx->open_devs))
1529 usbi_warn(ctx, "application left some devices open");
1532 if (usbi_backend->exit)
1533 usbi_backend->exit();
1535 usbi_mutex_static_lock(&default_context_lock);
1536 if (ctx == usbi_default_context) {
1537 usbi_dbg("freeing default context");
1538 usbi_default_context = NULL;
1540 usbi_mutex_static_unlock(&default_context_lock);
1542 usbi_mutex_destroy(&ctx->open_devs_lock);
1543 usbi_mutex_destroy(&ctx->usb_devs_lock);
1547 void usbi_log(struct libusb_context *ctx, enum usbi_log_level level,
1548 const char *function, const char *format, ...)
1551 FILE *stream = stdout;
1554 #ifndef ENABLE_DEBUG_LOGGING
1555 USBI_GET_CONTEXT(ctx);
1558 if (level == LOG_LEVEL_WARNING && ctx->debug < 2)
1560 if (level == LOG_LEVEL_INFO && ctx->debug < 3)
1565 case LOG_LEVEL_INFO:
1568 case LOG_LEVEL_WARNING:
1572 case LOG_LEVEL_ERROR:
1576 case LOG_LEVEL_DEBUG:
1586 fprintf(stream, "libusb:%s [%s] ", prefix, function);
1588 va_start (args, format);
1589 vfprintf(stream, format, args);
1592 fprintf(stream, "\n");
1596 * Returns a constant NULL-terminated string with an English short description
1597 * of the given error code. The caller should never free() the returned pointer
1598 * since it points to a constant string.
1599 * The returned string is encoded in ASCII form and always starts with a
1600 * capital letter and ends without any punctuation.
1601 * Future versions of libusb may return NULL if the library is compiled without
1602 * these messages included (e.g. for embedded systems).
1603 * This function is intended to be used for debugging purposes only.
1605 * \param errcode the error code whose description is desired
1606 * \returns a short description of the error code in English, or NULL if the
1607 * error descriptions are unavailable
1609 API_EXPORTED const char *libusb_strerror(enum libusb_error errcode)
1612 case LIBUSB_SUCCESS:
1614 case LIBUSB_ERROR_IO:
1615 return "Input/output error";
1616 case LIBUSB_ERROR_INVALID_PARAM:
1617 return "Invalid parameter";
1618 case LIBUSB_ERROR_ACCESS:
1619 return "Access denied (insufficient permissions)";
1620 case LIBUSB_ERROR_NO_DEVICE:
1621 return "No such device (it may have been disconnected)";
1622 case LIBUSB_ERROR_NOT_FOUND:
1623 return "Entity not found";
1624 case LIBUSB_ERROR_BUSY:
1625 return "Resource busy";
1626 case LIBUSB_ERROR_TIMEOUT:
1627 return "Operation timed out";
1628 case LIBUSB_ERROR_OVERFLOW:
1630 case LIBUSB_ERROR_PIPE:
1631 return "Pipe error";
1632 case LIBUSB_ERROR_INTERRUPTED:
1633 return "System call interrupted (perhaps due to signal)";
1634 case LIBUSB_ERROR_NO_MEM:
1635 return "Insufficient memory";
1636 case LIBUSB_ERROR_NOT_SUPPORTED:
1637 return "Operation not supported or unimplemented on this platform";
1638 case LIBUSB_ERROR_OTHER:
1639 return "Other error";
1641 return "Unknown error";