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
28 #include <sys/types.h>
33 const struct usbi_os_backend * const usbi_backend = &linux_usbfs_backend;
34 #elif defined(OS_DARWIN)
35 const struct usbi_os_backend * const usbi_backend = &darwin_backend;
36 #elif defined(OS_WINDOWS)
37 const struct usbi_os_backend * const usbi_backend = &windows_backend;
39 #error "Unsupported OS"
42 struct libusb_context *usbi_default_context = NULL;
43 static int default_context_refcnt = 0;
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 * transfers, 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 * The default context is reference-counted and can be shared. That means that
314 * if libusb_init(NULL) is called twice within the same process, the two
315 * users end up sharing the same context. The deinitialization and freeing of
316 * the default context will only happen when the last user calls libusb_exit().
317 * In other words, the default context is created and initialized when its
318 * reference count goes from 0 to 1, and is deinitialized and destroyed when
319 * its reference count goes from 1 to 0.
321 * You may be wondering why only a subset of libusb functions require a
322 * context pointer in their function definition. Internally, libusb stores
323 * context pointers in other objects (e.g. libusb_device instances) and hence
324 * can infer the context from those objects.
328 * @defgroup lib Library initialization/deinitialization
329 * This page details how to initialize and deinitialize libusb. Initialization
330 * must be performed before using any libusb functionality, and similarly you
331 * must not call any libusb functions after deinitialization.
335 * @defgroup dev Device handling and enumeration
336 * The functionality documented below is designed to help with the following
338 * - Enumerating the USB devices currently attached to the system
339 * - Choosing a device to operate from your software
340 * - Opening and closing the chosen device
342 * \section nutshell In a nutshell...
344 * The description below really makes things sound more complicated than they
345 * actually are. The following sequence of function calls will be suitable
346 * for almost all scenarios and does not require you to have such a deep
347 * understanding of the resource management issues:
350 libusb_device **list;
351 libusb_device *found = NULL;
352 ssize_t cnt = libusb_get_device_list(NULL, &list);
358 for (i = 0; i < cnt; i++) {
359 libusb_device *device = list[i];
360 if (is_interesting(device)) {
367 libusb_device_handle *handle;
369 err = libusb_open(found, &handle);
375 libusb_free_device_list(list, 1);
378 * The two important points:
379 * - You asked libusb_free_device_list() to unreference the devices (2nd
381 * - You opened the device before freeing the list and unreferencing the
384 * If you ended up with a handle, you can now proceed to perform I/O on the
387 * \section devshandles Devices and device handles
388 * libusb has a concept of a USB device, represented by the
389 * \ref libusb_device opaque type. A device represents a USB device that
390 * is currently or was previously connected to the system. Using a reference
391 * to a device, you can determine certain information about the device (e.g.
392 * you can read the descriptor data).
394 * The libusb_get_device_list() function can be used to obtain a list of
395 * devices currently connected to the system. This is known as device
398 * Just because you have a reference to a device does not mean it is
399 * necessarily usable. The device may have been unplugged, you may not have
400 * permission to operate such device, or another program or driver may be
403 * When you've found a device that you'd like to operate, you must ask
404 * libusb to open the device using the libusb_open() function. Assuming
405 * success, libusb then returns you a <em>device handle</em>
406 * (a \ref libusb_device_handle pointer). All "real" I/O operations then
407 * operate on the handle rather than the original device pointer.
409 * \section devref Device discovery and reference counting
411 * Device discovery (i.e. calling libusb_get_device_list()) returns a
412 * freshly-allocated list of devices. The list itself must be freed when
413 * you are done with it. libusb also needs to know when it is OK to free
414 * the contents of the list - the devices themselves.
416 * To handle these issues, libusb provides you with two separate items:
417 * - A function to free the list itself
418 * - A reference counting system for the devices inside
420 * New devices presented by the libusb_get_device_list() function all have a
421 * reference count of 1. You can increase and decrease reference count using
422 * libusb_ref_device() and libusb_unref_device(). A device is destroyed when
423 * its reference count reaches 0.
425 * With the above information in mind, the process of opening a device can
426 * be viewed as follows:
427 * -# Discover devices using libusb_get_device_list().
428 * -# Choose the device that you want to operate, and call libusb_open().
429 * -# Unref all devices in the discovered device list.
430 * -# Free the discovered device list.
432 * The order is important - you must not unreference the device before
433 * attempting to open it, because unreferencing it may destroy the device.
435 * For convenience, the libusb_free_device_list() function includes a
436 * parameter to optionally unreference all the devices in the list before
437 * freeing the list itself. This combines steps 3 and 4 above.
439 * As an implementation detail, libusb_open() actually adds a reference to
440 * the device in question. This is because the device remains available
441 * through the handle via libusb_get_device(). The reference is deleted during
445 /** @defgroup misc Miscellaneous */
447 /* we traverse usbfs without knowing how many devices we are going to find.
448 * so we create this discovered_devs model which is similar to a linked-list
449 * which grows when required. it can be freed once discovery has completed,
450 * eliminating the need for a list node in the libusb_device structure
452 #define DISCOVERED_DEVICES_SIZE_STEP 8
454 static struct discovered_devs *discovered_devs_alloc(void)
456 struct discovered_devs *ret =
457 malloc(sizeof(*ret) + (sizeof(void *) * DISCOVERED_DEVICES_SIZE_STEP));
461 ret->capacity = DISCOVERED_DEVICES_SIZE_STEP;
466 /* append a device to the discovered devices collection. may realloc itself,
467 * returning new discdevs. returns NULL on realloc failure. */
468 struct discovered_devs *discovered_devs_append(
469 struct discovered_devs *discdevs, struct libusb_device *dev)
471 size_t len = discdevs->len;
474 /* if there is space, just append the device */
475 if (len < discdevs->capacity) {
476 discdevs->devices[len] = libusb_ref_device(dev);
481 /* exceeded capacity, need to grow */
482 usbi_dbg("need to increase capacity");
483 capacity = discdevs->capacity + DISCOVERED_DEVICES_SIZE_STEP;
484 discdevs = realloc(discdevs,
485 sizeof(*discdevs) + (sizeof(void *) * capacity));
487 discdevs->capacity = capacity;
488 discdevs->devices[len] = libusb_ref_device(dev);
495 static void discovered_devs_free(struct discovered_devs *discdevs)
499 for (i = 0; i < discdevs->len; i++)
500 libusb_unref_device(discdevs->devices[i]);
505 /* Allocate a new device with a specific session ID. The returned device has
506 * a reference count of 1. */
507 struct libusb_device *usbi_alloc_device(struct libusb_context *ctx,
508 unsigned long session_id)
510 size_t priv_size = usbi_backend->device_priv_size;
511 struct libusb_device *dev = malloc(sizeof(*dev) + priv_size);
517 r = usbi_mutex_init(&dev->lock, NULL);
525 dev->session_data = session_id;
526 memset(&dev->os_priv, 0, priv_size);
528 usbi_mutex_lock(&ctx->usb_devs_lock);
529 list_add(&dev->list, &ctx->usb_devs);
530 usbi_mutex_unlock(&ctx->usb_devs_lock);
534 /* Perform some final sanity checks on a newly discovered device. If this
535 * function fails (negative return code), the device should not be added
536 * to the discovered device list. */
537 int usbi_sanitize_device(struct libusb_device *dev)
540 unsigned char raw_desc[DEVICE_DESC_LENGTH];
541 uint8_t num_configurations;
544 r = usbi_backend->get_device_descriptor(dev, raw_desc, &host_endian);
548 num_configurations = raw_desc[DEVICE_DESC_LENGTH - 1];
549 if (num_configurations > USB_MAXCONFIG) {
550 usbi_err(DEVICE_CTX(dev), "too many configurations");
551 return LIBUSB_ERROR_IO;
552 } else if (num_configurations < 1) {
553 usbi_dbg("no configurations?");
554 return LIBUSB_ERROR_IO;
557 dev->num_configurations = num_configurations;
561 /* Examine libusb's internal list of known devices, looking for one with
562 * a specific session ID. Returns the matching device if it was found, and
564 struct libusb_device *usbi_get_device_by_session_id(struct libusb_context *ctx,
565 unsigned long session_id)
567 struct libusb_device *dev;
568 struct libusb_device *ret = NULL;
570 usbi_mutex_lock(&ctx->usb_devs_lock);
571 list_for_each_entry(dev, &ctx->usb_devs, list, struct libusb_device)
572 if (dev->session_data == session_id) {
576 usbi_mutex_unlock(&ctx->usb_devs_lock);
582 * Returns a list of USB devices currently attached to the system. This is
583 * your entry point into finding a USB device to operate.
585 * You are expected to unreference all the devices when you are done with
586 * them, and then free the list with libusb_free_device_list(). Note that
587 * libusb_free_device_list() can unref all the devices for you. Be careful
588 * not to unreference a device you are about to open until after you have
591 * This return value of this function indicates the number of devices in
592 * the resultant list. The list is actually one element larger, as it is
595 * \param ctx the context to operate on, or NULL for the default context
596 * \param list output location for a list of devices. Must be later freed with
597 * libusb_free_device_list().
598 * \returns the number of devices in the outputted list, or LIBUSB_ERROR_NO_MEM
599 * on memory allocation failure.
601 API_EXPORTED ssize_t libusb_get_device_list(libusb_context *ctx,
602 libusb_device ***list)
604 struct discovered_devs *discdevs = discovered_devs_alloc();
605 struct libusb_device **ret;
608 USBI_GET_CONTEXT(ctx);
612 return LIBUSB_ERROR_NO_MEM;
614 r = usbi_backend->get_device_list(ctx, &discdevs);
620 /* convert discovered_devs into a list */
622 ret = malloc(sizeof(void *) * (len + 1));
624 len = LIBUSB_ERROR_NO_MEM;
629 for (i = 0; i < len; i++) {
630 struct libusb_device *dev = discdevs->devices[i];
631 ret[i] = libusb_ref_device(dev);
636 discovered_devs_free(discdevs);
641 * Frees a list of devices previously discovered using
642 * libusb_get_device_list(). If the unref_devices parameter is set, the
643 * reference count of each device in the list is decremented by 1.
644 * \param list the list to free
645 * \param unref_devices whether to unref the devices in the list
647 API_EXPORTED void libusb_free_device_list(libusb_device **list,
655 struct libusb_device *dev;
657 while ((dev = list[i++]) != NULL)
658 libusb_unref_device(dev);
664 * Get the number of the bus that a device is connected to.
665 * \param dev a device
666 * \returns the bus number
668 API_EXPORTED uint8_t libusb_get_bus_number(libusb_device *dev)
670 return dev->bus_number;
674 * Get the address of the device on the bus it is connected to.
675 * \param dev a device
676 * \returns the device address
678 API_EXPORTED uint8_t libusb_get_device_address(libusb_device *dev)
680 return dev->device_address;
683 static const struct libusb_endpoint_descriptor *find_endpoint(
684 struct libusb_config_descriptor *config, unsigned char endpoint)
687 for (iface_idx = 0; iface_idx < config->bNumInterfaces; iface_idx++) {
688 const struct libusb_interface *iface = &config->interface[iface_idx];
691 for (altsetting_idx = 0; altsetting_idx < iface->num_altsetting;
693 const struct libusb_interface_descriptor *altsetting
694 = &iface->altsetting[altsetting_idx];
697 for (ep_idx = 0; ep_idx < altsetting->bNumEndpoints; ep_idx++) {
698 const struct libusb_endpoint_descriptor *ep =
699 &altsetting->endpoint[ep_idx];
700 if (ep->bEndpointAddress == endpoint)
709 * Convenience function to retrieve the wMaxPacketSize value for a particular
710 * endpoint in the active device configuration.
712 * This function was originally intended to be of assistance when setting up
713 * isochronous transfers, but a design mistake resulted in this function
714 * instead. It simply returns the wMaxPacketSize value without considering
715 * its contents. If you're dealing with isochronous transfers, you probably
716 * want libusb_get_max_iso_packet_size() instead.
718 * \param dev a device
719 * \param endpoint address of the endpoint in question
720 * \returns the wMaxPacketSize value
721 * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
722 * \returns LIBUSB_ERROR_OTHER on other failure
724 API_EXPORTED int libusb_get_max_packet_size(libusb_device *dev,
725 unsigned char endpoint)
727 struct libusb_config_descriptor *config;
728 const struct libusb_endpoint_descriptor *ep;
731 r = libusb_get_active_config_descriptor(dev, &config);
733 usbi_err(DEVICE_CTX(dev),
734 "could not retrieve active config descriptor");
735 return LIBUSB_ERROR_OTHER;
738 ep = find_endpoint(config, endpoint);
740 return LIBUSB_ERROR_NOT_FOUND;
742 r = ep->wMaxPacketSize;
743 libusb_free_config_descriptor(config);
748 * Calculate the maximum packet size which a specific endpoint is capable is
749 * sending or receiving in the duration of 1 microframe
751 * Only the active configution is examined. The calculation is based on the
752 * wMaxPacketSize field in the endpoint descriptor as described in section
753 * 9.6.6 in the USB 2.0 specifications.
755 * If acting on an isochronous or interrupt endpoint, this function will
756 * multiply the value found in bits 0:10 by the number of transactions per
757 * microframe (determined by bits 11:12). Otherwise, this function just
758 * returns the numeric value found in bits 0:10.
760 * This function is useful for setting up isochronous transfers, for example
761 * you might pass the return value from this function to
762 * libusb_set_iso_packet_lengths() in order to set the length field of every
763 * isochronous packet in a transfer.
767 * \param dev a device
768 * \param endpoint address of the endpoint in question
769 * \returns the maximum packet size which can be sent/received on this endpoint
770 * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
771 * \returns LIBUSB_ERROR_OTHER on other failure
773 API_EXPORTED int libusb_get_max_iso_packet_size(libusb_device *dev,
774 unsigned char endpoint)
776 struct libusb_config_descriptor *config;
777 const struct libusb_endpoint_descriptor *ep;
778 enum libusb_transfer_type ep_type;
782 r = libusb_get_active_config_descriptor(dev, &config);
784 usbi_err(DEVICE_CTX(dev),
785 "could not retrieve active config descriptor");
786 return LIBUSB_ERROR_OTHER;
789 ep = find_endpoint(config, endpoint);
791 return LIBUSB_ERROR_NOT_FOUND;
793 val = ep->wMaxPacketSize;
794 ep_type = ep->bmAttributes & 0x3;
795 libusb_free_config_descriptor(config);
798 if (ep_type == LIBUSB_TRANSFER_TYPE_ISOCHRONOUS
799 || ep_type == LIBUSB_TRANSFER_TYPE_INTERRUPT)
800 r *= (1 + ((val >> 11) & 3));
805 * Increment the reference count of a device.
806 * \param dev the device to reference
807 * \returns the same device
809 API_EXPORTED libusb_device *libusb_ref_device(libusb_device *dev)
811 usbi_mutex_lock(&dev->lock);
813 usbi_mutex_unlock(&dev->lock);
818 * Decrement the reference count of a device. If the decrement operation
819 * causes the reference count to reach zero, the device shall be destroyed.
820 * \param dev the device to unreference
822 API_EXPORTED void libusb_unref_device(libusb_device *dev)
829 usbi_mutex_lock(&dev->lock);
830 refcnt = --dev->refcnt;
831 usbi_mutex_unlock(&dev->lock);
834 usbi_dbg("destroy device %d.%d", dev->bus_number, dev->device_address);
836 if (usbi_backend->destroy_device)
837 usbi_backend->destroy_device(dev);
839 usbi_mutex_lock(&dev->ctx->usb_devs_lock);
840 list_del(&dev->list);
841 usbi_mutex_unlock(&dev->ctx->usb_devs_lock);
843 usbi_mutex_destroy(&dev->lock);
849 * Interrupt the iteration of the event handling thread, so that it picks
852 void usbi_fd_notification(struct libusb_context *ctx)
854 unsigned char dummy = 1;
860 /* record that we are messing with poll fds */
861 usbi_mutex_lock(&ctx->pollfd_modify_lock);
862 ctx->pollfd_modify++;
863 usbi_mutex_unlock(&ctx->pollfd_modify_lock);
865 /* write some data on control pipe to interrupt event handlers */
866 r = usbi_write(ctx->ctrl_pipe[1], &dummy, sizeof(dummy));
868 usbi_warn(ctx, "internal signalling write failed");
869 usbi_mutex_lock(&ctx->pollfd_modify_lock);
870 ctx->pollfd_modify--;
871 usbi_mutex_unlock(&ctx->pollfd_modify_lock);
875 /* take event handling lock */
876 libusb_lock_events(ctx);
878 /* read the dummy data */
879 r = usbi_read(ctx->ctrl_pipe[0], &dummy, sizeof(dummy));
881 usbi_warn(ctx, "internal signalling read failed");
883 /* we're done with modifying poll fds */
884 usbi_mutex_lock(&ctx->pollfd_modify_lock);
885 ctx->pollfd_modify--;
886 usbi_mutex_unlock(&ctx->pollfd_modify_lock);
888 /* Release event handling lock and wake up event waiters */
889 libusb_unlock_events(ctx);
893 * Open a device and obtain a device handle. A handle allows you to perform
894 * I/O on the device in question.
896 * Internally, this function adds a reference to the device and makes it
897 * available to you through libusb_get_device(). This reference is removed
898 * during libusb_close().
900 * This is a non-blocking function; no requests are sent over the bus.
902 * \param dev the device to open
903 * \param handle output location for the returned device handle pointer. Only
904 * populated when the return code is 0.
905 * \returns 0 on success
906 * \returns LIBUSB_ERROR_NO_MEM on memory allocation failure
907 * \returns LIBUSB_ERROR_ACCESS if the user has insufficient permissions
908 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
909 * \returns another LIBUSB_ERROR code on other failure
911 API_EXPORTED int libusb_open(libusb_device *dev, libusb_device_handle **handle)
913 struct libusb_context *ctx = DEVICE_CTX(dev);
914 struct libusb_device_handle *_handle;
915 size_t priv_size = usbi_backend->device_handle_priv_size;
917 usbi_dbg("open %d.%d", dev->bus_number, dev->device_address);
919 _handle = malloc(sizeof(*_handle) + priv_size);
921 return LIBUSB_ERROR_NO_MEM;
923 r = usbi_mutex_init(&_handle->lock, NULL);
926 return LIBUSB_ERROR_OTHER;
929 _handle->dev = libusb_ref_device(dev);
930 _handle->claimed_interfaces = 0;
931 memset(&_handle->os_priv, 0, priv_size);
933 r = usbi_backend->open(_handle);
935 libusb_unref_device(dev);
936 usbi_mutex_destroy(&_handle->lock);
941 usbi_mutex_lock(&ctx->open_devs_lock);
942 list_add(&_handle->list, &ctx->open_devs);
943 usbi_mutex_unlock(&ctx->open_devs_lock);
946 /* At this point, we want to interrupt any existing event handlers so
947 * that they realise the addition of the new device's poll fd. One
948 * example when this is desirable is if the user is running a separate
949 * dedicated libusb events handling thread, which is running with a long
950 * or infinite timeout. We want to interrupt that iteration of the loop,
951 * so that it picks up the new fd, and then continues. */
952 usbi_fd_notification(ctx);
958 * Convenience function for finding a device with a particular
959 * <tt>idVendor</tt>/<tt>idProduct</tt> combination. This function is intended
960 * for those scenarios where you are using libusb to knock up a quick test
961 * application - it allows you to avoid calling libusb_get_device_list() and
962 * worrying about traversing/freeing the list.
964 * This function has limitations and is hence not intended for use in real
965 * applications: if multiple devices have the same IDs it will only
966 * give you the first one, etc.
968 * \param ctx the context to operate on, or NULL for the default context
969 * \param vendor_id the idVendor value to search for
970 * \param product_id the idProduct value to search for
971 * \returns a handle for the first found device, or NULL on error or if the
972 * device could not be found. */
973 API_EXPORTED libusb_device_handle *libusb_open_device_with_vid_pid(
974 libusb_context *ctx, uint16_t vendor_id, uint16_t product_id)
976 struct libusb_device **devs;
977 struct libusb_device *found = NULL;
978 struct libusb_device *dev;
979 struct libusb_device_handle *handle = NULL;
983 if (libusb_get_device_list(ctx, &devs) < 0)
986 while ((dev = devs[i++]) != NULL) {
987 struct libusb_device_descriptor desc;
988 r = libusb_get_device_descriptor(dev, &desc);
991 if (desc.idVendor == vendor_id && desc.idProduct == product_id) {
998 r = libusb_open(found, &handle);
1004 libusb_free_device_list(devs, 1);
1008 static void do_close(struct libusb_context *ctx,
1009 struct libusb_device_handle *dev_handle)
1011 usbi_mutex_lock(&ctx->open_devs_lock);
1012 list_del(&dev_handle->list);
1013 usbi_mutex_unlock(&ctx->open_devs_lock);
1015 usbi_backend->close(dev_handle);
1016 libusb_unref_device(dev_handle->dev);
1017 usbi_mutex_destroy(&dev_handle->lock);
1022 * Close a device handle. Should be called on all open handles before your
1023 * application exits.
1025 * Internally, this function destroys the reference that was added by
1026 * libusb_open() on the given device.
1028 * This is a non-blocking function; no requests are sent over the bus.
1030 * \param dev_handle the handle to close
1032 API_EXPORTED void libusb_close(libusb_device_handle *dev_handle)
1034 struct libusb_context *ctx;
1035 unsigned char dummy = 1;
1042 ctx = HANDLE_CTX(dev_handle);
1044 /* Similarly to libusb_open(), we want to interrupt all event handlers
1045 * at this point. More importantly, we want to perform the actual close of
1046 * the device while holding the event handling lock (preventing any other
1047 * thread from doing event handling) because we will be removing a file
1048 * descriptor from the polling loop. */
1050 /* record that we are messing with poll fds */
1051 usbi_mutex_lock(&ctx->pollfd_modify_lock);
1052 ctx->pollfd_modify++;
1053 usbi_mutex_unlock(&ctx->pollfd_modify_lock);
1055 /* write some data on control pipe to interrupt event handlers */
1056 r = usbi_write(ctx->ctrl_pipe[1], &dummy, sizeof(dummy));
1058 usbi_warn(ctx, "internal signalling write failed, closing anyway");
1059 do_close(ctx, dev_handle);
1060 usbi_mutex_lock(&ctx->pollfd_modify_lock);
1061 ctx->pollfd_modify--;
1062 usbi_mutex_unlock(&ctx->pollfd_modify_lock);
1066 /* take event handling lock */
1067 libusb_lock_events(ctx);
1069 /* read the dummy data */
1070 r = usbi_read(ctx->ctrl_pipe[0], &dummy, sizeof(dummy));
1072 usbi_warn(ctx, "internal signalling read failed, closing anyway");
1074 /* Close the device */
1075 do_close(ctx, dev_handle);
1077 /* we're done with modifying poll fds */
1078 usbi_mutex_lock(&ctx->pollfd_modify_lock);
1079 ctx->pollfd_modify--;
1080 usbi_mutex_unlock(&ctx->pollfd_modify_lock);
1082 /* Release event handling lock and wake up event waiters */
1083 libusb_unlock_events(ctx);
1087 * Get the underlying device for a handle. This function does not modify
1088 * the reference count of the returned device, so do not feel compelled to
1089 * unreference it when you are done.
1090 * \param dev_handle a device handle
1091 * \returns the underlying device
1093 API_EXPORTED libusb_device *libusb_get_device(libusb_device_handle *dev_handle)
1095 return dev_handle->dev;
1099 * Determine the bConfigurationValue of the currently active configuration.
1101 * You could formulate your own control request to obtain this information,
1102 * but this function has the advantage that it may be able to retrieve the
1103 * information from operating system caches (no I/O involved).
1105 * If the OS does not cache this information, then this function will block
1106 * while a control transfer is submitted to retrieve the information.
1108 * This function will return a value of 0 in the <tt>config</tt> output
1109 * parameter if the device is in unconfigured state.
1111 * \param dev a device handle
1112 * \param config output location for the bConfigurationValue of the active
1113 * configuration (only valid for return code 0)
1114 * \returns 0 on success
1115 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1116 * \returns another LIBUSB_ERROR code on other failure
1118 API_EXPORTED int libusb_get_configuration(libusb_device_handle *dev,
1121 int r = LIBUSB_ERROR_NOT_SUPPORTED;
1124 if (usbi_backend->get_configuration)
1125 r = usbi_backend->get_configuration(dev, config);
1127 if (r == LIBUSB_ERROR_NOT_SUPPORTED) {
1129 usbi_dbg("falling back to control message");
1130 r = libusb_control_transfer(dev, LIBUSB_ENDPOINT_IN,
1131 LIBUSB_REQUEST_GET_CONFIGURATION, 0, 0, &tmp, 1, 1000);
1133 usbi_err(HANDLE_CTX(dev), "zero bytes returned in ctrl transfer?");
1134 r = LIBUSB_ERROR_IO;
1135 } else if (r == 1) {
1139 usbi_dbg("control failed, error %d", r);
1144 usbi_dbg("active config %d", *config);
1150 * Set the active configuration for a device.
1152 * The operating system may or may not have already set an active
1153 * configuration on the device. It is up to your application to ensure the
1154 * correct configuration is selected before you attempt to claim interfaces
1155 * and perform other operations.
1157 * If you call this function on a device already configured with the selected
1158 * configuration, then this function will act as a lightweight device reset:
1159 * it will issue a SET_CONFIGURATION request using the current configuration,
1160 * causing most USB-related device state to be reset (altsetting reset to zero,
1161 * endpoint halts cleared, toggles reset).
1163 * You cannot change/reset configuration if your application has claimed
1164 * interfaces - you should free them with libusb_release_interface() first.
1165 * You cannot change/reset configuration if other applications or drivers have
1166 * claimed interfaces.
1168 * A configuration value of -1 will put the device in unconfigured state.
1169 * The USB specifications state that a configuration value of 0 does this,
1170 * however buggy devices exist which actually have a configuration 0.
1172 * You should always use this function rather than formulating your own
1173 * SET_CONFIGURATION control request. This is because the underlying operating
1174 * system needs to know when such changes happen.
1176 * This is a blocking function.
1178 * \param dev a device handle
1179 * \param configuration the bConfigurationValue of the configuration you
1180 * wish to activate, or -1 if you wish to put the device in unconfigured state
1181 * \returns 0 on success
1182 * \returns LIBUSB_ERROR_NOT_FOUND if the requested configuration does not exist
1183 * \returns LIBUSB_ERROR_BUSY if interfaces are currently claimed
1184 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1185 * \returns another LIBUSB_ERROR code on other failure
1187 API_EXPORTED int libusb_set_configuration(libusb_device_handle *dev,
1190 usbi_dbg("configuration %d", configuration);
1191 return usbi_backend->set_configuration(dev, configuration);
1195 * Claim an interface on a given device handle. You must claim the interface
1196 * you wish to use before you can perform I/O on any of its endpoints.
1198 * It is legal to attempt to claim an already-claimed interface, in which
1199 * case libusb just returns 0 without doing anything.
1201 * Claiming of interfaces is a purely logical operation; it does not cause
1202 * any requests to be sent over the bus. Interface claiming is used to
1203 * instruct the underlying operating system that your application wishes
1204 * to take ownership of the interface.
1206 * This is a non-blocking function.
1208 * \param dev a device handle
1209 * \param interface_number the <tt>bInterfaceNumber</tt> of the interface you
1211 * \returns 0 on success
1212 * \returns LIBUSB_ERROR_NOT_FOUND if the requested interface does not exist
1213 * \returns LIBUSB_ERROR_BUSY if another program or driver has claimed the
1215 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1216 * \returns a LIBUSB_ERROR code on other failure
1218 API_EXPORTED int libusb_claim_interface(libusb_device_handle *dev,
1219 int interface_number)
1223 usbi_dbg("interface %d", interface_number);
1224 if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
1225 return LIBUSB_ERROR_INVALID_PARAM;
1227 usbi_mutex_lock(&dev->lock);
1228 if (dev->claimed_interfaces & (1 << interface_number))
1231 r = usbi_backend->claim_interface(dev, interface_number);
1233 dev->claimed_interfaces |= 1 << interface_number;
1236 usbi_mutex_unlock(&dev->lock);
1241 * Release an interface previously claimed with libusb_claim_interface(). You
1242 * should release all claimed interfaces before closing a device handle.
1244 * This is a blocking function. A SET_INTERFACE control request will be sent
1245 * to the device, resetting interface state to the first alternate setting.
1247 * \param dev a device handle
1248 * \param interface_number the <tt>bInterfaceNumber</tt> of the
1249 * previously-claimed interface
1250 * \returns 0 on success
1251 * \returns LIBUSB_ERROR_NOT_FOUND if the interface was not claimed
1252 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1253 * \returns another LIBUSB_ERROR code on other failure
1255 API_EXPORTED int libusb_release_interface(libusb_device_handle *dev,
1256 int interface_number)
1260 usbi_dbg("interface %d", interface_number);
1261 if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
1262 return LIBUSB_ERROR_INVALID_PARAM;
1264 usbi_mutex_lock(&dev->lock);
1265 if (!(dev->claimed_interfaces & (1 << interface_number))) {
1266 r = LIBUSB_ERROR_NOT_FOUND;
1270 r = usbi_backend->release_interface(dev, interface_number);
1272 dev->claimed_interfaces &= ~(1 << interface_number);
1275 usbi_mutex_unlock(&dev->lock);
1280 * Activate an alternate setting for an interface. The interface must have
1281 * been previously claimed with libusb_claim_interface().
1283 * You should always use this function rather than formulating your own
1284 * SET_INTERFACE control request. This is because the underlying operating
1285 * system needs to know when such changes happen.
1287 * This is a blocking function.
1289 * \param dev a device handle
1290 * \param interface_number the <tt>bInterfaceNumber</tt> of the
1291 * previously-claimed interface
1292 * \param alternate_setting the <tt>bAlternateSetting</tt> of the alternate
1293 * setting to activate
1294 * \returns 0 on success
1295 * \returns LIBUSB_ERROR_NOT_FOUND if the interface was not claimed, or the
1296 * requested alternate setting does not exist
1297 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1298 * \returns another LIBUSB_ERROR code on other failure
1300 API_EXPORTED int libusb_set_interface_alt_setting(libusb_device_handle *dev,
1301 int interface_number, int alternate_setting)
1303 usbi_dbg("interface %d altsetting %d",
1304 interface_number, alternate_setting);
1305 if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
1306 return LIBUSB_ERROR_INVALID_PARAM;
1308 usbi_mutex_lock(&dev->lock);
1309 if (!(dev->claimed_interfaces & (1 << interface_number))) {
1310 usbi_mutex_unlock(&dev->lock);
1311 return LIBUSB_ERROR_NOT_FOUND;
1313 usbi_mutex_unlock(&dev->lock);
1315 return usbi_backend->set_interface_altsetting(dev, interface_number,
1320 * Clear the halt/stall condition for an endpoint. Endpoints with halt status
1321 * are unable to receive or transmit data until the halt condition is stalled.
1323 * You should cancel all pending transfers before attempting to clear the halt
1326 * This is a blocking function.
1328 * \param dev a device handle
1329 * \param endpoint the endpoint to clear halt status
1330 * \returns 0 on success
1331 * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
1332 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1333 * \returns another LIBUSB_ERROR code on other failure
1335 API_EXPORTED int libusb_clear_halt(libusb_device_handle *dev,
1336 unsigned char endpoint)
1338 usbi_dbg("endpoint %x", endpoint);
1339 return usbi_backend->clear_halt(dev, endpoint);
1343 * Perform a USB port reset to reinitialize a device. The system will attempt
1344 * to restore the previous configuration and alternate settings after the
1345 * reset has completed.
1347 * If the reset fails, the descriptors change, or the previous state cannot be
1348 * restored, the device will appear to be disconnected and reconnected. This
1349 * means that the device handle is no longer valid (you should close it) and
1350 * rediscover the device. A return code of LIBUSB_ERROR_NOT_FOUND indicates
1351 * when this is the case.
1353 * This is a blocking function which usually incurs a noticeable delay.
1355 * \param dev a handle of the device to reset
1356 * \returns 0 on success
1357 * \returns LIBUSB_ERROR_NOT_FOUND if re-enumeration is required, or if the
1358 * device has been disconnected
1359 * \returns another LIBUSB_ERROR code on other failure
1361 API_EXPORTED int libusb_reset_device(libusb_device_handle *dev)
1364 return usbi_backend->reset_device(dev);
1368 * Determine if a kernel driver is active on an interface. If a kernel driver
1369 * is active, you cannot claim the interface, and libusb will be unable to
1372 * \param dev a device handle
1373 * \param interface_number the interface to check
1374 * \returns 0 if no kernel driver is active
1375 * \returns 1 if a kernel driver is active
1376 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1377 * \returns another LIBUSB_ERROR code on other failure
1378 * \see libusb_detach_kernel_driver()
1380 API_EXPORTED int libusb_kernel_driver_active(libusb_device_handle *dev,
1381 int interface_number)
1383 usbi_dbg("interface %d", interface_number);
1384 if (usbi_backend->kernel_driver_active)
1385 return usbi_backend->kernel_driver_active(dev, interface_number);
1387 return LIBUSB_ERROR_NOT_SUPPORTED;
1391 * Detach a kernel driver from an interface. If successful, you will then be
1392 * able to claim the interface and perform I/O.
1394 * \param dev a device handle
1395 * \param interface_number the interface to detach the driver from
1396 * \returns 0 on success
1397 * \returns LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
1398 * \returns LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
1399 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1400 * \returns another LIBUSB_ERROR code on other failure
1401 * \see libusb_kernel_driver_active()
1403 API_EXPORTED int libusb_detach_kernel_driver(libusb_device_handle *dev,
1404 int interface_number)
1406 usbi_dbg("interface %d", interface_number);
1407 if (usbi_backend->detach_kernel_driver)
1408 return usbi_backend->detach_kernel_driver(dev, interface_number);
1410 return LIBUSB_ERROR_NOT_SUPPORTED;
1414 * Re-attach an interface's kernel driver, which was previously detached
1415 * using libusb_detach_kernel_driver().
1417 * \param dev a device handle
1418 * \param interface_number the interface to attach the driver from
1419 * \returns 0 on success
1420 * \returns LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
1421 * \returns LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
1422 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1423 * \returns LIBUSB_ERROR_BUSY if the driver cannot be attached because the
1424 * interface is claimed by a program or driver
1425 * \returns another LIBUSB_ERROR code on other failure
1426 * \see libusb_kernel_driver_active()
1428 API_EXPORTED int libusb_attach_kernel_driver(libusb_device_handle *dev,
1429 int interface_number)
1431 usbi_dbg("interface %d", interface_number);
1432 if (usbi_backend->attach_kernel_driver)
1433 return usbi_backend->attach_kernel_driver(dev, interface_number);
1435 return LIBUSB_ERROR_NOT_SUPPORTED;
1439 * Set message verbosity.
1440 * - Level 0: no messages ever printed by the library (default)
1441 * - Level 1: error messages are printed to stderr
1442 * - Level 2: warning and error messages are printed to stderr
1443 * - Level 3: informational messages are printed to stdout, warning and error
1444 * messages are printed to stderr
1446 * The default level is 0, which means no messages are ever printed. If you
1447 * choose to increase the message verbosity level, ensure that your
1448 * application does not close the stdout/stderr file descriptors.
1450 * You are advised to set level 3. libusb is conservative with its message
1451 * logging and most of the time, will only log messages that explain error
1452 * conditions and other oddities. This will help you debug your software.
1454 * If the LIBUSB_DEBUG environment variable was set when libusb was
1455 * initialized, this function does nothing: the message verbosity is fixed
1456 * to the value in the environment variable.
1458 * If libusb was compiled without any message logging, this function does
1459 * nothing: you'll never get any messages.
1461 * If libusb was compiled with verbose debug message logging, this function
1462 * does nothing: you'll always get messages from all levels.
1464 * \param ctx the context to operate on, or NULL for the default context
1465 * \param level debug level to set
1467 API_EXPORTED void libusb_set_debug(libusb_context *ctx, int level)
1469 USBI_GET_CONTEXT(ctx);
1470 if (!ctx->debug_fixed)
1475 * Initialize libusb. This function must be called before calling any other
1478 * If you do not provide an output location for a context pointer, a default
1479 * context will be created. If there was already a default context, it will
1480 * be reused (and nothing will be initialized/reinitialized).
1482 * \param context Optional output location for context pointer.
1483 * Only valid on return code 0.
1484 * \returns 0 on success, or a LIBUSB_ERROR code on failure
1487 API_EXPORTED int libusb_init(libusb_context **context)
1489 char *dbg = getenv("LIBUSB_DEBUG");
1490 struct libusb_context *ctx;
1493 usbi_mutex_static_lock(&default_context_lock);
1494 if (!context && usbi_default_context) {
1496 usbi_dbg("reusing default context");
1497 default_context_refcnt++;
1498 usbi_mutex_static_unlock(&default_context_lock);
1502 ctx = malloc(sizeof(*ctx));
1504 r = LIBUSB_ERROR_NO_MEM;
1507 memset(ctx, 0, sizeof(*ctx));
1510 ctx->debug = atoi(dbg);
1512 ctx->debug_fixed = 1;
1517 if (usbi_backend->init) {
1518 r = usbi_backend->init(ctx);
1523 usbi_mutex_init(&ctx->usb_devs_lock, NULL);
1524 usbi_mutex_init(&ctx->open_devs_lock, NULL);
1525 list_init(&ctx->usb_devs);
1526 list_init(&ctx->open_devs);
1528 r = usbi_io_init(ctx);
1530 if (usbi_backend->exit)
1531 usbi_backend->exit();
1532 goto err_destroy_mutex;
1537 } else if (!usbi_default_context) {
1538 usbi_dbg("created default context");
1539 usbi_default_context = ctx;
1540 default_context_refcnt++;
1542 usbi_mutex_static_unlock(&default_context_lock);
1547 usbi_mutex_destroy(&ctx->open_devs_lock);
1548 usbi_mutex_destroy(&ctx->usb_devs_lock);
1552 usbi_mutex_static_unlock(&default_context_lock);
1557 * Deinitialize libusb. Should be called after closing all open devices and
1558 * before your application terminates.
1559 * \param ctx the context to deinitialize, or NULL for the default context
1561 API_EXPORTED void libusb_exit(struct libusb_context *ctx)
1564 USBI_GET_CONTEXT(ctx);
1566 /* if working with default context, only actually do the deinitialization
1567 * if we're the last user */
1568 if (ctx == usbi_default_context) {
1569 usbi_mutex_static_lock(&default_context_lock);
1570 if (--default_context_refcnt > 0) {
1571 usbi_dbg("not destroying default context");
1572 usbi_mutex_static_unlock(&default_context_lock);
1575 usbi_dbg("destroying default context");
1576 usbi_default_context = NULL;
1577 usbi_mutex_static_unlock(&default_context_lock);
1580 /* a little sanity check. doesn't bother with open_devs locking because
1581 * unless there is an application bug, nobody will be accessing this. */
1582 if (!list_empty(&ctx->open_devs))
1583 usbi_warn(ctx, "application left some devices open");
1586 if (usbi_backend->exit)
1587 usbi_backend->exit();
1589 usbi_mutex_destroy(&ctx->open_devs_lock);
1590 usbi_mutex_destroy(&ctx->usb_devs_lock);
1594 void usbi_log_v(struct libusb_context *ctx, enum usbi_log_level level,
1595 const char *function, const char *format, va_list args)
1597 FILE *stream = stdout;
1600 #ifndef ENABLE_DEBUG_LOGGING
1601 USBI_GET_CONTEXT(ctx);
1604 if (level == LOG_LEVEL_WARNING && ctx->debug < 2)
1606 if (level == LOG_LEVEL_INFO && ctx->debug < 3)
1611 case LOG_LEVEL_INFO:
1614 case LOG_LEVEL_WARNING:
1618 case LOG_LEVEL_ERROR:
1622 case LOG_LEVEL_DEBUG:
1632 fprintf(stream, "libusb:%s [%s] ", prefix, function);
1634 vfprintf(stream, format, args);
1636 fprintf(stream, "\n");
1639 void usbi_log(struct libusb_context *ctx, enum usbi_log_level level,
1640 const char *function, const char *format, ...)
1644 va_start (args, format);
1645 usbi_log_v(ctx, level, function, format, args);
1650 * Returns a constant NULL-terminated string with an English short description
1651 * of the given error code. The caller should never free() the returned pointer
1652 * since it points to a constant string.
1653 * The returned string is encoded in ASCII form and always starts with a
1654 * capital letter and ends without any punctuation.
1655 * Future versions of libusb may return NULL if the library is compiled without
1656 * these messages included (e.g. for embedded systems).
1657 * This function is intended to be used for debugging purposes only.
1659 * \param errcode the error code whose description is desired
1660 * \returns a short description of the error code in English, or NULL if the
1661 * error descriptions are unavailable
1663 API_EXPORTED const char *libusb_strerror(enum libusb_error errcode)
1666 case LIBUSB_SUCCESS:
1668 case LIBUSB_ERROR_IO:
1669 return "Input/output error";
1670 case LIBUSB_ERROR_INVALID_PARAM:
1671 return "Invalid parameter";
1672 case LIBUSB_ERROR_ACCESS:
1673 return "Access denied (insufficient permissions)";
1674 case LIBUSB_ERROR_NO_DEVICE:
1675 return "No such device (it may have been disconnected)";
1676 case LIBUSB_ERROR_NOT_FOUND:
1677 return "Entity not found";
1678 case LIBUSB_ERROR_BUSY:
1679 return "Resource busy";
1680 case LIBUSB_ERROR_TIMEOUT:
1681 return "Operation timed out";
1682 case LIBUSB_ERROR_OVERFLOW:
1684 case LIBUSB_ERROR_PIPE:
1685 return "Pipe error";
1686 case LIBUSB_ERROR_INTERRUPTED:
1687 return "System call interrupted (perhaps due to signal)";
1688 case LIBUSB_ERROR_NO_MEM:
1689 return "Insufficient memory";
1690 case LIBUSB_ERROR_NOT_SUPPORTED:
1691 return "Operation not supported or unimplemented on this platform";
1692 case LIBUSB_ERROR_OTHER:
1693 return "Other error";
1695 return "Unknown error";