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>
34 static int usbi_debug = 0;
35 static int debug_fixed = 0;
38 const struct usbi_os_backend * const usbi_backend = &linux_usbfs_backend;
40 #error "Unsupported OS"
43 static struct list_head usb_devs;
44 static pthread_mutex_t usb_devs_lock = PTHREAD_MUTEX_INITIALIZER;
46 /* A list of open handles. Backends are free to traverse this if required. */
47 struct list_head usbi_open_devs;
48 pthread_mutex_t usbi_open_devs_lock = PTHREAD_MUTEX_INITIALIZER;
51 * \mainpage libusb-1.0 API Reference
53 * \section intro Introduction
55 * libusb is an open source library that allows you to communicate with USB
56 * devices from userspace. For more info, see the
57 * <a href="http://libusb.sourceforge.net">libusb homepage</a>.
59 * This documentation is aimed at application developers wishing to
60 * communicate with USB peripherals from their own software. After reviewing
61 * this documentation, feedback and questions can be sent to the
62 * <a href="http://sourceforge.net/mail/?group_id=1674">libusb-devel mailing
65 * This documentation assumes knowledge of how to operate USB devices from
66 * a software standpoint (descriptors, configurations, interfaces, endpoints,
67 * control/bulk/interrupt/isochronous transfers, etc). Full information
68 * can be found in the <a href="http://www.usb.org/developers/docs/">USB 2.0
69 * Specification</a> which is available for free download. You can probably
70 * find less verbose introductions by searching the web.
72 * \section features Library features
74 * - All transfer types supported (control/bulk/interrupt/isochronous)
75 * - 2 transfer interfaces:
76 * -# Synchronous (simple)
77 * -# Asynchronous (more complicated, but more powerful)
78 * - Thread safe (although the asynchronous interface means that you
79 * usually won't need to thread)
80 * - Lightweight with lean API
81 * - Compatible with libusb-0.1 through the libusb-compat-0.1 translation layer
83 * \section gettingstarted Getting Started
85 * To begin reading the API documentation, start with the Modules page which
86 * links to the different categories of libusb's functionality.
88 * One decision you will have to make is whether to use the synchronous
89 * or the asynchronous data transfer interface. The \ref io documentation
90 * provides some insight into this topic.
92 * Some example programs can be found in the libusb source distribution under
93 * the "examples" subdirectory. The libusb homepage includes a list of
94 * real-life project examples which use libusb.
96 * \section errorhandling Error handling
98 * libusb functions typically return 0 on success or a negative error code
99 * on failure. These negative error codes relate to LIBUSB_ERROR constants
100 * which are listed on the \ref misc "miscellaneous" documentation page.
102 * \section msglog Debug message logging
104 * libusb does not log any messages by default. Your application is therefore
105 * free to close stdout/stderr and those descriptors may be reused without
108 * The libusb_set_debug() function can be used to enable stdout/stderr logging
109 * of certain messages. Under standard configuration, libusb doesn't really
110 * log much at all, so you are advised to use this function to enable all
111 * error/warning/informational messages. It will help you debug problems with
114 * The LIBUSB_DEBUG environment variable can be used to enable message logging
115 * at run-time. This environment variable should be set to a number, which is
116 * interpreted the same as the libusb_set_debug() parameter. When this
117 * environment variable is set, the message logging verbosity level is fixed
118 * and libusb_set_debug() effectively does nothing.
120 * libusb can be compiled without any logging functions, useful for embedded
121 * systems. In this case, libusb_set_debug() and the LIBUSB_DEBUG environment
122 * variable have no effects.
124 * libusb can also be compiled with verbose debugging messages. When the
125 * library is compiled in this way, all messages of all verbosities are always
126 * logged. libusb_set_debug() and the LIBUSB_DEBUG environment variable have
129 * \section remarks Other remarks
131 * libusb does have imperfections. The \ref caveats "caveats" page attempts
136 * \page caveats Caveats
138 * \section devresets Device resets
140 * The libusb_reset_device() function allows you to reset a device. If your
141 * program has to call such a function, it should obviously be aware that
142 * the reset will cause device state to change (e.g. register values may be
145 * The problem is that any other program could reset the device your program
146 * is working with, at any time. libusb does not offer a mechanism to inform
147 * you when this has happened, so if someone else resets your device it will
148 * not be clear to your own program why the device state has changed.
150 * Ultimately, this is a limitation of writing drivers in userspace.
151 * Separation from the USB stack in the underlying kernel makes it difficult
152 * for the operating system to deliver such notifications to your program.
153 * The Linux kernel USB stack allows such reset notifications to be delivered
154 * to in-kernel USB drivers, but it is not clear how such notifications could
155 * be delivered to second-class drivers that live in userspace.
157 * \section blockonly Blocking-only functionality
159 * The functionality listed below is only available through synchronous,
160 * blocking functions. There are no asynchronous/non-blocking alternatives,
161 * and no clear ways of implementing these.
163 * - Configuration activation (libusb_set_configuration())
164 * - Interface/alternate setting activation (libusb_set_interface_alt_setting())
165 * - Releasing of interfaces (libusb_release_interface())
166 * - Clearing of halt/stall condition (libusb_clear_halt())
167 * - Device resets (libusb_reset_device())
169 * \section nohotplug No hotplugging
171 * libusb-1.0 lacks functionality for providing notifications of when devices
172 * are added or removed. This functionality is planned to be implemented
175 * That said, there is basic disconnection handling for open device handles:
176 * - If there are ongoing transfers, libusb's handle_events loop will detect
177 * disconnections and complete ongoing transfers with the
178 * LIBUSB_TRANSFER_NO_DEVICE status code.
179 * - Many functions such as libusb_set_configuration() return the special
180 * LIBUSB_ERROR_NO_DEVICE error code when the device has been disconnected.
182 * \section configsel Configuration selection and handling
184 * When libusb presents a device handle to an application, there is a chance
185 * that the corresponding device may be in unconfigured state. For devices
186 * with multiple configurations, there is also a chance that the configuration
187 * currently selected is not the one that the application wants to use.
189 * The obvious solution is to add a call to libusb_set_configuration() early
190 * on during your device initialization routines, but there are caveats to
192 * -# If the device is already in the desired configuration, calling
193 * libusb_set_configuration() using the same configuration value will cause
194 * a lightweight device reset. This may not be desirable behaviour.
195 * -# libusb will be unable to change configuration if the device is in
196 * another configuration and other programs or drivers have claimed
197 * interfaces under that configuration.
198 * -# In the case where the desired configuration is already active, libusb
199 * may not even be able to perform a lightweight device reset. For example,
200 * take my USB keyboard with fingerprint reader: I'm interested in driving
201 * the fingerprint reader interface through libusb, but the kernel's
202 * USB-HID driver will almost always have claimed the keyboard interface.
203 * Because the kernel has claimed an interface, it is not even possible to
204 * perform the lightweight device reset, so libusb_set_configuration() will
205 * fail. (Luckily the device in question only has a single configuration.)
207 * One solution to some of the above problems is to consider the currently
208 * active configuration. If the configuration we want is already active, then
209 * we don't have to select any configuration:
211 cfg = libusb_get_configuration(dev);
213 libusb_set_configuration(dev, desired);
216 * This is probably suitable for most scenarios, but is inherently racy:
217 * another application or driver may change the selected configuration
218 * <em>after</em> the libusb_get_configuration() call.
220 * Even in cases where libusb_set_configuration() succeeds, consider that other
221 * applications or drivers may change configuration after your application
222 * calls libusb_set_configuration().
224 * One possible way to lock your device into a specific configuration is as
226 * -# Set the desired configuration (or use the logic above to realise that
227 * it is already in the desired configuration)
228 * -# Claim the interface that you wish to use
229 * -# Check that the currently active configuration is the one that you want
232 * The above method works because once an interface is claimed, no application
233 * or driver is able to select another configuration.
237 * @defgroup lib Library initialization/deinitialization
238 * This page details how to initialize and deinitialize libusb. Initialization
239 * must be performed before using any libusb functionality, and similarly you
240 * must not call any libusb functions after deinitialization.
244 * @defgroup dev Device handling and enumeration
245 * The functionality documented below is designed to help with the following
247 * - Enumerating the USB devices currently attached to the system
248 * - Choosing a device to operate from your software
249 * - Opening and closing the chosen device
251 * \section nutshell In a nutshell...
253 * The description below really makes things sound more complicated than they
254 * actually are. The following sequence of function calls will be suitable
255 * for almost all scenarios and does not require you to have such a deep
256 * understanding of the resource management issues:
259 libusb_device **list;
260 libusb_device *found = NULL;
261 size_t cnt = libusb_get_device_list(&list);
267 for (i = 0; i < cnt; i++) {
268 libusb_device *device = list[i];
269 if (is_interesting(device)) {
276 libusb_device_handle *handle;
278 err = libusb_open(found, &handle);
284 libusb_free_device_list(list, 1);
287 * The two important points:
288 * - You asked libusb_free_device_list() to unreference the devices (2nd
290 * - You opened the device before freeing the list and unreferencing the
293 * If you ended up with a handle, you can now proceed to perform I/O on the
296 * \section devshandles Devices and device handles
297 * libusb has a concept of a USB device, represented by the
298 * \ref libusb_device opaque type. A device represents a USB device that
299 * is currently or was previously connected to the system. Using a reference
300 * to a device, you can determine certain information about the device (e.g.
301 * you can read the descriptor data).
303 * The libusb_get_device_list() function can be used to obtain a list of
304 * devices currently connected to the system. This is known as device
307 * Just because you have a reference to a device does not mean it is
308 * necessarily usable. The device may have been unplugged, you may not have
309 * permission to operate such device, or another program or driver may be
312 * When you've found a device that you'd like to operate, you must ask
313 * libusb to open the device using the libusb_open() function. Assuming
314 * success, libusb then returns you a <em>device handle</em>
315 * (a \ref libusb_device_handle pointer). All "real" I/O operations then
316 * operate on the handle rather than the original device pointer.
318 * \section devref Device discovery and reference counting
320 * Device discovery (i.e. calling libusb_get_device_list()) returns a
321 * freshly-allocated list of devices. The list itself must be freed when
322 * you are done with it. libusb also needs to know when it is OK to free
323 * the contents of the list - the devices themselves.
325 * To handle these issues, libusb provides you with two separate items:
326 * - A function to free the list itself
327 * - A reference counting system for the devices inside
329 * New devices presented by the libusb_get_device_list() function all have a
330 * reference count of 1. You can increase and decrease reference count using
331 * libusb_ref_device() and libusb_unref_device(). A device is destroyed when
332 * it's reference count reaches 0.
334 * With the above information in mind, the process of opening a device can
335 * be viewed as follows:
336 * -# Discover devices using libusb_get_device_list().
337 * -# Choose the device that you want to operate, and call libusb_open().
338 * -# Unref all devices in the discovered device list.
339 * -# Free the discovered device list.
341 * The order is important - you must not unreference the device before
342 * attempting to open it, because unreferencing it may destroy the device.
344 * For convenience, the libusb_free_device_list() function includes a
345 * parameter to optionally unreference all the devices in the list before
346 * freeing the list itself. This combines steps 3 and 4 above.
348 * As an implementation detail, libusb_open() actually adds a reference to
349 * the device in question. This is because the device remains available
350 * through the handle via libusb_get_device(). The reference is deleted during
354 /** @defgroup misc Miscellaneous */
356 /* we traverse usbfs without knowing how many devices we are going to find.
357 * so we create this discovered_devs model which is similar to a linked-list
358 * which grows when required. it can be freed once discovery has completed,
359 * eliminating the need for a list node in the libusb_device structure
361 #define DISCOVERED_DEVICES_SIZE_STEP 8
363 static struct discovered_devs *discovered_devs_alloc(void)
365 struct discovered_devs *ret =
366 malloc(sizeof(*ret) + (sizeof(void *) * DISCOVERED_DEVICES_SIZE_STEP));
370 ret->capacity = DISCOVERED_DEVICES_SIZE_STEP;
375 /* append a device to the discovered devices collection. may realloc itself,
376 * returning new discdevs. returns NULL on realloc failure. */
377 struct discovered_devs *discovered_devs_append(
378 struct discovered_devs *discdevs, struct libusb_device *dev)
380 size_t len = discdevs->len;
383 /* if there is space, just append the device */
384 if (len < discdevs->capacity) {
385 discdevs->devices[len] = libusb_ref_device(dev);
390 /* exceeded capacity, need to grow */
391 usbi_dbg("need to increase capacity");
392 capacity = discdevs->capacity + DISCOVERED_DEVICES_SIZE_STEP;
393 discdevs = realloc(discdevs,
394 sizeof(*discdevs) + (sizeof(void *) * capacity));
396 discdevs->capacity = capacity;
397 discdevs->devices[len] = libusb_ref_device(dev);
404 static void discovered_devs_free(struct discovered_devs *discdevs)
408 for (i = 0; i < discdevs->len; i++)
409 libusb_unref_device(discdevs->devices[i]);
414 /* Allocate a new device with a specific session ID. The returned device has
415 * a reference count of 1. */
416 struct libusb_device *usbi_alloc_device(unsigned long session_id)
418 size_t priv_size = usbi_backend->device_priv_size;
419 struct libusb_device *dev = malloc(sizeof(*dev) + priv_size);
425 r = pthread_mutex_init(&dev->lock, NULL);
430 dev->session_data = session_id;
431 memset(&dev->os_priv, 0, priv_size);
433 pthread_mutex_lock(&usb_devs_lock);
434 list_add(&dev->list, &usb_devs);
435 pthread_mutex_unlock(&usb_devs_lock);
439 /* Perform some final sanity checks on a newly discovered device. If this
440 * function fails (negative return code), the device should not be added
441 * to the discovered device list. */
442 int usbi_sanitize_device(struct libusb_device *dev)
445 unsigned char raw_desc[DEVICE_DESC_LENGTH];
446 uint8_t num_configurations;
449 r = usbi_backend->get_device_descriptor(dev, raw_desc, &host_endian);
453 num_configurations = raw_desc[DEVICE_DESC_LENGTH - 1];
454 if (num_configurations > USB_MAXCONFIG) {
455 usbi_err("too many configurations");
456 return LIBUSB_ERROR_IO;
457 } else if (num_configurations < 1) {
458 usbi_dbg("no configurations?");
459 return LIBUSB_ERROR_IO;
462 dev->num_configurations = num_configurations;
466 /* Examine libusb's internal list of known devices, looking for one with
467 * a specific session ID. Returns the matching device if it was found, and
469 struct libusb_device *usbi_get_device_by_session_id(unsigned long session_id)
471 struct libusb_device *dev;
472 struct libusb_device *ret = NULL;
474 pthread_mutex_lock(&usb_devs_lock);
475 list_for_each_entry(dev, &usb_devs, list)
476 if (dev->session_data == session_id) {
480 pthread_mutex_unlock(&usb_devs_lock);
486 * Returns a list of USB devices currently attached to the system. This is
487 * your entry point into finding a USB device to operate.
489 * You are expected to unreference all the devices when you are done with
490 * them, and then free the list with libusb_free_device_list(). Note that
491 * libusb_free_device_list() can unref all the devices for you. Be careful
492 * not to unreference a device you are about to open until after you have
495 * This return value of this function indicates the number of devices in
496 * the resultant list. The list is actually one element larger, as it is
499 * \param list output location for a list of devices. Must be later freed with
500 * libusb_free_device_list().
501 * \returns the number of devices in the outputted list, or LIBUSB_ERROR_NO_MEM
502 * on memory allocation failure.
504 API_EXPORTED ssize_t libusb_get_device_list(libusb_device ***list)
506 struct discovered_devs *discdevs = discovered_devs_alloc();
507 struct libusb_device **ret;
514 return LIBUSB_ERROR_NO_MEM;
516 r = usbi_backend->get_device_list(&discdevs);
522 /* convert discovered_devs into a list */
524 ret = malloc(sizeof(void *) * (len + 1));
526 len = LIBUSB_ERROR_NO_MEM;
531 for (i = 0; i < len; i++) {
532 struct libusb_device *dev = discdevs->devices[i];
533 ret[i] = libusb_ref_device(dev);
538 discovered_devs_free(discdevs);
543 * Frees a list of devices previously discovered using
544 * libusb_get_device_list(). If the unref_devices parameter is set, the
545 * reference count of each device in the list is decremented by 1.
546 * \param list the list to free
547 * \param unref_devices whether to unref the devices in the list
549 API_EXPORTED void libusb_free_device_list(libusb_device **list,
557 struct libusb_device *dev;
559 while ((dev = list[i++]) != NULL)
560 libusb_unref_device(dev);
566 * Get the number of the bus that a device is connected to.
567 * \param dev a device
568 * \returns the bus number
570 API_EXPORTED uint8_t libusb_get_bus_number(libusb_device *dev)
572 return dev->bus_number;
576 * Get the address of the device on the bus it is connected to.
577 * \param dev a device
578 * \returns the device address
580 API_EXPORTED uint8_t libusb_get_device_address(libusb_device *dev)
582 return dev->device_address;
586 * Convenience function to retrieve the wMaxPacketSize value for a particular
587 * endpoint in the active device configuration. This is useful for setting up
588 * isochronous transfers.
590 * \param dev a device
591 * \param endpoint address of the endpoint in question
592 * \returns the wMaxPacketSize value
593 * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
594 * \returns LIBUSB_ERROR_OTHER on other failure
596 API_EXPORTED int libusb_get_max_packet_size(libusb_device *dev,
597 unsigned char endpoint)
600 struct libusb_config_descriptor *config;
603 r = libusb_get_active_config_descriptor(dev, &config);
605 usbi_err("could not retrieve active config descriptor");
606 return LIBUSB_ERROR_OTHER;
609 r = LIBUSB_ERROR_NOT_FOUND;
610 for (iface_idx = 0; iface_idx < config->bNumInterfaces; iface_idx++) {
611 const struct libusb_interface *iface = &config->interface[iface_idx];
614 for (altsetting_idx = 0; altsetting_idx < iface->num_altsetting;
616 const struct libusb_interface_descriptor *altsetting
617 = &iface->altsetting[altsetting_idx];
620 for (ep_idx = 0; ep_idx < altsetting->bNumEndpoints; ep_idx++) {
621 const struct libusb_endpoint_descriptor *ep =
622 &altsetting->endpoint[ep_idx];
623 if (ep->bEndpointAddress == endpoint) {
624 r = ep->wMaxPacketSize;
632 libusb_free_config_descriptor(config);
637 * Increment the reference count of a device.
638 * \param dev the device to reference
639 * \returns the same device
641 API_EXPORTED libusb_device *libusb_ref_device(libusb_device *dev)
643 pthread_mutex_lock(&dev->lock);
645 pthread_mutex_unlock(&dev->lock);
650 * Decrement the reference count of a device. If the decrement operation
651 * causes the reference count to reach zero, the device shall be destroyed.
652 * \param dev the device to unreference
654 API_EXPORTED void libusb_unref_device(libusb_device *dev)
661 pthread_mutex_lock(&dev->lock);
662 refcnt = --dev->refcnt;
663 pthread_mutex_unlock(&dev->lock);
666 usbi_dbg("destroy device %d.%d", dev->bus_number, dev->device_address);
668 if (usbi_backend->destroy_device)
669 usbi_backend->destroy_device(dev);
671 pthread_mutex_lock(&usb_devs_lock);
672 list_del(&dev->list);
673 pthread_mutex_unlock(&usb_devs_lock);
680 * Open a device and obtain a device handle. A handle allows you to perform
681 * I/O on the device in question.
683 * Internally, this function adds a reference to the device and makes it
684 * available to you through libusb_get_device(). This reference is removed
685 * during libusb_close().
687 * This is a non-blocking function; no requests are sent over the bus.
689 * \param dev the device to open
690 * \param handle output location for the returned device handle pointer. Only
691 * populated when the return code is 0.
692 * \returns 0 on success
693 * \returns LIBUSB_ERROR_NO_MEM on memory allocation failure
694 * \returns LIBUSB_ERROR_ACCESS if the user has insufficient permissions
695 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
696 * \returns another LIBUSB_ERROR code on other failure
698 API_EXPORTED int libusb_open(libusb_device *dev, libusb_device_handle **handle)
700 struct libusb_device_handle *_handle;
701 size_t priv_size = usbi_backend->device_handle_priv_size;
703 usbi_dbg("open %d.%d", dev->bus_number, dev->device_address);
705 _handle = malloc(sizeof(*_handle) + priv_size);
707 return LIBUSB_ERROR_NO_MEM;
709 r = pthread_mutex_init(&_handle->lock, NULL);
711 return LIBUSB_ERROR_OTHER;
713 _handle->dev = libusb_ref_device(dev);
714 _handle->claimed_interfaces = 0;
715 memset(&_handle->os_priv, 0, priv_size);
717 r = usbi_backend->open(_handle);
719 libusb_unref_device(dev);
724 pthread_mutex_lock(&usbi_open_devs_lock);
725 list_add(&_handle->list, &usbi_open_devs);
726 pthread_mutex_unlock(&usbi_open_devs_lock);
732 * Convenience function for finding a device with a particular
733 * <tt>idVendor</tt>/<tt>idProduct</tt> combination. This function is intended
734 * for those scenarios where you are using libusb to knock up a quick test
735 * application - it allows you to avoid calling libusb_get_device_list() and
736 * worrying about traversing/freeing the list.
738 * This function has limitations and is hence not intended for use in real
739 * applications: if multiple devices have the same IDs it will only
740 * give you the first one, etc.
742 * \param vendor_id the idVendor value to search for
743 * \param product_id the idProduct value to search for
744 * \returns a handle for the first found device, or NULL on error or if the
745 * device could not be found. */
746 API_EXPORTED libusb_device_handle *libusb_open_device_with_vid_pid(
747 uint16_t vendor_id, uint16_t product_id)
749 struct libusb_device **devs;
750 struct libusb_device *found = NULL;
751 struct libusb_device *dev;
752 struct libusb_device_handle *handle = NULL;
756 if (libusb_get_device_list(&devs) < 0)
759 while ((dev = devs[i++]) != NULL) {
760 struct libusb_device_descriptor desc;
761 r = libusb_get_device_descriptor(dev, &desc);
764 if (desc.idVendor == vendor_id && desc.idProduct == product_id) {
771 r = libusb_open(found, &handle);
777 libusb_free_device_list(devs, 1);
781 static void do_close(struct libusb_device_handle *dev_handle)
783 usbi_backend->close(dev_handle);
784 libusb_unref_device(dev_handle->dev);
788 * Close a device handle. Should be called on all open handles before your
791 * Internally, this function destroys the reference that was added by
792 * libusb_open() on the given device.
794 * This is a non-blocking function; no requests are sent over the bus.
796 * \param dev_handle the handle to close
798 API_EXPORTED void libusb_close(libusb_device_handle *dev_handle)
804 pthread_mutex_lock(&usbi_open_devs_lock);
805 list_del(&dev_handle->list);
806 pthread_mutex_unlock(&usbi_open_devs_lock);
808 do_close(dev_handle);
813 * Get the underlying device for a handle. This function does not modify
814 * the reference count of the returned device, so do not feel compelled to
815 * unreference it when you are done.
816 * \param dev_handle a device handle
817 * \returns the underlying device
819 API_EXPORTED libusb_device *libusb_get_device(libusb_device_handle *dev_handle)
821 return dev_handle->dev;
825 * Determine the bConfigurationValue of the currently active configuration.
827 * You could formulate your own control request to obtain this information,
828 * but this function has the advantage that it may be able to retrieve the
829 * information from operating system caches (no I/O involved).
831 * If the OS does not cache this information, then this function will block
832 * while a control transfer is submitted to retrieve the information.
834 * This function will return a value of 0 in the <tt>config</tt> output
835 * parameter if the device is in unconfigured state.
837 * \param dev a device handle
838 * \param config output location for the bConfigurationValue of the active
839 * configuration (only valid for return code 0)
840 * \returns 0 on success
841 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
842 * \returns another LIBUSB_ERROR code on other failure
844 API_EXPORTED int libusb_get_configuration(libusb_device_handle *dev,
847 int r = LIBUSB_ERROR_NOT_SUPPORTED;
850 if (usbi_backend->get_configuration)
851 r = usbi_backend->get_configuration(dev, config);
853 if (r == LIBUSB_ERROR_NOT_SUPPORTED) {
855 usbi_dbg("falling back to control message");
856 r = libusb_control_transfer(dev, LIBUSB_ENDPOINT_IN,
857 LIBUSB_REQUEST_GET_CONFIGURATION, 0, 0, &tmp, 1, 1000);
859 usbi_err("zero bytes returned in ctrl transfer?");
865 usbi_dbg("control failed, error %d", r);
870 usbi_dbg("active config %d", *config);
876 * Set the active configuration for a device.
878 * The operating system may or may not have already set an active
879 * configuration on the device. It is up to your application to ensure the
880 * correct configuration is selected before you attempt to claim interfaces
881 * and perform other operations.
883 * If you call this function on a device already configured with the selected
884 * configuration, then this function will act as a lightweight device reset:
885 * it will issue a SET_CONFIGURATION request using the current configuration,
886 * causing most USB-related device state to be reset (altsetting reset to zero,
887 * endpoint halts cleared, toggles reset).
889 * You cannot change/reset configuration if your application has claimed
890 * interfaces - you should free them with libusb_release_interface() first.
891 * You cannot change/reset configuration if other applications or drivers have
892 * claimed interfaces.
894 * A configuration value of -1 will put the device in unconfigured state.
895 * The USB specifications state that a configuration value of 0 does this,
896 * however buggy devices exist which actually have a configuration 0.
898 * You should always use this function rather than formulating your own
899 * SET_CONFIGURATION control request. This is because the underlying operating
900 * system needs to know when such changes happen.
902 * This is a blocking function.
904 * \param dev a device handle
905 * \param configuration the bConfigurationValue of the configuration you
906 * wish to activate, or -1 if you wish to put the device in unconfigured state
907 * \returns 0 on success
908 * \returns LIBUSB_ERROR_NOT_FOUND if the requested configuration does not exist
909 * \returns LIBUSB_ERROR_BUSY if interfaces are currently claimed
910 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
911 * \returns another LIBUSB_ERROR code on other failure
913 API_EXPORTED int libusb_set_configuration(libusb_device_handle *dev,
916 usbi_dbg("configuration %d", configuration);
917 return usbi_backend->set_configuration(dev, configuration);
921 * Claim an interface on a given device handle. You must claim the interface
922 * you wish to use before you can perform I/O on any of its endpoints.
924 * It is legal to attempt to claim an already-claimed interface, in which
925 * case libusb just returns 0 without doing anything.
927 * Claiming of interfaces is a purely logical operation; it does not cause
928 * any requests to be sent over the bus. Interface claiming is used to
929 * instruct the underlying operating system that your application wishes
930 * to take ownership of the interface.
932 * This is a non-blocking function.
934 * \param dev a device handle
935 * \param interface_number the <tt>bInterfaceNumber</tt> of the interface you
937 * \returns 0 on success
938 * \returns LIBUSB_ERROR_NOT_FOUND if the requested interface does not exist
939 * \returns LIBUSB_ERROR_BUSY if another program or driver has claimed the
941 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
942 * \returns a LIBUSB_ERROR code on other failure
944 API_EXPORTED int libusb_claim_interface(libusb_device_handle *dev,
945 int interface_number)
949 usbi_dbg("interface %d", interface_number);
950 if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
951 return LIBUSB_ERROR_INVALID_PARAM;
953 pthread_mutex_lock(&dev->lock);
954 if (dev->claimed_interfaces & (1 << interface_number))
957 r = usbi_backend->claim_interface(dev, interface_number);
959 dev->claimed_interfaces |= 1 << interface_number;
962 pthread_mutex_unlock(&dev->lock);
967 * Release an interface previously claimed with libusb_claim_interface(). You
968 * should release all claimed interfaces before closing a device handle.
970 * This is a blocking function. A SET_INTERFACE control request will be sent
971 * to the device, resetting interface state to the first alternate setting.
973 * \param dev a device handle
974 * \param interface_number the <tt>bInterfaceNumber</tt> of the
975 * previously-claimed interface
976 * \returns 0 on success
977 * \returns LIBUSB_ERROR_NOT_FOUND if the interface was not claimed
978 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
979 * \returns another LIBUSB_ERROR code on other failure
981 API_EXPORTED int libusb_release_interface(libusb_device_handle *dev,
982 int interface_number)
986 usbi_dbg("interface %d", interface_number);
987 if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
988 return LIBUSB_ERROR_INVALID_PARAM;
990 pthread_mutex_lock(&dev->lock);
991 if (!(dev->claimed_interfaces & (1 << interface_number))) {
992 r = LIBUSB_ERROR_NOT_FOUND;
996 r = usbi_backend->release_interface(dev, interface_number);
998 dev->claimed_interfaces &= ~(1 << interface_number);
1001 pthread_mutex_unlock(&dev->lock);
1006 * Activate an alternate setting for an interface. The interface must have
1007 * been previously claimed with libusb_claim_interface().
1009 * You should always use this function rather than formulating your own
1010 * SET_INTERFACE control request. This is because the underlying operating
1011 * system needs to know when such changes happen.
1013 * This is a blocking function.
1015 * \param dev a device handle
1016 * \param interface_number the <tt>bInterfaceNumber</tt> of the
1017 * previously-claimed interface
1018 * \param alternate_setting the <tt>bAlternateSetting</tt> of the alternate
1019 * setting to activate
1020 * \returns 0 on success
1021 * \returns LIBUSB_ERROR_NOT_FOUND if the interface was not claimed, or the
1022 * requested alternate setting does not exist
1023 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1024 * \returns another LIBUSB_ERROR code on other failure
1026 API_EXPORTED int libusb_set_interface_alt_setting(libusb_device_handle *dev,
1027 int interface_number, int alternate_setting)
1029 usbi_dbg("interface %d altsetting %d", interface_number, alternate_setting);
1030 if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
1031 return LIBUSB_ERROR_INVALID_PARAM;
1033 pthread_mutex_lock(&dev->lock);
1034 if (!(dev->claimed_interfaces & (1 << interface_number))) {
1035 pthread_mutex_unlock(&dev->lock);
1036 return LIBUSB_ERROR_NOT_FOUND;
1038 pthread_mutex_unlock(&dev->lock);
1040 return usbi_backend->set_interface_altsetting(dev, interface_number,
1045 * Clear the halt/stall condition for an endpoint. Endpoints with halt status
1046 * are unable to receive or transmit data until the halt condition is stalled.
1048 * You should cancel all pending transfers before attempting to clear the halt
1051 * This is a blocking function.
1053 * \param dev a device handle
1054 * \param endpoint the endpoint to clear halt status
1055 * \returns 0 on success
1056 * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
1057 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1058 * \returns another LIBUSB_ERROR code on other failure
1060 API_EXPORTED int libusb_clear_halt(libusb_device_handle *dev,
1061 unsigned char endpoint)
1063 usbi_dbg("endpoint %x", endpoint);
1064 return usbi_backend->clear_halt(dev, endpoint);
1068 * Perform a USB port reset to reinitialize a device. The system will attempt
1069 * to restore the previous configuration and alternate settings after the
1070 * reset has completed.
1072 * If the reset fails, the descriptors change, or the previous state cannot be
1073 * restored, the device will appear to be disconnected and reconnected. This
1074 * means that the device handle is no longer valid (you should close it) and
1075 * rediscover the device. A return code of LIBUSB_ERROR_NOT_FOUND indicates
1076 * when this is the case.
1078 * This is a blocking function which usually incurs a noticeable delay.
1080 * \param dev a handle of the device to reset
1081 * \returns 0 on success
1082 * \returns LIBUSB_ERROR_NOT_FOUND if re-enumeration is required, or if the
1083 * device has been disconnected
1084 * \returns another LIBUSB_ERROR code on other failure
1086 API_EXPORTED int libusb_reset_device(libusb_device_handle *dev)
1089 return usbi_backend->reset_device(dev);
1093 * Determine if a kernel driver is active on an interface. If a kernel driver
1094 * is active, you cannot claim the interface, and libusb will be unable to
1097 * \param dev a device handle
1098 * \param interface the interface to check
1099 * \returns 0 if no kernel driver is active
1100 * \returns 1 if a kernel driver is active
1101 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1102 * \returns another LIBUSB_ERROR code on other failure
1103 * \see libusb_detach_kernel_driver()
1105 API_EXPORTED int libusb_kernel_driver_active(libusb_device_handle *dev,
1108 usbi_dbg("interface %d", interface);
1109 if (usbi_backend->kernel_driver_active)
1110 return usbi_backend->kernel_driver_active(dev, interface);
1112 return LIBUSB_ERROR_NOT_SUPPORTED;
1116 * Detach a kernel driver from an interface. If successful, you will then be
1117 * able to claim the interface and perform I/O.
1119 * \param dev a device handle
1120 * \param interface the interface to detach the driver from
1121 * \returns 0 on success
1122 * \returns LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
1123 * \returns LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
1124 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1125 * \returns another LIBUSB_ERROR code on other failure
1126 * \see libusb_kernel_driver_active()
1128 API_EXPORTED int libusb_detach_kernel_driver(libusb_device_handle *dev,
1131 usbi_dbg("interface %d", interface);
1132 if (usbi_backend->detach_kernel_driver)
1133 return usbi_backend->detach_kernel_driver(dev, interface);
1135 return LIBUSB_ERROR_NOT_SUPPORTED;
1139 * Set message verbosity.
1140 * - Level 0: no messages ever printed by the library (default)
1141 * - Level 1: error messages are printed to stderr
1142 * - Level 2: warning and error messages are printed to stderr
1143 * - Level 3: informational messages are printed to stdout, warning and error
1144 * messages are printed to stderr
1146 * The default level is 0, which means no messages are ever printed. If you
1147 * choose to increase the message verbosity level, ensure that your
1148 * application does not close the stdout/stderr file descriptors.
1150 * You are advised to set level 3. libusb is conservative with it's message
1151 * logging and most of the time, will only log messages that explain error
1152 * conditions and other oddities. This will help you debug your software.
1154 * If the LIBUSB_DEBUG environment variable was set when libusb was
1155 * initialized, this function does nothing: the message verbosity is fixed
1156 * to the value in the environment variable.
1158 * If libusb was compiled without any message logging, this function does
1159 * nothing: you'll never get any messages.
1161 * If libusb was compiled with verbose debug message logging, this function
1162 * does nothing: you'll always get messages from all levels.
1164 * \param level debug level to set
1166 API_EXPORTED void libusb_set_debug(int level)
1173 * Initialize libusb. This function must be called before calling any other
1175 * \returns 0 on success, or a LIBUSB_ERROR code on failure
1177 API_EXPORTED int libusb_init(void)
1179 char *dbg = getenv("LIBUSB_DEBUG");
1181 usbi_debug = atoi(dbg);
1187 if (usbi_backend->init) {
1188 int r = usbi_backend->init();
1193 list_init(&usb_devs);
1194 list_init(&usbi_open_devs);
1200 * Deinitialize libusb. Should be called after closing all open devices and
1201 * before your application terminates.
1203 API_EXPORTED void libusb_exit(void)
1207 pthread_mutex_lock(&usbi_open_devs_lock);
1208 if (!list_empty(&usbi_open_devs)) {
1209 struct libusb_device_handle *devh;
1210 struct libusb_device_handle *tmp;
1212 usbi_dbg("naughty app left some devices open!");
1213 list_for_each_entry_safe(devh, tmp, &usbi_open_devs, list) {
1214 list_del(&devh->list);
1219 pthread_mutex_unlock(&usbi_open_devs_lock);
1221 if (usbi_backend->exit)
1222 usbi_backend->exit();
1225 void usbi_log(enum usbi_log_level level, const char *function,
1226 const char *format, ...)
1229 FILE *stream = stdout;
1232 #ifndef ENABLE_DEBUG_LOGGING
1235 if (level == LOG_LEVEL_WARNING && usbi_debug < 2)
1237 if (level == LOG_LEVEL_INFO && usbi_debug < 3)
1242 case LOG_LEVEL_INFO:
1245 case LOG_LEVEL_WARNING:
1249 case LOG_LEVEL_ERROR:
1253 case LOG_LEVEL_DEBUG:
1263 fprintf(stream, "libusb:%s [%s] ", prefix, function);
1265 va_start (args, format);
1266 vfprintf(stream, format, args);
1269 fprintf(stream, "\n");