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.
184 * @defgroup lib Library initialization/deinitialization
185 * This page details how to initialize and deinitialize libusb. Initialization
186 * must be performed before using any libusb functionality, and similarly you
187 * must not call any libusb functions after deinitialization.
191 * @defgroup dev Device handling and enumeration
192 * The functionality documented below is designed to help with the following
194 * - Enumerating the USB devices currently attached to the system
195 * - Choosing a device to operate from your software
196 * - Opening and closing the chosen device
198 * \section nutshell In a nutshell...
200 * The description below really makes things sound more complicated than they
201 * actually are. The following sequence of function calls will be suitable
202 * for almost all scenarios and does not require you to have such a deep
203 * understanding of the resource management issues:
206 libusb_device **list;
207 libusb_device *found = NULL;
208 size_t cnt = libusb_get_device_list(&list);
213 for (i = 0; i < cnt; i++) {
214 libusb_device *device = list[i];
215 if (is_interesting(device)) {
222 libusb_device_handle *handle = libusb_open(found);
226 libusb_free_device_list(list, 1);
229 * The two important points:
230 * - You asked libusb_free_device_list() to unreference the devices (2nd
232 * - You opened the device before freeing the list and unreferencing the
235 * If you ended up with a handle, you can now proceed to perform I/O on the
238 * \section devshandles Devices and device handles
239 * libusb has a concept of a USB device, represented by the
240 * \ref libusb_device opaque type. A device represents a USB device that
241 * is currently or was previously connected to the system. Using a reference
242 * to a device, you can determine certain information about the device (e.g.
243 * you can read the descriptor data).
245 * The libusb_get_device_list() function can be used to obtain a list of
246 * devices currently connected to the system. This is known as device
249 * Just because you have a reference to a device does not mean it is
250 * necessarily usable. The device may have been unplugged, you may not have
251 * permission to operate such device, or another program or driver may be
254 * When you've found a device that you'd like to operate, you must ask
255 * libusb to open the device using the libusb_open() function. Assuming
256 * success, libusb then returns you a <em>device handle</em>
257 * (a \ref libusb_device_handle pointer). All "real" I/O operations then
258 * operate on the handle rather than the original device pointer.
260 * \section devref Device discovery and reference counting
262 * Device discovery (i.e. calling libusb_get_device_list()) returns a
263 * freshly-allocated list of devices. The list itself must be freed when
264 * you are done with it. libusb also needs to know when it is OK to free
265 * the contents of the list - the devices themselves.
267 * To handle these issues, libusb provides you with two separate items:
268 * - A function to free the list itself
269 * - A reference counting system for the devices inside
271 * New devices presented by the libusb_get_device_list() function all have a
272 * reference count of 1. You can increase and decrease reference count using
273 * libusb_ref_device() and libusb_unref_device(). A device is destroyed when
274 * it's reference count reaches 0.
276 * With the above information in mind, the process of opening a device can
277 * be viewed as follows:
278 * -# Discover devices using libusb_get_device_list().
279 * -# Choose the device that you want to operate, and call libusb_open().
280 * -# Unref all devices in the discovered device list.
281 * -# Free the discovered device list.
283 * The order is important - you must not unreference the device before
284 * attempting to open it, because unreferencing it may destroy the device.
286 * For convenience, the libusb_free_device_list() function includes a
287 * parameter to optionally unreference all the devices in the list before
288 * freeing the list itself. This combines steps 3 and 4 above.
290 * As an implementation detail, libusb_open() actually adds a reference to
291 * the device in question. This is because the device remains available
292 * through the handle via libusb_get_device(). The reference is deleted during
296 /** @defgroup misc Miscellaneous */
298 /* we traverse usbfs without knowing how many devices we are going to find.
299 * so we create this discovered_devs model which is similar to a linked-list
300 * which grows when required. it can be freed once discovery has completed,
301 * eliminating the need for a list node in the libusb_device structure
303 #define DISCOVERED_DEVICES_SIZE_STEP 8
305 static struct discovered_devs *discovered_devs_alloc(void)
307 struct discovered_devs *ret =
308 malloc(sizeof(*ret) + (sizeof(void *) * DISCOVERED_DEVICES_SIZE_STEP));
312 ret->capacity = DISCOVERED_DEVICES_SIZE_STEP;
317 /* append a device to the discovered devices collection. may realloc itself,
318 * returning new discdevs. returns NULL on realloc failure. */
319 struct discovered_devs *discovered_devs_append(
320 struct discovered_devs *discdevs, struct libusb_device *dev)
322 size_t len = discdevs->len;
325 /* if there is space, just append the device */
326 if (len < discdevs->capacity) {
327 discdevs->devices[len] = libusb_ref_device(dev);
332 /* exceeded capacity, need to grow */
333 usbi_dbg("need to increase capacity");
334 capacity = discdevs->capacity + DISCOVERED_DEVICES_SIZE_STEP;
335 discdevs = realloc(discdevs,
336 sizeof(*discdevs) + (sizeof(void *) * capacity));
338 discdevs->capacity = capacity;
339 discdevs->devices[len] = libusb_ref_device(dev);
346 static void discovered_devs_free(struct discovered_devs *discdevs)
350 for (i = 0; i < discdevs->len; i++)
351 libusb_unref_device(discdevs->devices[i]);
356 /* Allocate a new device with a specific session ID. The returned device has
357 * a reference count of 1. */
358 struct libusb_device *usbi_alloc_device(unsigned long session_id)
360 size_t priv_size = usbi_backend->device_priv_size;
361 struct libusb_device *dev = malloc(sizeof(*dev) + priv_size);
367 r = pthread_mutex_init(&dev->lock, NULL);
372 dev->session_data = session_id;
373 memset(&dev->os_priv, 0, priv_size);
375 pthread_mutex_lock(&usb_devs_lock);
376 list_add(&dev->list, &usb_devs);
377 pthread_mutex_unlock(&usb_devs_lock);
381 /* Perform some final sanity checks on a newly discovered device. If this
382 * function fails (negative return code), the device should not be added
383 * to the discovered device list. */
384 int usbi_sanitize_device(struct libusb_device *dev)
387 unsigned char raw_desc[DEVICE_DESC_LENGTH];
388 uint8_t num_configurations;
391 r = usbi_backend->get_device_descriptor(dev, raw_desc, &host_endian);
395 num_configurations = raw_desc[DEVICE_DESC_LENGTH - 1];
396 if (num_configurations > USB_MAXCONFIG) {
397 usbi_err("too many configurations");
398 return LIBUSB_ERROR_IO;
399 } else if (num_configurations < 1) {
400 usbi_dbg("no configurations?");
401 return LIBUSB_ERROR_IO;
404 dev->num_configurations = num_configurations;
408 /* Examine libusb's internal list of known devices, looking for one with
409 * a specific session ID. Returns the matching device if it was found, and
411 struct libusb_device *usbi_get_device_by_session_id(unsigned long session_id)
413 struct libusb_device *dev;
414 struct libusb_device *ret = NULL;
416 pthread_mutex_lock(&usb_devs_lock);
417 list_for_each_entry(dev, &usb_devs, list)
418 if (dev->session_data == session_id) {
422 pthread_mutex_unlock(&usb_devs_lock);
428 * Returns a list of USB devices currently attached to the system. This is
429 * your entry point into finding a USB device to operate.
431 * You are expected to unreference all the devices when you are done with
432 * them, and then free the list with libusb_free_device_list(). Note that
433 * libusb_free_device_list() can unref all the devices for you. Be careful
434 * not to unreference a device you are about to open until after you have
437 * This return value of this function indicates the number of devices in
438 * the resultant list. The list is actually one element larger, as it is
441 * \param list output location for a list of devices. Must be later freed with
442 * libusb_free_device_list().
443 * \returns the number of devices in the outputted list, or LIBUSB_ERROR_NO_MEM
444 * on memory allocation failure.
446 API_EXPORTED ssize_t libusb_get_device_list(libusb_device ***list)
448 struct discovered_devs *discdevs = discovered_devs_alloc();
449 struct libusb_device **ret;
456 return LIBUSB_ERROR_NO_MEM;
458 r = usbi_backend->get_device_list(&discdevs);
464 /* convert discovered_devs into a list */
466 ret = malloc(sizeof(void *) * (len + 1));
468 len = LIBUSB_ERROR_NO_MEM;
473 for (i = 0; i < len; i++) {
474 struct libusb_device *dev = discdevs->devices[i];
475 ret[i] = libusb_ref_device(dev);
480 discovered_devs_free(discdevs);
485 * Frees a list of devices previously discovered using
486 * libusb_get_device_list(). If the unref_devices parameter is set, the
487 * reference count of each device in the list is decremented by 1.
488 * \param list the list to free
489 * \param unref_devices whether to unref the devices in the list
491 API_EXPORTED void libusb_free_device_list(libusb_device **list,
499 struct libusb_device *dev;
501 while ((dev = list[i++]) != NULL)
502 libusb_unref_device(dev);
508 * Get the number of the bus that a device is connected to.
509 * \param dev a device
510 * \returns the bus number
512 API_EXPORTED uint8_t libusb_get_bus_number(libusb_device *dev)
514 return dev->bus_number;
518 * Get the address of the device on the bus it is connected to.
519 * \param dev a device
520 * \returns the device address
522 API_EXPORTED uint8_t libusb_get_device_address(libusb_device *dev)
524 return dev->device_address;
528 * Convenience function to retrieve the wMaxPacketSize value for a particular
529 * endpoint in the active device configuration. This is useful for setting up
530 * isochronous transfers.
532 * \param dev a device
533 * \param endpoint address of the endpoint in question
534 * \returns the wMaxPacketSize value
535 * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
536 * \returns LIBUSB_ERROR_OTHER on other failure
538 API_EXPORTED int libusb_get_max_packet_size(libusb_device *dev,
539 unsigned char endpoint)
542 struct libusb_config_descriptor *config;
545 r = libusb_get_active_config_descriptor(dev, &config);
547 usbi_err("could not retrieve active config descriptor");
548 return LIBUSB_ERROR_OTHER;
551 r = LIBUSB_ERROR_NOT_FOUND;
552 for (iface_idx = 0; iface_idx < config->bNumInterfaces; iface_idx++) {
553 const struct libusb_interface *iface = &config->interface[iface_idx];
556 for (altsetting_idx = 0; altsetting_idx < iface->num_altsetting;
558 const struct libusb_interface_descriptor *altsetting
559 = &iface->altsetting[altsetting_idx];
562 for (ep_idx = 0; ep_idx < altsetting->bNumEndpoints; ep_idx++) {
563 const struct libusb_endpoint_descriptor *ep =
564 &altsetting->endpoint[ep_idx];
565 if (ep->bEndpointAddress == endpoint) {
566 r = ep->wMaxPacketSize;
574 libusb_free_config_descriptor(config);
579 * Increment the reference count of a device.
580 * \param dev the device to reference
581 * \returns the same device
583 API_EXPORTED libusb_device *libusb_ref_device(libusb_device *dev)
585 pthread_mutex_lock(&dev->lock);
587 pthread_mutex_unlock(&dev->lock);
592 * Decrement the reference count of a device. If the decrement operation
593 * causes the reference count to reach zero, the device shall be destroyed.
594 * \param dev the device to unreference
596 API_EXPORTED void libusb_unref_device(libusb_device *dev)
603 pthread_mutex_lock(&dev->lock);
604 refcnt = --dev->refcnt;
605 pthread_mutex_unlock(&dev->lock);
608 usbi_dbg("destroy device %d.%d", dev->bus_number, dev->device_address);
610 if (usbi_backend->destroy_device)
611 usbi_backend->destroy_device(dev);
613 pthread_mutex_lock(&usb_devs_lock);
614 list_del(&dev->list);
615 pthread_mutex_unlock(&usb_devs_lock);
622 * Open a device and obtain a device handle. A handle allows you to perform
623 * I/O on the device in question.
625 * Internally, this function adds a reference to the device and makes it
626 * available to you through libusb_get_device(). This reference is removed
627 * during libusb_close().
629 * This is a non-blocking function; no requests are sent over the bus.
631 * \param dev the device to open
632 * \param handle output location for the returned device handle pointer. Only
633 * populated when the return code is 0.
634 * \returns 0 on success
635 * \returns LIBUSB_ERROR_NO_MEM on memory allocation failure
636 * \returns LIBUSB_ERROR_ACCESS if the user has insufficient permissions
637 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
638 * \returns another LIBUSB_ERROR code on other failure
640 API_EXPORTED int libusb_open(libusb_device *dev, libusb_device_handle **handle)
642 struct libusb_device_handle *_handle;
643 size_t priv_size = usbi_backend->device_handle_priv_size;
645 usbi_dbg("open %d.%d", dev->bus_number, dev->device_address);
647 _handle = malloc(sizeof(*_handle) + priv_size);
649 return LIBUSB_ERROR_NO_MEM;
651 r = pthread_mutex_init(&_handle->lock, NULL);
653 return LIBUSB_ERROR_OTHER;
655 _handle->dev = libusb_ref_device(dev);
656 _handle->claimed_interfaces = 0;
657 memset(&_handle->os_priv, 0, priv_size);
659 r = usbi_backend->open(_handle);
661 libusb_unref_device(dev);
666 pthread_mutex_lock(&usbi_open_devs_lock);
667 list_add(&_handle->list, &usbi_open_devs);
668 pthread_mutex_unlock(&usbi_open_devs_lock);
674 * Convenience function for finding a device with a particular
675 * <tt>idVendor</tt>/<tt>idProduct</tt> combination. This function is intended
676 * for those scenarios where you are using libusb to knock up a quick test
677 * application - it allows you to avoid calling libusb_get_device_list() and
678 * worrying about traversing/freeing the list.
680 * This function has limitations and is hence not intended for use in real
681 * applications: if multiple devices have the same IDs it will only
682 * give you the first one, etc.
684 * \param vendor_id the idVendor value to search for
685 * \param product_id the idProduct value to search for
686 * \returns a handle for the first found device, or NULL on error or if the
687 * device could not be found. */
688 API_EXPORTED libusb_device_handle *libusb_open_device_with_vid_pid(
689 uint16_t vendor_id, uint16_t product_id)
691 struct libusb_device **devs;
692 struct libusb_device *found = NULL;
693 struct libusb_device *dev;
694 struct libusb_device_handle *handle = NULL;
698 if (libusb_get_device_list(&devs) < 0)
701 while ((dev = devs[i++]) != NULL) {
702 struct libusb_device_descriptor desc;
703 r = libusb_get_device_descriptor(dev, &desc);
706 if (desc.idVendor == vendor_id && desc.idProduct == product_id) {
713 r = libusb_open(found, &handle);
719 libusb_free_device_list(devs, 1);
723 static void do_close(struct libusb_device_handle *dev_handle)
725 usbi_backend->close(dev_handle);
726 libusb_unref_device(dev_handle->dev);
730 * Close a device handle. Should be called on all open handles before your
733 * Internally, this function destroys the reference that was added by
734 * libusb_open() on the given device.
736 * This is a non-blocking function; no requests are sent over the bus.
738 * \param dev_handle the handle to close
740 API_EXPORTED void libusb_close(libusb_device_handle *dev_handle)
746 pthread_mutex_lock(&usbi_open_devs_lock);
747 list_del(&dev_handle->list);
748 pthread_mutex_unlock(&usbi_open_devs_lock);
750 do_close(dev_handle);
755 * Get the underlying device for a handle. This function does not modify
756 * the reference count of the returned device, so do not feel compelled to
757 * unreference it when you are done.
758 * \param dev_handle a device handle
759 * \returns the underlying device
761 API_EXPORTED libusb_device *libusb_get_device(libusb_device_handle *dev_handle)
763 return dev_handle->dev;
767 * Determine the bConfigurationValue of the currently active configuration.
769 * You could formulate your own control request to obtain this information,
770 * but this function has the advantage that it may be able to retrieve the
771 * information from operating system caches (no I/O involved).
773 * If the OS does not cache this information, then this function will block
774 * while a control transfer is submitted to retrieve the information.
776 * This function will return a value of 0 in the <tt>config</tt> output
777 * parameter if the device is in unconfigured state.
779 * \param dev a device handle
780 * \param config output location for the bConfigurationValue of the active
781 * configuration (only valid for return code 0)
782 * \returns 0 on success
783 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
784 * \returns another LIBUSB_ERROR code on other failure
786 API_EXPORTED int libusb_get_configuration(libusb_device_handle *dev,
789 int r = LIBUSB_ERROR_NOT_SUPPORTED;
792 if (usbi_backend->get_configuration)
793 r = usbi_backend->get_configuration(dev, config);
795 if (r == LIBUSB_ERROR_NOT_SUPPORTED) {
797 usbi_dbg("falling back to control message");
798 r = libusb_control_transfer(dev, LIBUSB_ENDPOINT_IN,
799 LIBUSB_REQUEST_GET_CONFIGURATION, 0, 0, &tmp, 1, 1000);
801 usbi_err("zero bytes returned in ctrl transfer?");
807 usbi_dbg("control failed, error %d", r);
812 usbi_dbg("active config %d", *config);
818 * Set the active configuration for a device. The operating system may have
819 * already set an active configuration on the device, but for portability
820 * reasons you should use this function to select the configuration you want
821 * before claiming any interfaces.
823 * If you wish to change to another configuration at some later time, you
824 * must release all claimed interfaces using libusb_release_interface() before
825 * setting a new active configuration. Also, consider that other applications
826 * or drivers may have claimed interfaces, in which case you are unable to
827 * change the configuration.
829 * A configuration value of -1 will put the device in unconfigured state.
830 * The USB specifications state that a configuration value of 0 does this,
831 * however buggy devices exist which actually have a configuration 0.
833 * This function checks the current active configuration before setting the
834 * new one. If the requested configuration is already active, this function
837 * This function is inherently racy: there is a small chance that someone may
838 * change the configuration after libusb has determined the active
839 * configuration but before the new one has been applied (or not applied, if
840 * libusb thinks the specified configuration is already active). After changing
841 * configuration, you may choose to claim an interface and then call
842 * libusb_get_configuration() to ensure that the requested change actually took
843 * place. The fact that you have now claimed an interface means that nobody
844 * else can change the configuration.
846 * You should always use this function rather than formulating your own
847 * SET_CONFIGURATION control request. This is because the underlying operating
848 * system needs to know when such changes happen.
850 * This is a blocking function.
852 * \param dev a device handle
853 * \param configuration the bConfigurationValue of the configuration you
854 * wish to activate, or -1 if you wish to put the device in unconfigured state
855 * \returns 1 if the configuration was changed
856 * \returns 0 if the configuration was already active
857 * \returns LIBUSB_ERROR_NOT_FOUND if the requested configuration does not exist
858 * \returns LIBUSB_ERROR_BUSY if interfaces are currently claimed
859 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
860 * \returns another LIBUSB_ERROR code on other failure
862 API_EXPORTED int libusb_set_configuration(libusb_device_handle *dev,
868 usbi_dbg("configuration %d", configuration);
869 r = libusb_get_configuration(dev, &active);
874 if (active == configuration) {
875 usbi_dbg("already active");
879 r = usbi_backend->set_configuration(dev, configuration);
886 * Claim an interface on a given device handle. You must claim the interface
887 * you wish to use before you can perform I/O on any of its endpoints.
889 * It is legal to attempt to claim an already-claimed interface, in which
890 * case libusb just returns 0 without doing anything.
892 * Claiming of interfaces is a purely logical operation; it does not cause
893 * any requests to be sent over the bus. Interface claiming is used to
894 * instruct the underlying operating system that your application wishes
895 * to take ownership of the interface.
897 * This is a non-blocking function.
899 * \param dev a device handle
900 * \param interface_number the <tt>bInterfaceNumber</tt> of the interface you
902 * \returns 0 on success
903 * \returns LIBUSB_ERROR_NOT_FOUND if the requested interface does not exist
904 * \returns LIBUSB_ERROR_BUSY if another program or driver has claimed the
906 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
907 * \returns a LIBUSB_ERROR code on other failure
909 API_EXPORTED int libusb_claim_interface(libusb_device_handle *dev,
910 int interface_number)
914 usbi_dbg("interface %d", interface_number);
915 if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
916 return LIBUSB_ERROR_INVALID_PARAM;
918 pthread_mutex_lock(&dev->lock);
919 if (dev->claimed_interfaces & (1 << interface_number))
922 r = usbi_backend->claim_interface(dev, interface_number);
924 dev->claimed_interfaces |= 1 << interface_number;
927 pthread_mutex_unlock(&dev->lock);
932 * Release an interface previously claimed with libusb_claim_interface(). You
933 * should release all claimed interfaces before closing a device handle.
935 * This is a blocking function. A SET_INTERFACE control request will be sent
936 * to the device, resetting interface state to the first alternate setting.
938 * \param dev a device handle
939 * \param interface_number the <tt>bInterfaceNumber</tt> of the
940 * previously-claimed interface
941 * \returns 0 on success
942 * \returns LIBUSB_ERROR_NOT_FOUND if the interface was not claimed
943 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
944 * \returns another LIBUSB_ERROR code on other failure
946 API_EXPORTED int libusb_release_interface(libusb_device_handle *dev,
947 int interface_number)
951 usbi_dbg("interface %d", interface_number);
952 if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
953 return LIBUSB_ERROR_INVALID_PARAM;
955 pthread_mutex_lock(&dev->lock);
956 if (!(dev->claimed_interfaces & (1 << interface_number))) {
957 r = LIBUSB_ERROR_NOT_FOUND;
961 r = usbi_backend->release_interface(dev, interface_number);
963 dev->claimed_interfaces &= ~(1 << interface_number);
966 pthread_mutex_unlock(&dev->lock);
971 * Activate an alternate setting for an interface. The interface must have
972 * been previously claimed with libusb_claim_interface().
974 * You should always use this function rather than formulating your own
975 * SET_INTERFACE control request. This is because the underlying operating
976 * system needs to know when such changes happen.
978 * This is a blocking function.
980 * \param dev a device handle
981 * \param interface_number the <tt>bInterfaceNumber</tt> of the
982 * previously-claimed interface
983 * \param alternate_setting the <tt>bAlternateSetting</tt> of the alternate
984 * setting to activate
985 * \returns 0 on success
986 * \returns LIBUSB_ERROR_NOT_FOUND if the interface was not claimed, or the
987 * requested alternate setting does not exist
988 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
989 * \returns another LIBUSB_ERROR code on other failure
991 API_EXPORTED int libusb_set_interface_alt_setting(libusb_device_handle *dev,
992 int interface_number, int alternate_setting)
994 usbi_dbg("interface %d altsetting %d", interface_number, alternate_setting);
995 if (interface_number >= sizeof(dev->claimed_interfaces) * 8)
996 return LIBUSB_ERROR_INVALID_PARAM;
998 pthread_mutex_lock(&dev->lock);
999 if (!(dev->claimed_interfaces & (1 << interface_number))) {
1000 pthread_mutex_unlock(&dev->lock);
1001 return LIBUSB_ERROR_NOT_FOUND;
1003 pthread_mutex_unlock(&dev->lock);
1005 return usbi_backend->set_interface_altsetting(dev, interface_number,
1010 * Clear the halt/stall condition for an endpoint. Endpoints with halt status
1011 * are unable to receive or transmit data until the halt condition is stalled.
1013 * You should cancel all pending transfers before attempting to clear the halt
1016 * This is a blocking function.
1018 * \param dev a device handle
1019 * \param endpoint the endpoint to clear halt status
1020 * \returns 0 on success
1021 * \returns LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist
1022 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1023 * \returns another LIBUSB_ERROR code on other failure
1025 API_EXPORTED int libusb_clear_halt(libusb_device_handle *dev,
1026 unsigned char endpoint)
1028 usbi_dbg("endpoint %x", endpoint);
1029 return usbi_backend->clear_halt(dev, endpoint);
1033 * Perform a USB port reset to reinitialize a device. The system will attempt
1034 * to restore the previous configuration and alternate settings after the
1035 * reset has completed.
1037 * If the reset fails, the descriptors change, or the previous state cannot be
1038 * restored, the device will appear to be disconnected and reconnected. This
1039 * means that the device handle is no longer valid (you should close it) and
1040 * rediscover the device. A return code of LIBUSB_ERROR_NOT_FOUND indicates
1041 * when this is the case.
1043 * This is a blocking function which usually incurs a noticeable delay.
1045 * \param dev a handle of the device to reset
1046 * \returns 0 on success
1047 * \returns LIBUSB_ERROR_NOT_FOUND if re-enumeration is required, or if the
1048 * device has been disconnected
1049 * \returns another LIBUSB_ERROR code on other failure
1051 API_EXPORTED int libusb_reset_device(libusb_device_handle *dev)
1054 return usbi_backend->reset_device(dev);
1058 * Determine if a kernel driver is active on an interface. If a kernel driver
1059 * is active, you cannot claim the interface, and libusb will be unable to
1062 * \param dev a device handle
1063 * \param interface the interface to check
1064 * \returns 0 if no kernel driver is active
1065 * \returns 1 if a kernel driver is active
1066 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1067 * \returns another LIBUSB_ERROR code on other failure
1068 * \see libusb_detach_kernel_driver()
1070 API_EXPORTED int libusb_kernel_driver_active(libusb_device_handle *dev,
1073 usbi_dbg("interface %d", interface);
1074 if (usbi_backend->kernel_driver_active)
1075 return usbi_backend->kernel_driver_active(dev, interface);
1077 return LIBUSB_ERROR_NOT_SUPPORTED;
1081 * Detach a kernel driver from an interface. If successful, you will then be
1082 * able to claim the interface and perform I/O.
1084 * \param dev a device handle
1085 * \param interface the interface to detach the driver from
1086 * \returns 0 on success
1087 * \returns LIBUSB_ERROR_NOT_FOUND if no kernel driver was active
1088 * \returns LIBUSB_ERROR_INVALID_PARAM if the interface does not exist
1089 * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
1090 * \returns another LIBUSB_ERROR code on other failure
1091 * \see libusb_kernel_driver_active()
1093 API_EXPORTED int libusb_detach_kernel_driver(libusb_device_handle *dev,
1096 usbi_dbg("interface %d", interface);
1097 if (usbi_backend->detach_kernel_driver)
1098 return usbi_backend->detach_kernel_driver(dev, interface);
1100 return LIBUSB_ERROR_NOT_SUPPORTED;
1104 * Set message verbosity.
1105 * - Level 0: no messages ever printed by the library (default)
1106 * - Level 1: error messages are printed to stderr
1107 * - Level 2: warning and error messages are printed to stderr
1108 * - Level 3: informational messages are printed to stdout, warning and error
1109 * messages are printed to stderr
1111 * The default level is 0, which means no messages are ever printed. If you
1112 * choose to increase the message verbosity level, ensure that your
1113 * application does not close the stdout/stderr file descriptors.
1115 * You are advised to set level 3. libusb is conservative with it's message
1116 * logging and most of the time, will only log messages that explain error
1117 * conditions and other oddities. This will help you debug your software.
1119 * If the LIBUSB_DEBUG environment variable was set when libusb was
1120 * initialized, this function does nothing: the message verbosity is fixed
1121 * to the value in the environment variable.
1123 * If libusb was compiled without any message logging, this function does
1124 * nothing: you'll never get any messages.
1126 * If libusb was compiled with verbose debug message logging, this function
1127 * does nothing: you'll always get messages from all levels.
1129 * \param level debug level to set
1131 API_EXPORTED void libusb_set_debug(int level)
1138 * Initialize libusb. This function must be called before calling any other
1140 * \returns 0 on success, or a LIBUSB_ERROR code on failure
1142 API_EXPORTED int libusb_init(void)
1144 char *dbg = getenv("LIBUSB_DEBUG");
1146 usbi_debug = atoi(dbg);
1152 if (usbi_backend->init) {
1153 int r = usbi_backend->init();
1158 list_init(&usb_devs);
1159 list_init(&usbi_open_devs);
1165 * Deinitialize libusb. Should be called after closing all open devices and
1166 * before your application terminates.
1168 API_EXPORTED void libusb_exit(void)
1172 pthread_mutex_lock(&usbi_open_devs_lock);
1173 if (!list_empty(&usbi_open_devs)) {
1174 struct libusb_device_handle *devh;
1175 struct libusb_device_handle *tmp;
1177 usbi_dbg("naughty app left some devices open!");
1178 list_for_each_entry_safe(devh, tmp, &usbi_open_devs, list) {
1179 list_del(&devh->list);
1184 pthread_mutex_unlock(&usbi_open_devs_lock);
1186 if (usbi_backend->exit)
1187 usbi_backend->exit();
1190 void usbi_log(enum usbi_log_level level, const char *function,
1191 const char *format, ...)
1194 FILE *stream = stdout;
1197 #ifndef ENABLE_DEBUG_LOGGING
1200 if (level == LOG_LEVEL_WARNING && usbi_debug < 2)
1202 if (level == LOG_LEVEL_INFO && usbi_debug < 3)
1207 case LOG_LEVEL_INFO:
1210 case LOG_LEVEL_WARNING:
1214 case LOG_LEVEL_ERROR:
1218 case LOG_LEVEL_DEBUG:
1228 fprintf(stream, "libusb:%s [%s] ", prefix, function);
1230 va_start (args, format);
1231 vfprintf(stream, format, args);
1234 fprintf(stream, "\n");