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34 .Nd "USB access library"
43 library contains interfaces for directly managing a usb device.
44 The current implementation supports v1.0 of the libusb API.
45 .Sh LIBRARY INITIALISATION / DEINITIALISATION
47 .Fn libusb_init libusb_context **ctx
48 This function initialises libusb.
49 It must be called at the beginning
50 of the program, before other libusb routines are used.
51 This function returns 0 on success or LIBUSB_ERROR on
55 .Fn libusb_exit "libusb_context *ctx"
57 Must be called at the end of the application.
58 Other libusb routines may not be called after this function.
61 .Fn libusb_strerror "int code"
62 Get the ASCII representation of the error given by the
65 This function does not return NULL.
68 .Fn libusb_error_name "int code"
69 Get the ASCII representation of the error enum given by the
72 This function does not return NULL.
75 .Fn libusb_set_debug "libusb_context *ctx" "int level"
76 Set the debug level to
80 .Fn libusb_get_device_list "libusb_context *ctx" "libusb_device ***list"
83 with the list of usb devices available, adding a reference to each
85 All the list entries created by this
86 function must have their reference counter
87 decremented when you are done with them,
88 and the list itself must be freed.
90 function returns the number of devices in the list or a LIBUSB_ERROR code.
93 .Fn libusb_free_device_list "libusb_device **list" "int unref_devices"
94 Free the list of devices discovered by libusb_get_device_list.
97 is set to 1 all devices in the list have their reference
98 counter decremented once.
101 .Fn libusb_get_bus_number "libusb_device *dev"
102 Returns the number of the bus contained by the device
106 .Fn libusb_get_port_numbers "libusb_device *dev" "uint8_t *buf" "uint8_t bufsize"
107 Stores, in the buffer
111 the list of all port numbers from root for the device
115 .Fn libusb_get_port_path "libusb_context *ctx" "libusb_device *dev" "uint8_t *buf" "uint8_t bufsize"
116 Deprecated function equivalent to libusb_get_port_numbers.
119 .Fn libusb_get_device_address "libusb_device *dev"
120 Returns the device_address contained by the device
123 .Ft enum libusb_speed
124 .Fn libusb_get_device_speed "libusb_device *dev"
125 Returns the wire speed at which the device is connected.
126 See the LIBUSB_SPEED_XXX enums for more information.
127 LIBUSB_SPEED_UNKNOWN is returned in case of unknown wire speed.
130 .Fn libusb_get_max_packet_size "libusb_device *dev" "unsigned char endpoint"
131 Returns the wMaxPacketSize value on success, LIBUSB_ERROR_NOT_FOUND if the
132 endpoint does not exist and LIBUSB_ERROR_OTHERS on other failure.
135 .Fn libusb_get_max_iso_packet_size "libusb_device *dev" "unsigned char endpoint"
136 Returns the packet size multiplied by the packet multiplier on success,
137 LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist and
138 LIBUSB_ERROR_OTHERS on other failure.
141 .Fn libusb_ref_device "libusb_device *dev"
142 Increment the reference counter of the device
146 .Fn libusb_unref_device "libusb_device *dev"
147 Decrement the reference counter of the device
151 .Fn libusb_open "libusb_device *dev" "libusb_device_handle **devh"
152 Open a device and obtain a device_handle.
153 Returns 0 on success,
154 LIBUSB_ERROR_NO_MEM on memory allocation problems, LIBUSB_ERROR_ACCESS
155 on permissions problems, LIBUSB_ERROR_NO_DEVICE if the device has been
156 disconnected and a LIBUSB_ERROR code on other errors.
158 .Ft libusb_device_handle *
159 .Fn libusb_open_device_with_vid_pid "libusb_context *ctx" "uint16_t vid" "uint16_t pid"
160 A convenience function to open a device by vendor and product IDs
164 Returns NULL on error.
167 .Fn libusb_close "libusb_device_handle *devh"
168 Close a device handle.
171 .Fn libusb_get_device "libusb_device_handle *devh"
172 Get the device contained by devh.
173 Returns NULL on error.
176 .Fn libusb_get_configuration "libusb_device_handle *devh" "int *config"
177 Returns the value of the current configuration.
179 on success, LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
180 and a LIBUSB_ERROR code on error.
183 .Fn libusb_set_configuration "libusb_device_handle *devh" "int config"
184 Set the active configuration to
186 for the device contained by
188 This function returns 0 on success, LIBUSB_ERROR_NOT_FOUND if the requested
189 configuration does not exist, LIBUSB_ERROR_BUSY if the interfaces are currently
190 claimed, LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and a
191 LIBUSB_ERROR code on failure.
194 .Fn libusb_claim_interface "libusb_device_handle *devh" "int interface_number"
195 Claim an interface in a given libusb_handle
197 This is a non-blocking function.
198 It returns 0 on success, LIBUSB_ERROR_NOT_FOUND
199 if the requested interface does not exist, LIBUSB_ERROR_BUSY if a program or
200 driver has claimed the interface, LIBUSB_ERROR_NO_DEVICE if the device has
201 been disconnected and a LIBUSB_ERROR code on failure.
204 .Fn libusb_release_interface "libusb_device_handle *devh" "int interface_number"
205 This function releases an interface.
206 All the claimed interfaces on a device must be released
207 before closing the device.
208 Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if the
209 interface was not claimed, LIBUSB_ERROR_NO_DEVICE if the device has been
210 disconnected and LIBUSB_ERROR on failure.
213 .Fn libusb_set_interface_alt_setting "libusb_device_handle *dev" "int interface_number" "int alternate_setting"
214 Activate an alternate setting for an interface.
215 Returns 0 on success,
216 LIBUSB_ERROR_NOT_FOUND if the interface was not claimed or the requested
217 setting does not exist, LIBUSB_ERROR_NO_DEVICE if the device has been
218 disconnected and a LIBUSB_ERROR code on failure.
221 .Fn libusb_clear_halt "libusb_device_handle *devh" "unsigned char endpoint"
222 Clear an halt/stall for a endpoint.
223 Returns 0 on success, LIBUSB_ERROR_NOT_FOUND
224 if the endpoint does not exist, LIBUSB_ERROR_NO_DEVICE if the device has been
225 disconnected and a LIBUSB_ERROR code on failure.
228 .Fn libusb_reset_device "libusb_device_handle *devh"
229 Perform an USB port reset for an usb device.
230 Returns 0 on success,
231 LIBUSB_ERROR_NOT_FOUND if re-enumeration is required or if the device has
232 been disconnected and a LIBUSB_ERROR code on failure.
235 .Fn libusb_check_connected "libusb_device_handle *devh"
236 Test if the USB device is still connected.
237 Returns 0 on success,
238 LIBUSB_ERROR_NO_DEVICE if it has been disconnected and a LIBUSB_ERROR
242 .Fn libusb_kernel_driver_active "libusb_device_handle *devh" "int interface"
243 Determine if a driver is active on a interface.
244 Returns 0 if no kernel driver is active
245 and 1 if a kernel driver is active, LIBUSB_ERROR_NO_DEVICE
246 if the device has been disconnected and a LIBUSB_ERROR code on failure.
249 .Fn libusb_get_driver "libusb_device_handle *devh" "int interface" "char *name" "int namelen"
252 .Fn libusb_get_driver_np "libusb_device_handle *devh" "int interface" "char *name" "int namelen"
253 Copy the name of the driver attached to the given
261 Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if no kernel driver is attached
262 to the given interface and LIBUSB_ERROR_INVALID_PARAM if the interface does
264 This function is non-portable.
265 The buffer pointed to by
267 is only zero terminated on success.
270 .Fn libusb_detach_kernel_driver "libusb_device_handle *devh" "int interface"
273 .Fn libusb_detach_kernel_driver_np "libusb_device_handle *devh" "int interface"
274 Detach a kernel driver from an interface.
275 This is needed to claim an interface already claimed by a kernel driver.
276 Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if no kernel driver was active,
277 LIBUSB_ERROR_INVALID_PARAM if the interface does not exist,
278 LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
279 and a LIBUSB_ERROR code on failure.
280 This function is non-portable.
283 .Fn libusb_attach_kernel_driver "libusb_device_handle *devh" "int interface"
284 Re-attach an interface kernel driver that was previously detached.
285 Returns 0 on success,
286 LIBUSB_ERROR_INVALID_PARAM if the interface does not exist,
287 LIBUSB_ERROR_NO_DEVICE
288 if the device has been disconnected, LIBUSB_ERROR_BUSY if the driver cannot be
289 attached because the interface is claimed by a program or driver and a
290 LIBUSB_ERROR code on failure.
293 .Fn libusb_get_device_descriptor "libusb_device *dev" "libusb_device_descriptor *desc"
294 Get the USB device descriptor for the device
296 This is a non-blocking function.
297 Returns 0 on success and a LIBUSB_ERROR code on
301 .Fn libusb_get_active_config_descriptor "libusb_device *dev" "struct libusb_config_descriptor **config"
302 Get the USB configuration descriptor for the active configuration.
304 success, LIBUSB_ERROR_NOT_FOUND if the device is in
305 an unconfigured state
306 and a LIBUSB_ERROR code on error.
309 .Fn libusb_get_config_descriptor "libusb_device *dev" "uint8_t config_index" "libusb_config_descriptor **config"
310 Get a USB configuration descriptor based on its index
312 Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if the configuration does not exist
313 and a LIBUSB_ERROR code on error.
316 .Fn libusb_get_config_descriptor_by_value "libusb_device *dev" "uint8 bConfigurationValue" "libusb_config_descriptor **config"
317 Get a USB configuration descriptor with a specific bConfigurationValue.
319 a non-blocking function which does not send a request through the device.
321 on success, LIBUSB_ERROR_NOT_FOUND if the configuration
323 LIBUSB_ERROR code on failure.
326 .Fn libusb_free_config_descriptor "libusb_config_descriptor *config"
327 Free a configuration descriptor.
330 .Fn libusb_get_string_descriptor_ascii "libusb_device_handle *devh" "uint8_t desc_idx" "unsigned char *data" "int length"
331 Retrieve a string descriptor in C style ASCII.
332 Returns the positive number of bytes in the resulting ASCII string
333 on success and a LIBUSB_ERROR code on failure.
336 .Fn libusb_parse_ss_endpoint_comp "const void *buf" "int len" "libusb_ss_endpoint_companion_descriptor **ep_comp"
337 This function parses the USB 3.0 endpoint companion descriptor in host endian format pointed to by
339 and having a length of
341 Typically these arguments are the extra and extra_length fields of the
343 On success the pointer to resulting descriptor is stored at the location given by
345 Returns zero on success and a LIBUSB_ERROR code on failure.
346 On success the parsed USB 3.0 endpoint companion descriptor must be
347 freed using the libusb_free_ss_endpoint_comp function.
350 .Fn libusb_free_ss_endpoint_comp "libusb_ss_endpoint_companion_descriptor *ep_comp"
351 This function is NULL safe and frees a parsed USB 3.0 endpoint companion descriptor.
354 .Fn libusb_parse_bos_descriptor "const void *buf" "int len" "libusb_bos_descriptor **bos"
355 This function parses a Binary Object Store, BOS, descriptor into host endian format pointed to by
357 and having a length of
359 On success the pointer to resulting descriptor is stored at the location given by
361 Returns zero on success and a LIBUSB_ERROR code on failure.
362 On success the parsed BOS descriptor must be freed using the
363 libusb_free_bos_descriptor function.
366 .Fn libusb_free_bos_descriptor "libusb_bos_descriptor *bos"
367 This function is NULL safe and frees a parsed BOS descriptor.
368 .Sh USB ASYNCHRONOUS I/O
369 .Ft struct libusb_transfer *
370 .Fn libusb_alloc_transfer "int iso_packets"
371 Allocate a transfer with the number of isochronous packet descriptors
374 Returns NULL on error.
377 .Fn libusb_free_transfer "struct libusb_transfer *tr"
381 .Fn libusb_submit_transfer "struct libusb_transfer *tr"
382 This function will submit a transfer and returns immediately.
383 Returns 0 on success, LIBUSB_ERROR_NO_DEVICE if
384 the device has been disconnected and a
385 LIBUSB_ERROR code on other failure.
388 .Fn libusb_cancel_transfer "struct libusb_transfer *tr"
389 This function asynchronously cancels a transfer.
390 Returns 0 on success and a LIBUSB_ERROR code on failure.
391 .Sh USB SYNCHRONOUS I/O
393 .Fn libusb_control_transfer "libusb_device_handle *devh" "uint8_t bmRequestType" "uint8_t bRequest" "uint16_t wValue" "uint16_t wIndex" "unsigned char *data" "uint16_t wLength" "unsigned int timeout"
394 Perform a USB control transfer.
395 Returns the actual number of bytes
396 transferred on success, in the range from and including zero up to and
399 On error a LIBUSB_ERROR code is returned, for example
400 LIBUSB_ERROR_TIMEOUT if the transfer timed out, LIBUSB_ERROR_PIPE if the
401 control request was not supported, LIBUSB_ERROR_NO_DEVICE if the
402 device has been disconnected and another LIBUSB_ERROR code on other failures.
403 The LIBUSB_ERROR codes are all negative.
406 .Fn libusb_bulk_transfer "struct libusb_device_handle *devh" "unsigned char endpoint" "unsigned char *data" "int length" "int *transferred" "unsigned int timeout"
407 Perform an USB bulk transfer.
408 A timeout value of zero means no timeout.
409 The timeout value is given in milliseconds.
410 Returns 0 on success, LIBUSB_ERROR_TIMEOUT
411 if the transfer timed out, LIBUSB_ERROR_PIPE if the control request was not
412 supported, LIBUSB_ERROR_OVERFLOW if the device offered more data,
413 LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and
414 a LIBUSB_ERROR code on other failure.
417 .Fn libusb_interrupt_transfer "struct libusb_device_handle *devh" "unsigned char endpoint" "unsigned char *data" "int length" "int *transferred" "unsigned int timeout"
418 Perform an USB Interrupt transfer.
419 A timeout value of zero means no timeout.
420 The timeout value is given in milliseconds.
421 Returns 0 on success, LIBUSB_ERROR_TIMEOUT
422 if the transfer timed out, LIBUSB_ERROR_PIPE if the control request was not
423 supported, LIBUSB_ERROR_OVERFLOW if the device offered more data,
424 LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and
425 a LIBUSB_ERROR code on other failure.
428 .Fn libusb_try_lock_events "libusb_context *ctx"
429 Try to acquire the event handling lock.
430 Returns 0 if the lock was obtained and 1 if not.
433 .Fn libusb_lock_events "libusb_context *ctx"
434 Acquire the event handling lock.
435 This function is blocking.
438 .Fn libusb_unlock_events "libusb_context *ctx"
439 Release the event handling lock.
440 This will wake up any thread blocked
442 .Fn libusb_wait_for_event .
445 .Fn libusb_event_handling_ok "libusb_context *ctx"
446 Determine if it still OK for this thread to be doing event handling.
448 if event handling can start or continue.
449 Returns 0 if this thread must give up
453 .Fn libusb_event_handler_active "libusb_context *ctx"
454 Determine if an active thread is handling events.
455 Returns 1 if there is a thread handling events and 0 if there
456 are no threads currently handling events.
459 .Fn libusb_lock_event_waiters "libusb_context *ctx"
460 Acquire the event_waiters lock.
461 This lock is designed to be obtained in the
462 situation where you want to be aware when events are completed, but some other
463 thread is event handling so calling libusb_handle_events() is not allowed.
466 .Fn libusb_unlock_event_waiters "libusb_context *ctx"
467 Release the event_waiters lock.
470 .Fn libusb_wait_for_event "libusb_context *ctx" "struct timeval *tv"
471 Wait for another thread to signal completion of an event.
473 with the event waiters lock held, see libusb_lock_event_waiters().
475 block until the timeout expires or a transfer completes or a thread releases
476 the event handling lock through libusb_unlock_events().
478 transfer completes or another thread stops event handling, and 1 if the
482 .Fn libusb_handle_events_timeout "libusb_context *ctx" "struct timeval *tv"
483 Handle any pending events by checking if timeouts have expired and by
484 checking the set of file descriptors for activity.
485 Returns 0 on success, or a
486 LIBUSB_ERROR code on failure.
489 .Fn libusb_handle_events "libusb_context *ctx"
490 Handle any pending events in blocking mode with a sensible timeout.
492 on success and a LIBUSB_ERROR code on failure.
495 .Fn libusb_handle_events_locked "libusb_context *ctx" "struct timeval *tv"
496 Handle any pending events by polling file descriptors, without checking if
497 another thread is already doing so.
498 Must be called with the event lock held.
501 .Fn libusb_get_next_timeout "libusb_context *ctx" "struct timeval *tv"
502 Determine the next internal timeout that libusb needs to handle.
504 if there are no pending timeouts, 1 if a timeout was returned, or a LIBUSB_ERROR
508 .Fn libusb_set_pollfd_notifiers "libusb_context *ctx" "libusb_pollfd_added_cb added_cb" "libusb_pollfd_removed_cb remove_cb" "void *user_data"
509 Register notification functions for file descriptor additions/removals.
510 These functions will be invoked for every new or removed file descriptor
511 that libusb uses as an event source.
513 .Ft const struct libusb_pollfd **
514 .Fn libusb_get_pollfds "libusb_context *ctx"
515 Retrive a list of file descriptors that should be polled by your main loop as
516 libusb event sources.
517 Returns a NULL-terminated list on success or NULL on failure.
518 .Sh LIBUSB VERSION 0.1 COMPATIBILITY
519 The library is also compliant with LibUSB version 0.1.12.
524 .Fn usb_get_string_simple
525 .Fn usb_get_descriptor_by_endpoint
526 .Fn usb_get_descriptor
527 .Fn usb_parse_descriptor
528 .Fn usb_parse_configuration
529 .Fn usb_destroy_configuration
530 .Fn usb_fetch_and_parse_descriptors
533 .Fn usb_interrupt_write
534 .Fn usb_interrupt_read
536 .Fn usb_set_configuration
537 .Fn usb_claim_interface
538 .Fn usb_release_interface
539 .Fn usb_set_altinterface
550 .Fn usb_check_connected
551 .Fn usb_get_driver_np
552 .Fn usb_detach_kernel_driver_np
559 .Pa http://libusb.sourceforge.net/
562 support first appeared in