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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 "libusb_device_handle *devh" "uint8_t desc_idx" "uint16_t langid" "unsigned char *data" "int length"
331 Retrieve a string descriptor in raw format.
332 Returns the number of bytes actually transferred on success
333 or a negative LIBUSB_ERROR code on failure.
336 .Fn libusb_get_string_descriptor_ascii "libusb_device_handle *devh" "uint8_t desc_idx" "unsigned char *data" "int length"
337 Retrieve a string descriptor in C style ASCII.
338 Returns the positive number of bytes in the resulting ASCII string
339 on success and a LIBUSB_ERROR code on failure.
342 .Fn libusb_parse_ss_endpoint_comp "const void *buf" "int len" "libusb_ss_endpoint_companion_descriptor **ep_comp"
343 This function parses the USB 3.0 endpoint companion descriptor in host endian format pointed to by
345 and having a length of
347 Typically these arguments are the extra and extra_length fields of the
349 On success the pointer to resulting descriptor is stored at the location given by
351 Returns zero on success and a LIBUSB_ERROR code on failure.
352 On success the parsed USB 3.0 endpoint companion descriptor must be
353 freed using the libusb_free_ss_endpoint_comp function.
356 .Fn libusb_free_ss_endpoint_comp "libusb_ss_endpoint_companion_descriptor *ep_comp"
357 This function is NULL safe and frees a parsed USB 3.0 endpoint companion descriptor.
360 .Fn libusb_parse_bos_descriptor "const void *buf" "int len" "libusb_bos_descriptor **bos"
361 This function parses a Binary Object Store, BOS, descriptor into host endian format pointed to by
363 and having a length of
365 On success the pointer to resulting descriptor is stored at the location given by
367 Returns zero on success and a LIBUSB_ERROR code on failure.
368 On success the parsed BOS descriptor must be freed using the
369 libusb_free_bos_descriptor function.
372 .Fn libusb_free_bos_descriptor "libusb_bos_descriptor *bos"
373 This function is NULL safe and frees a parsed BOS descriptor.
374 .Sh USB ASYNCHRONOUS I/O
375 .Ft struct libusb_transfer *
376 .Fn libusb_alloc_transfer "int iso_packets"
377 Allocate a transfer with the number of isochronous packet descriptors
380 Returns NULL on error.
383 .Fn libusb_free_transfer "struct libusb_transfer *tr"
387 .Fn libusb_submit_transfer "struct libusb_transfer *tr"
388 This function will submit a transfer and returns immediately.
389 Returns 0 on success, LIBUSB_ERROR_NO_DEVICE if
390 the device has been disconnected and a
391 LIBUSB_ERROR code on other failure.
394 .Fn libusb_cancel_transfer "struct libusb_transfer *tr"
395 This function asynchronously cancels a transfer.
396 Returns 0 on success and a LIBUSB_ERROR code on failure.
397 .Sh USB SYNCHRONOUS I/O
399 .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"
400 Perform a USB control transfer.
401 Returns the actual number of bytes
402 transferred on success, in the range from and including zero up to and
405 On error a LIBUSB_ERROR code is returned, for example
406 LIBUSB_ERROR_TIMEOUT if the transfer timed out, LIBUSB_ERROR_PIPE if the
407 control request was not supported, LIBUSB_ERROR_NO_DEVICE if the
408 device has been disconnected and another LIBUSB_ERROR code on other failures.
409 The LIBUSB_ERROR codes are all negative.
412 .Fn libusb_bulk_transfer "struct libusb_device_handle *devh" "unsigned char endpoint" "unsigned char *data" "int length" "int *transferred" "unsigned int timeout"
413 Perform an USB bulk transfer.
414 A timeout value of zero means no timeout.
415 The timeout value is given in milliseconds.
416 Returns 0 on success, LIBUSB_ERROR_TIMEOUT
417 if the transfer timed out, LIBUSB_ERROR_PIPE if the control request was not
418 supported, LIBUSB_ERROR_OVERFLOW if the device offered more data,
419 LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and
420 a LIBUSB_ERROR code on other failure.
423 .Fn libusb_interrupt_transfer "struct libusb_device_handle *devh" "unsigned char endpoint" "unsigned char *data" "int length" "int *transferred" "unsigned int timeout"
424 Perform an USB Interrupt transfer.
425 A timeout value of zero means no timeout.
426 The timeout value is given in milliseconds.
427 Returns 0 on success, LIBUSB_ERROR_TIMEOUT
428 if the transfer timed out, LIBUSB_ERROR_PIPE if the control request was not
429 supported, LIBUSB_ERROR_OVERFLOW if the device offered more data,
430 LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and
431 a LIBUSB_ERROR code on other failure.
434 .Fn libusb_try_lock_events "libusb_context *ctx"
435 Try to acquire the event handling lock.
436 Returns 0 if the lock was obtained and 1 if not.
439 .Fn libusb_lock_events "libusb_context *ctx"
440 Acquire the event handling lock.
441 This function is blocking.
444 .Fn libusb_unlock_events "libusb_context *ctx"
445 Release the event handling lock.
446 This will wake up any thread blocked
448 .Fn libusb_wait_for_event .
451 .Fn libusb_event_handling_ok "libusb_context *ctx"
452 Determine if it still OK for this thread to be doing event handling.
454 if event handling can start or continue.
455 Returns 0 if this thread must give up
459 .Fn libusb_event_handler_active "libusb_context *ctx"
460 Determine if an active thread is handling events.
461 Returns 1 if there is a thread handling events and 0 if there
462 are no threads currently handling events.
465 .Fn libusb_lock_event_waiters "libusb_context *ctx"
466 Acquire the event_waiters lock.
467 This lock is designed to be obtained in the
468 situation where you want to be aware when events are completed, but some other
469 thread is event handling so calling libusb_handle_events() is not allowed.
472 .Fn libusb_unlock_event_waiters "libusb_context *ctx"
473 Release the event_waiters lock.
476 .Fn libusb_wait_for_event "libusb_context *ctx" "struct timeval *tv"
477 Wait for another thread to signal completion of an event.
479 with the event waiters lock held, see libusb_lock_event_waiters().
481 block until the timeout expires or a transfer completes or a thread releases
482 the event handling lock through libusb_unlock_events().
484 transfer completes or another thread stops event handling, and 1 if the
488 .Fn libusb_handle_events_timeout "libusb_context *ctx" "struct timeval *tv"
489 Handle any pending events by checking if timeouts have expired and by
490 checking the set of file descriptors for activity.
491 Returns 0 on success, or a
492 LIBUSB_ERROR code on failure.
495 .Fn libusb_handle_events "libusb_context *ctx"
496 Handle any pending events in blocking mode with a sensible timeout.
498 on success and a LIBUSB_ERROR code on failure.
501 .Fn libusb_handle_events_locked "libusb_context *ctx" "struct timeval *tv"
502 Handle any pending events by polling file descriptors, without checking if
503 another thread is already doing so.
504 Must be called with the event lock held.
507 .Fn libusb_get_next_timeout "libusb_context *ctx" "struct timeval *tv"
508 Determine the next internal timeout that libusb needs to handle.
510 if there are no pending timeouts, 1 if a timeout was returned, or a LIBUSB_ERROR
514 .Fn libusb_set_pollfd_notifiers "libusb_context *ctx" "libusb_pollfd_added_cb added_cb" "libusb_pollfd_removed_cb remove_cb" "void *user_data"
515 Register notification functions for file descriptor additions/removals.
516 These functions will be invoked for every new or removed file descriptor
517 that libusb uses as an event source.
519 .Ft const struct libusb_pollfd **
520 .Fn libusb_get_pollfds "libusb_context *ctx"
521 Retrive a list of file descriptors that should be polled by your main loop as
522 libusb event sources.
523 Returns a NULL-terminated list on success or NULL on failure.
524 .Sh LIBUSB VERSION 0.1 COMPATIBILITY
525 The library is also compliant with LibUSB version 0.1.12.
530 .Fn usb_get_string_simple
531 .Fn usb_get_descriptor_by_endpoint
532 .Fn usb_get_descriptor
533 .Fn usb_parse_descriptor
534 .Fn usb_parse_configuration
535 .Fn usb_destroy_configuration
536 .Fn usb_fetch_and_parse_descriptors
539 .Fn usb_interrupt_write
540 .Fn usb_interrupt_read
542 .Fn usb_set_configuration
543 .Fn usb_claim_interface
544 .Fn usb_release_interface
545 .Fn usb_set_altinterface
556 .Fn usb_check_connected
557 .Fn usb_get_driver_np
558 .Fn usb_detach_kernel_driver_np
565 .Pa http://libusb.sourceforge.net/
568 support first appeared in