.\"
.\" Copyright (c) 2009 Sylvestre Gallon
.\"
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.\" $FreeBSD$
.\"
.Dd June 22, 2009
.Dt LIBUSB 3
.Os
.Sh NAME
.Nm libusb
.
.Nd "USB access library"
.
.
.Sh LIBRARY
.
.
USB access library (libusb -lusb)
.
.
.Sh SYNOPSIS
.
.
.In libusb.h
.
.
.Sh DESCRIPTION
The
.Nm
library contains interfaces for directly managing a usb device.
The current implementation supports v1.0 of the libusb API.
.
.
.Sh LIBRARY INITIALISATION / DEINITIALISATION
.
.Pp
.
.Ft int
.Fn libusb_init libusb_context **ctx
This function initialises libusb. Must be called at the beginning
of the program. This function returns 0 on success or LIBUSB_ERROR on 
failure.
. 
.Pp
.
.Ft void
.Fn libusb_exit "libusb_context *ctx"
Deinitialise libusb. Must be called at the end of the application.
.
.Pp
.
.Ft void
.Fn libusb_set_debug "libusb_context *ctx" "int level"
Set debug to the
.Fa level
level.
.
.Pp
.
.Ft ssize_t
.Fn libusb_get_device_list "libusb_context *ctx" "libusb_device ***list"
Fill into
.Fa list 
the list of usb device available. All the device created by this
function must be unref and free when you are done with them. This
function returns the number of devices in list or a LIBUSB_ERROR code.
.
.Pp
.
.Ft void
.Fn libusb_free_device_list "libusb_device **list" "int unref_devices"
Free the list of devices discovered by libusb_get_device_list. If 
.Fa unref_device
is set to 1 all devices are unref one time.
.
.Pp
.
.Ft uint8_t
.Fn libusb_get_bus_number "libusb_device *dev"
Returns the number of the bus contained by the device
.Fa dev.
.
.Pp
.
.Ft uint8_t
.Fn libusb_get_device_address "libusb_device *dev"
Return the device_address contained by the device
.Fa dev.
.
.Pp
.
.Ft int
.Fn libusb_get_max_packet_size "libusb_device *dev" "unsigned char endpoint"
Return the wMaxPacketSize value on success, LIBUSB_ERROR_NOT_FOUND if the 
endpoint does not exist and LIBUSB_ERROR_OTHERS on other failure.
.
.Pp
.
.Ft libusb_device *
.Fn libusb_ref_device "libusb_device *dev"
Increment the reference counter of the device
.Fa dev.
.
.Pp
.
.Ft void
.Fn libusb_unref_device "libusb_device *dev"
Decrement the reference counter of the device
.Fa dev.
.
.Pp
.
.Ft int
.Fn libusb_open "libusb_device *dev" "libusb_device_handle **devh"
Open a device and obtain a device_handle. Return 0 on success, 
LIBUSB_ERROR_NO_MEM on memory allocation problem, LIBUSB_ERROR_ACCESS 
on permission problem, LIBUSB_ERROR_NO_DEVICE if the device has been 
disconnected and a LIBUSB_ERROR code on error.
.
.Pp
.
.Ft libusb_device_handle *
.Fn libusb_open_device_with_vid_pid "libusb_context *ctx" "uint16_t vid" "uint16_t pid"
Conveniance function to open a device with is 
.Fa vid 
and 
.Fa pid.
Return NULL on error.
.
.Pp
.
.Ft void
.Fn libusb_close "libusb_device_handle *devh"
Close a device handle.
.
.Pp
.
.Ft libusb_device *
.Fn libusb_get_device(libusb_device_handle *devh)
Get the device contained by devh. Return NULL on error.
.
.Pp
.
.Ft int
.Fn libusb_get_configuration "libusb_device_handle *devh" "int *config"
Return the bConfiguration value of the current configuration. return 0
on success, LIBUSB_ERROR_NO_DEVICE if the device has been disconnected 
and a LIBUSB_ERROR code on error.
.
.Pp
.
.Ft int
.Fn libusb_set_configuration "libusb_device_handle *devh" "int config"
Set the active configuration
.Fa config
for the device contained by
.Fa devh.
This function return 0 on success, LIBUSB_ERROR_NOT_FOUND if the requested
configuration does not exist, LIBUSB_ERROR_BUSY if the interfaces are currently 
claimed, LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and a 
LIBUSB_ERROR code on failure.
.
.Pp
.
.Ft int
.Fn libusb_claim_interface "libusb_device_handle *devh" "int interface_number"
Claim an interface in a given libusb_handle
.Fa devh.
This is a non-blocking function. It return 0 success, LIBUSB_ERROR_NOT_FOUND 
if the requested interface does not exist, LIBUSB_ERROR_BUSY if a program or 
driver has claimed the interface, LIBUSB_ERROR_NO_DEVICE if the device has 
been disconnected and a LIBUSB_ERROR code on failure.
.
.Pp
.
.Ft int
.Fn libusb_release_interface "libusb_device_handle *devh" "int interface_number"
This function release an interface. All the claimed interface must be released
before closing a device. Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if the 
interface was not claimed, LIBUSB_ERROR_NO_DEVICE if the device has been 
disconnected and LIBUSB_ERROR on failure.
.
.Pp
.
.Ft int
.Fn libusb_set_interface_alt_setting "libusb_device_handle *dev" "int interface_number" "int alternate_setting"
Activate an alternate setting for an interface. Returns 0 on success, 
LIBUSB_ERROR_NOT_FOUND if the interface was not claimed or the requested 
setting does not exist, LIBUSB_ERROR_NO_DEVICE if the device has been 
disconnected and LIBUSB_ERROR code on failure.
.
.Pp
.
.Ft int
.Fn libusb_clear_halt "libusb_device_handle *devh" "unsigned char endpoint"
Clear an halt/stall for a endpoint. Returns 0 on success, LIBUSB_ERROR_NOT_FOUND
if the endpoint does not exist, LIBUSB_ERROR_NO_DEVICE if the device has been 
disconnected and a LIBUSB_ERROR code on failure.
.
.Pp
.
.Ft int
.Fn libusb_reset_device "libusb_device_handle *devh"
Perform an USB port reset for an usb device. Returns 0 on success,
LIBUSB_ERROR_NOT_FOUND if re-enumeration is required or if the device has
been disconnected and a LIBUSB_ERROR code on failure.
.
.Pp
.
.Ft int
.Fn libusb_kernel_driver_active "libusb_device_handle *devh" "int interface"
Determine if a driver is active on a interface. Returns 0 if no kernel driver
is active, returns 1 if a kernel driver is active, returns LIBUSB_ERROR_NO_DEVICE
if the device has been disconnected and return a LIBUSB_ERROR code on failure.
.
.Pp
.
.Ft int
.Fn libusb_detach_kernel_driver "libusb_device_handle *devh" "int interface"
Detach a kernel driver from an interface. This is needed to claim an interface
required by a kernel driver. Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if
no kernel driver was active, LIBUSB_ERROR_INVALID_PARAM if the interface does not
exist, LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and a 
LIBUSB_ERROR code on failure. 
.
.Pp
.
.Ft int
.Fn libusb_attach_kernel_driver "libusb_device_handle *devh" "int interface"
Re-attach an interface kernel driver previously detached. Returns 0 on success, 
LIBUSB_ERROR_INVALID_PARAM if the interface does not exist, LIBUSB_ERROR_NO_DEVICE
if the device has been disconnect, LIBUSB_ERROR_BUSY if the driver cannot be 
attached because the interface is claimed by a program or driver and a 
LIBUSB_ERROR code on failure.
.
.Pp
.
.Sh USB DESCRIPTORS
.
.Pp
.
.Ft int
.Fn libusb_get_device_descriptor "libusb_device *dev" "libusb_device_descriptor *desc"
Get the USB device descriptor for the device
.Fa dev.
This is a non-blocking function. Returns 0 on success and a LIBUSB_ERROR code on 
failure.
.
.Pp
.Ft int 
.Fn libsub_get_active_config_descriptor "libusb_device *dev" "libusb_device_descriptor **config"
Get the USB configuration descriptor for the active configuration. Returns 0 on 
success, returns LIBUSB_ERROR_NOT_FOUND if the device is in unconfigured state 
and return another LIBUSB_ERROR code on error.
.
.Pp
.Ft int 
.Fn libusb_get_config_descriptor "libusb_device *dev" "uint8_t config_index" "libusb_config_descriptor **config"
Get USB configuration descriptor based on its index 
.Fa idx.
Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if the configuration does not exist 
and returns another LIBUSB_ERROR code on error.
.
.Pp
.Ft int
.Fn libusb_get_config_descriptor_by_value "libusb_device *dev" "uint8 bConfigurationValue" "libusb_config_descriptor **config"
Get a USB configuration descriptor with a specific bConfigurationValue. This is 
a non-blocking function which does not send request through the device. Returns 0 
on success, LIBUSB_ERROR_NOT_FOUND if the configuration does not exist and another 
LIBUSB_ERROR code on failure.
.
.Pp
.Ft void
.Fn libusb_free_config_descriptor "libusb_config_descriptor *config"
Free a configuration descriptor.
.
.Pp
.Ft int
.Fn libusb_get_string_descriptor_ascii "libusb_device_handle *devh" "uint8_t desc_idx" "unsigned char *data" "int length"
Retrieve a string descriptor in C style ascii. Returns a number of byte on success 
and a LIBUSB_ERROR code on failure.
.
.Pp
.
.Sh USB ASYNCHRONOUS I/O
.
.Pp
.Ft struct libusb_transfer *
.Fn libusb_alloc_transfer "int iso_packets"
Allocate a transfer with
.Fa iso_packets
numbers of isochronous packet descriptors. Returns NULL on error.
.
.Pp
.Ft void
.Fn libusb_free_transfer "struct libusb_transfer *tr"
Free a transfer.
.
.Pp
.Ft int
.Fn libusb_submit_transfer "struct libusb_transfer *tr"
This function will submit a transfer and returns immediately. Returns 0 on 
success, LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and 
LIBUSB_ERROR code on other failure.
.
.Pp
.Ft int
.Fn libusb_cancel_transfer "struct libusb_transfer *tr"
This function asynchronously cancel a transfer. Returns 0 on success and 
LIBUSB_ERROR code on failure.
.
.Pp
.Sh USB SYNCHRONOUS I/O
.
.Pp
.Ft int
.Fn libusb_control_transfer "libusb_device_handle *devh" "uint8_t bmRequestType" "uint16_t wIndex" "unsigned char *data" "uint16_t wLength" "unsigned int timeout"
Perform a USB control transfer. Returns 0 on success, LIBUSB_ERROR_TIMEOUT 
if the transfer timeout, LIBUSB_ERROR_PIPE if the control request was not 
supported, LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and 
LIBUSB_ERROR code on other failure.
.
.Pp
.Ft int
.Fn libusb_bulk_transfer "struct libusb_device_handle *devh" "unsigned char endpoint" "unsigned char *data" "int length" "int *transferred" "unsigned int timeout"
Perform an USB bulk transfer. Returns 0 on success, LIBUSB_ERROR_TIMEOUT 
if the transfer timeout, LIBUSB_ERROR_PIPE if the control request was not 
supported, LIBUSB_ERROR_OVERFLOW if the device offered more data, 
LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and 
LIBUSB_ERROR code on other failure.
.
.Pp
.Ft int
.Fn libusb_interrupt_transfer "struct libusb_device_handle *devh" "unsigned char endpoint" "unsigned char *data" "int length" "int *transferred" "unsigned int timeout"
Perform an USB Interrupt transfer. Returns 0 on success, LIBUSB_ERROR_TIMEOUT 
if the transfer timeout, LIBUSB_ERROR_PIPE if the control request was not 
supported, LIBUSB_ERROR_OVERFLOW if the device offered more data, 
LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and 
LIBUSB_ERROR code on other failure.
.
.Pp
.Sh USB EVENTS
.
.Pp
.Ft int
.Fn libusb_try_lock_events "libusb_context *ctx"
Try to acquire the event handling lock. Returns 0 if the lock was obtained and 1
if not.
.
.Pp
.Ft void
.Fn libusb_lock_events "libusb_context *ctx"
Acquire the event handling lock. This function is blocking.
.
.Pp
.Ft void
.Fn libusb_unlock_events "libusb_context *ctx"
Release the event handling lock. This will wake up any thread blocked
on libusb_wait_for_event().
.
.Pp
.Ft int
.Fn libusb_event_handling_ok "libusb_context *ctx"
Determine if it still OK for this thread to be doing event handling. Returns 1
if event handling can start or continue. Returns 0 if this thread must give up
the events lock.
.
.Pp
.Ft int
.Fn libusb_event_handler_active "libusb_context *ctx"
Determine if an active thread is handling events. Returns 1 if yes and 0 if there
are no threads currently handling events.
.
.Pp
.Ft void
.Fn libusb_lock_event_waiters "libusb_context *ctx"
Acquire the event_waiters lock. This lock is designed to be obtained under the
situation where you want to be aware when events are completed, but some other
thread is event handling so calling libusb_handle_events() is not allowed.
.
.Pp
.Ft void
.Fn libusb_unlock_event_waiters "libusb_context *ctx"
Release the event_waiters lock.
.
.Pp
.Ft int 
.Fn libusb_wait_for_event "libusb_context *ctx" "struct timeval *tv"
Wait for another thread to signal completion of an event. Must be called
with the event waiters lock held, see libusb_lock_event_waiters(). This will
block until the timeout expires or a transfer completes or a thread releases
the event handling lock through libusb_unlock_events(). Returns 0 after a 
transfer completes or another thread stops event handling, returns 1 if the
timeout expired.
.
.Pp
.Ft int
.Fn libusb_handle_events_timeout "libusb_context *ctx" "struct timeval *tv"
Handle any pending events by checking if timeouts have expired and by 
checking the set of file descriptors for activity. Returns 0 on success, or a
LIBUSB_ERROR code on failure.
.
.Pp
.Ft int
.Fn libusb_handle_events "libusb_context *ctx"
Handle any pending events in blocking mode with a sensible timeout. Returns 0
on success, returns a LIBUSB_ERROR code on failure.
.
.Pp
.Ft int
.Fn libusb_handle_events_locked "libusb_context *ctx" "struct timeval *tv"
Handle any pending events by polling file desciptors, without checking if
another threads are already doing so. Must be called with the event lock held.
.
.Pp
.Ft int
.Fn libusb_get_next_timeout "libusb_context *ctx" "struct timeval *tv"
Determine the next internal timeout that libusb needs to handle. Returns 0
if there are no pending timeouts, 1 if a timeout was returned, or LIBUSB_ERROR
code on failure.
.
.Pp
.Ft void
.Fn libusb_set_pollfd_notifiers "libusb_context *ctx" "libusb_pollfd_added_cb added_cb" "libusb_pollfd_removed_cb remove_cb" "void *user_data"
Register notification functions for file descriptor additions/removals.
These functions will be invoked for every new or removed file descriptor
that libusb uses as an event source.
.
.Pp
.Ft const struct libusb_pollfd **
.Fn libusb_get_pollfds "libusb_context *ctx"
Retrive a list of file descriptors that should be polled by your main loop as 
libusb event sources. Returns a NULL-terminated list on success or NULL on failure.
.
.Sh LIBUSB VERSION 0.1 COMPATIBILITY
.Pp
The library is also compliant with LibUSB version 0.1.12.
.Pp
.Fn usb_open
.Fn usb_close
.Fn usb_get_string
.Fn usb_get_string_simple
.Fn usb_get_descriptor_by_endpoint
.Fn usb_get_descriptor
.Fn usb_parse_descriptor
.Fn usb_parse_configuration
.Fn usb_destroy_configuration
.Fn usb_fetch_and_parse_descriptors
.Fn usb_bulk_write
.Fn usb_bulk_read
.Fn usb_interrupt_write
.Fn usb_interrupt_read
.Fn usb_control_msg
.Fn usb_set_configuration
.Fn usb_claim_interface
.Fn usb_release_interface
.Fn usb_set_altinterface
.Fn usb_resetep
.Fn usb_clear_halt
.Fn usb_reset
.Fn usb_strerror
.Fn usb_init
.Fn usb_set_debug
.Fn usb_find_busses
.Fn usb_find_devices
.Fn usb_device
.Fn usb_get_busses
.
.Sh SEE ALSO
.Xr libusb20 3 ,
.Xr usb 4 ,
.Xr usbconfig 8
.Pp
.Pa http://libusb.sourceforge.net/
.
.Sh HISTORY
.
.Nm
support first appeared in
.Fx 8.0 .