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LIBUSB(3) FreeBSD Library Functions Manual LIBUSB(3)
NAME
libusb - USB access library
LIBRARY
USB access library (libusb, -lusb)
SYNOPSIS
#include <libusb.h>
DESCRIPTION
The libusb library contains interfaces for directly managing a usb
device. The current implementation supports v1.0 of the libusb API.
LIBRARY INITIALISATION AND DEINITIALISATION
const struct libusb_version * libusb_get_version(void) This function
returns version information about LibUSB.
int libusb_init(libusb_context **ctx) Call this function before any other
libusb v1.0 API function, to initialise a valid libusb v1.0 context. If
the ctx argument is non-NULL, a pointer to the libusb context is stored
at the given location. This function returns 0 upon success or
LIBUSB_ERROR on failure.
int libusb_init_context(libusb_context **ctx, const struct
libusb_init_option [], int num_options) Call this function before any
other libusb v1.0 API function, to initialise a valid libusb v1.0
context. If the ctx argument is non-NULL, a pointer to the libusb
context is stored at the given location. Additional options, like the
USB debug level, may be given using the second and third argument. If no
options are needed, simply use libusb_init(). This function returns 0
upon success or a LIBUSB_ERROR value on failure.
void libusb_exit(libusb_context *ctx) Deinitialise libusb. Must be
called at the end of the application. Other libusb routines may not be
called after this function.
int libusb_has_capability(uint32_t capability) This function checks the
runtime capabilities of libusb. This function will return non-zero if
the given capability is supported, 0 if it is not supported. The valid
values for capability are:
LIBUSB_CAP_HAS_CAPABILITY
libusb supports libusb_has_capability().
LIBUSB_CAP_HAS_HOTPLUG
libusb supports hotplug notifications.
LIBUSB_CAP_HAS_HID_ACCESS
libusb can access HID devices without requiring user
intervention.
LIBUSB_CAP_SUPPORTS_DETACH_KERNEL_DRIVER
libusb supports detaching of the default USB driver
with libusb_detach_kernel_driver().
const char * libusb_strerror(int code) Get the ASCII representation of
the error given by the code argument. This function does not return
to level.
ssize_t libusb_get_device_list(libusb_context *ctx, libusb_device
***list) Populate list with the list of usb devices available, adding a
reference to each device in the list. All the list entries created by
this function must have their reference counter decremented when you are
done with them, and the list itself must be freed. This function returns
the number of devices in the list or a LIBUSB_ERROR code.
void libusb_free_device_list(libusb_device **list, int unref_devices)
Free the list of devices discovered by libusb_get_device_list. If
unref_device is set to 1 all devices in the list have their reference
counter decremented once.
uint8_t libusb_get_bus_number(libusb_device *dev) Returns the number of
the bus contained by the device dev.
uint8_t libusb_get_port_number(libusb_device *dev) Returns the port
number which the device given by dev is attached to.
int libusb_get_port_numbers(libusb_device *dev, uint8_t *buf, uint8_t
bufsize) Stores, in the buffer buf of size bufsize, the list of all port
numbers from root for the device dev.
int libusb_get_port_path(libusb_context *ctx, libusb_device *dev, uint8_t
*buf, uint8_t bufsize) Deprecated function equivalent to
libusb_get_port_numbers.
uint8_t libusb_get_device_address(libusb_device *dev) Returns the
device_address contained by the device dev.
enum libusb_speed libusb_get_device_speed(libusb_device *dev) Returns the
wire speed at which the device is connected. See the LIBUSB_SPEED_XXX
enums for more information. LIBUSB_SPEED_UNKNOWN is returned in case of
unknown wire speed.
int libusb_get_max_packet_size(libusb_device *dev, unsigned char
endpoint) Returns the wMaxPacketSize value on success,
LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist and
LIBUSB_ERROR_OTHERS on other failure.
int libusb_get_max_iso_packet_size(libusb_device *dev, unsigned char
endpoint) Returns the packet size multiplied by the packet multiplier on
success, LIBUSB_ERROR_NOT_FOUND if the endpoint does not exist and
LIBUSB_ERROR_OTHERS on other failure.
libusb_device * libusb_ref_device(libusb_device *dev) Increment the
reference counter of the device dev.
void libusb_unref_device(libusb_device *dev) Decrement the reference
counter of the device dev.
int libusb_open(libusb_device *dev, libusb_device_handle **devh) Open a
device and obtain a device_handle. Returns 0 on success,
LIBUSB_ERROR_NO_MEM on memory allocation problems, LIBUSB_ERROR_ACCESS on
permissions problems, LIBUSB_ERROR_NO_DEVICE if the device has been
disconnected and a LIBUSB_ERROR code on other errors.
libusb_device_handle * libusb_open_device_with_vid_pid(libusb_context
int libusb_get_configuration(libusb_device_handle *devh, int *config)
Returns the value of the current configuration. Returns 0 on success,
LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and a
LIBUSB_ERROR code on error.
int libusb_set_configuration(libusb_device_handle *devh, int config) Set
the active configuration to config for the device contained by devh.
This function returns 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.
int libusb_claim_interface(libusb_device_handle *devh, int
interface_number) Claim an interface in a given libusb_handle devh. This
is a non-blocking function. It returns 0 on 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.
int libusb_release_interface(libusb_device_handle *devh, int
interface_number) This function releases an interface. All the claimed
interfaces on a device must be released before closing the 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.
int 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 a
LIBUSB_ERROR code on failure.
int 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.
int 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.
int libusb_check_connected(libusb_device_handle *devh) Test if the USB
device is still connected. Returns 0 on success, LIBUSB_ERROR_NO_DEVICE
if it has been disconnected and a LIBUSB_ERROR code on failure.
int 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 and 1 if a kernel driver is active,
LIBUSB_ERROR_NO_DEVICE if the device has been disconnected and a
LIBUSB_ERROR code on failure.
int libusb_get_driver(libusb_device_handle *devh, int interface, char
*name, int namelen) or int libusb_get_driver_np(libusb_device_handle
*devh, int interface, char *name, int namelen) Copy the name of the
int libusb_detach_kernel_driver(libusb_device_handle *devh, int
interface) or int libusb_detach_kernel_driver_np(libusb_device_handle
*devh, int interface) Detach a kernel driver from an interface. This is
needed to claim an interface already claimed 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. This function is non-portable.
int libusb_attach_kernel_driver(libusb_device_handle *devh, int
interface) Re-attach an interface kernel driver that was 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
disconnected, 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.
int libusb_set_auto_detach_kernel_driver(libusb_device_handle *devh, int
enable) This function enables automatic kernel interface driver detach
when an interface is claimed. When the interface is restored the kernel
driver is allowed to be re-attached. If the enable argument is non-zero
the feature is enabled. Else disabled. Returns 0 on success and a
LIBUSB_ERROR code on failure.
USB DESCRIPTORS
int libusb_get_device_descriptor(libusb_device *dev,
libusb_device_descriptor *desc) Get the USB device descriptor for the
device dev. This is a non-blocking function. Returns 0 on success and a
LIBUSB_ERROR code on failure.
int libusb_get_active_config_descriptor(libusb_device *dev, struct
libusb_config_descriptor **config) Get the USB configuration descriptor
for the active configuration. Returns 0 on success,
LIBUSB_ERROR_NOT_FOUND if the device is in an unconfigured state and a
LIBUSB_ERROR code on error.
int libusb_get_config_descriptor(libusb_device *dev, uint8_t
config_index, libusb_config_descriptor **config) Get a USB configuration
descriptor based on its index idx. Returns 0 on success,
LIBUSB_ERROR_NOT_FOUND if the configuration does not exist and a
LIBUSB_ERROR code on error.
int 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 a request through the device.
Returns 0 on success, LIBUSB_ERROR_NOT_FOUND if the configuration does
not exist and a LIBUSB_ERROR code on failure.
void libusb_free_config_descriptor(libusb_config_descriptor *config) Free
a configuration descriptor.
int libusb_get_string_descriptor(libusb_device_handle *devh, uint8_t
desc_idx, uint16_t langid, unsigned char *data, int length) Retrieve a
string descriptor in raw format. Returns the number of bytes actually
transferred on success or a negative LIBUSB_ERROR code on failure.
int libusb_get_string_descriptor_ascii(libusb_device_handle *devh,
uint8_t desc_idx, unsigned char *data, int length) Retrieve a string
extra and extra_length fields of the endpoint descriptor. On success the
pointer to resulting descriptor is stored at the location given by
ep_comp. Returns zero on success and a LIBUSB_ERROR code on failure. On
success the parsed USB 3.0 endpoint companion descriptor must be freed
using the libusb_free_ss_endpoint_comp function.
void libusb_free_ss_endpoint_comp(libusb_ss_endpoint_companion_descriptor
*ep_comp) This function is NULL safe and frees a parsed USB 3.0 endpoint
companion descriptor given by ep_comp.
int libusb_get_ss_endpoint_companion_descriptor(struct libusb_context
*ctx, const struct libusb_endpoint_descriptor *endpoint, struct
libusb_ss_endpoint_companion_descriptor **ep_comp) This function finds
and parses the USB 3.0 endpoint companion descriptor given by endpoint.
Returns zero on success and a LIBUSB_ERROR code on failure. On success
the parsed USB 3.0 endpoint companion descriptor must be freed using the
libusb_free_ss_endpoint_companion_descriptor function.
void libusb_free_ss_endpoint_companion_descriptor(struct
libusb_ss_endpoint_companion_descriptor *ep_comp) This function is NULL
safe and frees a parsed USB 3.0 endpoint companion descriptor given by
ep_comp.
int libusb_get_bos_descriptor(libusb_device_handle *handle, struct
libusb_bos_descriptor **bos) This function queries the USB device given
by handle and stores a pointer to a parsed BOS descriptor into bos.
Returns zero on success and a LIBUSB_ERROR code on failure. On success
the parsed BOS descriptor must be freed using the
libusb_free_bos_descriptor function.
int libusb_parse_bos_descriptor(const void *buf, int len,
libusb_bos_descriptor **bos) This function parses a Binary Object Store,
BOS, descriptor into host endian format pointed to by buf and having a
length of len. On success the pointer to resulting descriptor is stored
at the location given by bos. Returns zero on success and a LIBUSB_ERROR
code on failure. On success the parsed BOS descriptor must be freed
using the libusb_free_bos_descriptor function.
void libusb_free_bos_descriptor(libusb_bos_descriptor *bos) This function
is NULL safe and frees a parsed BOS descriptor given by bos.
int libusb_get_usb_2_0_extension_descriptor(struct libusb_context *ctx,
struct libusb_bos_dev_capability_descriptor *dev_cap, struct
libusb_usb_2_0_extension_descriptor **usb_2_0_extension) This function
parses the USB 2.0 extension descriptor from the descriptor given by
dev_cap and stores a pointer to the parsed descriptor into
usb_2_0_extension. Returns zero on success and a LIBUSB_ERROR code on
failure. On success the parsed USB 2.0 extension descriptor must be
freed using the libusb_free_usb_2_0_extension_descriptor function.
void libusb_free_usb_2_0_extension_descriptor(struct
libusb_usb_2_0_extension_descriptor *usb_2_0_extension) This function is
NULL safe and frees a parsed USB 2.0 extension descriptor given by
usb_2_0_extension.
int libusb_get_ss_usb_device_capability_descriptor(struct libusb_context
*ctx, struct libusb_bos_dev_capability_descriptor *dev_cap, struct
libusb_ss_usb_device_capability_descriptor **ss_usb_device_capability)
This function parses the SuperSpeed device capability descriptor from the
libusb_ss_usb_device_capability_descriptor *ss_usb_device_capability)
This function is NULL safe and frees a parsed SuperSpeed device
capability descriptor given by ss_usb_device_capability.
int libusb_get_container_id_descriptor(struct libusb_context *ctx, struct
libusb_bos_dev_capability_descriptor *dev_cap, struct
libusb_container_id_descriptor **container_id) This function parses the
container ID descriptor from the descriptor given by dev_cap and stores a
pointer to the parsed descriptor into container_id. Returns zero on
success and a LIBUSB_ERROR code on failure. On success the parsed
container ID descriptor must be freed using the
libusb_free_container_id_descriptor function.
void libusb_free_container_id_descriptor(struct
libusb_container_id_descriptor *container_id) This function is NULL safe
and frees a parsed container ID descriptor given by container_id.
USB ASYNCHRONOUS I/O
struct libusb_transfer * libusb_alloc_transfer(int iso_packets) Allocate
a transfer with the number of isochronous packet descriptors specified by
iso_packets. Returns NULL on error.
void libusb_free_transfer(struct libusb_transfer *tr) Free a transfer.
int 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 a
LIBUSB_ERROR code on other failure.
int libusb_cancel_transfer(struct libusb_transfer *tr) This function
asynchronously cancels a transfer. Returns 0 on success and a
LIBUSB_ERROR code on failure.
USB SYNCHRONOUS I/O
int 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) Perform a
USB control transfer. Returns the actual number of bytes transferred on
success, in the range from and including zero up to and including
wLength. On error a LIBUSB_ERROR code is returned, for example
LIBUSB_ERROR_TIMEOUT if the transfer timed out, LIBUSB_ERROR_PIPE if the
control request was not supported, LIBUSB_ERROR_NO_DEVICE if the device
has been disconnected and another LIBUSB_ERROR code on other failures.
The LIBUSB_ERROR codes are all negative.
int 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. A timeout value of zero means no
timeout. The timeout value is given in milliseconds. Returns 0 on
success, LIBUSB_ERROR_TIMEOUT if the transfer timed out,
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 a
LIBUSB_ERROR code on other failure.
int 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. A timeout value
of zero means no timeout. The timeout value is given in milliseconds.
int libusb_alloc_streams(libusb_device_handle *dev, uint32_t num_streams,
unsigned char *endpoints, int num_endpoints) This function verifies that
the given number of streams using the given number of endpoints is
allowed and allocates the resources needed to use so-called USB streams.
Currently only a single stream per endpoint is supported to simplify the
internals of LibUSB. This function returns 0 on success or a
LIBUSB_ERROR code on failure.
int libusb_free_streams(libusb_device_handle *dev, unsigned char
*endpoints, int num_endpoints) This function release resources needed for
streams usage. Returns 0 on success or a LIBUSB_ERROR code on failure.
void libusb_transfer_set_stream_id(struct libusb_transfer *transfer,
uint32_t stream_id) This function sets the stream ID for the given USB
transfer.
uint32_t libusb_transfer_get_stream_id(struct libusb_transfer *transfer)
This function returns the stream ID for the given USB transfer. If no
stream ID is used a value of zero is returned.
USB EVENTS
int 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.
void libusb_lock_events(libusb_context *ctx) Acquire the event handling
lock. This function is blocking.
void libusb_unlock_events(libusb_context *ctx) Release the event handling
lock. This will wake up any thread blocked on libusb_wait_for_event().
int 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.
int libusb_event_handler_active(libusb_context *ctx) Determine if an
active thread is handling events. Returns 1 if there is a thread
handling events and 0 if there are no threads currently handling events.
void libusb_interrupt_event_handler(libusb_context *ctx) Causes the
libusb_handle_events() familiy of functions to return to the caller one
time. The libusb_handle_events() functions may be called again after
calling this function.
void libusb_lock_event_waiters(libusb_context *ctx) Acquire the
event_waiters lock. This lock is designed to be obtained in 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.
void libusb_unlock_event_waiters(libusb_context *ctx) Release the
event_waiters lock.
int 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, and
to by the completed argument to non-zero. If the tv argument is not
equal to NULL, this function will return LIBUSB_ERROR_TIMEOUT after the
given timeout. Returns 0 on success, or a LIBUSB_ERROR code on failure
or timeout.
int libusb_handle_events_completed(libusb_context *ctx, int *completed)
Handle any pending events by checking the set of file descriptors for
activity. If the completed argument is not equal to NULL, this function
will loop until a transfer completion callback sets the variable pointed
to by the completed argument to non-zero. Returns 0 on success, or a
LIBUSB_ERROR code on failure.
int 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 or timeout.
int libusb_handle_events(libusb_context *ctx) Handle any pending events
in blocking mode with a sensible timeout. Returns 0 on success and a
LIBUSB_ERROR code on failure.
int libusb_handle_events_locked(libusb_context *ctx, struct timeval *tv)
Handle any pending events by polling file descriptors, without checking
if another thread is already doing so. Must be called with the event
lock held.
int 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 a
LIBUSB_ERROR code on failure or timeout.
void 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.
const struct libusb_pollfd ** libusb_get_pollfds(libusb_context *ctx)
Retrieve 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.
int libusb_hotplug_register_callback(libusb_context *ctx,
libusb_hotplug_event events, libusb_hotplug_flag flags, int vendor_id,
int product_id, int dev_class, libusb_hotplug_callback_fn cb_fn, void
*user_data, libusb_hotplug_callback_handle *handle) This function
registers a hotplug filter. The events argument select which events
makes the hotplug filter trigger. Available event values are
LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED and LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT.
One or more events must be specified. The vendor_id, product_id and
dev_class arguments can be set to LIBUSB_HOTPLUG_MATCH_ANY to match any
value in the USB device descriptor. Else the specified value is used for
matching. If the flags argument is set to LIBUSB_HOTPLUG_ENUMERATE, all
currently attached and matching USB devices will be passed to the hotplug
filter, given by the cb_fn argument. Else the flags argument should be
set to LIBUSB_HOTPLUG_NO_FLAGS. This function returns 0 upon success or
a LIBUSB_ERROR code on failure.
int libusb_hotplug_callback_fn(libusb_context *ctx, libusb_device
void libusb_hotplug_deregister_callback(libusb_context *ctx,
libusb_hotplug_callback_handle handle) This function unregisters a
hotplug filter.
LIBUSB VERSION 0.1 COMPATIBILITY
The library is also compliant with LibUSB version 0.1.12.
usb_open() usb_close() usb_get_string() usb_get_string_simple()
usb_get_descriptor_by_endpoint() usb_get_descriptor()
usb_parse_descriptor() usb_parse_configuration()
usb_destroy_configuration() usb_fetch_and_parse_descriptors()
usb_bulk_write() usb_bulk_read() usb_interrupt_write()
usb_interrupt_read() usb_control_msg() usb_set_configuration()
usb_claim_interface() usb_release_interface() usb_set_altinterface()
usb_resetep() usb_clear_halt() usb_reset() usb_strerror() usb_init()
usb_set_debug() usb_find_busses() usb_find_devices() usb_device()
usb_get_busses() usb_check_connected() usb_get_driver_np()
usb_detach_kernel_driver_np()
SEE ALSO
libusb20(3), usb(4), usbconfig(8), usbdump(8)
https://libusb.info/
HISTORY
libusb support first appeared in FreeBSD 8.0.
FreeBSD 14.0-RELEASE-p11 January, 26, 2023 FreeBSD 14.0-RELEASE-p11