freebsd-dev/lib/libusb/libusb.3

.\"
.\" Copyright (c) 2008 Hans Petter Selasky
.\"
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.\" $FreeBSD$
.\"
.Dd April 5, 2009
.Dt LIBUSB 3
.Os
.Sh NAME
.Nm libusb
.
.Nd "USB access library"
.
.
.Sh LIBRARY
.
.
USB access library (libusb -lusb)
.
.
.
.Sh SYNOPSIS
.In libusb20.h
.Ft int
.Fn libusb20_tr_close "struct libusb20_transfer *xfer"
.Ft int
.Fn libusb20_tr_open "struct libusb20_transfer *xfer" "uint32_t max_buf_size" "uint32_t max_frame_count" "uint8_t ep_no"
.Ft struct libusb20_transfer*
.Fn libusb20_tr_get_pointer "struct libusb20_device *pdev"  "uint16_t tr_index"
.Ft uint16_t
.Fn libusb20_tr_get_time_complete "struct libusb20_transfer *xfer"
.Ft uint32_t
.Fn libusb20_tr_get_actual_frames "struct libusb20_transfer *xfer"
.Ft uint32_t
.Fn libusb20_tr_get_actual_length "struct libusb20_transfer *xfer"
.Ft uint32_t
.Fn libusb20_tr_get_max_frames "struct libusb20_transfer *xfer"
.Ft uint32_t
.Fn libusb20_tr_get_max_packet_length "struct libusb20_transfer *xfer"
.Ft uint32_t
.Fn libusb20_tr_get_max_total_length "struct libusb20_transfer *xfer"
.Ft uint8_t
.Fn libusb20_tr_get_status "struct libusb20_transfer *xfer"
.Ft uint8_t
.Fn libusb20_tr_pending "struct libusb20_transfer *xfer"
.Ft void
.Fn libusb20_tr_callback_wrapper "struct libusb20_transfer *xfer"
.Ft void
.Fn libusb20_tr_clear_stall_sync "struct libusb20_transfer *xfer"
.Ft void
.Fn libusb20_tr_drain "struct libusb20_transfer *xfer"
.Ft void
.Fn libusb20_tr_set_buffer "struct libusb20_transfer *xfer" "void *buffer" "uint16_t fr_index"
.Ft void
.Fn libusb20_tr_set_callback "struct libusb20_transfer *xfer" "libusb20_tr_callback_t *cb"
.Ft void
.Fn libusb20_tr_set_flags "struct libusb20_transfer *xfer" "uint8_t flags"
.Ft void
.Fn libusb20_tr_set_length "struct libusb20_transfer *xfer" "uint32_t length" "uint16_t fr_index"
.Ft void
.Fn libusb20_tr_set_priv_sc0 "struct libusb20_transfer *xfer" "void *sc0"
.Ft void
.Fn libusb20_tr_set_priv_sc1 "struct libusb20_transfer *xfer" "void *sc1"
.Ft void
.Fn libusb20_tr_set_timeout "struct libusb20_transfer *xfer" "uint32_t timeout"
.Ft void
.Fn libusb20_tr_set_total_frames "struct libusb20_transfer *xfer" "uint32_t nframes"
.Ft void
.Fn libusb20_tr_setup_bulk "struct libusb20_transfer *xfer" "void *pbuf" "uint32_t length" "uint32_t timeout"
.Ft void
.Fn libusb20_tr_setup_control "struct libusb20_transfer *xfer" "void *psetup" "void *pbuf" "uint32_t timeout"
.Ft void
.Fn libusb20_tr_setup_intr "struct libusb20_transfer *xfer" "void *pbuf" "uint32_t length" "uint32_t timeout"
.Ft void
.Fn libusb20_tr_setup_isoc "struct libusb20_transfer *xfer" "void *pbuf" "uint32_t length" "uint61_t fr_index"
.Ft void
.Fn libusb20_tr_start "struct libusb20_transfer *xfer"
.Ft void
.Fn libusb20_tr_stop "struct libusb20_transfer *xfer"
.Ft void
.Fn libusb20_tr_submit "struct libusb20_transfer *xfer"
.Ft void *
.Fn libusb20_tr_get_priv_sc0 "struct libusb20_transfer *xfer"
.Ft void *
.Fn libusb20_tr_get_priv_sc1 "struct libusb20_transfer *xfer"
.Ft const char *
.Fn libusb20_dev_get_backend_name "struct libusb20_device *"
.Ft int
.Fn libusb20_dev_get_info "struct libusb20_device *pdev" "struct usb2_device_info *pinfo"
.Ft int
.Fn libusb20_dev_get_iface_desc "struct libusb20_device *pdev" "uint8_t iface_index" "char *buf" "uint8_t len"
.Ft const char *
.Fn libusb20_dev_get_desc "struct libusb20_device *pdev"
.Ft int
.Fn libusb20_dev_claim_interface "struct libusb20_device *pdev" "uint8_t iface_index"
.Ft int
.Fn libusb20_dev_close "struct libusb20_device *pdev"
.Ft int
.Fn libusb20_dev_detach_kernel_driver "struct libusb20_device *pdev" "uint8_t iface_index"
.Ft int
.Fn libusb20_dev_set_config_index "struct libusb20_device *pdev" "uint8_t configIndex"
.Ft int
.Fn libusb20_dev_get_debug "struct libusb20_device *pdev"
.Ft int
.Fn libusb20_dev_get_fd "struct libusb20_device *pdev"
.Ft int
.Fn libusb20_dev_kernel_driver_active "struct libusb20_device *pdev" "uint8_t iface_index"
.Ft int
.Fn libusb20_dev_open "struct libusb20_device *pdev" "uint16_t transfer_max"
.Ft int
.Fn libusb20_dev_process "struct libusb20_device *pdev"
.Ft int
.Fn libusb20_dev_release_interface "struct libusb20_device *pdev" "uint8_t iface_index"
.Ft int
.Fn libusb20_dev_request_sync "struct libusb20_device *pdev" "struct LIBUSB20_CONTROL_SETUP_DECODED *setup" "void *data" "uint16_t *pactlen" "uint32_t timeout" "uint8_t flags"
.Ft int
.Fn libusb20_dev_req_string_sync "struct libusb20_device *pdev" "uint8_t index" "uint16_t langid" "void *ptr" "uint16_t len"
.Ft int
.Fn libusb20_dev_req_string_simple_sync "struct libusb20_device *pdev" "uint8_t index" "void *ptr" "uint16_t len"
.Ft int
.Fn libusb20_dev_reset "struct libusb20_device *pdev"
.Ft int
.Fn libusb20_dev_set_power_mode "struct libusb20_device *pdev" "uint8_t power_mode"
.Ft uint8_t
.Fn libusb20_dev_get_power_mode "struct libusb20_device *pdev"
.Ft int
.Fn libusb20_dev_set_alt_index "struct libusb20_device *pdev" "uint8_t iface_index" "uint8_t alt_index"
.Ft int
.Fn libusb20_dev_get_device_desc "struct libusb20_device *pdev" "uint8_t iface_indexr", "char *buf" "uint8_t len"
.Ft struct libusb20_config *
.Fn libusb20_dev_alloc_config "struct libusb20_device *pdev" "uint8_t config_index"
.Ft struct libusb20_device *
.Fn libusb20_dev_alloc "void"
.Ft uint8_t
.Fn libusb20_dev_get_address "struct libusb20_device *pdev"
.Ft uint8_t
.Fn libusb20_dev_get_bus_number "struct libusb20_device *pdev"
.Ft uint8_t
.Fn libusb20_dev_get_mode "struct libusb20_device *pdev"
.Ft uint8_t
.Fn libusb20_dev_get_speed "struct libusb20_device *pdev"
.Ft uint8_t
.Fn libusb20_dev_get_config_index "struct libusb20_device *pdev"
.Ft void
.Fn libusb20_dev_free "struct libusb20_device *pdev"
.Ft void
.Fn libusb20_dev_set_debug "struct libusb20_device *pdev" "int debug"
.Ft void
.Fn libusb20_dev_wait_process "struct libusb20_device *pdev" "int timeout"
.Ft int
.Fn libusb20_be_get_template "struct libusb20_backend *pbe" "int *ptemp"
.Ft int
.Fn libusb20_be_set_template "struct libusb20_backend *pbe" "int temp"
.Ft int
.Fn libusb20_be_get_dev_quirk "struct libusb20_backend *pber", "uint16_t index" "struct libusb20_quirk *pq"
.Ft int
.Fn libusb20_be_get_quirk_name "struct libusb20_backend *pbe" "uint16_t index" "struct libusb20_quirk *pq"
.Ft int
.Fn libusb20_be_add_dev_quirk "struct libusb20_backend *pbe" "struct libusb20_quirk *pq"
.Ft int
.Fn libusb20_be_remove_dev_quirk "struct libusb20_backend *pbe" "struct libusb20_quirk *pq"
.Ft struct libusb20_backend *
.Fn libusb20_be_alloc_linux "void"
.Ft struct libusb20_device *
.Fn libusb20_be_device_foreach  "struct libusb20_backend *pbe" "struct libusb20_device *pdev"
.Ft void
.Fn libusb20_be_dequeue_device "struct libusb20_backend *pbe" "struct libusb20_device *pdev"
.Ft void
.Fn libusb20_be_enqueue_device "struct libusb20_backend *pbe" "struct libusb20_device *pdev"
.Ft void
.Fn libusb20_be_free "struct libusb20_backend *pbe"
.Ft uint8_t
.Fn libusb20_me_get_1 "const struct libusb20_me_struct *me" "uint16_t off"
.Ft uint16_t
.Fn libusb20_me_get_2 "const struct libusb20_me_struct *me" "uint16_t off"
.Ft uint16_t
.Fn libusb20_me_encode "void *pdata" "uint16_t len" "const void *pdecoded"
.Ft uint16_t
.Fn libusb20_me_decode "const void *pdata" "uint16_t len" "void *pdecoded"
.Ft "const uint8_t *"
.Fn libusb20_desc_foreach "const struct libusb20_me_struct *me" "const uint8_t *pdesc"
.
.
.Sh DESCRIPTION
.
The
.Nm
library implements functions to be able to easily access and control
USB through the USB file system interface.
.
.
.Sh USB TRANSFER OPERATIONS
.
.Pp
.
.Fn libusb20_tr_close
will release all kernel resources associated with an USB
.Fa xfer .
.
This function returns zero upon success.
.
Non-zero return values indicate a LIBUSB20_ERROR value.
.
.Pp
.
.Fn libusb20_tr_open
will allocate kernel resources like
.Fa max_buf_size
and
.Fa max_frame_count
associated with an USB
.Fa pxfer
and bind the transfer to the specified
.Fa ep_no .
.
This function returns zero upon success.
.
Non-zero return values indicate a LIBUSB20_ERROR value.
.
.Pp
.
.Fn libusb20_tr_get_pointer
will return a pointer to the allocated USB transfer according to the
.Fa pdev
and
.Fa tr_index
arguments.
.
This function returns NULL in case of failure.
.
.Pp
.
.Fn libusb20_tr_get_time_complete
will return the completion time of an USB transfer in
millisecond units. This function is most useful for isochronous USB
transfers when doing echo cancelling.
.
.Pp
.
.Fn libusb20_tr_get_actual_frames
will return the actual number of USB frames after an USB
transfer completed. A value of zero means that no data was transferred.
.
.Pp
.
.Fn libusb20_tr_get_actual_length
will return the sum of the actual length for all
transferred USB frames for the given USB transfer.
.
.Pp
.
.Fn libusb20_tr_get_max_frames
will return the maximum number of USB frames that were
allocated when an USB transfer was setup for the given USB transfer.
.
.Pp
.
.Fn libusb20_tr_get_max_packet_length
will return the maximum packet length in bytes
associated with the given USB transfer.
.
The packet length can be used round up buffer sizes so that short USB
packets are avoided for proxy buffers.
.
.
.Pp
.
.Fn libusb20_tr_get_max_total_length
function will return the maximum value for the length sum of all
USB frames associated with an USB transfer.
.
.Pp
.
.Fn libusb20_tr_get_status
will return the status of an USB transfer.
.
Status values are defined by a set of LIBUSB20_TRANSFER_XXX enums.
.
.Pp
.
.Fn libusb20_tr_pending
will return non-zero if the given USB transfer is
pending for completion.
.
Else this function returns zero.
.
.Pp
.
.Fn libusb20_tr_callback_wrapper
This is an internal function used to wrap asynchronous USB callbacks.
.
.Pp
.
.Fn libusb20_tr_clear_stall_sync
This is an internal function used to synchronously clear the stall on
the given USB transfer.
.
Please see the USB specification for more information on stall
clearing.
.
If the given USB transfer is pending when this function is called, the
USB transfer will complete with an error after that this function has
been called.
.
.Pp
.
.Fn libusb20_tr_drain
will stop the given USB transfer and will not return
until the USB transfer has been stopped in hardware.
.
.Pp
.
.Fn libusb20_tr_set_buffer
is used to set the
.Fa buffer
pointer for the given USB transfer and
.Fa fr_index .
.
Typically the frame index is zero.
.
.
.Pp
.
.Fn libusb20_tr_set_callback
is used to set the USB callback for asynchronous USB
transfers.
.
The callback type is defined by libusb20_tr_callback_t.
.
.Pp
.
.Fn libusb20_tr_set_flags
is used to set various USB flags for the given USB transfer.
.Bl -tag
.It LIBUSB20_TRANSFER_SINGLE_SHORT_NOT_OK
Report a short frame as error.
.It LIBUSB20_TRANSFER_MULTI_SHORT_NOT_OK
Multiple short frames are not allowed.
.It LIBUSB20_TRANSFER_FORCE_SHORT
All transmitted frames are short terminated.
.It LIBUSB20_TRANSFER_DO_CLEAR_STALL
Will do a clear-stall before starting the transfer.
.El
.
.Pp
.
.Fn libusb20_tr_set_length
sets the length of a given USB transfer and frame index.
.
.Pp
.
.Fn libusb20_tr_set_priv_sc0
sets private driver pointer number zero.
.
.Pp
.
.Fn libusb20_tr_set_priv_sc1
sets private driver pointer number one.
.
.Pp
.
.Fn libusb20_tr_set_timeout
sets the timeout for the given USB transfer.
.
A timeout value of zero means no timeout.
.
The timeout is given in milliseconds.
.
.Pp
.
.Fn libusb20_tr_set_total_frames
sets the total number of frames that should be executed when the USB transfer is submitted.
.
The total number of USB frames must be less than the maximum number of USB frames associated with the given USB transfer.
.
.Pp
.
.Fn libusb20_tr_setup_bulk
is a helper function for setting up a single frame USB BULK transfer.
.
.Pp
.
.Fn libusb20_tr_setup_control
is a helper function for setting up a single or dual
frame USB CONTROL transfer depending on the control transfer length.
.
.Pp
.
.Fn libusb20_tr_setup_intr
is a helper function for setting up a single frame USB INTERRUPT transfer.
.
.Pp
.
.Fn libusb20_tr_setup_isoc
is a helper function for setting up a multi frame USB ISOCHRONOUS transfer.
.
.Pp
.
.Fn libusb20_tr_start
will get the USB transfer started, if not already
started.
.
This function will not get the transfer queued in hardware.
.
This function is non-blocking.
.
.Pp
.
.Fn libusb20_tr_stop
will get the USB transfer stopped, if not already stopped.
.
This function is non-blocking, which means that the actual stop can
happen after the return of this function.
.
.Pp
.
.Fn libusb20_tr_submit
will get the USB transfer queued in hardware.
.
.
.Pp
.
.Fn libusb20_tr_get_priv_sc0
returns private driver pointer number zero associated
with an USB transfer.
.
.
.Pp
.
.Fn libusb20_tr_get_priv_sc1
returns private driver pointer number one associated
with an USB transfer.
.
.
.Sh USB DEVICE OPERATIONS
.
.Pp
.
.Fn libusb20_dev_get_backend_name
returns a zero terminated string describing the backend used.
.
.Pp
.
.Fn libusb20_dev_get_info
retrives the BSD specific usb2_device_info structure into the memory location given by 
.Fa pinfo .
The USB device given by
.Fa pdev
must be opened before this function will succeed.
This function returns zero on success else a LIBUSB20_ERROR value is returned.
.
.Pp
.
.Fn libusb20_dev_get_iface_desc
retrieves the kernel interface description for the given USB
.Fa iface_index .
The format of the USB interface description is: "drivername<unit>: <description>"
The description string is always zero terminated.
A zero length string is written in case no driver is attached to the given interface.
The USB device given by
.Fa pdev
must be opened before this function will succeed.
This function returns zero on success else a LIBUSB20_ERROR value is returned.
.
.Pp
.
.Fn libusb20_dev_get_desc
returns a zero terminated string describing the given USB device.
The format of the string is: "drivername<unit>: <description>"
.
.Pp
.
.Fn libusb20_dev_claim_interface
This function will try to claim the given USB interface given by
.Fa iface_index .
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
.Pp
.
.Fn libusb20_dev_close
will close the given USB device.
.
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
.Pp
.
.Fn libusb20_dev_detach_kernel_driver
will try to detach the kernel driver for the USB interface given by
.Fa iface_index .
.
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
.Pp
.
.Fn libusb20_dev_set_config_index
will try to set the configuration index on an USB
device.
.
The first configuration index is zero.
.
The un-configure index is 255.
.
This function returns zero on success else a LIBUSB20_ERROR value is returned.
.
.Pp
.
.Fn libusb20_dev_get_debug
returns the debug level of an USB device.
.
.Pp
.
.Fn libusb20_dev_get_fd
returns the file descriptor of the given USB device.
.
A negative value is returned when no file descriptor is present.
.
The file descriptor can be used for polling purposes.
.
.Pp
.
.Fn libusb20_dev_kernel_driver_active
returns a non-zero value if a kernel driver is active on
the given USB interface.
.
Else zero is returned.
.
.Pp
.
.Fn libusb20_dev_open
opens an USB device so that setting up USB transfers
becomes possible.
.
The number of USB transfers can be zero which means only control
transfers are allowed.
.
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
A return value of LIBUSB20_ERROR_BUSY means that the device is already
opened.
.
.Pp
.
.Fn libusb20_dev_process
is called to sync kernel USB transfers with userland USB
transfers.
.
This function returns zero on success else a LIBUSB20_ERROR value is
returned typically indicating that the given USB device has been
detached.
.
.Pp
.
.Fn libusb20_dev_release_interface
will try to release a claimed USB interface for the specified USB device.
.
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
.Pp
.
.Fn libusb20_dev_request_sync
will perform a synchronous control request on the given
USB device.
.
Before this call will succeed the USB device must be opened.
.
.Fa setup
is a pointer to a decoded and host endian SETUP packet.
.Fa data
is a pointer to a data transfer buffer associated with the control transaction. This argument can be NULL.
.Fa pactlen
is a pointer to a variable that will hold the actual transfer length after the control transaction is complete.
.Fa timeout
is the transaction timeout given in milliseconds.
A timeout of zero means no timeout.
.Fa flags
is used to specify transaction flags, for example LIBUSB20_TRANSFER_SINGLE_SHORT_NOT_OK.
.
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
.Pp
.
.Fn libusb20_dev_req_string_sync
will synchronously request an USB string by language ID
and string index into the given buffer limited by a maximum length.
.
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
.Pp
.
.Fn libusb20_dev_req_string_simple_sync
will synchronously request an USB string using the
default language ID and convert the string into ASCII before storing
the string into the given buffer limited by a maximum length which
includes the terminating zero.
.
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
.
.Pp
.
.Fn libusb20_dev_reset
will try to BUS reset the given USB device and restore
the last set USB configuration.
.
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
.Pp
.
.Fn libusb20_dev_set_power_mode
sets the power mode of the USB device.
.
Valid power modes:
.Bl -tag
.It LIBUSB20_POWER_OFF
.It LIBUSB20_POWER_ON
.It LIBUSB20_POWER_SAVE
.It LIBUSB20_POWER_SUSPEND
.It LIBUSB20_POWER_RESUME
.El
.
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
.Pp
.
.Fn libusb20_dev_get_power_mode
returns the currently selected power mode for the given
USB device.
.
.Pp
.
.Fn libusb20_dev_set_alt_index
will try to set the given alternate index for the given
USB interface index.
.
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
.Pp
.
.Fn libusb20_dev_get_device_desc
returns a pointer to the decoded and host endian version
of the device descriptor.
.
The USB device need not be opened when calling this function.
.
.Pp
.
.Fn libusb20_dev_alloc_config
will read out and decode the USB config descriptor for
the given USB device and config index. This function returns a pointer
to the decoded configuration which must eventually be passed to
free(). NULL is returned in case of failure.
.
.Pp
.
.Fn libusb20_dev_alloc
is an internal function to allocate a new USB device.
.
.Pp
.
.Fn libusb20_dev_get_address
returns the internal and not necessarily the real
hardware address of the given USB device.
.
.Pp
.
.Fn libusb20_dev_get_bus_number
returns the internal bus number which the given USB
device belongs to.
.
.Pp
.
.Fn libusb20_dev_get_mode
returns the current operation mode of the USB entity.
.
Valid return values are:
.Bl -tag
.It LIBUSB20_MODE_HOST
.It LIBUSB20_MODE_DEVICE
.El
.
.Pp
.
.Fn libusb20_dev_get_speed
returns the current speed of the given USB device.
.
.Bl -tag
.It LIBUSB20_SPEED_UNKNOWN
.It LIBUSB20_SPEED_LOW
.It LIBUSB20_SPEED_FULL
.It LIBUSB20_SPEED_HIGH
.It LIBUSB20_SPEED_VARIABLE
.It LIBUSB20_SPEED_SUPER
.El
.
.Pp
.
.Fn libusb20_dev_get_config_index
This function returns the currently select config index for the given
USB device.
.
.Pp
.
.Fn libusb20_dev_free
will free the given USB device and all associated USB
transfers.
.
.Pp
.
.Fn libusb20_dev_set_debug
will set the debug level for the given USB device.
.
.Pp
.
.Fn libusb20_dev_wait_process
function will wait until a pending USB transfer has completed on
the given USB device.
.
A timeout value can be specified which is passed on to the
.Xr 2 poll
function.
.
.Sh USB BACKEND OPERATIONS
.
.Fn libusb20_be_get_template
will return the currently selected global USB device
side mode template into the integer pointer
.Fa ptemp .
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
.Pp
.
.Fn libusb20_be_set_template
will set the global USB device side mode template to
.Fa temp .
The new template is not activated until after the next USB
enumeration.
The template number decides how the USB device will present itself to
the USB Host, like Mass Storage Device, USB Ethernet Device. Also see
the
.Xr usb2_template 4
module.
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
.Pp
.
.Fn libusb20_be_get_dev_quirk
This function will return the device quirk according to
.Fa index
into the libusb20_quirk structure pointed to by
.Fa pq .
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
If the given quirk does not exist LIBUSB20_ERROR_NOT_FOUND is
returned.
.
.Pp
.
.Fn libusb20_be_get_quirk_name
will return the quirk name according to
.Fa index
into the libusb20_quirk structure pointed to by
.Fa pq .
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
If the given quirk does not exist LIBUSB20_ERROR_NOT_FOUND is
returned.
.
.Pp
.
.Fn libusb20_be_add_dev_quirk
will add the libusb20_quirk structure pointed to by the
.Fa pq
argument into the device quirk list.
.
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
If the given quirk cannot be added LIBUSB20_ERROR_NO_MEM is
returned.
.
.Pp
.
.Fn libusb20_be_remove_dev_quirk
will remove the quirk matching the libusb20_quirk structure pointed to by the
.Fa pq
argument from the device quirk list.
.
This function returns zero on success else a LIBUSB20_ERROR value is
returned.
.
If the given quirk does not exist LIBUSB20_ERROR_NOT_FOUND is
returned.
.
.Fn libusb20_be_alloc_linux
These functions are used to allocate a specific USB backend or the
operating system default USB backend. Allocating a backend is a way to
scan for currently present USB devices.
.
.Pp
.
.Fn libusb20_be_device_foreach
is used to iterate USB devices present in a USB backend.
.
The starting value of
.Fa pdev
is NULL.
.
This function returns the next USB device in the list.
.
If NULL is returned the end of the USB device list has been reached.
.
.Pp
.
.Fn libusb20_be_dequeue_device
will dequeue the given USB device pointer from the
backend USB device list.
.
Dequeued USB devices will not be freed when the backend is freed.
.
.Pp
.
.Fn libusb20_be_enqueue_device
This function will enqueue the given USB device pointer in the backend USB device list.
.
Enqueued USB devices will get freed when the backend is freed.
.
.Pp
.
.Fn libusb20_be_free
will free the given backend and all USB devices in its device list.
.
.
.Sh USB DESCRIPTOR PARSING
.
.Fn libusb20_me_get_1 pie offset
This function will return a byte at the given byte offset of a message
entity.
.
This function is safe against invalid offsets.
.
.Pp
.
.Fn libusb20_me_get_2 pie offset
This function will return a little endian 16-bit value at the given byte offset of a message
entity.
.
This function is safe against invalid offsets.
.
.Pp
.
.Fn libusb20_me_encode pbuf len pdecoded
This function will encode a so-called *DECODED structure into binary
format.
.
The total encoded length that will fit in the given buffer is
returned.
.
If the buffer pointer is NULL no data will be written to the buffer
location.
.
.Pp
.
.Fn libusb20_me_decode pbuf len pdecoded
This function will decode a binary structure into a so-called *DECODED
structure.
.
The total decoded length is returned.
.
The buffer pointer cannot be NULL.
.
.
.Sh LIBUSB VERSION 0.1 COMPATIBILITY
.
.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
These functions are compliant with LibUSB version 0.1.12.
.
.Sh FILES
.
.
/dev/usb
.Sh SEE ALSO
.Xr usb2_core 4 ,
.Xr usbconfig 8
.
.
.Sh HISTORY
.
.
Some parts of the
.Nm
API derives from the libusb project at sourceforge.