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NAME

     usb_fifo_alloc_buffer, usb_fifo_attach, usb_fifo_detach, usb_fifo_free_buffer,
     usb_fifo_get_data, usb_fifo_get_data_buffer, usb_fifo_get_data_error,
     usb_fifo_get_data_linear, usb_fifo_put_bytes_max, usb_fifo_put_data,
     usb_fifo_put_data_buffer, usb_fifo_put_data_error, usb_fifo_put_data_linear, usb_fifo_reset,
     usb_fifo_softc, usb_fifo_wakeup, usbd_do_request, usbd_do_request_flags, usbd_errstr,
     usbd_lookup_id_by_info, usbd_lookup_id_by_uaa, usbd_transfer_clear_stall,
     usbd_transfer_drain, usbd_transfer_pending, usbd_transfer_poll, usbd_transfer_setup,
     usbd_transfer_start, usbd_transfer_stop, usbd_transfer_submit, usbd_transfer_unsetup,
     usbd_xfer_clr_flag, usbd_xfer_frame_data, usbd_xfer_frame_len, usbd_xfer_get_frame,
     usbd_xfer_get_priv, usbd_xfer_is_stalled, usbd_xfer_max_framelen, usbd_xfer_max_frames,
     usbd_xfer_max_len, usbd_xfer_set_flag, usbd_xfer_set_frame_data, usbd_xfer_set_frame_len,
     usbd_xfer_set_frame_offset, usbd_xfer_set_frames, usbd_xfer_set_interval,
     usbd_xfer_set_priv, usbd_xfer_set_stall, usbd_xfer_set_timeout, usbd_xfer_softc,
     usbd_xfer_state, usbd_xfer_state, usbd_xfer_status — Universal Serial Bus driver programming
     interface

SYNOPSIS

     #include <dev/usb/usb.h>
     #include <dev/usb/usbdi.h>
     #include <dev/usb/usbdi_util.h>

DESCRIPTION

     The Universal Serial Bus (USB) driver programming interface provides USB peripheral drivers
     with a host controller independent API for controlling and communicating with USB
     peripherals.  The usb module supports both USB Host and USB Device side mode.

USB KERNEL PROGRAMMING

     Here is a list of commonly used functions:

     usb_error_t usbd_transfer_setup(udev, ifaces, pxfer, setup_start, n_setup, priv_sc,
     priv_mtx)

     void usbd_transfer_unsetup(pxfer, n_setup)

     void usbd_transfer_start(xfer)

     void usbd_transfer_stop(xfer)

     void usbd_transfer_drain(xfer)

USB TRANSFER MANAGEMENT FUNCTIONS

     The USB standard defines four types of USB transfers.  Control transfers, Bulk transfers,
     Interrupt transfers and Isochronous transfers.  All the transfer types are managed using the
     following five functions:

     usbd_transfer_setup() This function will allocate memory for and initialise an array of USB
     transfers and all required DMA memory.  This function can sleep or block waiting for
     resources to become available.  udev is a pointer to "struct usb_device".  ifaces is an
     array of interface index numbers to use. See "if_index".  pxfer is a pointer to an array of
     USB transfer pointers that are initialized to NULL, and then pointed to allocated USB
     transfers.  setup_start is a pointer to an array of USB config structures.  n_setup is a
     number telling the USB system how many USB transfers should be setup.  priv_sc is the
     private softc pointer, which will be used to initialize "xfer->priv_sc".  priv_mtx is the
     private mutex protecting the transfer structure and the softc. This pointer is used to
     initialize "xfer->priv_mtx".  This function returns zero upon success. A non-zero return
     value indicates failure.

     usbd_transfer_unsetup() This function will release the given USB transfers and all allocated
     resources associated with these USB transfers.  pxfer is a pointer to an array of USB
     transfer pointers, that may be NULL, that should be freed by the USB system.  n_setup is a
     number telling the USB system how many USB transfers should be unsetup.  This function can
     sleep waiting for USB transfers to complete.  This function is NULL safe with regard to the
     USB transfer structure pointer.  It is not allowed to call this function from the USB
     transfer callback.

     usbd_transfer_start() This function will start the USB transfer pointed to by xfer, if not
     already started.  This function is always non-blocking and must be called with the so-called
     private USB mutex locked.  This function is NULL safe with regard to the USB transfer
     structure pointer.

     usbd_transfer_stop() This function will stop the USB transfer pointed to by xfer, if not
     already stopped.  This function is always non-blocking and must be called with the so-called
     private USB mutex locked.  This function can return before the USB callback has been called.
     This function is NULL safe with regard to the USB transfer structure pointer.  If the
     transfer was in progress, the callback will called with "USB_ST_ERROR" and "error =
     USB_ERR_CANCELLED".

     usbd_transfer_drain() This function will stop an USB transfer, if not already stopped and
     wait for any additional USB hardware operations to complete.  Buffers that are loaded into
     DMA using "usbd_xfer_set_frame_data()" can safely be freed after that this function has
     returned.  This function can block the caller and will not return before the USB callback
     has been called.  This function is NULL safe with regard to the USB transfer structure
     pointer.

USB TRANSFER CALLBACK

     The USB callback has three states.  USB_ST_SETUP, USB_ST_TRANSFERRED and USB_ST_ERROR.
     USB_ST_SETUP is the initial state.  After the callback has been called with this state it
     will always be called back at a later stage in one of the other two states.  The USB
     callback should not restart the USB transfer in case the error cause is USB_ERR_CANCELLED.
     The USB callback is protected from recursion.  That means one can start and stop whatever
     transfer from the callback of another transfer one desires.  Also the transfer that is
     currently called back.  Recursion is handled like this that when the callback that wants to
     recurse returns it is called one more time.

     usbd_transfer_submit() This function should only be called from within the USB callback and
     is used to start the USB hardware.  An USB transfer can have multiple frames consisting of
     one or more USB packets making up an I/O vector for all USB transfer types.

           void
           usb_default_callback(struct usb_xfer *xfer, usb_error_t error)
           {
                   int actlen;

                   usbd_xfer_status(xfer, &actlen, NULL, NULL, NULL);

                   switch (USB_GET_STATE(xfer)) {
                   case USB_ST_SETUP:
                           /*
                            * Setup xfer frame lengths/count and data
                            */
                           usbd_transfer_submit(xfer);
                           break;

                   case USB_ST_TRANSFERRED:
                           /*
                            * Read usb frame data, if any.
                            * "actlen" has the total length for all frames
                            * transfered.
                            */
                           break;

                   default: /* Error */
                           /*
                            * Print error message and clear stall
                            * for example.
                            */
                           break;
                   }
                   /*
                    * Here it is safe to do something without the private
                    * USB mutex locked.
                    */
                   return;
           }

USB CONTROL TRANSFERS

     An USB control transfer has three parts.  First the SETUP packet, then DATA packet(s) and
     then a STATUS packet.  The SETUP packet is always pointed to by frame 0 and the length is
     set by usbd_xfer_frame_len() also if there should not be sent any SETUP packet! If an USB
     control transfer has no DATA stage, then the number of frames should be set to 1.  Else the
     default number of frames is 2.

           Example1: SETUP + STATUS
            usbd_xfer_set_frames(xfer, 1);
            usbd_xfer_set_frame_len(xfer, 0, 8);
            usbd_transfer_submit(xfer);

           Example2: SETUP + DATA + STATUS
            usbd_xfer_set_frames(xfer, 2);
            usbd_xfer_set_frame_len(xfer, 0, 8);
            usbd_xfer_set_frame_len(xfer, 1, 1);
            usbd_transfer_submit(xfer);

           Example3: SETUP + DATA + STATUS - split
           1st callback:
            usbd_xfer_set_frames(xfer, 1);
            usbd_xfer_set_frame_len(xfer, 0, 8);
            usbd_transfer_submit(xfer);

           2nd callback:
            /* IMPORTANT: frbuffers[0] must still point at the setup packet! */
            usbd_xfer_set_frames(xfer, 2);
            usbd_xfer_set_frame_len(xfer, 0, 0);
            usbd_xfer_set_frame_len(xfer, 1, 1);
            usbd_transfer_submit(xfer);

           Example4: SETUP + STATUS - split
           1st callback:
            usbd_xfer_set_frames(xfer, 1);
            usbd_xfer_set_frame_len(xfer, 0, 8);
            usbd_xfer_set_flag(xfer, USB_MANUAL_STATUS);
            usbd_transfer_submit(xfer);

           2nd callback:
            usbd_xfer_set_frames(xfer, 1);
            usbd_xfer_set_frame_len(xfer, 0, 0);
            usbd_xfer_clr_flag(xfer, USB_MANUAL_STATUS);
            usbd_transfer_submit(xfer);

USB TRANSFER CONFIG

     To simply the search for endpoints the usb module defines a USB config structure where it is
     possible to specify the characteristics of the wanted endpoint.

           struct usb_config {
                   bufsize,
                   callback
                   direction,
                   endpoint,
                   frames,
                   index flags,
                   interval,
                   timeout,
                   type,
           };

     type field selects the USB pipe type.  Valid values are: UE_INTERRUPT, UE_CONTROL, UE_BULK,
     UE_ISOCHRONOUS.  The special value UE_BULK_INTR will select BULK and INTERRUPT pipes.  This
     field is mandatory.

     endpoint field selects the USB endpoint number.  A value of 0xFF, "-1" or "UE_ADDR_ANY" will
     select the first matching endpoint.  This field is mandatory.

     direction field selects the USB endpoint direction.  A value of "UE_DIR_ANY" will select the
     first matching endpoint.  Else valid values are: "UE_DIR_IN" and "UE_DIR_OUT".  "UE_DIR_IN"
     and "UE_DIR_OUT" can be binary OR'ed by "UE_DIR_SID" which means that the direction will be
     swapped in case of USB_MODE_DEVICE.  Note that "UE_DIR_IN" refers to the data transfer
     direction of the "IN" tokens and "UE_DIR_OUT" refers to the data transfer direction of the
     "OUT" tokens.  This field is mandatory.

     interval field selects the interrupt interval.  The value of this field is given in
     milliseconds and is independent of device speed.  Depending on the endpoint type, this field
     has different meaning:

     UE_INTERRUPT  "0" use the default interrupt interval based on endpoint descriptor.  "Else"
                   use the given value for polling rate.

     UE_ISOCHRONOUS
                   "0" use default. "Else" the value is ignored.

     UE_BULK

     UE_CONTROL    "0" no transfer pre-delay. "Else" a delay as given by this field in
                   milliseconds is inserted before the hardware is started when
                   "usbd_transfer_submit()" is called.

                   NOTE: The transfer timeout, if any, is started after that the pre-delay has
                   elapsed!

     timeout field, if non-zero, will set the transfer timeout in milliseconds. If the "timeout"
     field is zero and the transfer type is ISOCHRONOUS a timeout of 250ms will be used.

     frames field sets the maximum number of frames. If zero is specified it will yield the
     following results:

     UE_BULK       xfer->nframes = 1;

     UE_INTERRUPT  xfer->nframes = 1;

     UE_CONTROL    xfer->nframes = 2;

     UE_ISOCHRONOUS
                   Not allowed. Will cause an error.

     ep_index field allows you to give a number, in case more endpoints match the description,
     that selects which matching "ep_index" should be used.

     if_index field allows you to select which of the interface numbers in the "ifaces" array
     parameter passed to "usbd_transfer_setup" that should be used when setting up the given USB
     transfer.

     flags field has type "struct usb_xfer_flags" and allows one to set initial flags an USB
     transfer. Valid flags are:

     force_short_xfer
                   This flag forces the last transmitted USB packet to be short.  A short packet
                   has a length of less than "xfer->max_packet_size", which derives from
                   "wMaxPacketSize". This flag can be changed during operation.

     short_xfer_ok
                   This flag allows the received transfer length, "xfer->actlen" to be less than
                   "xfer->sumlen" upon completion of a transfer.  This flag can be changed during
                   operation.

     short_frames_ok
                   This flag allows the reception of multiple short USB frames. This flag only
                   has effect for BULK and INTERRUPT endpoints and if the number of frames
                   received is greater than 1. This flag can be changed during operation.

     pipe_bof      This flag causes a failing USB transfer to remain first in the PIPE queue
                   except in the case of "xfer->error" equal to "USB_ERR_CANCELLED". No other USB
                   transfers in the affected PIPE queue will be started until either:

                   1             The failing USB transfer is stopped using
                                 "usbd_transfer_stop()".

                   2             The failing USB transfer performs a successful transfer.
                   The purpose of this flag is to avoid races when multiple transfers are queued
                   for execution on an USB endpoint, and the first executing transfer fails
                   leading to the need for clearing of stall for example.  In this case this flag
                   is used to prevent the following USB transfers from being executed at the same
                   time the clear-stall command is executed on the USB control endpoint.  This
                   flag can be changed during operation.

                   "BOF" is short for "Block On Failure"

                   NOTE: This flag should be set on all BULK and INTERRUPT USB transfers which
                   use an endpoint that can be shared between userland and kernel.

     proxy_buffer  Setting this flag will cause that the total buffer size will be rounded up to
                   the nearest atomic hardware transfer size.  The maximum data length of any USB
                   transfer is always stored in the "xfer->max_data_length".  For control
                   transfers the USB kernel will allocate additional space for the 8-bytes of
                   SETUP header.  These 8-bytes are not counted by the "xfer->max_data_length"
                   variable.  This flag can not be changed during operation.

     ext_buffer    Setting this flag will cause that no data buffer will be allocated.  Instead
                   the USB client must supply a data buffer.  This flag can not be changed during
                   operation.

     manual_status
                   Setting this flag prevents an USB STATUS stage to be appended to the end of
                   the USB control transfer.  If no control data is transferred this flag must be
                   cleared.  Else an error will be returned to the USB callback.  This flag is
                   mostly useful for the USB device side.  This flag can be changed during
                   operation.

     no_pipe_ok    Setting this flag causes the USB_ERR_NO_PIPE error to be ignored. This flag
                   can not be changed during operation.

     stall_pipe

                   Device Side Mode
                                 Setting this flag will cause STALL pids to be sent to the
                                 endpoint belonging to this transfer before the transfer is
                                 started.  The transfer is started at the moment the host issues
                                 a clear-stall command on the STALL'ed endpoint.  This flag can
                                 be changed during operation.

                   Host Side Mode
                                 Setting this flag will cause a clear-stall control request to be
                                 executed on the endpoint before the USB transfer is started.

                   If this flag is changed outside the USB callback function you have to use the
                   "usbd_xfer_set_stall()" and "usbd_transfer_clear_stall()" functions! This flag
                   is automatically cleared after that the stall or clear stall has been
                   executed.

     bufsize field sets the total buffer size in bytes.  If this field is zero, "wMaxPacketSize"
     will be used, multiplied by the "frames" field if the transfer type is ISOCHRONOUS.  This is
     useful for setting up interrupt pipes.  This field is mandatory.

     NOTE: For control transfers "bufsize" includes the length of the request structure.

     callback pointer sets the USB callback. This field is mandatory.

USB LINUX COMPAT LAYER

     The usb module supports the Linux USB API.

SEE ALSO

     libusb(3), usb(4), usbconfig(8)

STANDARDS

     The usb module complies with the USB 2.0 standard.

HISTORY

     The usb module has been inspired by the NetBSD USB stack initially written by Lennart
     Augustsson. The usb module was written by Hans Petter Selasky <hselasky@freebsd.org>.