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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_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
                            * transferred.
                            */
                           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.

     pre_scale_frames  If this flag is set the number of frames specified is
                       assumed to give the buffering time in milliseconds
                       instead of frames.  During transfer setup the frames
                       field is pre scaled with the corresponding value for
                       the endpoint and rounded to the nearest number of
                       frames greater than zero.  This option only has effect
                       for ISOCHRONOUS transfers.

     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⟩.



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