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⟩.