USB_INTR_REQUEST(9S) Data Structures for Drivers USB_INTR_REQUEST(9S)


usb_intr_req, usb_intr_req_t, usb_intr_request - USB interrupt request


#include <sys/usb/usba.h>


illumos DDI specific (illumos DDI)


An interrupt request (that is, a request sent through an interrupt pipe),
is used to transfer small amounts of data infrequently, but with
bounded service periods. (Data flows in either direction.) Please refer
to Section 5.7 of the USB 2.0 specification for information on interrupt
transfers. (The USB 2.0 specification is available at

The fields in the usb_intr_req_t are used to format an interrupt request.
Please see below for acceptable combinations of flags and attributes.

The usb_intr_req_t fields are:

ushort_t intr_len; /* Size of pkt. Must be set */
/* Max size is 8K for low/full speed */
/* Max size is 20K for high speed */
mblk_t *intr_data; /* Data for the data phase */
/* IN: zero-len mblk alloc by client */
/* OUT: allocated by client */
usb_opaque_t intr_client_private; /* client specific information */
uint_t intr_timeout; /* only with ONE TIME POLL, in secs */
/* If set to zero, defaults to 5 sec */
usb_req_attrs_t intr_attributes;

/* Normal callback function, called upon completion. */
void (*intr_cb)(
usb_pipe_handle_t ph, struct usb_intr_req *req);

/* Exception callback function, for error handling. */
void (*intr_exc_cb)(
usb_pipe_handle_t ph, struct usb_intr_req *req);

/* set by USBA/HCD on completion */
usb_cr_t intr_completion_reason; /* overall completion status */
/* See usb_completion_reason(9S) */
usb_cb_flags_t intr_cb_flags; /* recovery done by callback hndlr */
/* See usb_callback_flags(9S) */

Request attributes define special handling for transfers. The following
attributes are valid for interrupt requests:

Accept transfers where less data is received
than expected.

Have USB framework reset pipe and clear
functional stalls automatically on exception.

Have USB framework reset pipe automatically on

Perform a single IN transfer. Do not start
periodic transfers with this request.

Please see usb_request_attributes(9S) for more information.

Interrupt transfers/requests are subject to the following
constraints and caveats:

1) The following table indicates combinations of
usb_pipe_intr_xfer() flags argument and fields
of the usb_intr_req_t request argument (X = don't care):

"none" as attributes in the table below indicates

flags Type attributes data timeout semantics
X IN X !=NULL X illegal

X IN !ONE_XFER X !=0 illegal

X IN !ONE_XFER NULL 0 See table note (A)

no sleep IN ONE_XFER NULL 0 See table note (B)

no sleep IN ONE_XFER NULL !=0 See table note (C)

sleep IN ONE_XFER NULL 0 See table note (D)

sleep IN ONE_XFER NULL !=0 See table note (E)

X OUT X NULL X illegal

X OUT ONE_XFER X X illegal


no sleep OUT none !=NULL 0 See table note (F)

no sleep OUT none !=NULL !=0 See table note (G)

sleep OUT none !=NULL 0 See table note (H)

sleep OUT none !=NULL !=0 See table note (I)

Table notes:

A) Continuous polling, new data is returned in cloned request
structures via continuous callbacks, original request is
returned on stop polling.

B) One time poll, no timeout, callback when data is

C) One time poll, with timeout, callback when data
is received.

D) One time poll, no timeout, one callback, unblock
when transfer completes.

E) One time poll, timeout, one callback, unblock when
transfer completes or timeout occurs.

F) Transfer until data exhausted, no timeout, callback
when done.

G) Transfer until data exhausted, timeout, callback
when done.

H) Transfer until data exhausted, no timeout, unblock
when data is received.

I) Transfer until data exhausted, timeout, unblock
when data is received.

2) USB_FLAGS_SLEEP indicates here just to wait for
resources, except when ONE_XFER is set, in which case it
also waits for completion before returning.

3) Reads (IN):

a) The client driver does *not* provide a data buffer.
By default, a READ request would mean continuous
polling for data IN. The USBA framework allocates a
new data buffer for each poll. intr_len specifies
the amount of 'periodic data' for each poll.

b) The USBA framework issues a callback to the client
at the end of a polling interval when there is data to
return. Each callback returns its data in a new request
cloned from the original. Note that the amount of data
read IN is either intr_len or "wMaxPacketSize" in length.

c) Normally, the HCD keeps polling the interrupt endpoint
forever even if there is no data to be read IN. A
client driver may stop this polling by calling

d) If a client driver chooses to pass USB_ATTRS_ONE_XFER
as 'xfer_attributes' the HCD polls for data until
some data is received. The USBA framework reads in
the data, does a callback, and stops polling for any
more data. In this case, the client
driver need not explicitly call

e) All requests with USB_ATTRS_ONE_XFER require callbacks
to be specified.

f) When continuous polling is stopped, the original
request is returned with USB_CR_STOPPED_POLLING.

g) If the USB_ATTRS_SHORT_XFER_OK attribute is not set
and a short transfer is received while polling,
an error is assumed and polling is stopped. In this
case or the case of other errors, the error must be cleared
and polling restarted by the client driver. Setting the
USB_ATTRS_AUTOCLEARING attribute will clear the error
but not restart polling. (NOTE: Polling can be
restarted from an exception callback corresponding to
an original request. Please see usb_pipe_intr_xfer(9F)
for more information.

4) Writes (OUT):

a) A client driver provides the data buffer, and
data, needed for intr write.

b) Unlike read (see previous section), there
is no continuous write mode.

c) The USB_ATTRS_ONE_XFER attribute is illegal.
By default USBA keeps writing intr data until
the provided data buffer has been
written out. The USBA framework does ONE
callback to the client driver.

d) Queueing is supported.

The intr_completion_reason indicates the status
of the transfer. See usb_completion_reason(9S) for
usb_cr_t definitions.

The intr_cb_flags are set prior to calling the
exception callback handler, to summarize recovery actions
taken and errors encountered during
recovery. See usb_callback_flags(9S) for
usb_cb_flags_t definitions.

--- Callback handling ---

All usb request types share the same callback
handling. Please see usb_callback_flags(9S) for a
description of use and operation.


See attributes(7) for descriptions of the following attributes:

|Architecture | PCI-based systems |
|Interface stability | Committed |


usb_alloc_request(9F), usb_pipe_bulk_xfer(9F), usb_pipe_ctrl_xfer(9F),
usb_pipe_intr_xfer(9F), usb_pipe_isoc_xfer(9F), usb_bulk_request(9S),
usb_callback_flags(9S), usb_completion_reason(9S), usb_ctrl_request(9S),
usb_isoc_request(9S), usb_request_attributes(9S)

illumos April 9, 2016 USB_INTR_REQUEST(9S)