illumos: manual page: usb_pipe_drain

USB_PIPE_DRAIN_REQS(9F) Kernel Functions for Drivers USB_PIPE_DRAIN_REQS(9F)

NAME

usb_pipe_drain_reqs - Allow completion of pending pipe requests

SYNOPSIS

#include <sys/usb/usba.h>

int usb_pipe_drain_reqs(dev_info_t *dip, usb_pipe_handle_t pipe_handle,
uint_t timeout, usb_flags_t usb_flags,
void (*callback)(usb_pipe_handle_t pipe_handle,
usb_opaque_t callback_arg, int rval, usb_cb_flags_t flags),
usb_opaque_t callback_arg);

INTERFACE LEVEL

illumos DDI specific (illumos DDI)

PARAMETERS

dip
Pointer to the device's dev_info structure.

pipe_handle
Handle of the pipe containing pending requests.

timeout
Maximum wait time for requests to drain. Must be a non-
negative value in seconds. Zero specifies no timeout.

flags
USB_FLAGS_SLEEP is the only flag recognized. Wait for
completion and do not call callback.

callback
Callback handler to notify of asynchronous completion.

callback_arg
Second argument passed to callback function.

DESCRIPTION

The usb_pipe_drain_reqs() function provides waits for pending requests to
complete and then provides synchronous or asynchronous notification that
all pending requests on a non-shared pipe indicated by pipe_handle have
completed. For a shared pipe (such as the default control pipe used by
multiple drivers each managing one interface of a device), this function
provides notification that all pending requests on that pipe that are
associated with a given dip are completed.

The usb_pipe_drain_reqs() function can be used to notify a close
procedure when the default control pipe is clear during device closure,
thereby allowing the close procedure to continue safely. Normally, a
synchronous call to usb_pipe_close(9F) allows all requests in a pipe to
finish before returning. However, a client driver cannot close the
default control pipe.

If USB_FLAGS_SLEEP is set in flags, block until all pending requests are
completed. Otherwise, return immediately and call the callback handler
when all pending requests are completed.

The callback parameter accepts the asynchronous callback handler, which
takes the following arguments:

usb_pipe_handle_t default_pipe_handle

Handle of the pipe to drain.

usb_opaque_t callback_arg

callback_arg specified to usb_pipe_drain_reqs().

int rval

Request status.

usb_cb_flags_t callback_flags

Status of the queueing operation. Can be:

USB_CB_NO_INFO
Callback was uneventful.

USB_CB_ASYNC_REQ_FAILED
Error starting asynchronous request.

RETURN VALUES

USB_SUCCESS
Request is successful.

USB_INVALID_ARGS
dip argument is NULL. USB_FLAGS_SLEEP is clear and
callback is NULL.

USB_INVALID_CONTEXT
Called from callback context with the
USB_FLAGS_SLEEP flag set.

USB_INVALID_PIPE
Pipe is not open, is closing or is closed.

CONTEXT

May be called from user or kernel context.

If the USB_CB_ASYNC_REQ_FAILED bit is clear in usb_cb_flags_t, the
callback, if supplied, can block because it is executing in kernel
context. Otherwise the callback cannot block. Please see
usb_callback_flags(9S) for more information on callbacks.

EXAMPLES

mydev_detach(dev_info_t *dip, ddi_detach_cmd_t cmd)
{

...
...

mydev_state->pipe_state = CLOSED;

/* Wait for pending requests of a pipe to finish. Don't timeout. */
(void) usb_pipe_drain_reqs(
dip, pipe_handle, 0, USB_FLAGS_SLEEP, NULL, 0);

/*
* Dismantle streams and tear down this instance,
* now that all requests have been sent.
*/
qprocsoff(q);
...
...
ddi_remove_minor_node(dip, NULL);
...
...
}

NOTES

For pipes other than the default control pipe, it is recommended to close
the pipe using a synchronous usb_pipe_close(). usb_pipe_close() with the
USB_FLAGS_SLEEP flag allows any pending requests in that pipe to complete
before returning.

Do not call usb_pipe_drain_reqs() while additional requests are being
submitted by a different thread. This action can stall the calling thread
of usb_pipe_drain_reqs() unnecessarily.

ATTRIBUTES