Tribblix: manual page: usb_pipe_drain

USB_PIPE_DRAIN_REQS(9F) Kernel Functions for Drivers

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