NAME
usb_add_task,
usb_rem_task, usb_wait_task,
usb_rem_wait_task,
usb_init_task —
USB task queues
SYNOPSIS
#include
<dev/usb/usbdi.h>
void
usb_add_task(struct
usbd_device *dev, struct
usb_task *task);
void
usb_rem_task(struct
usbd_device *dev, struct
usb_task *task);
void
usb_wait_task(struct
usbd_device *dev, struct
usb_task *task);
void
usb_rem_wait_task(struct
usbd_device *dev, struct
usb_task *task);
void
usb_init_task(struct
usb_task *task, void
(*fn)(void *), void
*arg, char
type);
DESCRIPTION
The USB stack provides an API to manage task execution in a thread context at the soonest opportunity. There are three different task queues that are executed on two separate threads. All tasks executed via the USB task API are serialized with USB events such as device detachments.
The
usb_add_task()
function enqueues a task to be executed by the task thread. Subsequent calls
to usb_add_task() will not result in multiple
executions being scheduled. The task structure must already be initialised
by usb_init_task().
The
usb_rem_task()
function removes a scheduled task from its queue. If the work was already
executed or has not been added to the task queue, the call will have no
effect. Calling usb_rem_task() while the task is
executing will not abort it.
The
usb_wait_task()
function sleeps until the given task is neither queued for execution nor
currently running.
The
usb_rem_wait_task()
function is the equivalent of calling usb_rem_task()
followed by usb_wait_task().
The
usb_init_task()
macro prepares the task structure task to be used in
future calls to usb_add_task(),
usb_rem_task(),
usb_wait_task(), and
usb_rem_wait_task(). task will
be prepared to call the function fn with the argument
specified by arg. The type of
the task determines the queue and thread that will be used for its
execution:
USB_TASK_TYPE_GENERIC- Tasks used for general work that need to happen in a process context.
USB_TASK_TYPE_EXPLORE- Device discovery tasks exploring the tree from the root.
USB_TASK_TYPE_ABORT- Tasks of this type execute on a dedicated thread not shared with other USB task types.
Most drivers will only define tasks of type
USB_TASK_TYPE_GENERIC. Note that
USB_TASK_TYPE_ABORT tasks are only used by host
controller drivers and should never be used by drivers. Once initialised,
the task can be used repeatedly in the API functions
listed above and does not need to be reinitialised unless the function
called and/or its argument must change.
CONTEXT
usb_task_add() can be called from any
context.