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

NAME

ddi_periodic_add - request periodic function invocation

SYNOPSIS

#include <sys/dditypes.h>
#include <sys/sunddi.h>

ddi_periodic_t ddi_periodic_add(void (*func)(void *), void *arg,
hrtime_t interval, int level);

INTERFACE LEVEL

illumos DDI specific (illumos DDI)

PARAMETERS

func
The callback function to be invoked periodically in the
specified interval.


arg
The argument passed to the callback function.


interval
The periodic interval time in nanoseconds.


level
The callback function is invoked at this priority level.
If the value of level is zero, the callback function is
invoked in kernel context. If the value is greater than
zero, but less than or equal to ten, the callback
function is invoked in interrupt context at the specified
interrupt level, which may be used for real time
applications.

This value must be in range of 0-10, which can be either
an integer literal, a pre-defined macro (DDI_IPL_0, ... ,
DDI_IPL_10), or the DDI_INTR_PRI macro with the interrupt
priority.

DESCRIPTION

The ddi_periodic_add() function schedules the specified function to
be periodically invoked in the nanosecond interval time.


As with timeout(9F), the exact time interval over which the function
takes effect cannot be guaranteed, but the value given is a close
approximation. If the callback function has not finished execution
when the next interval expires, the system will skip running the
callback for that interval.

RETURN VALUES

ddi_periodic_add() returns the non-zero opaque value
(ddi_periodic_t), which is later used to cancel the periodic request
with ddi_periodic_delete(9F).

CONTEXT

The ddi_periodic_add() function may be called from user or kernel
context.

EXAMPLES

Example 1: Using ddi_periodic_add() for a periodic callback function

In the following example, the device driver registers a periodic
callback function invoked in kernel context.


static void
my_periodic_func(void *arg)
{
/*
* This handler is invoked periodically.
*/
struct my_state *statep = (struct my_state *)arg;

mutex_enter(&statep->lock);
if (load_unbalanced(statep)) {
balance_tasks(statep);
}
mutex_exit(&statep->lock);
}

static void
start_periodic_timer(struct my_state *statep)
{
hrtime_t interval = CHECK_INTERVAL;

mutex_init(&statep->lock, NULL, MUTEX_DRIVER, DDI_IPL_0);

/*
* Register my_callback which is invoked periodically
* in CHECK_INTERVAL in kernel context.
*/
statep->periodic_id = ddi_periodic_add(my_periodic_func,
statep, interval, DDI_IPL_0);


In the following example, the device driver registers a callback
function invoked in interrupt context at level 7.

/*
* This handler is invoked periodically in interrupt context.
*/
static void
my_periodic_int7_func(void *arg)
{
struct my_state *statep = (struct my_state *)arg;
mutex_enter(&statep->lock);
monitor_device(statep);
mutex_exit(&statep->lock);
}

static void
start_monitor_device(struct my_state *statep)
{
hrtime_t interval = MONITOR_INTERVAL;

mutex_init(&statep->lock, NULL, MUTEX_DRIVER, DDI_IPL_7);

/*
* Register the callback function invoked periodically
* at interrupt level 7.
*/
statep->periodic_id = ddi_periodic_add(my_periodic_int7_func,
statep, interval, DDI_IPL_7);
}

SEE ALSO

cv_timedwait(9F), ddi_intr_get_pri(9F), ddi_intr_get_softint_pri(9F),
ddi_periodic_delete(9F), qtimeout(9F), quntimeout(9F), timeout(9F),
untimeout(9F)

NOTES

The caller must specify interval as an even, non-zero multiple of
10ms. No other values are supported at this time. The interval
specified is a lower bound on the interval between executions of the
callback.

May 4, 2017 DDI_PERIODIC_ADD(9F)