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

ddi_periodic_add - request periodic function invocation

#include <sys/dditypes.h>
#include <sys/sunddi.h>
ddi_periodic_t ddi_periodic_add(void (*func)(void *), void *arg,
     hrtime_t interval, int level);

illumos DDI specific (illumos DDI)

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.

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.

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).

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

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);
    }

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

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 OmniOS