Manual Pages for UNIX Operating System command usage for man ddi_periodic_add

Kernel Functions for Drivers                 ddi_periodic_add(9F)



NAME
     ddi_periodic_add  -  issue   nanosecond   periodic   timeout
     requests

SYNOPSIS
     #include 
     #include 

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


INTERFACE LEVEL
     Solaris DDI specific (Solaris DDI)

PARAMETERS
     func        The callback function is invoked periodically in
                 the specified interval. If the argument level is
                 zero, the function is invoked in kernel context.
                 Otherwise,  it's invoked in interrupt context at
                 the specified level.


     arg         The argument passed to the callback function.


     interval    Interval time in nanoseconds.


     level       Callback interrupt level. If the value is  zero,
                 the  callback function is invoked in kernel con-
                 text. If the value is more 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 a numeric number, 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 inter-
     val 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.



SunOS 5.11          Last change: 13 Apr 2009                    1






Kernel Functions for Drivers                 ddi_periodic_add(9F)



RETURN VALUES
     ddi_periodic_add()returns   the   non-zero   opaque    value
     (ddi_periodic_t),     which     might     be     used    for
     ddi_periodic_delete(9F) to specify the request.

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,
                    (void *)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.



SunOS 5.11          Last change: 13 Apr 2009                    2






Kernel Functions for Drivers                 ddi_periodic_add(9F)



       /*
        * 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,
                     (void *)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_periodic_delete(9F),       ddi_intr_get_softint_pri(9F),
     delay(9F), drv_usectohz(9F),  qtimeout(9F),  quntimeout(9F),
     timeout(9F), untimeout(9F)

NOTES
     A caller can only specify an interval in an integral  multi-
     ple of 10ms. No other values are supported at this time. The
     interval specified is a lower bound on the interval on which
     the callback occurs.















SunOS 5.11          Last change: 13 Apr 2009                    3