pm_power_has_changed(9F)

NAME

     pm_power_has_changed - Notify Power Management framework  of
     autonomous power level change

SYNOPSIS

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

     int pm_power_has_changed(dev_info_t *dip, int component, int
     level);

INTERFACE LEVEL

     Solaris DDI specific (Solaris DDI)

PARAMETERS

     dip   Pointer to the device dev_info structure

     component
           Number of the component that has changed power level

     level Power level  to  which  the  indicated  component  has
           changed

DESCRIPTION

     The  pm_power_has_changed(9)  function  notifies  the  Power
     Management  framework  that  the power level of component of
     dip has changed to level.

     Normally power level changes  are  initiated  by  the  Power
     Management  framework  due  to device idleness, or through a
     request   to   the   framework   from   the    driver    via
     pm_raise_power(9F)  or  pm_lower_power(9F), but some devices
     may change power levels on their own. For the  framework  to
     track  the  power  level  of  the  device  under  these cir-
     cumstances, the framework must  be  notified  of  autonomous
     power level changes by a call to pm_power_has_changed().

     Because of the asynchronous  nature  of  these  events,  the
     Power  Management  framework  might  have  called  power(9E)
     between the device's autonomous power level change  and  the
     driver  calling pm_power_has_changed(), or the framework may
     be  in  the  process  of  changing  the  power  level   when
     pm_power_has_changed() is called. To handle these situations
     correctly, the driver  should  verify  that  the  device  is
     indeed  at  the  level  or set the device to the level if it
     doesn't support inquirying of power levels,  before  calling
     pm_power_has_changed().   In  addition,  the  driver  should
     prevent a power(9E) entry point  from  running  in  parallel
     with pm_power_has_changed().

RETURN VALUES

     The pm_power_has_changed() function returns:

     DDI_SUCCESS
           The power level of component was successfully  updated
           to level.

     DDI_FAILURE
           Invalid component component or power level level

CONTEXT

     This function can be called from  user  or  kernel  context.
     This  function  can  also  be called from interrupt context,
     providing that it is not the first Power Management function
     called by the driver.

EXAMPLES

     A hypothetical driver might  include  this  code  to  handle
     pm_power_has_changed(9):

     static int
     xxusb_intr(struct buf *bp)
     {

          ...

          /*
           * At this point the device has informed us that it has
           * changed power level on its own. Inform this to framework.
           * We need to take care of the case when framework has
           * already called power() entry point and changed power level
           * before we were able to inform framework of this change.
              * Handle this by comparing the informed power level with
           * the actual power level and only doing the call if they
           * are same. In addition, make sure that power() doesn't get
           * run in parallel with this code by holding the mutex.
           */
             ASSERT(mutex_owned(&xsp->lock));
          if (level_informed == *(xsp->level_reg_addr)) {
               if (pm_power_has_changed(xsp->dip, XXUSB_COMPONENT,
                   level_informed) != DDI_SUCCESS) {
                    mutex_exit( &xsp->lock);
                    return(DDI_INTR_UNCLAIMED);
               }
             }

          ....

     }

     xxdisk_power(dev_info *dip, int comp, int level)
     {
          mutex_enter( xsp->lock);

          ...

          ...

     }

ATTRIBUTES

     See attributes(5) for a description of the following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Stability level             | Evolving                    |
    |_____________________________|_____________________________|

SEE ALSO

     power.conf(4),  pm(7D),  power(9E),  pm_busy_components(9F),
     pm_idle_components(9F),                  pm_raise_power(9F),
     pm_lower_power(9F), pm(9P), pm-components(9P)

      Writing Device Drivers