Manual Pages for UNIX Operating System command usage for man pm_power_has_changed

Kernel Functions for Drivers             pm_power_has_changed(9F)



NAME
     pm_power_has_changed - Notify Power Management framework  of
     autonomous power level change

SYNOPSIS
     #include 
     #include 

     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



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Kernel Functions for Drivers             pm_power_has_changed(9F)



     prevent a power(9E) entry point  from  running  in  parallel
     with pm_power_has_changed().

     Note -

       If this function is called as a result of entry  into  the
       driver's  attach(9E), detach(9E) or power(9E) entry point,
       this function must be called from the  same  thread  which
       entered attach(9E), detach(9E) or power(9E).

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,



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Kernel Functions for Drivers             pm_power_has_changed(9F)



                     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       |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|


SEE ALSO
     power.conf(4), pm(7D),  attach(9E),  detach(9E),  power(9E),
     pm_busy_component(9F),                pm_idle_component(9F),
     pm_raise_power(9F),    pm_lower_power(9F),    pm(9P),    pm-
     components(9P)


     Writing Device Drivers












SunOS 5.11          Last change: 22 July 2004                   3