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Kernel Functions for Driverspm_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 circumstances, 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 attributes:

ATTRIBUTE TYPEATTRIBUTE VALUE
Stability levelEvolving

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


SunOS 5.9Go To TopLast Changed 15 Sep 1999

 
      
      
Copyright 2002 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.