PM_POWER_HAS_CHANGED(9F) 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 <sys/ddi.h>
#include <sys/sunddi.h>

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


INTERFACE LEVEL


illumos DDI specific (illumos 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(9F) 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().

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(9F):

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(7) for a description of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Committed |
+--------------------+-----------------+

SEE ALSO


pm(4D), power.conf(5), attach(9E), detach(9E), power(9E),
pm_busy_component(9F), pm_idle_component(9F), pm_lower_power(9F),
pm_raise_power(9F), pm(9P), pm-components(9P)


Writing Device Drivers


July 22, 2004 PM_POWER_HAS_CHANGED(9F)