Tribblix: manual page: pm_power_has

PM_POWER_HAS_CHANGED(9F) Kernel Functions for Drivers

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