pm_power_has_changed(9F) Kernel Functions for Drivers pm_power_has_changed(9F)NAMEpm_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 Manage‐
ment framework might have called power(9E) between the device's autono‐
mous 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 lev‐
els, 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(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 TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Stability level │Evolving │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOpower.conf(4), pm(7D), attach(9E), detach(9E), power(9E), pm_busy_com‐
ponent(9F), pm_idle_component(9F), pm_raise_power(9F),
pm_lower_power(9F), pm(9P), pm-components(9P)
Writing Device Drivers
SunOS 5.10 22 July 2004 pm_power_has_changed(9F)
