PM(9P) Kernel Properties for Drivers PM(9P)

NAME

pm - Power Management properties

DESCRIPTION

The pm-hardware-state property can be used to influence the behavior
of the Power Management framework. Its syntax and interpretation is
described below.


Note that this property is only interpreted by the system immediately
after the device has successfully attached. Changes in the property
made by the driver after the driver has attached will not be
recognized.


pm-hardware-state is a string-valued property. The existence of the
pm-hardware-state property indicates that a device needs special
handling by the Power Management framework with regard to its
hardware state.


If the value of this property is needs-suspend-resume, the device has
a hardware state that cannot be deduced by the framework. The
framework definition of a device with hardware state is one with a
reg property. Some drivers, such as SCSI disk and tape drivers, have
no reg property but manage devices with "remote" hardware. Such a
device must have a pm-hardware-state property with a value of needs-
suspend-resume for the system to identify it as needing a call to its
detach(9E) entry point with command DDI_SUSPEND when system is
suspended, and a call to attach(9E) with command DDI_RESUME when
system is resumed. For devices using original Power Management
interfaces (which are now obsolete) detach(9E) is also called with
DDI_PM_SUSPEND before power is removed from the device, and
attach(9E) is called with DDI_PM_RESUME after power is restored.


A value of no-suspend-resume indicates that, in spite of the
existence of a reg property, a device has no hardware state that
needs saving and restoring. A device exporting this property will not
have its detach() entry point called with command DDI_SUSPEND when
system is suspended, nor will its attach() entry point be called with
command DDI_RESUME when system is resumed. For devices using the
original (and now obsolete) Power Management interfaces, detach(9E)
will not be called with DDI_PM_SUSPEND command before power is
removed from the device, nor attach(9E) will be called with
DDI_PM_RESUME command after power is restored to the device.


A value of parental-suspend-resume indicates that the device does not
implement the detach(9E) DDI_SUSPEND semantics, nor the attach()
DDI_RESUME semantics, but that a call should be made up the device
tree by the framework to effect the saving and/or restoring of
hardware state for this device. For devices using original Power
Management interfaces (which are now obsolete), it also indicates
that the device does not implement the detach(9E) DDI_PM_SUSPEND
semantics, nor the attach(9E) DDI_PM_RESUME semantics, but that a
call should be made up the device tree by the framework to effect the
saving and/or restoring the hardware state for this device.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


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

SEE ALSO

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


Writing Device Drivers

January 20, 2004 PM(9P)