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A device that might be damaged by power cycles should export the boolean (zero length) property no-involuntary-power-cycles to notify the system that all power cycles for the device must be under the control of the device driver.
The presence of this property prevents power from being removed from a device or any ancestor of the device while the device driver is detached, unless the device was voluntarily powered off as a result of the device driver calling pm_lower_power(9F).
The presence of no-involuntary-power-cycles also forces attachment of the device driver during a CPR suspend operation and prevents the suspend from taking place, unless the device driver returns DDI_SUCCESS when its detach(9E) entry point is called with DDI_SUSPEND.
The presence of no-involuntary-power-cycles does not prevent the system from being powered off due to a halt(8) or uadmin(8) invocation, except for CPR suspend.
This property can be exported by a device that is not power manageable, in which case power is not removed from the device or from any of its ancestors, even when the driver for the device and the drivers for its ancestors are detached.
Example 1 Use of Property in Driver's Configuration File
The following is an example of a no-involuntary-power-cycles entry in a driver's .conf file:
no-involuntary-power-cycles=1; ...
Example 2 Use of Property in attach() Function
The following is an example of how the preceding .conf file entry would be implemented in the attach(9E) function of a driver:
xxattach(dev_info_t *dip, ddi_attach_cmd_t cmd)
{
...
if (ddi_prop_create(DDI_DEV_T_NONE, dip, DDI_PROP_CANSLEEP,
"no-involuntary-power-cycles", NULL, 0) != DDI_PROP_SUCCESS)
goto failed;
...
}
See attributes(7) for descriptions of the following attributes:
| ATTRIBUTE TYPE ATTRIBUTE VALUE |
| Interface stability Committed |
pm (4D), attributes (7), attach (9E), detach (9E), ddi_prop_create (9F)
Writing Device Drivers