Advanced Configuration and Power Interface Specification

Advanced Configuration and Power Interface Specification
Note: For event numbers less than 255, _Exx and _Lxx methods may be used instead. In this case, they
take precedence and _EVT will not be invoked.
Example:
Scope (\_SB.GPI2)
{
Method (_EVT,1) {
// Handle all ACPI Events signaled by GPIO Controller GPI2
Switch (Arg0)
{
Case (300) {
…
Notify (\_SB.DEVX, 0x80)
}
Case (1801) {
…
Notify (\_SB.DEVY, 0x80)
}
Case (14…) {
…
Notify (\_SB.DEVZ, 0x80)
}
…
}
} //End of Method
} //End of Scope
5.6.6 Device Object Notifications
During normal operation, the platform needs to notify OSPM of various device-related events. These
notifications are accomplished using the Notify operator, which indicates a target device, thermal
zone, or processor object and a notification value that signifies the purpose of the notification.
Notification values from 0 through 0x7F are common across all device object types. Notification
values of 0xC0 and above are reserved for definition by hardware vendors for hardware specific
notifications. Notification values from 0x80 to 0xBF are device-specific and defined by each such
device. For more information on the Notify operator, see Section 19.6.92, “Notify (Notify).”
Table 5-142 Device Object Notification Values
Value Description
0 Bus Check. This notification is performed on a device object to indicate to OSPM that it
needs to perform a Plug and Play re-enumeration operation on the device tree starting from
the point where it has been notified. OSPM will typically perform a full enumeration
automatically at boot time, but after system initialization it is the responsibility of the ACPI
AML code to notify OSPM whenever a re-enumeration operation is required. The more
accurately and closer to the actual change in the device tree the notification can be done, the
more efficient the operating system’s response will be; however, it can also be an issue
when a device change cannot be confirmed. For example, if the hardware cannot recognize
a device change for a particular location during a system sleeping state, it issues a Bus
Check notification on wake to inform OSPM that it needs to check the configuration for a
device change.
250 April, 2015 Version 6.0