Advanced Configuration and Power Interface Specification

ACPI Software Programming Model
5.6.5.3 The Event (_EVT) Method for Handling GPIO-signaled Events
GPIO Interrupt Connection Descriptors assign GPIO pins a controller-relative, 0-based pin number.
GPIO Pin numbers can be as large as 65, 535. GPIO Interrupt Connections that are assigned by the
platform to signal ACPI events are listed in the _AEI object under the GPIO controller. Since the
GPIO interrupt connection descriptor also provides the mode of the interrupt associated with an
event, it gives OSPM all the information it needs to invoke a handler method for the event. No
naming convention is required to encode the mode and pin number of the event. Instead, a handler
for a GPIO-signaled event simply needs to have a well-known name and take the pin number of the
event as a parameter. A single instance of the method handles all ACPI events for a given GPIO
controller device.
For GPIO-signaled events, the Event (_EVT) method is used.
_EVT is defined as follows:
Arguments: (1)
Arg0 - EventNumber. An Integer indicating the event number (Controller-relative zero-based GPIO
pin number) of the current event. Must be in the range 0x0000 - 0xffff.
Return Value:
None
Description
The _EVT method handles a GPIO-signaled event. It must appear within the scope of the GPIO
controller device whose pins are used to signal the event.
OSPM handles GPIO-signaled events as follows:
• The GPIO interrupt is handled by OSPM because it is listed in the _AEI object under a GPIO
controller.
• When the event fires, OSPM handles the interrupt according to its mode and invokes the _EVT
method, passing it the pin number of the event.
• From this point on, handling is exactly like that for GPEs. The _EVT method does a Notify() on
the appropriate device, and OS-specific mechanisms are used to notify the driver of the event.
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