Advanced Configuration and Power Interface Specification

ACPI Software Programming Model
event value and T indicates the event EOI protocol to use (either ‘E’ for edge triggered, or ‘L’ for
level triggered). The event values for status bits in GPE0_BLK start at zero (_T00), end at the
(GPE0_BLK_LEN / 2) - 1, and correspond to each status bit index within GPE0_BLK. The event
values for status bits in GPE1_BLK are offset by GPE_BASE and therefore start at GPE1_BASE
and end at GPE1_BASE + (GPE1_BLK_LEN / 2) - 1.
For example, suppose an OEM supplies a wake event for a communications port and uses bit 4 of the
GPE0_STS bits to raise the wake event status. In an OEM-provided Definition Block, there must be
a Method declaration that uses the name \_GPE._L04 or \GPE._E04 to handle the event. An example
of a control method declaration using such a name is the following:
Method (\_GPE._L04) { // GPE 4 level wake handler
Notify (\_SB.PCIO.COM0, 2)
}
The control method performs whatever action is appropriate for the event it handles. For example, if
the event means that a device has appeared in a slot, the control method might acknowledge the
event to some other hardware register and signal a change notify request of the appropriate device
object. Or, the cause of the general-purpose event can result from more then one source, in which
case the control method for that event determines the source and takes the appropriate action.
When a general-purpose event is raised from the GPE bit tied to an embedded controller, the
embedded controller driver uses another naming convention defined by ACPI for the embedded
controller driver to determine which control method to queue for execution. The queries that the
embedded controller driver exchanges with the embedded controller are numbered from 0 through
FF, yielding event codes 01 through FF. (A query response of 0 from the embedded controller is
reserved for “no outstanding events.”) The name of the control method to queue is always of the
form _Qxx where xx is the number of the query acknowledged by the embedded controller. An
example declaration for a control method that handles an embedded controller query is the
following:
Method(_Q34) { // embedded controller event for thermal
Notify (\_SB.TZ0.THM1, 0x80)
}
When an SMBus alarm is handled by the SMBus driver, the SMBus driver uses a similar naming
convention defined by ACPI for the driver to determine the control method to queue for execution.
When an alarm is received by the SMBus host controller, it generally receives the SMBus address of
the device issuing the alarm and one word of data. On implementations that use SMBALERT# for
notifications, only the device address will be received. The name of the control method to queue is
always of the form _Qxx where xx is the SMBus address of the device that issued the alarm. The
SMBus address is 7 bits long corresponding to hex values 0 through 7F, although some addresses are
reserved and will not be used. The control method will always be queued with one argument that
contains the word of data received with the alarm. An exception is the case of an SMBus using
SMBALERT# for notifications, in this case the argument will be 0. An example declaration for a
control method that handles a SMBus alarm follows:
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