Advanced Configuration and Power Interface Specification

Device Configuration
Before OSPM ejects a device via the device’s _EJx methods, all dependent devices listed in the
package returned by _EDL are prepared for removal. Notice that _EJx methods under the dependent
devices are not executed.
When describing a platform that includes a docking station, an _EDL object is declared under the
docking station device. For example, if a mobile system can attach to two different types of docking
stations, _EDL is declared under both docking station devices and evaluates to the packaged list of
devices that must be ejected when the system is ejected from the docking station.
An ACPI-compliant OS evaluates the _EDL method just prior to ejecting the device.
6.3.2 _EJD (Ejection Dependent Device)
This object is used to specify the name of a device on which the device, under which this object is
declared, is dependent. This object is primarily used to support docking stations. Before the device
indicated by _EJD is ejected, OSPM will prepare the dependent device (in other words, the device
under which this object is declared) for removal.
Arguments:
None
Return Value:
A String containing the device name
_EJD is evaluated once when the ACPI table loads. The EJx methods of the device indicated by
_EJD will be used to eject all the dependent devices. A device’s dependents will be ejected when the
device itself is ejected.
Note: OSPM will not execute a dependent device’s _EJx methods when the device indicated by _EJD is
ejected.
When describing a platform that includes a docking station, usually more than one _EJD object will
be needed. For example, if a dock attaches both a PCI device and an ACPI-configured device to a
mobile system, then both the PCI device description package and the ACPI-configured device
description package must include an _EJD object that evaluates to the name of the docking station
(the name specified in an _ADR or _HID object in the docking station’s description package). Thus,
when the docking connector signals an eject request, OSPM first attempts to disable and unload the
drivers for both the PCI and ACPI configured devices.
Note: An ACPI 1.0 OS evaluates the _EJD methods only once during the table load process. This
greatly restricts a table designer’s freedom to describe dynamic dependencies such as those
created in scenarios with multiple docking stations. This restriction is illustrated in the example
below; the _EJD information supplied via and ACPI 1.0-compatible namespace omits the IDE2
device from DOCK2’s list of ejection dependencies. Starting in ACPI 2.0, OSPM is presented with
a more in-depth view of the ejection dependencies in a system by use of the _EDL methods.
Example
An example use of _EJD and _EDL is as follows:
300 Hewlett-Packard/Intel/Microsoft/Phoenix/Toshiba