Advanced Configuration and Power Interface Specification

Device Configuration
Return Value:
None
For hot removal, the device must be immediately ejected when OSPM calls the _EJ0 control
method. The _EJ0 control method does not return until ejection is complete. After calling _EJ0,
OSPM verifies the device no longer exists to determine if the eject succeeded. For _HID devices,
OSPM evaluates the _STA method. For _ADR devices, OSPM checks with the bus driver for that
device.
For warm removal, the _EJ1–_EJ4 control methods do not cause the device to be immediately
ejected. Instead, they set proprietary registers to prepare the hardware to eject when the system goes
into the given sleep state. The hardware ejects the device only after OSPM has put the system in a
sleep state by writing to the SLP_EN register. After the system resumes, OSPM calls _STA to
determine if the eject succeeded.
A device object may have multiple _EJx control methods. First, it lists an EJx control method for the
preferred sleeping state to eject the device. Optionally, the device may list an EJ4 control method to
be used when the system has no power (for example, no battery) after the eject. For example, a hotdocking
notebook might list _EJ0 and _EJ4.
6.3.4 _LCK (Lock)
This control method is optional and is required only for a device that supports a software-controlled
locking mechanism. When the OS invokes this control method, the associated device is to be locked
or unlocked based upon the value of the argument that is passed. On a lock request, the control
method must not complete until the device is completely locked.
Arguments: (1)
Arg0 – An Integer containing a device lock control
0 – Unlock the device
1 – Lock the device
Return Value:
None
When describing a platform, devices use either a _LCK control method or an _EJx control method
for a device.
6.3.5 _OST (OSPM Status Indication)
This object is an optional control method that is invoked by OSPM to indicate processing status to
the platform. During device ejection, device hot add, or other event processing, OSPM may need to
perform specific handshaking with the platform. OSPM may also need to indicate to the platform its
inability to complete a requested operation; for example, when a user presses an ejection button for a
device that is currently in use or is otherwise currently incapable of being ejected. In this case, the
processing of the ACPI Eject Request notification by OSPM fails. OSPM may indicate this failure
to the platform through the invocation of the _OST control method. As a result of the status
notification indicating ejection failure, the platform may take certain action including reissuing the
notification or perhaps turning on an appropriate indicator light to signal the failure to the user.
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