DEVICE_CAPABILITIES structure (wdm.h)
A DEVICE_CAPABILITIES structure describes PnP and power capabilities of a device. This structure is returned in response to an IRP_MN_QUERY_CAPABILITIES IRP.
Syntax
typedef struct _DEVICE_CAPABILITIES {
USHORT Size;
USHORT Version;
ULONG DeviceD1 : 1;
ULONG DeviceD2 : 1;
ULONG LockSupported : 1;
ULONG EjectSupported : 1;
ULONG Removable : 1;
ULONG DockDevice : 1;
ULONG UniqueID : 1;
ULONG SilentInstall : 1;
ULONG RawDeviceOK : 1;
ULONG SurpriseRemovalOK : 1;
ULONG WakeFromD0 : 1;
ULONG WakeFromD1 : 1;
ULONG WakeFromD2 : 1;
ULONG WakeFromD3 : 1;
ULONG HardwareDisabled : 1;
ULONG NonDynamic : 1;
ULONG WarmEjectSupported : 1;
ULONG NoDisplayInUI : 1;
ULONG Reserved1 : 1;
ULONG WakeFromInterrupt : 1;
ULONG SecureDevice : 1;
ULONG ChildOfVgaEnabledBridge : 1;
ULONG DecodeIoOnBoot : 1;
ULONG Reserved : 9;
ULONG Address;
ULONG UINumber;
DEVICE_POWER_STATE DeviceState[POWER_SYSTEM_MAXIMUM];
SYSTEM_POWER_STATE SystemWake;
DEVICE_POWER_STATE DeviceWake;
ULONG D1Latency;
ULONG D2Latency;
ULONG D3Latency;
} DEVICE_CAPABILITIES, *PDEVICE_CAPABILITIES;
Members
Size
Specifies the size of the structure, in bytes. This field is set by the component that sends the IRP_MN_QUERY_CAPABILITIES request.
Version
Specifies the version of the structure, currently version 1. This field is set by the component that sends the IRP_MN_QUERY_CAPABILITIES request.
DeviceD1
Specifies whether the device hardware supports the D1 power state. Drivers should not change this value.
DeviceD2
Specifies whether the device hardware supports the D2 power state. Drivers should not change this value.
LockSupported
Specifies whether the device supports physical-device locking that prevents device ejection. This member pertains to ejecting the device from its slot, rather than ejecting a piece of removable media from the device.
EjectSupported
Specifies whether the device supports software-controlled device ejection while the system is in the PowerSystemWorking state. This member pertains to ejecting the device from its slot, rather than ejecting a piece of removable media from the device.
Removable
Specifies whether the device can be dynamically removed from its immediate parent. If Removable is set to TRUE, the device does not belong to the same physical object as its parent.
For example, if Removable is set to TRUE for a USB composite device inside a multifunction printer, the composite device does not belong to the physical object of its immediate parent, such as a USB hub inside a notebook PC.
In most cases the bus driver, not the function driver, should determine the value of the Removable parameter of the device. For USB devices, the USB hub driver sets the Removable parameter. It should not be modified by the function driver.
If Removable is set to TRUE, the device is displayed in the Unplug or Eject Hardware program, unless SurpriseRemovalOK is also set to TRUE.
DockDevice
Specifies whether the device is a docking peripheral.
UniqueID
Specifies whether the device's instance ID is unique system-wide. This bit is clear if the instance ID is unique only within the scope of the bus. For more information, see Device Identification Strings.
SilentInstall
Specifies whether Device Manager should suppress all installation dialog boxes; except required dialog boxes such as "no compatible drivers found."
RawDeviceOK
Specifies whether the driver for the underlying bus can drive the device if there is no function driver (for example, SCSI devices in pass-through mode). This mode of operation is called raw mode.
SurpriseRemovalOK
Specifies whether the function driver for the device can handle the case where the device is removed before Windows can send IRP_MN_QUERY_REMOVE_DEVICE to it. If SurpriseRemovalOK is set to TRUE, the device can be safely removed from its immediate parent regardless of the state that its driver is in.
For example, a standard USB mouse does not maintain any state in its hardware and thus can be safely removed at any time. However, an external hard disk whose driver caches writes in memory cannot be safely removed without first letting the driver flush its cache to the hardware.
Drivers for USB devices that support surprise removal must set this to TRUE only when the IRP is being passed back up the driver stack.
WakeFromD0
Specifies whether the device can respond to an external wake signal while in the D0 state. Drivers should not change this value.
WakeFromD1
Specifies whether the device can respond to an external wake signal while in the D1 state. Drivers should not change this value.
WakeFromD2
Specifies whether the device can respond to an external wake signal while in the D2 state. Drivers should not change this value.
WakeFromD3
Specifies whether the device can respond to an external wake signal while in the D3 state. Drivers should not change this value.
HardwareDisabled
When set, this flag specifies that the device's hardware is disabled.
A device's parent bus driver or a bus filter driver sets this flag when such a driver determines that the device hardware is disabled.
The PnP manager sends one IRP_MN_QUERY_CAPABILITIES IRP right after a device is enumerated and sends another after the device has been started. The PnP manager only checks this bit right after the device is enumerated. Once the device is started, this bit is ignored.
NonDynamic
Reserved for future use.
WarmEjectSupported
Reserved for future use.
NoDisplayInUI
Do not display the device in the user interface. If this bit is set, the device is never displayed in the user interface, even if the device is present but fails to start. Only bus drivers and associated bus filter drivers should set this bit. (Also see the PNP_DEVICE_DONT_DISPLAY_IN_UI flag in the PNP_DEVICE_STATE structure.)
Reserved1
Reserved for system use.
WakeFromInterrupt
Indicates whether the driver or ACPI is responsible for handling the wake event. If set, the driver is responsible for handling the wake event. ACPI arms the device when it receives an IRP_MN_WAIT_WAKE IRP, but does not connect the interrupt, complete the IRP to notify the device stack of a wake event.
SecureDevice
Indicates whether the device is a secure device.
ChildOfVgaEnabledBridge
For a VGA device, indicates whether the parent bridge has the VGA decoding bit set.
DecodeIoOnBoot
Indictates whether the device has IO decode enabled on boot.
Reserved
Reserved for system use.
Address
Specifies an address indicating where the device is located on its underlying bus.
The interpretation of this number is bus-specific. If the address is unknown or the bus driver does not support an address, the bus driver leaves this member at its default value of 0xFFFFFFFF.
The following list describes the information certain bus drivers store in the Address field for their child devices:
| Bus | Description |
|---|---|
| 1394 | Does not supply an address because the addresses are volatile. Defaults to 0xFFFFFFFF. |
| EISA | Slot Number (0-F). |
| IDE | For an IDE device, the address contains the target ID and LUN. For an IDE channel, the address is zero or one (0 = primary channel and 1 = secondary channel). |
| ISApnp | Does not supply an address. Defaults to 0xFFFFFFFF. |
| PC Card (PCMCIA) | The socket number (typically 0x00 or 0x40). |
| PCI | The device number in the high word and the function number in the low word. |
| SCSI | The target ID. |
| USB | The port number. |
UINumber
Specifies a number associated with the device that can be displayed in the user interface.
This number is typically a user-perceived slot number, such as a number printed next to the slot on the board, or some other number that makes locating the physical device easier for the user. For buses with no such convention, or when the UINumber is unknown, the bus driver leaves this member at its default value of 0xFFFFFFFF.
DeviceState[POWER_SYSTEM_MAXIMUM]
An array of values indicating the most-powered device power state that the device can maintain for each system power state. The DeviceState[PowerSystemWorking] element of the array corresponds to the S0 system state. The entry for PowerSystemUnspecified is reserved for system use.
The entries in this array are based on the capabilities of the parent devnode. As a general rule, a driver should not change these values. However, if necessary, a driver can lower the value, for example, from PowerDeviceD1 to PowerDeviceD2.
If the bus driver is unable to determine the appropriate device power state for a root-enumerated device, it sets DeviceState[PowerSystemWorking] to PowerDeviceD0 and all other entries to PowerDeviceD3.
SystemWake
Specifies the least-powered system power state from which the device can signal a wake event. A value of PowerSystemUnspecified indicates that the device cannot wake the system.
A bus driver can get this information from its parent devnode.
In general, a driver should not change this value. If necessary, however, a driver can raise the power state, for example, from PowerSystemHibernate to PowerSystemS1, to indicate that its device cannot wake the system from a hibernation state but can from a higher-powered sleep state.
DeviceWake
Specifies the least-powered device power state from which the device can signal a wake event. A value of PowerDeviceUnspecified indicates that the device cannot signal a wake event.
D1Latency
Specifies the device's approximate worst-case latency, in 100-microsecond units, for returning the device to the PowerDeviceD0 state from the PowerDeviceD1 state. Set to zero if the device does not support the D1 state.
D2Latency
Specifies the device's approximate worst-case latency, in 100-microsecond units, for returning the device to the PowerDeviceD0 state from the PowerDeviceD2 state. Set to zero if the device does not support the D2 state.
D3Latency
Specifies the device's approximate worst-case latency, in 100-microsecond units, for returning the device to the PowerDeviceD0 state from the PowerDeviceD3 state. Set to zero if the device does not support the D3 state.
Remarks
Bus drivers set the appropriate values in this structure in response to an IRP_MN_QUERY_CAPABILITIES IRP. Bus filter drivers, function drivers, and filter drivers might alter the capabilities set by the bus driver.
Drivers that send an IRP_MN_QUERY_CAPABILITIES request must initialize the Size, Version, Address, and UINumber members of this structure before sending the IRP.
For more information about using the DEVICE_CAPABILITIES structure to describe a device's power capabilities, see Reporting Device Power Capabilities.
Requirements
| Requirement | Value |
|---|---|
| Header | wdm.h (include Wdm.h, Ntddk.h, Ntifs.h) |
See also
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