CM_Request_Device_Eject function

The CM_Request_Device_Eject function prepares a local device instance for safe removal, if the device is removable. If the device can be physically ejected, it will be.


WINAPI CM_Request_Device_Eject(
  _In_      DEVINST        dnDevInst,
  _Out_opt_ PPNP_VETO_TYPE pVetoType,
  _Out_opt_ LPTSTR         pszVetoName,
  _In_      ULONG          ulNameLength,
  _In_      ULONG          ulFlags


dnDevInst [in]

Caller-supplied device instance handle that is bound to the local machine.

pVetoType [out, optional]

(Optional.) If not NULL, this points to a location that, if the removal request fails, receives a PNP_VETO_TYPE-typed value indicating the reason for the failure.

pszVetoName [out, optional]

(Optional.) If not NULL, this is a caller-supplied pointer to a string buffer that receives a text string. The type of information this string provides is dependent on the value received by pVetoType. For information about these strings, see PNP_VETO_TYPE.

ulNameLength [in]

(Optional.) Caller-supplied value representing the length of the string buffer supplied by pszVetoName. This should be set to MAX_PATH.

ulFlags [in]

Not used.

Return value

If the operation succeeds, the function returns CR_SUCCESS. Otherwise, it returns one of the CR_-prefixed error codes defined in Cfgmgr32.h.


If pszVetoName is NULL, the PnP manager displays a message to the user indicating the device was removed or, if the request failed, identifying the reason for the failure. If pszVetoName is not NULL, the PnP manager does not display a message. (Note, however, that for Microsoft Windows 2000 only, the PnP manager displays a message even if pszVetoName is not NULL, if the device's CM_DEVCAP_DOCKDEVICE capability is set.)

Callers of CM_Request_Device_Eject sometimes require SeUndockPrivilege or SeLoadDriverPrivilege, as follows:

  • If the device's CM_DEVCAP_DOCKDEVICE capability is set (the device is a "dock" device), callers must have SeUndockPrivilege. (SeLoadDriverPrivilege is not required.)

  • If the device's CM_DEVCAP_DOCKDEVICE capability is not set (the device is not a "dock" device), and if the calling process is either not interactive or is running in a multi-user environment in a session not attached to the physical console (such as a remote Terminal Services session), callers of this function must have SeLoadDriverPrivilege.

Privileges are described in the Microsoft Windows SDK documentation.

For information about using device instance handles that are bound to the local machine, see CM_Get_Child.


Target platform



Available in Microsoft Windows 2000 and later versions of Windows.


Cfgmgr32.h (include Cfgmgr32.h)



Unicode and ANSI names

CM_Request_Device_EjectW (Unicode)

See also




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