This message requests that the given device instance be made active. It is also used to request either exclusive or exclusive instance rights for this instance.

ulParam1 (ULONG)

This parameter can contain any of the following flags:

MCI_NOTIFY

A notification message will be posted to the window specified in the hwndCallback parameter of the data structure pointed to by the pParam2 parameter. The notification will be posted when the action indicated by this message is completed or when an error occurs.
MCI_WAIT
Control is not to be returned until the action indicated by this message is completed or an error occurs.
MCI_ACQUIRE_QUEUE
An MCI_ACQUIREDEVICE message is queued and executed as soon as device resources are available. If the request can be satisfied immediately, then it is not queued. If an MCI_ACQUIREDEVICE message is queued and an MCI_RELEASEDEVICE or MCI_CLOSE message is sent for that instance, the queued MCI_ACQUIREDEVICE message is cancelled.
MCI_EXCLUSIVE
Resources are to be exclusively allocated for the device instance. Exclusive use of resources can be released with an MCI_RELEASEDEVICE message.
MCI_EXCLUSIVE_INSTANCE
Acquires the device instance for exclusive use without acquiring the entire device resource for exclusive use. This flag locks the device instance and prevents it from being made inactive until the application sends an MCI_RELEASEDEVICE or MCI_CLOSE message. The MCI_RELEASEDEVICE puts the instance back into the fully shareable state.

pParam2 (PMCI_GENERIC_PARMS)

A pointer to the default media control interface parameter data structure.

rc (ULONG)

Return codes indicating success or type of failure:

MCIERR_SUCCESS

The function is successful.
MCIERR_INVALID_DEVICE_ID
The device ID is not valid.
MCIERR_DEVICE_LOCKED
The device is acquired for exclusive use.
MCIERR_INVALID_FLAG
Flag is invalid (ulParam1).
MCIERR_FLAGS_NOT_COMPATIBLE
Flags cannot be used together.
MCIERR_INVALID_CALLBACK_HANDLE
The callback handle given is not correct.

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