The usDeviceType field of the MCI_SYSINFO_PARMS data structure is used to indicate the device type of the query. Specifying MCI_ALL_DEVICE_ID as the usDeviceType parameter, the media control interface returns information on all devices open by the current process. If MCI_ALL_DEVICE_ID and MCI_SYSINFO_NAME are specified together then the ulNumber field of the MCI_SYSINFO_PARMS data structure is ignored and names for all devices are returned. The names will be returned separated by a single blank and null terminated.

The MCI_SYSINFO ulItem actions are intended to be used by applications that need to update the MMPM2.INI file, such as installation and setup. The MCI_SYSINFO ulItem actions MCI_SYSINFO_INSTALL_DRIVER and MCI_SYSINFO_DELETE_DRIVER do not take effect until the next time the system is started. All other MCI_SYSINFO ulItem actions take effect during the current session.