The MCIDRV commands provide subsystem communication between MDM and the MCDs. The current set of MCIDRV commands provide for device resource management. The MCIDRV_SAVE and MCIDRV_RESTORE messages allow MDM to manage devices that support multiple device contexts either concurrently or serially. The MCIDRV_CHANGERESOURCE message allows MCDs to change the resource consumed by a device context as required. MCIDRV_CHANGERESOURCE is sent from an MCD to MDM. A device context is made active when the MCD receives an MCIDRV_RESTORE from MDM. An MCI_OPEN command is not complete (the device is not active) until MDM has sent the MCD an MCIDRV_RESTORE. Similarly, when MDM sends an MCD the MCIDRV_SAVE command, the MCD will make the device context inactive. These commands provide multiple device contexts the ability to share one device.