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UEFI does not provide a direct method to disconnect the existing driver of a specific protocol from a handle. We currently use DisconnectController() to remove all drivers from a handle that we want to drive ourselves, and then rely on recursion in the call to ConnectController() to reconnect any drivers that did not need to be disconnected in the first place. Experience shows that OEMs tend not to ever test the disconnection code paths in their UEFI drivers, and it is common to find drivers that refuse to disconnect, fail to close opened handles, fail to function correctly after reconnection, or lock up the entire system. Implement a more selective form of disconnection, in which we use OpenProtocolInformation() to identify the driver associated with a specific protocol, and then disconnect only that driver. Perform disconnections in reverse order of attachment priority, since this is the order likely to minimise the number of cascaded implicit disconnections. This allows our MNP driver to avoid performing any disconnections at all, since it does not require exclusive access to the MNP protocol. It also avoids performing unnecessary disconnections and reconnections of unrelated drivers such as the "UEFI WiFi Connection Manager" that attaches to wireless network interfaces in order to manage wireless network associations. Signed-off-by: Michael Brown <mcb30@ipxe.org>
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