From: Foster Snowhill <forst@xxxxxx> [ Upstream commit 67927a1b255d883881be9467508e0af9a5e0be9d ] Apart from the standard "configurations", "interfaces" and "alternate interface settings" in USB, iOS devices also have a notion of "modes". In different modes, the device exposes a different set of available configurations. Depending on the iOS version, and depending on the current mode, the length and contents of the carrier state control message differs: * 1 byte (seen on iOS 4.2.1, 8.4): * 03: carrier off (mode 0) * 04: carrier on (mode 0) * 3 bytes (seen on iOS 10.3.4, 15.7.6): * 03 03 03: carrier off (mode 0) * 04 04 03: carrier on (mode 0) * 4 bytes (seen on iOS 16.5, 17.6): * 03 03 03 00: carrier off (mode 0) * 04 03 03 00: carrier off (mode 1) * 06 03 03 00: carrier off (mode 4) * 04 04 03 04: carrier on (mode 0 and 1) * 06 04 03 04: carrier on (mode 4) Before this change, the driver always used the first byte of the response to determine carrier state.