As "driver_status = 0x8" indicates, there is sense code which should be interpreted. Decoding the sense code yields: sg_decode_sense 70 00 05 00 00 00 00 0a 00 00 00 00 20 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Fixed format, current; Sense key: Illegal Request Additional sense: Invalid command operation code