Reading serial data is something ordinary when comes from devices connected by direct serial 9-pin cables. But happens with usb devices ? Considering that actually USB is a Universal Serial Bus, is it possible to read data from any device, like USB flash drives, USB keyboards & mice, USB DVB-T ?
Unless I am misreading your question, the answer is yes; were it not possible to do, no device drivers could exist.
You won't be able to read any USB device as plaintext or anything like that, though, and you will need direct access to the usb device node. Drivers may interfere with reading from them. But on a theoretical level, yes, one may read data from any serial device. That's just how drivers work - They read data from a USB line, and decide what to do with it.