Linux kernel documentation

• Documentation/usb

• Linux Device Drivers - Read Chapter 13 on USB

USB intro

• USB in a nutshell - A somewhat dated, but short overview of the USB 2.0 specification

• USB specifications - official bus and device class specifications from the USB-IF

• xHCI specification - eXtensible Host Controller Interface (xHCI) specification (email xhcisupport@intel.com for the latest spec)

Talks on USB

• "Superspeed Me: USB 3.0 for Linux" - video (2010)

• "USB port power off Kernel/Userspace API" - video, slides (2012)

• "Vampire Mice: How USB Power Management impacts you" - video, slides (2013)