Re: Conceptual USB doc?

[Greg Troxel <gdt%lexort.com@localhost>]

No pointers, but:

  endpoint is sort of a subaddress on a device, kind of like a scsi
  target id

  there are normal endpoints, and then I think "isochronous" for things
  like streaming audio

  USB devices often conform to a class definition so that a driver for
  the class doesn't have to know about the specific device.   e.g. umass.

  Many don't, e.g. the various serial ports that attach to
  chipset-specific drivers and then attach that, eg:
    uslsa0 at uhub3 port 4 configuration 1 interface 0
    uslsa0: Silicon Labs (0x10c4) CP2104 USB to UART Bridge Controller (0xea60), rev 2.00/1.00, addr 4
    ucom0 at uslsa0: Silicon Labs CP210x
  See also umodem(4) for the device class driver.

  You are wanting to talk to a "USB device". You need specs about what
  the device does.  Until then, it's sort of like "I have this device
  that you talk to via ethernet".

  ugen is a kernel driver for doing reads/writes to endpoints from user
  space.  For many odd devices that attach via USB, that's useful.

  libusb is a wrapper for many operating systems, that is sort of like
  (waves hands extra wildly) a ugen abstraction layer.