USB

/* pick defaults that works with all speeds, without short packets.
*
* Best per-frame data rates:
* high speed, bulk 512 * 13 * 8 = 53248
* interrupt 1024 * 3 * 8 = 24576
* full speed, bulk/intr 64 * 19 = 1216
* interrupt 64 * 1 = 64
* low speed, interrupt 8 * 1 = 8
*/