Questions

sysfs

kobjects?

What is an ioctl and how were they used in usbfs?

Major/minor numbers

definition from LDD2
How do I know which major number to pick? Are there a list of "taken" major numbers?
- For now, we can do dynamic allocation of a major number. Later we can apply to be assigned a major number for exclusive use.

udev

definition from wikipedia
LDD2 only talks about devfs instead of udev, but calls to register major numbers seem to be the same. What are the differences for using the two systems?

Files to look at

drivers/usb/core/usb.c
drivers/usb/core/file.c (where the USB major number is registered)
drivers/usb/core/endpoint.c
/sys/class/usb_endpoint/