/proc/devices 和/dev关系

/proc/devices/下的设备是驱动程序生成的，它可产生一个major供mknod作为参数。
/dev/下的设备是通过mknod加上去的，用户通过此设备名来访问驱动。

The following script, scull_load, is part of the scull distribution. The user of a driver that is distributed in the form of a module can invoke such a script from the system's rc.local file or call it manually whenever the module is needed.

#!/bin/sh
module="scull"
device="scull"
mode="664"

# invoke insmod with all arguments we got
# and use a pathname, as newer modutils don't look in . by default
/sbin/insmod ./$module.ko $* || exit 1

# remove stale nodes
rm -f /dev/${device}[0-3]

major=$(awk "\\$2=  =\"$module\" {print \\$1}" /proc/devices)

mknod /dev/${device}0 c $major 0
mknod /dev/${device}1 c $major 1
mknod /dev/${device}2 c $major 2
mknod /dev/${device}3 c $major 3

# give appropriate group/permissions, and change the group.
# Not all distributions have staff, some have "wheel" instead.
group="staff"
grep -q '^staff:' /etc/group || group="wheel"

chgrp $group /dev/${device}[0-3]
chmod $mode  /dev/${device}[0-3]