Character and Block Device Major Number Registration
There's one additional step involved in getting devices supported by
NetBSD, and that's to include their device major numbers in the file
arch/arm/conf/majors.arm32. This involves including a line in this file
of the form
device-major <name> char <num> [block <num>] [<rule>]
The name must be the prefix of the cdevsw or bdevsw struct name in the
source file - or rather, the corresponding character device switch
structure variable must be obtained by appending "_cdevsw" to the name
used in this file (and block devices should append "_bdevsw").
For the vx115_com serial device here, the cdevsw struct is named
in the source file vx115_com.c, and the corresponding line added to the majors.arm32 file is
device-major vx115_com char 110 vx115_com
The major number 110 was selected arbitrarily as an available (unused) major number.
This process is described in detail in the document "The Auto-Generation Block/Character Device Switch Tables by config(8)".