V8/usr/sys/conf/config_how

config makes the following files for each system:
	conf.c
	ioconf.c
	ubglue.s
	makefile
	zillions of header files

to build a system from scratch,
	mkdir /usr/sys/sysname
	cd /usr/sys/sysname
	(create a machine description in `conf')
	/etc/config
	make

to change a configuration, edit `conf,' run /etc/config, and make.

to add a piece to the system:
put the filename in conf/files, with appropriate annotations (device-driver,
pseudo-device, optional, and all that).
if it's a device driver, line discipline, or filesystem handler, add an
entry to conf/devices as well.
if you just want to test things, addenda to `files' and `devices' can be
put in /usr/sys/sysname; they'll be treated as if appended to the ones in
/usr/sys/conf.

the fields in devices are
	[standard] typeofthing
		typeofthing is (character) device, block-device, stream-device,
		file-system, line-discipline.
	major device number (or filesystem number, or line discipline number)
	driver name.  the one you use in the conf file, and in conf/files.
	driver routine prefix.  see below.
	entry points:
		for a block device, some of open close strategy B_TAPE
			(the last puts B_TAPE into d_flags in bdevsw)
		for a character device, open close read write ioctl reset
		for a stream device or a line discipline, info
		for a filesystem, put get free updat read write trinc stat nami mount ioctl
entry points are catenated with the prefix.  example:
device 13		up	up	read write reset
defines device up:
major character device 13
has entry points named upread upwrite upreset

default entry points are generally `nodev'.
exceptions: open close default to `nulldev,' except for stream devices.
reset defaults to nulldev always.
info (obviously) defaults to NULL.