Reimplement the /dev/console device node.

One of the pieces of code that I had left alone during the development
of the MPSAFE TTY layer, was tty_cons.c. This file actually has two
different functions:

- It contains low-level console input/output routines (cnputc(), etc).

- It creates /dev/console and wraps all its cdevsw calls to the
  appropriate TTY.

This commit reimplements the second set of functions by moving it
directly into the TTY layer. /dev/console is now a character device node
that's basically a regular TTY, but does a lookup of `si_drv1' each time
you open it. d_write has also been changed to call log_console().
d_close() is not present, because we must make sure we don't revoke the
TTY after writing a log message to it.

Even though I'm not convinced this is in line with the future directions
of our console code, it is a good move for now. It removes recursive
locking from the top half of the TTY layer. The previous implementation
called into the TTY layer with Giant held.

I'm renaming tty_cons.c to kern_cons.c now. The code hardly contains any
TTY related bits, so we'd better give it a less misleading name.

Tested by:	Andrzej Tobola <ato iem pw edu pl>,
		Carlos A.M. dos Santos <unixmania gmail com>,
		Eygene Ryabinkin <rea-fbsd codelabs ru>

1 files changed, 1 insertions, 1 deletions

diff --git a/sys/conf/files b/sys/conf/files
index fba04aa..ad5a19a 100644
--- a/sys/conf/files
+++ b/sys/conf/files
@@ -1596,6 +1596,7 @@ kern/kern_alq.c			optional alq
 kern/kern_clock.c		standard
 kern/kern_condvar.c		standard
 kern/kern_conf.c		standard
+kern/kern_cons.c		standard
 kern/kern_cpu.c			standard
 kern/kern_cpuset.c		standard
 kern/kern_context.c		standard
@@ -1708,7 +1709,6 @@ kern/sysv_sem.c			optional sysvsem
 kern/sysv_shm.c			optional sysvshm
 kern/tty.c			standard
 kern/tty_compat.c		optional compat_43tty
-kern/tty_cons.c			standard
 kern/tty_info.c			standard
 kern/tty_inq.c			standard
 kern/tty_outq.c			standard