powerpc: udbg-based backend for hvc_console

This adds a new backend for the hvc console based on the low-level
udbg callbacks.  This effectively implements a working runtime console
in terms of the simple udbg primitives.  This is kind of a hack -
since udbg isn't something you really want to be using routinely - but
it's really useful during bringup.

This can be used to quickly implement a userspace-usable console while
you're working on a proper driver for whatever console I/O device the
hardware has.  Or, it can be used to avoid writing a full blown
tty/console driver entirely for quick-and-dirty I/O hardware that will
later be replaced by something else.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 43b35d0369d6..19e255c49f15 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -631,6 +631,12 @@ config HVC_XEN
         help
           Xen virtual console device driver
 
+config HVC_UDBG
+       bool "udbg based fake hypervisor console"
+       depends on PPC && EXPERIMENTAL
+       select HVC_DRIVER
+       default n
+
 config VIRTIO_CONSOLE
         tristate "Virtio console"
         depends on VIRTIO