vt: Fix replacement console check when unbinding

I don't fully understand the magic of the vt register/unregister
logic, but apparently everything but the inital console (as set
in the conswitchp pointer) is marked with FLAG_MODULE. Which means
if something unregistered the boot vt driver (e.g. i915.ko kicking
out vga_con) there's nothing left when trying to unbind e.g. fbcon
through sysfs.

But in most cases have the dummy console hanging around besides the
boot console, so this test is fairly dubious. What we actually want is
simply a different console than the one we want to unbind.

v2: Correct the commit message to clarify that the dummy console isn't
always around, but only in most cases (David).

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: David Herrmann <dh.herrmann@gmail.com>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 3ad0b61e35b47b00fa874c6bb1ab394499f9a168..ea600f482eeb45ba7bd985427ad7dc06b56b4c64 100644 (file)
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -3155,8 +3155,7 @@ int do_unbind_con_driver(const struct consw *csw, int first, int last, int deflt
        for (i = 0; i < MAX_NR_CON_DRIVER; i++) {
                con_back = &registered_con_driver[i];
 
-               if (con_back->con &&
-                   !(con_back->flag & CON_DRIVER_FLAG_MODULE)) {
+               if (con_back->con && con_back->con != csw) {
                        defcsw = con_back->con;
                        retval = 0;
                        break;