tty: Add a new VT mode which is like VT_PROCESS but doesn't require a VT_RELDISP ioctl call

This new VT mode (VT_PROCESS_AUTO) does everything that VT_PROCESS does
except that it doesn't wait for a VT_RELDISP ioctl before switching
away from a VT with that mode.

If the X server eventually uses this new mode, debugging and crash
recovery should become easier. This is because even when currently in
the VT of a frozen X server it would still be possible to switch out
by doing SysRq-r and then CTRL-<number of a text vt>, sshing in and
doing chvt <number of a text vt>, or any other method of VT switching.
The general concensus on #xorg-devel seems to be that it should be
safe to use this with X now that we have KMS.

This also moves the VT_ACKACQ define to a more appropriate place,
for clarity's sake.

Signed-off-by: Ari Entlich <atrigent@ccs.neu.edu>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/vt.h b/include/linux/vt.h
index d5dd0bc408fd..778b7b2a47d4 100644
--- a/include/linux/vt.h
+++ b/include/linux/vt.h
@@ -27,7 +27,7 @@ struct vt_mode {
 #define VT_SETMODE      0x5602  /* set mode of active vt */
 #define         VT_AUTO         0x00    /* auto vt switching */
 #define         VT_PROCESS      0x01    /* process controls switching */
-#define         VT_ACKACQ       0x02    /* acknowledge switch */
+#define         VT_PROCESS_AUTO 0x02    /* process is notified of switching */
 
 struct vt_stat {
         unsigned short v_active;        /* active vt */
@@ -38,6 +38,7 @@ struct vt_stat {
 #define VT_SENDSIG      0x5604  /* signal to send to bitmask of vts */
 
 #define VT_RELDISP      0x5605  /* release display */
+#define         VT_ACKACQ       0x02    /* acknowledge switch */
 
 #define VT_ACTIVATE     0x5606  /* make vt active */
 #define VT_WAITACTIVE   0x5607  /* wait for vt active */