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

This reverts commit eec9fe7d1ab4a0dfac4cb43047a7657fffd0002f.

Ari writes as the reason this should be reverted:
The problems with this patch include:
1. There's at least one subtlety I overlooked - switching
between X servers (i.e. from one X VT to another) still requires
the cooperation of both X servers. I was assuming that KMS
eliminated this.
2. It hasn't been tested at all (no X server patch exists which
uses the new mode).

As he was the original author of the patch, I'll revert it.

Cc: Ari Entlich <[e-mail]>
Cc: Alan Cox <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/char/vt_ioctl.c

···
 			ret = -EFAULT;
 			goto out;
 		}
-		if (tmp.mode != VT_AUTO && tmp.mode != VT_PROCESS && tmp.mode != VT_PROCESS_AUTO) {
+		if (tmp.mode != VT_AUTO && tmp.mode != VT_PROCESS) {
 			ret = -EINVAL;
 			goto out;
 		}
···
 	 * telling it that it has acquired. Also check if it has died and
 	 * clean up (similar to logic employed in change_console())
 	 */
-	if (vc->vt_mode.mode == VT_PROCESS || vc->vt_mode.mode == VT_PROCESS_AUTO) {
+	if (vc->vt_mode.mode == VT_PROCESS) {
 		/*
 		 * Send the signal as privileged - kill_pid() will
 		 * tell us if the process has gone or something else
···
 	 * vt to auto control.
 	 */
 	vc = vc_cons[fg_console].d;
-	if (vc->vt_mode.mode == VT_PROCESS || vc->vt_mode.mode == VT_PROCESS_AUTO) {
+	if (vc->vt_mode.mode == VT_PROCESS) {
 		/*
 		 * Send the signal as privileged - kill_pid() will
 		 * tell us if the process has gone or something else
···
 		 */
 		vc->vt_newvt = new_vc->vc_num;
 		if (kill_pid(vc->vt_pid, vc->vt_mode.relsig, 1) == 0) {
-			if(vc->vt_mode.mode == VT_PROCESS)
-				/*
-				 * It worked. Mark the vt to switch to and
-				 * return. The process needs to send us a
-				 * VT_RELDISP ioctl to complete the switch.
-				 */
-				return;
-		} else {
 			/*
-			 * The controlling process has died, so we revert back to
-			 * normal operation. In this case, we'll also change back
-			 * to KD_TEXT mode. I'm not sure if this is strictly correct
-			 * but it saves the agony when the X server dies and the screen
-			 * remains blanked due to KD_GRAPHICS! It would be nice to do
-			 * this outside of VT_PROCESS but there is no single process
-			 * to account for and tracking tty count may be undesirable.
+			 * It worked. Mark the vt to switch to and
+			 * return. The process needs to send us a
+			 * VT_RELDISP ioctl to complete the switch.
 			 */
-			reset_vc(vc);
+			return;
 		}
 
 		/*
-		 * Fall through to normal (VT_AUTO and VT_PROCESS_AUTO) handling of the switch...
+		 * The controlling process has died, so we revert back to
+		 * normal operation. In this case, we'll also change back
+		 * to KD_TEXT mode. I'm not sure if this is strictly correct
+		 * but it saves the agony when the X server dies and the screen
+		 * remains blanked due to KD_GRAPHICS! It would be nice to do
+		 * this outside of VT_PROCESS but there is no single process
+		 * to account for and tracking tty count may be undesirable.
+		 */
+		reset_vc(vc);
+
+		/*
+		 * Fall through to normal (VT_AUTO) handling of the switch...
 		 */
 	}
 

include/linux/vt.h

···
 #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_PROCESS_AUTO 0x02	/* process is notified of switching */
+#define		VT_ACKACQ	0x02	/* acknowledge switch */
 
 struct vt_stat {
 	unsigned short v_active;	/* active vt */
···
 #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 */