git: c4a0333b55e0 - main - vt: restore tty when console is ungrabbed

[Kyle Evans]

The branch main has been updated by kevans:

URL: https://cgit.FreeBSD.org/src/commit/?id=c4a0333b55e08f38985828a3a2d3ee533325c568

commit c4a0333b55e08f38985828a3a2d3ee533325c568
Author:     Kyle Evans <kevans at FreeBSD.org>
AuthorDate: 2020-12-31 16:50:43 +0000
Commit:     Kyle Evans <kevans at FreeBSD.org>
CommitDate: 2020-12-31 17:10:11 +0000

    vt: restore tty when console is ungrabbed
    
    When a break-to-debugger is triggered, kdb will grab the console and vt(4)
    will generally switch back to ttyv0. If one issues a continue from the
    debugger, then kdb will ungrab the console and the system rolls on.
    
    This change adds a perhaps minor feature: when we're down to grab == 0 and
    if vt actually switched away to ttyv0, switch back to the tty it was
    previously on before the console was grabbed.
    
    The justification behind this is that a typical flow is to work in
    !ttyv0 to avoid console spam while occasionally dropping to ddb to inspect
    system state before returning. This could easily enough be tossed behind
    a sysctl or something if it's not generally appreciated, but I anticipate
    indifference.
    
    Reviewed by:    ray
    Differential Revision:  https://reviews.freebsd.org/D27110
---
 sys/dev/vt/vt.h      | 1 +
 sys/dev/vt/vt_core.c | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/sys/dev/vt/vt.h b/sys/dev/vt/vt.h
index 7d960f68e83f..2d671d692384 100644
--- a/sys/dev/vt/vt.h
+++ b/sys/dev/vt/vt.h
@@ -124,6 +124,7 @@ struct vt_device {
 	struct vt_window	*vd_windows[VT_MAXWINDOWS]; /* (c) Windows. */
 	struct vt_window	*vd_curwindow;	/* (d) Current window. */
 	struct vt_window	*vd_savedwindow;/* (?) Saved for suspend. */
+	struct vt_window	*vd_grabwindow;	/* (?) Saved before cngrab. */
 	struct vt_pastebuf	 vd_pastebuf;	/* (?) Copy/paste buf. */
 	const struct vt_driver	*vd_driver;	/* (c) Graphics driver. */
 	void			*vd_softc;	/* (u) Driver data. */
diff --git a/sys/dev/vt/vt_core.c b/sys/dev/vt/vt_core.c
index c273b703de93..2352ed823424 100644
--- a/sys/dev/vt/vt_core.c
+++ b/sys/dev/vt/vt_core.c
@@ -1805,6 +1805,9 @@ vtterm_cngrab(struct terminal *tm)
 	vw = tm->tm_softc;
 	vd = vw->vw_device;
 
+	/* To be restored after we ungrab. */
+	if (vd->vd_grabwindow == NULL)
+		vd->vd_grabwindow = vd->vd_curwindow;
 
 	if (!cold)
 		vt_window_switch(vw);
@@ -1821,10 +1824,14 @@ vtterm_cnungrab(struct terminal *tm)
 	vw = tm->tm_softc;
 	vd = vw->vw_device;
 
+	MPASS(vd->vd_grabwindow != NULL);
 	if (vtterm_cnungrab_noswitch(vd, vw) != 0)
 		return;
 
+	if (!cold && vd->vd_grabwindow != vw)
+		vt_window_switch(vd->vd_grabwindow);
 
+	vd->vd_grabwindow = NULL;
 }
 
 static void