Use a common tunable to choose between vt(4)/sc(4)

With this change and previous work from ray@ it will be possible to put
both in GENERIC, and have one enabled by default, but allow the other to
be selected via the loader.

(The previous implementation had separate kern.vt.disable and
hw.syscons.disable tunables, and would panic if both drivers were
compiled in and neither was explicitly disabled.)

MFC after:	1 week
Sponsored by:	The FreeBSD Foundation

share/man/man4/vt.4

@@ -43,6 +43,7 @@
 In
 .Xr loader.conf 5 :
 .Cd hw.vga.textmode=1
+.Cd kern.vty=vt
 .Sh DESCRIPTION
 The
 .Nm
@@ -171,6 +172,12 @@ prompt or in
 Set to 1 to use virtual terminals in text mode instead of graphics mode.
 Features that require graphics mode, like loadable fonts, will be
 disabled.
+.It Va kern.vty
+Set to vt to choose the
+.Nm
+driver for the system console, if the
+.Xr syscons 4
+driver is also compiled in and is the default.
 .El
 .Sh FILES
 .Bl -tag -width /usr/share/syscons/keymaps/* -compact

sys/dev/syscons/syscons.c

@@ -266,6 +266,8 @@ static struct cdevsw consolectl_devsw = {
 int
 sc_probe_unit(int unit, int flags)
 {
+    if (!vty_enabled(VTY_SC))
+        return ENXIO;
     if (!scvidprobe(unit, flags, FALSE)) {
 	if (bootverbose)
 	    printf("%s%d: no video adapter found.\n", SC_DRIVER_NAME, unit);
@@ -491,6 +493,9 @@ sc_attach_unit(int unit, int flags)
     struct cdev *dev;
     int vc;
 
+    if (!vty_enabled(VTY_SC))
+        return ENXIO;
+
     flags &= ~SC_KERNEL_CONSOLE;
 
     if (sc_console_unit == unit) {
@@ -575,6 +580,8 @@ sc_attach_unit(int unit, int flags)
 static void
 scmeminit(void *arg)
 {
+    if (!vty_enabled(VTY_SC))
+        return;
     if (sc_malloc)
 	return;
     sc_malloc = TRUE;
@@ -1588,7 +1595,7 @@ sc_cnprobe(struct consdev *cp)
     int unit;
     int flags;
 
-    if (getenv("hw.syscons.disable")) {
+    if (!vty_enabled(VTY_SC)) {
 	cp->cn_pri = CN_DEAD;
 	return;
     }

sys/dev/syscons/sysmouse.c

@@ -37,6 +37,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/tty.h>
 #include <sys/ttydefaults.h>
 #include <sys/kernel.h>
+#include <sys/cons.h>
 #include <sys/consio.h>
 #include <sys/mouse.h>
 
@@ -165,7 +166,7 @@ static struct ttydevsw smdev_ttydevsw = {
 static void
 sm_attach_mouse(void *unused)
 {
-	if (getenv("hw.syscons.disable"))
+	if (!vty_enabled(VTY_SC))
 		return;
 	sysmouse_tty = tty_alloc(&smdev_ttydevsw, NULL);
 	tty_makedev(sysmouse_tty, NULL, "sysmouse");

sys/dev/vt/vt_consolectl.c

@@ -73,7 +73,7 @@ static void
 consolectl_drvinit(void *unused)
 {
 
-	if (getenv("kern.vt.disable"))
+	if (!vty_enabled(VTY_VT))
 		return;
 	make_dev(&consolectl_cdevsw, 0, UID_ROOT, GID_WHEEL, 0600,
 	    "consolectl");

sys/dev/vt/vt_core.c

@@ -215,7 +215,7 @@ static void
 vt_update_static(void *dummy)
 {
 
-	if (getenv("kern.vt.disable"))
+	if (!vty_enabled(VTY_VT))
 		return;
 	if (main_vd->vd_driver != NULL)
 		printf("VT: running with driver \"%s\".\n",
@@ -959,7 +959,7 @@ vtterm_cnprobe(struct terminal *tm, struct consdev *cp)
 	struct vt_device *vd = vw->vw_device;
 	struct winsize wsz;
 
-	if (getenv("kern.vt.disable"))
+	if (!vty_enabled(VTY_VT))
 		return;
 
 	if (vd->vd_flags & VDF_INITIALIZED)
@@ -1996,7 +1996,7 @@ vt_upgrade(struct vt_device *vd)
 	struct vt_window *vw;
 	unsigned int i;
 
-	if (getenv("kern.vt.disable"))
+	if (!vty_enabled(VTY_VT))
 		return;
 
 	for (i = 0; i < VT_MAXWINDOWS; i++) {
@@ -2064,7 +2064,7 @@ vt_allocate(struct vt_driver *drv, void *softc)
 	struct vt_device *vd;
 	struct winsize wsz;
 
-	if (getenv("kern.vt.disable"))
+	if (!vty_enabled(VTY_VT))
 		return;
 
 	if (main_vd->vd_driver == NULL) {

sys/dev/vt/vt_sysmouse.c

@@ -405,7 +405,7 @@ static void
 sysmouse_drvinit(void *unused)
 {
 
-	if (getenv("kern.vt.disable"))
+	if (!vty_enabled(VTY_VT))
 		return;
 	mtx_init(&sysmouse_lock, "sysmouse", NULL, MTX_DEF);
 	cv_init(&sysmouse_sleep, "sysmrd");

sys/kern/kern_cons.c

@@ -41,6 +41,7 @@
 __FBSDID("$FreeBSD$");
 
 #include "opt_ddb.h"
+#include "opt_syscons.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -648,3 +649,45 @@ sysbeep(int pitch __unused, int period __unused)
 
 #endif
 
+/*
+ * Temporary support for sc(4) to vt(4) transition.
+ */
+static char vty_name[16] = "";
+SYSCTL_STRING(_kern, OID_AUTO, vty, CTLFLAG_RDTUN, vty_name, 0,
+    "Console vty driver");
+
+int
+vty_enabled(unsigned vty)
+{
+	static unsigned vty_selected = 0;
+
+	if (vty_selected == 0) {
+		TUNABLE_STR_FETCH("kern.vty", vty_name, sizeof(vty_name));
+		do {
+#if defined(DEV_SC)
+			if (strcmp(vty_name, "sc") == 0) {
+				vty_selected = VTY_SC;
+				break;
+			}
+#endif
+#if defined(DEV_VT)
+			if (strcmp(vty_name, "vt") == 0) {
+				vty_selected = VTY_VT;
+				break;
+			}
+#endif
+#if defined(DEV_SC)
+			vty_selected = VTY_SC;
+#elif defined(DEV_VT)
+			vty_selected = VTY_VT;
+#endif
+		} while (0);
+
+		if (vty_selected == VTY_VT)
+			strcpy(vty_name, "vt");
+		else if (vty_selected == VTY_SC)
+			strcpy(vty_name, "sc");
+	}
+	return ((vty_selected & vty) != 0);
+}
+

sys/sys/cons.h

@@ -133,6 +133,11 @@ int	cnunavailable(void);
 void	constty_set(struct tty *tp);
 void	constty_clear(void);
 
+/* sc(4) / vt(4) coexistence shim */
+#define	VTY_SC 0x01
+#define	VTY_VT 0x02
+int	vty_enabled(unsigned int);
+
 #endif /* _KERNEL */
 
 #endif /* !_MACHINE_CONS_H_ */