kern cons: introduce infrastructure for console grabbing by kernel

At the moment grab and ungrab methods of all console drivers are no-ops.

Current intended meaning of the calls is that the kernel takes control of
console input.  In the future the semantics may be extended to mean that
the calling thread takes full ownership of the console (e.g. console
output from other threads could be suspended).

Inspired by:	bde
MFC after:	2 months

sys/dev/cfe/cfe_console.c

@@ -76,6 +76,8 @@ static cn_init_t	cfe_cninit;
 static cn_term_t	cfe_cnterm;
 static cn_getc_t	cfe_cngetc;
 static cn_putc_t	cfe_cnputc;
+static cn_grab_t	cfe_cngrab;
+static cn_ungrab_t	cfe_cnungrab;
 
 CONSOLE_DRIVER(cfe);
 
@@ -183,6 +185,18 @@ cfe_cnterm(struct consdev *cp)
 
 }
 
+static void
+cfe_cngrab(struct consdev *cp)
+{
+
+}
+
+static void
+cfe_cnungrab(struct consdev *cp)
+{
+
+}
+
 static int
 cfe_cngetc(struct consdev *cp)
 {

sys/dev/dcons/dcons_os.c

@@ -109,6 +109,8 @@ static cn_init_t	dcons_cninit;
 static cn_term_t	dcons_cnterm;
 static cn_getc_t	dcons_cngetc;
 static cn_putc_t	dcons_cnputc;
+static cn_grab_t	dcons_cngrab;
+static cn_ungrab_t	dcons_cnungrab;
 
 CONSOLE_DRIVER(dcons);
 
@@ -246,6 +248,16 @@ dcons_cnterm(struct consdev *cp)
 {
 }
 
+static void
+dcons_cngrab(struct consdev *cp)
+{
+}
+
+static void
+dcons_cnungrab(struct consdev *cp)
+{
+}
+
 static int
 dcons_cngetc(struct consdev *cp)
 {

sys/dev/ofw/ofw_console.c

@@ -74,6 +74,8 @@ static cn_init_t	ofw_cninit;
 static cn_term_t	ofw_cnterm;
 static cn_getc_t	ofw_cngetc;
 static cn_putc_t	ofw_cnputc;
+static cn_grab_t	ofw_cngrab;
+static cn_ungrab_t	ofw_cnungrab;
 
 CONSOLE_DRIVER(ofw);
 
@@ -192,6 +194,16 @@ ofw_cnterm(struct consdev *cp)
 {
 }
 
+static void
+ofw_cngrab(struct consdev *cp)
+{
+}
+
+static void
+ofw_cnungrab(struct consdev *cp)
+{
+}
+
 static int
 ofw_cngetc(struct consdev *cp)
 {

sys/dev/sio/sio.c

@@ -2293,6 +2293,8 @@ static cn_init_t sio_cninit;
 static cn_term_t sio_cnterm;
 static cn_getc_t sio_cngetc;
 static cn_putc_t sio_cnputc;
+static cn_grab_t sio_cngrab;
+static cn_ungrab_t sio_cnungrab;
 
 CONSOLE_DRIVER(sio);
 
@@ -2512,6 +2514,16 @@ sio_cnterm(cp)
 	comconsole = -1;
 }
 
+static void
+sio_cngrab(struct consdev *cp)
+{
+}
+
+static void
+sio_cnungrab(struct consdev *cp)
+{
+}
+
 static int
 sio_cngetc(struct consdev *cd)
 {

sys/dev/syscons/syscons.c

@@ -229,6 +229,8 @@ static cn_init_t	sc_cninit;
 static cn_term_t	sc_cnterm;
 static cn_getc_t	sc_cngetc;
 static cn_putc_t	sc_cnputc;
+static cn_grab_t	sc_cngrab;
+static cn_ungrab_t	sc_cnungrab;
 
 CONSOLE_DRIVER(sc);
 
@@ -1608,6 +1610,16 @@ sc_cnterm(struct consdev *cp)
     sc_console = NULL;
 }
 
+static void
+sc_cngrab(struct consdev *cp)
+{
+}
+
+static void
+sc_cnungrab(struct consdev *cp)
+{
+}
+
 static void
 sc_cnputc(struct consdev *cd, int c)
 {

sys/dev/uart/uart_tty.c

@@ -54,6 +54,8 @@ static cn_init_t uart_cninit;
 static cn_term_t uart_cnterm;
 static cn_getc_t uart_cngetc;
 static cn_putc_t uart_cnputc;
+static cn_grab_t uart_cngrab;
+static cn_ungrab_t uart_cnungrab;
 
 CONSOLE_DRIVER(uart);
 
@@ -107,6 +109,16 @@ uart_cnterm(struct consdev *cp)
 	uart_term(cp->cn_arg);
 }
 
+static void
+uart_cngrab(struct consdev *cp)
+{
+}
+
+static void
+uart_cnungrab(struct consdev *cp)
+{
+}
+
 static void
 uart_cnputc(struct consdev *cp, int c)
 {

sys/dev/usb/serial/usb_serial.c

@@ -1308,6 +1308,8 @@ static cn_init_t ucom_cninit;
 static cn_term_t ucom_cnterm;
 static cn_getc_t ucom_cngetc;
 static cn_putc_t ucom_cnputc;
+static cn_grab_t ucom_cngrab;
+static cn_ungrab_t ucom_cnungrab;
 
 CONSOLE_DRIVER(ucom);
 
@@ -1332,6 +1334,16 @@ ucom_cnterm(struct consdev  *cp)
 {
 }
 
+static void
+ucom_cngrab(struct consdev *cp)
+{
+}
+
+static void
+ucom_cnungrab(struct consdev *cp)
+{
+}
+
 static int
 ucom_cngetc(struct consdev *cd)
 {

sys/dev/xen/console/console.c

@@ -50,6 +50,8 @@ static cn_init_t        xc_cninit;
 static cn_term_t        xc_cnterm;
 static cn_getc_t        xc_cngetc;
 static cn_putc_t        xc_cnputc;
+static cn_grab_t        xc_cngrab;
+static cn_ungrab_t      xc_cnungrab;
 
 #define XC_POLLTIME 	(hz/10)
 
@@ -126,6 +128,16 @@ xc_cnterm(struct consdev *cp)
 { 
 }
 
+static void
+xc_cngrab(struct consdev *cp)
+{
+}
+
+static void
+xc_cnungrab(struct consdev *cp)
+{
+}
+
 static int
 xc_cngetc(struct consdev *dev)
 {

sys/gdb/gdb_cons.c

@@ -87,6 +87,16 @@ gdb_cnterm(struct consdev *cp)
 {
 }
 
+static void
+gdb_cngrab(struct consdev *cp)
+{
+}
+
+static void
+gdb_cnungrab(struct consdev *cp)
+{
+}
+
 static int
 gdb_cngetc(struct consdev *cp)
 {

sys/ia64/ia64/ssc.c

@@ -101,6 +101,16 @@ ssc_cnterm(struct consdev *cp)
 {
 }
 
+static void
+ssc_cngrab(struct consdev *cp)
+{
+}
+
+static void
+ssc_cnungrab(struct consdev *cp)
+{
+}
+
 static void
 ssc_cnattach(void *arg)
 {

sys/kern/kern_cons.c

@@ -344,6 +344,32 @@ SYSCTL_PROC(_kern, OID_AUTO, consmute, CTLTYPE_INT|CTLFLAG_RW,
 	0, sizeof(cn_mute), sysctl_kern_consmute, "I",
 	"State of the console muting");
 
+void
+cngrab()
+{
+	struct cn_device *cnd;
+	struct consdev *cn;
+
+	STAILQ_FOREACH(cnd, &cn_devlist, cnd_next) {
+		cn = cnd->cnd_cn;
+		if (!kdb_active || !(cn->cn_flags & CN_FLAG_NODEBUG))
+			cn->cn_ops->cn_grab(cn);
+	}
+}
+
+void
+cnungrab()
+{
+	struct cn_device *cnd;
+	struct consdev *cn;
+
+	STAILQ_FOREACH(cnd, &cn_devlist, cnd_next) {
+		cn = cnd->cnd_cn;
+		if (!kdb_active || !(cn->cn_flags & CN_FLAG_NODEBUG))
+			cn->cn_ops->cn_ungrab(cn);
+	}
+}
+
 /*
  * Low level console routines.
  */

sys/mips/adm5120/console.c

@@ -49,6 +49,8 @@ static cn_init_t	uart_cninit;
 static cn_term_t	uart_cnterm;
 static cn_getc_t	uart_cngetc;
 static cn_putc_t	uart_cnputc;
+static cn_grab_t	uart_cngrab;
+static cn_ungrab_t	uart_cnungrab;
 
 static void
 uart_cnprobe(struct consdev *cp)
@@ -90,4 +92,16 @@ uart_cnterm(struct consdev * cp)
 
 }
 
+static void
+uart_cngrab(struct consdev *cp)
+{
+
+}
+
+static void
+uart_cnungrab(struct consdev *cp)
+{
+
+}
+
 CONSOLE_DRIVER(uart);

sys/pc98/cbus/sio.c

@@ -3460,6 +3460,8 @@ static cn_init_t sio_cninit;
 static cn_term_t sio_cnterm;
 static cn_getc_t sio_cngetc;
 static cn_putc_t sio_cnputc;
+static cn_grab_t sio_cngrab;
+static cn_ungrab_t sio_cnungrab;
 
 CONSOLE_DRIVER(sio);
 
@@ -3679,6 +3681,16 @@ sio_cnterm(cp)
 	comconsole = -1;
 }
 
+static void
+sio_cngrab(struct consdev *cp)
+{
+}
+
+static void
+sio_cnungrab(struct consdev *cp)
+{
+}
+
 static int
 sio_cngetc(struct consdev *cd)
 {

sys/powerpc/mambo/mambo_console.c

@@ -69,6 +69,8 @@ static cn_init_t	mambo_cninit;
 static cn_term_t	mambo_cnterm;
 static cn_getc_t	mambo_cngetc;
 static cn_putc_t	mambo_cnputc;
+static cn_grab_t	mambo_cngrab;
+static cn_ungrab_t	mambo_cnungrab;
 
 CONSOLE_DRIVER(mambo);
 
@@ -146,6 +148,16 @@ mambo_cnterm(struct consdev *cp)
 {
 }
 
+static void
+mambo_cngrab(struct consdev *cp)
+{
+}
+
+static void
+mambo_cnungrab(struct consdev *cp)
+{
+}
+
 static int
 mambo_cngetc(struct consdev *cp)
 {

sys/sys/cons.h

@@ -44,6 +44,8 @@ struct tty;
 typedef	void	cn_probe_t(struct consdev *);
 typedef	void	cn_init_t(struct consdev *);
 typedef	void	cn_term_t(struct consdev *);
+typedef	void	cn_grab_t(struct consdev *);
+typedef	void	cn_ungrab_t(struct consdev *);
 typedef	int	cn_getc_t(struct consdev *);
 typedef	void	cn_putc_t(struct consdev *, int);
 
@@ -58,6 +60,10 @@ struct consdev_ops {
 				/* kernel getchar interface */
 	cn_putc_t	*cn_putc;
 				/* kernel putchar interface */
+	cn_grab_t	*cn_grab;
+				/* grab console for exclusive kernel use */
+	cn_ungrab_t	*cn_ungrab;
+				/* ungrab console */
 };
 
 struct consdev {
@@ -99,6 +105,8 @@ extern	struct tty *constty;	/* Temporary virtual console. */
 		.cn_term = name##_cnterm,				\
 		.cn_getc = name##_cngetc,				\
 		.cn_putc = name##_cnputc,				\
+		.cn_grab = name##_cngrab,				\
+		.cn_ungrab = name##_cnungrab,				\
 	};								\
 	CONSOLE_DEVICE(name##_consdev, name##_consdev_ops, NULL)
 
@@ -109,6 +117,8 @@ int	cnadd(struct consdev *);
 void	cnavailable(struct consdev *, int);
 void	cnremove(struct consdev *);
 void	cnselect(struct consdev *);
+void	cngrab(void);
+void	cnungrab(void);
 int	cncheckc(void);
 int	cngetc(void);
 void	cnputc(int);