Add option NO_SIO to work-around the hardcoded dependency on sio(4).

Without this option it is not possible to omit the driver from the
configuration file and successfully build a kernel.

This option is specific to alpha.

14 files changed, 257 insertions, 212 deletions

diff --git a/sys/alpha/alpha/api_up1000.c b/sys/alpha/alpha/api_up1000.c
index 12626f6..f21ec34 100644
--- a/sys/alpha/alpha/api_up1000.c
+++ b/sys/alpha/alpha/api_up1000.c
@@ -49,18 +49,21 @@ __FBSDID("$FreeBSD$");
 #include <alpha/pci/irongatereg.h>
 #include <alpha/pci/irongatevar.h>
 
+#ifndef NO_SIO
 #ifndef CONSPEED
 #define CONSPEED TTYDEF_SPEED
 #endif
 static int comcnrate = CONSPEED;
-
-void api_up1000_init(void);
-static void api_up1000_cons_init(void);
-
+extern int comconsole;
 extern int siocnattach(int, int);
 extern int siogdbattach(int, int);
+#endif
+
 extern int sccnattach(void);
 
+void api_up1000_init(void);
+static void api_up1000_cons_init(void);
+
 void
 api_up1000_init()
 {
@@ -75,38 +78,38 @@ api_up1000_init()
 	platform.cons_init = api_up1000_cons_init;
 }
 
-extern int comconsole;
-
 static void
 api_up1000_cons_init()
 {
 	struct ctb *ctb;
 
 	irongate_init();
+
+#ifndef NO_SIO
 #ifdef DDB
 	siogdbattach(0x2f8, 57600);
 #endif
+#endif
 
 	ctb = (struct ctb *)(((caddr_t)hwrpb) + hwrpb->rpb_ctb_off);
 
 	switch (ctb->ctb_term_type) {
-	case 2: 
+	case 2:
+#ifndef NO_SIO
 		/* serial console ... */
-		/* XXX */
-		{
-			/*
-			 * Delay to allow PROM putchars to complete.
-			 * FIFO depth * character time,
-			 * character time = (1000000 / (defaultrate / 10))
-			 */
-			DELAY(160000000 / comcnrate);
-			comconsole = 0;
-			if (siocnattach(0x3f8, comcnrate))
-				panic("can't init serial console");
-
-			boothowto |= RB_SERIAL;
-			break;
-		}
+		/*
+		 * Delay to allow PROM putchars to complete.
+		 * FIFO depth * character time,
+		 * character time = (1000000 / (defaultrate / 10))
+		 */
+		DELAY(160000000 / comcnrate);
+		comconsole = 0;
+		if (siocnattach(0x3f8, comcnrate))
+			panic("can't init serial console");
+
+		boothowto |= RB_SERIAL;
+#endif
+		break;
 
 	case 3:
 		/* display console ... */
diff --git a/sys/alpha/alpha/dec_1000a.c b/sys/alpha/alpha/dec_1000a.c
index 113eca2..a1d1d39 100644
--- a/sys/alpha/alpha/dec_1000a.c
+++ b/sys/alpha/alpha/dec_1000a.c
@@ -94,15 +94,21 @@ __FBSDID("$FreeBSD$");
 
 #include <dev/pci/pcivar.h>
 
+#ifndef NO_SIO
 #ifndef CONSPEED
 #define CONSPEED TTYDEF_SPEED
 #endif
 static int comcnrate = CONSPEED;
+extern int comconsole;
+extern int siocnattach(int, int);
+extern int siogdbattach(int, int);
+#endif
+
+extern int sccnattach(void);
 
 void dec_1000a_init(int);
 static void dec_1000a_cons_init(void);
 
-
 static void dec_1000_intr_map(void *);
 static void dec_1000_intr_disable(int);
 static void dec_1000_intr_enable(int);
@@ -113,11 +119,6 @@ static void dec_1000a_intr_disable(int);
 static void dec_1000a_intr_enable(int);
 static void dec_1000a_intr_init(void);
 
-extern int siocnattach(int, int);
-extern int siogdbattach(int, int);
-extern int sccnattach(void);
-
-
 static const struct alpha_variation_table dec_1000_variations[] = {
 	{ 0, "AlphaServer 1000" },
 	{ 0, NULL },
@@ -172,8 +173,6 @@ dec_1000a_init(int cputype)
 
 }
 
-/* XXX for forcing comconsole when srm serial console is used */
-extern int comconsole;
 
 static void
 dec_1000a_cons_init()
@@ -186,35 +185,36 @@ dec_1000a_cons_init()
 		apecs_init();
 	}
 
+#ifndef NO_SIO
 #ifdef DDB
 	siogdbattach(0x2f8, 57600);
 #endif
+#endif
 
 	ctb = (struct ctb *)(((caddr_t)hwrpb) + hwrpb->rpb_ctb_off);
 
 	switch (ctb->ctb_term_type) {
 	case 2:
+#ifndef NO_SIO
 		/* serial console ... */
-		/* XXX */
-		{
-			/*
-			 * Delay to allow PROM putchars to complete.
-			 * FIFO depth * character time,
-			 * character time = (1000000 / (defaultrate / 10)).
-			 */
-			DELAY(160000000 / comcnrate);
-
-                        /*
-                         * Force a comconsole on com1 if the SRM has a serial
-			 * console.
-                         */
-                        comconsole = 0;
-			if (siocnattach(0x3f8, comcnrate))
-				panic("can't init serial console");
-
-			boothowto |= RB_SERIAL;
-			break;
-		}
+		/*
+		 * Delay to allow PROM putchars to complete.
+		 * FIFO depth * character time,
+		 * character time = (1000000 / (defaultrate / 10)).
+		 */
+		DELAY(160000000 / comcnrate);
+
+		/*
+		 * Force a comconsole on com1 if the SRM has a serial
+		 * console.
+		 */
+		comconsole = 0;
+		if (siocnattach(0x3f8, comcnrate))
+			panic("can't init serial console");
+
+		boothowto |= RB_SERIAL;
+#endif
+		break;
 
 	case 3:
 		/* display console ... */
diff --git a/sys/alpha/alpha/dec_2100_a50.c b/sys/alpha/alpha/dec_2100_a50.c
index 11ea268..79138b2 100644
--- a/sys/alpha/alpha/dec_2100_a50.c
+++ b/sys/alpha/alpha/dec_2100_a50.c
@@ -54,21 +54,21 @@ __FBSDID("$FreeBSD$");
 #include <alpha/pci/apecsreg.h>
 #include <alpha/pci/apecsvar.h>
 
+#ifndef NO_SIO
 #ifndef	CONSPEED
 #define	CONSPEED TTYDEF_SPEED
 #endif
 static int comcnrate = CONSPEED;
+extern int comconsole;
+extern int siocnattach(int, int);
+extern int siogdbattach(int, int);
+#endif
+
+extern int sccnattach(void);
 
 void dec_2100_a50_init(void);
 static void dec_2100_a50_cons_init(void);
 static void dec_2100_a50_intr_map(void *);
-void sio_intr_establish(int);
-void sio_intr_disestablish(int);
-void sio_intr_setup(void);
-
-extern int siocnattach(int, int);
-extern int siogdbattach(int, int);
-extern int sccnattach(void);
 
 const struct alpha_variation_table dec_2100_a50_variations[] = {
 	{ SV_ST_AVANTI,	"AlphaStation 400 4/233 (\"Avanti\")" },
@@ -103,9 +103,6 @@ dec_2100_a50_init()
 	platform.pci_intr_map  = dec_2100_a50_intr_map;
 }
 
-/* XXX for forcing comconsole when srm serial console is used */
-extern int comconsole;
-
 static void
 dec_2100_a50_cons_init()
 {
@@ -113,32 +110,34 @@ dec_2100_a50_cons_init()
 
 	apecs_init();
 
+#ifndef NO_SIO
 #ifdef DDB
 	siogdbattach(0x2f8, 9600);
 #endif
+#endif
+
 	ctb = (struct ctb *)(((caddr_t)hwrpb) + hwrpb->rpb_ctb_off);
 
 	switch (ctb->ctb_term_type) {
 	case 2:
+#ifndef NO_SIO
 		/* serial console ... */
-		/* XXX */
-		{
-			/*
-			 * Delay to allow PROM putchars to complete.
-			 * FIFO depth * character time,
-			 * character time = (1000000 / (defaultrate / 10)).
-			 */
-			DELAY(160000000 / comcnrate);
-			/*
-			 * Force a comconsole on com1 if the SRM has a serial console.
-			 */
-			comconsole = 0;
-			if (siocnattach(0x3f8, comcnrate))
-				panic("can't init serial console");
-
-			boothowto |= RB_SERIAL;
-			break;
-		}
+		/*
+		 * Delay to allow PROM putchars to complete.
+		 * FIFO depth * character time,
+		 * character time = (1000000 / (defaultrate / 10)).
+		 */
+		DELAY(160000000 / comcnrate);
+		/*
+		 * Force a comconsole on com1 if the SRM has a serial console.
+		 */
+		comconsole = 0;
+		if (siocnattach(0x3f8, comcnrate))
+			panic("can't init serial console");
+
+		boothowto |= RB_SERIAL;
+#endif
+		break;
 
 	case 3:
 		/* display console ... */
diff --git a/sys/alpha/alpha/dec_2100_a500.c b/sys/alpha/alpha/dec_2100_a500.c
index ac53a9e6..547d4ed 100644
--- a/sys/alpha/alpha/dec_2100_a500.c
+++ b/sys/alpha/alpha/dec_2100_a500.c
@@ -47,19 +47,22 @@ __FBSDID("$FreeBSD$");
 #include <alpha/pci/t2var.h>
 #include <alpha/pci/t2reg.h>
 
+#ifndef NO_SIO
 #ifndef	CONSPEED
 #define	CONSPEED TTYDEF_SPEED
 #endif
 static int comcnrate = CONSPEED;
+extern int comconsole; 
+extern int siocnattach(int, int);
+extern int siogdbattach(int, int);
+#endif
+
+extern int sccnattach(void);
 
 void dec_2100_a500_init(int);
 static void dec_2100_a500_cons_init(void);
 static void dec_2100_a500_intr_init(void);
 
-extern int siocnattach(int, int);
-extern int siogdbattach(int, int);
-extern int sccnattach(void);
-
 void
 dec_2100_a500_init(int cputype)
 {
@@ -91,8 +94,6 @@ dec_2100_a500_init(int cputype)
 	t2_init();
 }
 
-/* XXX for forcing comconsole when srm serial console is used */
-extern int comconsole; 
 
 static void
 dec_2100_a500_cons_init()
@@ -100,15 +101,18 @@ dec_2100_a500_cons_init()
 	struct ctb *ctb;
 	t2_init();
 
+#ifndef NO_SIO
 #ifdef DDB
 	siogdbattach(0x2f8, 9600);
 #endif
+#endif
+
 	ctb = (struct ctb *)(((caddr_t)hwrpb) + hwrpb->rpb_ctb_off);
 
 	switch (ctb->ctb_term_type) {
 	case 2:
+#ifndef NO_SIO
 		/* serial console ... */
-		/* XXX */
 		/*
 		 * Delay to allow PROM putchars to complete.
 		 * FIFO depth * character time,
@@ -123,6 +127,7 @@ dec_2100_a500_cons_init()
 			panic("can't init serial console");
 
 		boothowto |= RB_SERIAL;
+#endif
 		break;
 
 	case 3:
diff --git a/sys/alpha/alpha/dec_axppci_33.c b/sys/alpha/alpha/dec_axppci_33.c
index 6188ac0..13e04ea 100644
--- a/sys/alpha/alpha/dec_axppci_33.c
+++ b/sys/alpha/alpha/dec_axppci_33.c
@@ -51,19 +51,22 @@ __FBSDID("$FreeBSD$");
 #include <dev/pci/pcivar.h>
 #include <alpha/pci/lcavar.h>
 
+#ifndef NO_SIO
 #ifndef	CONSPEED
 #define	CONSPEED TTYDEF_SPEED
 #endif
 static int comcnrate = CONSPEED;
+extern int comconsole;
+extern int siocnattach(int, int);
+extern int siogdbattach(int, int);
+#endif
+
+extern int sccnattach(void);
 
 void dec_axppci_33_init(void);
 static void dec_axppci_33_cons_init(void);
 static int dec_axppci_33_intr_route (device_t, device_t, int);
 
-extern int siocnattach(int, int);
-extern int siogdbattach(int, int);
-extern int sccnattach(void);
-
 const struct alpha_variation_table dec_axppci_33_variations[] = {
 	{ 0, "Alpha PC AXPpci33 (\"NoName\")" },
 	{ 0, NULL },
@@ -114,8 +117,6 @@ dec_axppci_33_init()
 	outb(NSIO_PORT + NSIO_DATA, cfg0val);
 }
 
-/* XXX for forcing comconsole when srm serial console is used */
-extern int comconsole;
 
 static void
 dec_axppci_33_cons_init()
@@ -124,32 +125,34 @@ dec_axppci_33_cons_init()
 
 	lca_init();
 
+#ifndef NO_SIO
 #ifdef DDB
 	siogdbattach(0x2f8, 9600);
 #endif
+#endif
+
 	ctb = (struct ctb *)(((caddr_t)hwrpb) + hwrpb->rpb_ctb_off);
 
 	switch (ctb->ctb_term_type) {
 	case 2:
+#ifndef NO_SIO
 		/* serial console ... */
-		/* XXX */
-		{
-			/*
-			 * Delay to allow PROM putchars to complete.
-			 * FIFO depth * character time,
-			 * character time = (1000000 / (defaultrate / 10))
-			 */
-			DELAY(160000000 / comcnrate);
-			/*
-			 * force a comconsole on com1 if the SRM has a serial console
-			 */
-			comconsole = 0;
-			if (siocnattach(0x3f8, comcnrate))
-				panic("can't init serial console");
-
-			boothowto |= RB_SERIAL;
-			break;
-		}
+		/*
+		 * Delay to allow PROM putchars to complete.
+		 * FIFO depth * character time,
+		 * character time = (1000000 / (defaultrate / 10))
+		 */
+		DELAY(160000000 / comcnrate);
+		/*
+		 * force a comconsole on com1 if the SRM has a serial console
+		 */
+		comconsole = 0;
+		if (siocnattach(0x3f8, comcnrate))
+			panic("can't init serial console");
+
+		boothowto |= RB_SERIAL;
+#endif
+		break;
 
 	case 3:
 		/* display console ... */
diff --git a/sys/alpha/alpha/dec_eb164.c b/sys/alpha/alpha/dec_eb164.c
index 7ee174d..fb7e701 100644
--- a/sys/alpha/alpha/dec_eb164.c
+++ b/sys/alpha/alpha/dec_eb164.c
@@ -48,10 +48,17 @@ __FBSDID("$FreeBSD$");
 
 #include <alpha/pci/ciavar.h>
 
+#ifndef NO_SIO
 #ifndef	CONSPEED
 #define	CONSPEED TTYDEF_SPEED
 #endif
 static int comcnrate = CONSPEED;
+extern int comconsole;
+extern int siocnattach(int, int);
+extern int siogdbattach(int, int);
+#endif
+
+extern int sccnattach(void);
 
 void dec_eb164_init(void);
 static void dec_eb164_cons_init(void);
@@ -61,10 +68,6 @@ extern void eb164_intr_disable(int irq);
 extern void eb164_intr_enable_icsr(int irq);
 extern void eb164_intr_disable_icsr(int irq);
 
-extern int siocnattach(int, int);
-extern int siogdbattach(int, int);
-extern int sccnattach(void);
-
 void
 dec_eb164_init()
 {
@@ -88,7 +91,6 @@ dec_eb164_init()
 	}
 }
 
-extern int comconsole; /* XXX for forcing comconsole when srm serial console is used */
 static void
 dec_eb164_cons_init()
 {
@@ -96,35 +98,36 @@ dec_eb164_cons_init()
 
 	cia_init();
 
+#ifndef NO_SIO
 #ifdef DDB
 	siogdbattach(0x2f8, 57600);
 #endif
+#endif
 
 	ctb = (struct ctb *)(((caddr_t)hwrpb) + hwrpb->rpb_ctb_off);
 
 	switch (ctb->ctb_term_type) {
 	case 2:
+#ifndef NO_SIO
 		/* serial console ... */
-		/* XXX */
-		{
-			/*
-			 * Delay to allow PROM putchars to complete.
-			 * FIFO depth * character time,
-			 * character time = (1000000 / (defaultrate / 10))
-			 */
-			DELAY(160000000 / comcnrate);
-
-			/*
-			 * Force a comconsole on com1 if the SRM has a serial
-			 * console.
-			 */
-			comconsole = 0;
-			if (siocnattach(0x3f8, comcnrate))
-				panic("can't init serial console");
-
-			boothowto |= RB_SERIAL;
-			break;
-		}
+		/*
+		 * Delay to allow PROM putchars to complete.
+		 * FIFO depth * character time,
+		 * character time = (1000000 / (defaultrate / 10))
+		 */
+		DELAY(160000000 / comcnrate);
+
+		/*
+		 * Force a comconsole on com1 if the SRM has a serial
+		 * console.
+		 */
+		comconsole = 0;
+		if (siocnattach(0x3f8, comcnrate))
+			panic("can't init serial console");
+
+		boothowto |= RB_SERIAL;
+#endif
+		break;
 
 	case 3:
 		/* display console ... */
diff --git a/sys/alpha/alpha/dec_eb64plus.c b/sys/alpha/alpha/dec_eb64plus.c
index 900f1c9..670e2ea 100644
--- a/sys/alpha/alpha/dec_eb64plus.c
+++ b/sys/alpha/alpha/dec_eb64plus.c
@@ -68,10 +68,16 @@ __FBSDID("$FreeBSD$");
 #include <alpha/pci/apecsreg.h>
 #include <alpha/pci/apecsvar.h>
 
+#ifndef NO_SIO
 #ifndef	CONSPEED
 #define	CONSPEED TTYDEF_SPEED
 #endif
 static int comcnrate = CONSPEED;
+extern int comconsole;
+extern int siocnattach(int, int);
+#endif
+
+extern int sccnattach(void);
 
 void dec_eb64plus_init(void);
 static void dec_eb64plus_cons_init(void);
@@ -83,9 +89,6 @@ extern void eb64plus_intr_disable(int irq);	/* ../pci/pci_eb64plus_intr.s */
 extern const char * bootdev_protocol(void);
 extern int bootdev_boot_dev_type(void);
 
-extern int siocnattach(int, int);
-extern int sccnattach(void);
-
 const struct alpha_variation_table dec_eb64plus_variations[] = {
 	{ 0, "DEC EB64-plus" },
 	{ 0, NULL },
@@ -116,8 +119,6 @@ dec_eb64plus_init()
 
 }
 
-/* XXX for forcing comconsole when srm serial console is used */
-extern int comconsole;
 
 /* init the console, serial or graphics */
 static void
@@ -131,27 +132,26 @@ dec_eb64plus_cons_init()
 
 	switch (ctb->ctb_term_type) {
 	case 2:
+#ifndef NO_SIO
 		/* serial console ... */
-		/* XXX */
-		{
-			/*
-			 * Delay to allow PROM putchars to complete.
-			 * FIFO depth * character time,
-			 * character time = (1000000 / (defaultrate / 10))
-			 */
-			DELAY(160000000 / comcnrate);
-
-			/*
-			 * force a comconsole on com1 if the SRM has a serial
-			 * console.
-			 */
-			comconsole = 0;
-			if (siocnattach(0x3f8, comcnrate))
-				panic("can't init serial console");
-
-			boothowto |= RB_SERIAL;
-			break;
-		}
+		/*
+		 * Delay to allow PROM putchars to complete.
+		 * FIFO depth * character time,
+		 * character time = (1000000 / (defaultrate / 10))
+		 */
+		DELAY(160000000 / comcnrate);
+
+		/*
+		 * force a comconsole on com1 if the SRM has a serial
+		 * console.
+		 */
+		comconsole = 0;
+		if (siocnattach(0x3f8, comcnrate))
+			panic("can't init serial console");
+
+		boothowto |= RB_SERIAL;
+#endif
+		break;
 
 	case 3:
 #ifdef DEV_SC
diff --git a/sys/alpha/alpha/dec_kn20aa.c b/sys/alpha/alpha/dec_kn20aa.c
index e2acd2d..de9b91b 100644
--- a/sys/alpha/alpha/dec_kn20aa.c
+++ b/sys/alpha/alpha/dec_kn20aa.c
@@ -51,10 +51,17 @@ __FBSDID("$FreeBSD$");
 #include <alpha/pci/ciareg.h>
 #include <alpha/pci/ciavar.h>
 
+#ifndef NO_SIO
 #ifndef	CONSPEED
 #define	CONSPEED TTYDEF_SPEED
 #endif
 static int comcnrate = CONSPEED;
+extern int comconsole;
+extern int siocnattach(int, int);
+extern int siogdbattach(int, int);
+#endif
+
+extern int sccnattach(void);
 
 void dec_kn20aa_init(void);
 static void dec_kn20aa_cons_init(void);
@@ -63,10 +70,6 @@ static void dec_kn20aa_intr_map(void *);
 static void dec_kn20aa_intr_disable(int);
 static void dec_kn20aa_intr_enable(int);
 
-extern int siocnattach(int, int);
-extern int siogdbattach(int, int);
-extern int sccnattach(void);
-
 #if 0
 static void dec_kn20aa_device_register(struct device *, void *);
 #endif
@@ -75,7 +78,6 @@ const struct alpha_variation_table dec_kn20aa_variations[] = {
 	{ 0, "AlphaStation 500 or 600 (KN20AA)" },
 	{ 0, NULL },
 };
-extern int comconsole; /* XXX for forcing comconsole when srm serial console is used */
 
 void
 dec_kn20aa_init()
@@ -106,29 +108,31 @@ dec_kn20aa_cons_init()
 
 	cia_init();
 
+#ifndef NO_SIO
 #ifdef DDB
 	siogdbattach(0x2f8, 9600);
 #endif
+#endif
+
 	ctb = (struct ctb *)(((caddr_t)hwrpb) + hwrpb->rpb_ctb_off);
 
 	switch (ctb->ctb_term_type) {
 	case 2:
+#ifndef NO_SIO
 		/* serial console ... */
-		/* XXX */
-		{
-			/*
-			 * Delay to allow PROM putchars to complete.
-			 * FIFO depth * character time,
-			 * character time = (1000000 / (defaultrate / 10))
-			 */
-			DELAY(160000000 / comcnrate);
-			comconsole = 0;
-			if (siocnattach(0x3f8, comcnrate))
-				panic("can't init serial console");
-
-			boothowto |= RB_SERIAL;
-			break;
-		}
+		/*
+		 * Delay to allow PROM putchars to complete.
+		 * FIFO depth * character time,
+		 * character time = (1000000 / (defaultrate / 10))
+		 */
+		DELAY(160000000 / comcnrate);
+		comconsole = 0;
+		if (siocnattach(0x3f8, comcnrate))
+			panic("can't init serial console");
+
+		boothowto |= RB_SERIAL;
+#endif
+		break;
 
 	case 3:
 		/* display console ... */
diff --git a/sys/alpha/alpha/dec_kn300.c b/sys/alpha/alpha/dec_kn300.c
index a03c9c0..fa1f830 100644
--- a/sys/alpha/alpha/dec_kn300.c
+++ b/sys/alpha/alpha/dec_kn300.c
@@ -54,10 +54,17 @@ __FBSDID("$FreeBSD$");
 #include <alpha/mcbus/mcbusreg.h>
 #include <alpha/mcbus/mcbusvar.h>
 
+#ifndef NO_SIO
 #ifndef	CONSPEED
 #define	CONSPEED	TTYDEF_SPEED
 #endif
 static int comcnrate = CONSPEED;
+extern int comconsole;
+extern int siocnattach(int, int);
+extern int siogdbattach(int, int);
+#endif
+
+extern int sccnattach(void);
 
 void dec_kn300_init(void);
 void dec_kn300_cons_init(void);
@@ -70,10 +77,6 @@ const struct alpha_variation_table dec_kn300_variations[] = {
 };
 
 
-extern int siocnattach(int, int);
-extern int siogdbattach(int, int);
-extern int sccnattach(void);
-
 void
 dec_kn300_init()
 {
@@ -92,22 +95,24 @@ dec_kn300_init()
 	platform.cons_init = dec_kn300_cons_init;
 }
 
-extern int comconsole;
-
 void
 dec_kn300_cons_init()
 {
 	struct ctb *ctb;
 
 	mcbus_init();
+
+#ifndef NO_SIO
 #ifdef	DDB
 	siogdbattach(0x2f8, 57600);
 #endif
+#endif
 
 	ctb = (struct ctb *)(((caddr_t)hwrpb) + hwrpb->rpb_ctb_off);
 
 	switch (ctb->ctb_term_type) {
 	case 2:
+#ifndef NO_SIO
 		/* serial console ... */
 		/*
 		 * Delay to allow PROM putchars to complete.
@@ -120,6 +125,7 @@ dec_kn300_cons_init()
 			panic("can't init serial console");
 
 		boothowto |= RB_SERIAL;
+#endif
 		break;
 
 	case 3:
diff --git a/sys/alpha/alpha/dec_st550.c b/sys/alpha/alpha/dec_st550.c
index 3a8a32c..e81e982 100644
--- a/sys/alpha/alpha/dec_st550.c
+++ b/sys/alpha/alpha/dec_st550.c
@@ -56,10 +56,17 @@ __FBSDID("$FreeBSD$");
 #include <alpha/pci/ciareg.h>
 #include <alpha/pci/ciavar.h>
 
+#ifndef NO_SIO
 #ifndef	CONSPEED
 #define	CONSPEED TTYDEF_SPEED
 #endif
 static int comcnrate = CONSPEED;
+extern int comconsole;
+extern int siocnattach(int, int);
+extern int siogdbattach(int, int);
+#endif
+
+extern int sccnattach(void);
 
 void st550_init(void);
 static void st550_cons_init(void);
@@ -72,10 +79,6 @@ static void st550_intr_map(void *);
 #define ST550_PCI_IRQ_BEGIN 8
 #define ST550_PCI_MAX_IRQ  47
 
-extern int siocnattach(int, int);
-extern int siogdbattach(int, int);
-extern int sccnattach(void);
-
 void
 st550_init()
 {
@@ -95,8 +98,6 @@ st550_init()
 	platform.pci_intr_enable = st550_intr_enable;
 }
 
-extern int comconsole;
-
 static void
 st550_cons_init()
 {
@@ -104,14 +105,17 @@ st550_cons_init()
 
 	cia_init();
 
+#ifndef NO_SIO
 #ifdef DDB
 	siogdbattach(0x2f8, 57600);
 #endif
+#endif
 
 	ctb = (struct ctb *)(((caddr_t)hwrpb) + hwrpb->rpb_ctb_off);
 
 	switch (ctb->ctb_term_type) {
 	case 2:
+#ifndef NO_SIO
 		/* serial console ... */
 		/* XXX */
 		/*
@@ -125,6 +129,7 @@ st550_cons_init()
 			panic("can't init serial console");
 
 		boothowto |= RB_SERIAL;
+#endif
 		break;
 
 	case 3:
diff --git a/sys/alpha/alpha/dec_st6600.c b/sys/alpha/alpha/dec_st6600.c
index 528ea7d..c940c62 100644
--- a/sys/alpha/alpha/dec_st6600.c
+++ b/sys/alpha/alpha/dec_st6600.c
@@ -48,10 +48,17 @@ __FBSDID("$FreeBSD$");
 #include <dev/pci/pcivar.h>
 #include <alpha/pci/tsunamivar.h>
 
+#ifndef NO_SIO
 #ifndef	CONSPEED
 #define	CONSPEED TTYDEF_SPEED
 #endif
 static int comcnrate = CONSPEED;
+extern int comconsole;
+extern int siocnattach(int, int);
+extern int siogdbattach(int, int);
+#endif
+
+extern int sccnattach(void);
 
 void st6600_init(void);
 static void st6600_cons_init(void);
@@ -60,10 +67,6 @@ static void st6600_intr_init(void);
 #define ST6600_PCI_IRQ_BEGIN 8
 #define ST6600_PCI_MAX_IRQ  63
 
-extern int siocnattach(int, int);
-extern int siogdbattach(int, int);
-extern int sccnattach(void);
-
 void
 st6600_init()
 {
@@ -79,38 +82,38 @@ st6600_init()
 	platform.pci_intr_init = st6600_intr_init;
 }
 
-extern int comconsole;
-
 static void
 st6600_cons_init()
 {
 	struct ctb *ctb;
 
 	tsunami_init();
+
+#ifndef NO_SIO
 #ifdef DDB
 	siogdbattach(0x2f8, 57600);
 #endif
+#endif
 
 	ctb = (struct ctb *)(((caddr_t)hwrpb) + hwrpb->rpb_ctb_off);
 
 	switch (ctb->ctb_term_type) {
 	case 2:
+#ifndef NO_SIO
 		/* serial console ... */
-		/* XXX */
-		{
-			/*
-			 * Delay to allow PROM putchars to complete.
-			 * FIFO depth * character time,
-			 * character time = (1000000 / (defaultrate / 10))
-			 */
-			DELAY(160000000 / comcnrate);
-			comconsole = 0;
-			if (siocnattach(0x3f8, comcnrate))
-				panic("can't init serial console");
-
-			boothowto |= RB_SERIAL;
-			break;
-		}
+		/*
+		 * Delay to allow PROM putchars to complete.
+		 * FIFO depth * character time,
+		 * character time = (1000000 / (defaultrate / 10))
+		 */
+		DELAY(160000000 / comcnrate);
+		comconsole = 0;
+		if (siocnattach(0x3f8, comcnrate))
+			panic("can't init serial console");
+
+		boothowto |= RB_SERIAL;
+#endif
+		break;
 
 	case 3:
 		/* display console ... */
diff --git a/sys/alpha/alpha/machdep.c b/sys/alpha/alpha/machdep.c
index fe9b276..8c79853 100644
--- a/sys/alpha/alpha/machdep.c
+++ b/sys/alpha/alpha/machdep.c
@@ -122,6 +122,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/sysctl.h>
 #include <sys/uio.h>
 #include <sys/linker.h>
+#include <sys/cons.h>
 #include <net/netisr.h>
 #include <vm/vm.h>
 #include <vm/vm_kern.h>
@@ -585,10 +586,18 @@ alpha_init(pfn, ptb, bim, bip, biv)
 	 * Initalize the real console, so the the bootstrap console is
 	 * no longer necessary.
 	 */
+#ifndef NO_SIO
 	if (platform.cons_init) {
 		platform.cons_init();
 		promcndetach();
 	}
+#else
+	if (platform.cons_init)
+		platform.cons_init();
+	promcndetach();
+	cninit();
+#endif
+
 	/* NO MORE FIRMWARE ACCESS ALLOWED */
 #ifdef _PMAP_MAY_USE_PROM_CONSOLE
 	/*
diff --git a/sys/alpha/conf/NOTES b/sys/alpha/conf/NOTES
index f963934..55f2da4 100644
--- a/sys/alpha/conf/NOTES
+++ b/sys/alpha/conf/NOTES
@@ -40,6 +40,9 @@ options 	DEC_KN8AE		# AlphaServer 8200/8400 (Turbolaser)
 options 	DEC_KN300		# AlphaServer 4100 (Rawhide),
 					# AlphaServer 1200 (Tincup)
 
+# Allow building a kernel without sio(4).
+options 	NO_SIO
+
 
 #####################################################################
 # HARDWARE BUS CONFIGURATION
diff --git a/sys/conf/options.alpha b/sys/conf/options.alpha
index 3f46d2c..407ce03 100644
--- a/sys/conf/options.alpha
+++ b/sys/conf/options.alpha
@@ -16,6 +16,8 @@ DEC_AXPPCI_33		opt_cpu.h
 DEC_1000A		opt_cpu.h
 API_UP1000		opt_cpu.h
 
+NO_SIO			opt_global.h
+
 MAXMEM
 
 PPC_PROBE_CHIPSET       opt_ppc.h