diff --git a/sys/dev/uart/uart.h b/sys/dev/uart/uart.h
index ba17e89bf8c7..5de4d420ac5c 100644
--- a/sys/dev/uart/uart.h
+++ b/sys/dev/uart/uart.h
@@ -36,11 +36,11 @@
  * other timing related computations.
  */
 struct uart_bas {
-	bus_addr_t iobase;
 	bus_space_tag_t bst;
 	bus_space_handle_t bsh;
-	u_int	regshft;
+	u_int	chan;
 	u_int	rclk;
+	u_int	regshft;
 };
 
 #define	uart_regofs(bas, reg)		((reg) << (bas)->regshft)
diff --git a/sys/dev/uart/uart_bus.h b/sys/dev/uart/uart_bus.h
index dde9ff803a29..3c45199d980d 100644
--- a/sys/dev/uart/uart_bus.h
+++ b/sys/dev/uart/uart_bus.h
@@ -172,7 +172,7 @@ extern char uart_driver_name[];
 
 int uart_bus_attach(device_t dev);
 int uart_bus_detach(device_t dev);
-int uart_bus_probe(device_t dev, int regshft, int rclk, int rid);
+int uart_bus_probe(device_t dev, int regshft, int rclk, int rid, int chan);
 
 int uart_tty_attach(struct uart_softc *);
 int uart_tty_detach(struct uart_softc *);
diff --git a/sys/dev/uart/uart_bus_acpi.c b/sys/dev/uart/uart_bus_acpi.c
index ac75f0cc6b41..a26357132d04 100644
--- a/sys/dev/uart/uart_bus_acpi.c
+++ b/sys/dev/uart/uart_bus_acpi.c
@@ -73,7 +73,7 @@ uart_acpi_probe(device_t dev)
 
 	if (!ISA_PNP_PROBE(parent, dev, acpi_ns8250_ids)) {
 		sc->sc_class = &uart_ns8250_class;
-		return (uart_bus_probe(dev, 0, 0, 0));
+		return (uart_bus_probe(dev, 0, 0, 0, 0));
 	}
 
 	/* Add checks for non-ns8250 IDs here. */
diff --git a/sys/dev/uart/uart_bus_ebus.c b/sys/dev/uart/uart_bus_ebus.c
index 0eab11fb41f5..9445c186b5e6 100644
--- a/sys/dev/uart/uart_bus_ebus.c
+++ b/sys/dev/uart/uart_bus_ebus.c
@@ -71,11 +71,11 @@ uart_ebus_probe(device_t dev)
 	nm = ebus_get_name(dev);
 	if (!strcmp(nm, "su")) {
 		sc->sc_class = &uart_ns8250_class;
-		return (uart_bus_probe(dev, 0, 0, 0));
+		return (uart_bus_probe(dev, 0, 0, 0, 0));
 	}
 	if (!strcmp(nm, "se")) {
 		sc->sc_class = &uart_sab82532_class;
-		error = uart_bus_probe(dev, 0, 0, 0);
+		error = uart_bus_probe(dev, 0, 0, 0, 1);
 		return ((error) ? error : -1);
 	}
 
diff --git a/sys/dev/uart/uart_bus_isa.c b/sys/dev/uart/uart_bus_isa.c
index 784d7f9a6d75..d6b5cda734bb 100644
--- a/sys/dev/uart/uart_bus_isa.c
+++ b/sys/dev/uart/uart_bus_isa.c
@@ -155,13 +155,13 @@ uart_isa_probe(device_t dev)
 
 	if (!ISA_PNP_PROBE(parent, dev, isa_ns8250_ids)) {
 		sc->sc_class = &uart_ns8250_class;
-		return (uart_bus_probe(dev, 0, 0, 0));
+		return (uart_bus_probe(dev, 0, 0, 0, 0));
 	}
 
 	/* Add checks for non-ns8250 IDs here. */
 
 	sc->sc_class = &uart_ns8250_class;
-	return (uart_bus_probe(dev, 0, 0, 0));
+	return (uart_bus_probe(dev, 0, 0, 0, 0));
 }
 
 DRIVER_MODULE(uart, isa, uart_isa_driver, uart_devclass, 0, 0);
diff --git a/sys/dev/uart/uart_bus_pccard.c b/sys/dev/uart/uart_bus_pccard.c
index c321060f332f..096392121788 100644
--- a/sys/dev/uart/uart_bus_pccard.c
+++ b/sys/dev/uart/uart_bus_pccard.c
@@ -95,7 +95,7 @@ uart_pccard_probe(dev)
 
 	/* Do not probe IRQ - pccard doesn't turn on the interrupt line */
 	/* until bus_setup_intr but how can I do so?*/
-	return (uart_bus_probe(dev, 0, 0, 0));
+	return (uart_bus_probe(dev, 0, 0, 0, 0));
 }
 
 DRIVER_MODULE(uart, pccard, uart_pccard_driver, uart_devclass, 0, 0);
diff --git a/sys/dev/uart/uart_bus_pci.c b/sys/dev/uart/uart_bus_pci.c
index 3555e5f4a8f5..2e4573d4e26b 100644
--- a/sys/dev/uart/uart_bus_pci.c
+++ b/sys/dev/uart/uart_bus_pci.c
@@ -111,7 +111,7 @@ uart_pci_probe(device_t dev)
  match:
 	if (id->desc)
 		device_set_desc(dev, id->desc);
-	return (uart_bus_probe(dev, 0, 0, id->rid));
+	return (uart_bus_probe(dev, 0, 0, id->rid, 0));
 }
 
 DRIVER_MODULE(uart, pci, uart_pci_driver, uart_devclass, 0, 0);
diff --git a/sys/dev/uart/uart_bus_puc.c b/sys/dev/uart/uart_bus_puc.c
index 94b042ef4d39..7277df99fc41 100644
--- a/sys/dev/uart/uart_bus_puc.c
+++ b/sys/dev/uart/uart_bus_puc.c
@@ -63,7 +63,7 @@ uart_puc_probe(device_t dev)
 {
 	device_t parent;
 	struct uart_softc *sc;
-	uintptr_t rclk, regshft, type;
+	uintptr_t port, rclk, regshft, type;
 
 	parent = device_get_parent(dev);
 	sc = device_get_softc(dev);
@@ -73,12 +73,17 @@ uart_puc_probe(device_t dev)
 	switch (type) {
 	case PUC_PORT_UART_NS8250:
 		sc->sc_class = &uart_ns8250_class;
+		port = 0;
 		break;
 	case PUC_PORT_UART_SAB82532:
 		sc->sc_class = &uart_sab82532_class;
+		if (BUS_READ_IVAR(parent, dev, PUC_IVAR_PORT, &port))
+			port = 0;
 		break;
 	case PUC_PORT_UART_Z8530:
 		sc->sc_class = &uart_z8530_class;
+		if (BUS_READ_IVAR(parent, dev, PUC_IVAR_PORT, &port))
+			port = 0;
 		break;
 	default:
 		return (ENXIO);
@@ -88,7 +93,7 @@ uart_puc_probe(device_t dev)
 		rclk = 0;
 	if (BUS_READ_IVAR(parent, dev, PUC_IVAR_REGSHFT, &regshft))
 		regshft = 0;
-	return (uart_bus_probe(dev, regshft, rclk, 0));
+	return (uart_bus_probe(dev, regshft, rclk, 0, port));
 }
 
 DRIVER_MODULE(uart, puc, uart_puc_driver, uart_devclass, 0, 0);
diff --git a/sys/dev/uart/uart_core.c b/sys/dev/uart/uart_core.c
index 501156fea0ad..18141c25769f 100644
--- a/sys/dev/uart/uart_core.c
+++ b/sys/dev/uart/uart_core.c
@@ -221,7 +221,7 @@ uart_intr(void *arg)
 }
 
 int
-uart_bus_probe(device_t dev, int regshft, int rclk, int rid)
+uart_bus_probe(device_t dev, int regshft, int rclk, int rid, int chan)
 {
 	struct uart_softc *sc;
 	struct uart_devinfo *sysdev;
@@ -267,14 +267,15 @@ uart_bus_probe(device_t dev, int regshft, int rclk, int rid)
 	 * accordingly. In general, you don't want to permanently disrupt
 	 * console I/O.
 	 */
-	sc->sc_bas.iobase = rman_get_start(sc->sc_rres);
 	sc->sc_bas.bsh = rman_get_bushandle(sc->sc_rres);
 	sc->sc_bas.bst = rman_get_bustag(sc->sc_rres);
+	sc->sc_bas.chan = chan;
 	sc->sc_bas.regshft = regshft;
 	sc->sc_bas.rclk = (rclk == 0) ? sc->sc_class->uc_rclk : rclk;
 
 	SLIST_FOREACH(sysdev, &uart_sysdevs, next) {
-		if (uart_cpu_eqres(&sc->sc_bas, &sysdev->bas)) {
+		if (chan == sysdev->bas.chan &&
+		    uart_cpu_eqres(&sc->sc_bas, &sysdev->bas)) {
 			/* XXX check if ops matches class. */
 			sc->sc_sysdev = sysdev;
 			break;
@@ -324,8 +325,6 @@ uart_bus_attach(device_t dev)
 	    0, ~0, sc->sc_class->uc_range, RF_ACTIVE);
 	if (sc->sc_rres == NULL)
 		return (ENXIO);
-
-	sc->sc_bas.iobase = rman_get_start(sc->sc_rres);
 	sc->sc_bas.bsh = rman_get_bushandle(sc->sc_rres);
 	sc->sc_bas.bst = rman_get_bustag(sc->sc_rres);
 
diff --git a/sys/dev/uart/uart_cpu_alpha.c b/sys/dev/uart/uart_cpu_alpha.c
index fffed6f83a9a..1d78d6a1853c 100644
--- a/sys/dev/uart/uart_cpu_alpha.c
+++ b/sys/dev/uart/uart_cpu_alpha.c
@@ -58,7 +58,7 @@ uart_cpu_getdev(int devtype, struct uart_devinfo *di)
 			return (ENXIO);
 		boothowto |= RB_SERIAL;
 		di->ops = uart_ns8250_ops;
-		di->bas.iobase = 0x3f8;
+		di->bas.chan = 0;
 		di->bas.bst = busspace_isa_io;
 		if (bus_space_map(di->bas.bst, 0x3f8, 8, 0, &di->bas.bsh) != 0)
 			return (ENXIO);
@@ -96,7 +96,7 @@ uart_cpu_getdev(int devtype, struct uart_devinfo *di)
 		 * only have ns8250 and successors on alpha.
 		 */
 		di->ops = uart_ns8250_ops;
-		di->bas.iobase = ivar;
+		di->bas.chan = 0;
 		di->bas.bst = busspace_isa_io;
 		if (bus_space_map(di->bas.bst, ivar, 8, 0, &di->bas.bsh) != 0)
 			continue;
diff --git a/sys/dev/uart/uart_cpu_amd64.c b/sys/dev/uart/uart_cpu_amd64.c
index 53f7d975833e..be0f619d2042 100644
--- a/sys/dev/uart/uart_cpu_amd64.c
+++ b/sys/dev/uart/uart_cpu_amd64.c
@@ -75,7 +75,7 @@ uart_cpu_getdev(int devtype, struct uart_devinfo *di)
 		 * ns8250 and successors on i386.
 		 */
 		di->ops = uart_ns8250_ops;
-		di->bas.iobase = ivar;
+		di->bas.chan = 0;
 		di->bas.bst = AMD64_BUS_SPACE_IO;
 		if (bus_space_map(di->bas.bst, ivar, 8, 0, &di->bas.bsh) != 0)
 			continue;
diff --git a/sys/dev/uart/uart_cpu_i386.c b/sys/dev/uart/uart_cpu_i386.c
index 8f252bb649b1..30b6e3ae517d 100644
--- a/sys/dev/uart/uart_cpu_i386.c
+++ b/sys/dev/uart/uart_cpu_i386.c
@@ -75,7 +75,7 @@ uart_cpu_getdev(int devtype, struct uart_devinfo *di)
 		 * ns8250 and successors on i386.
 		 */
 		di->ops = uart_ns8250_ops;
-		di->bas.iobase = ivar;
+		di->bas.chan = 0;
 		di->bas.bst = I386_BUS_SPACE_IO;
 		if (bus_space_map(di->bas.bst, ivar, 8, 0, &di->bas.bsh) != 0)
 			continue;
diff --git a/sys/dev/uart/uart_cpu_ia64.c b/sys/dev/uart/uart_cpu_ia64.c
index 8fa5b058e325..eeaea3b479cf 100644
--- a/sys/dev/uart/uart_cpu_ia64.c
+++ b/sys/dev/uart/uart_cpu_ia64.c
@@ -56,6 +56,7 @@ uart_cpu_getdev(int devtype, struct uart_devinfo *di)
 {
 	struct dig64_hcdp_table *tbl;
 	struct dig64_hcdp_entry *ent;
+	bus_addr_t addr;
 	unsigned int i, ivar;
 
 	/*
@@ -74,14 +75,14 @@ uart_cpu_getdev(int devtype, struct uart_devinfo *di)
 			    ent->type != DIG64_HCDP_DBGPORT)
 				continue;
 
+			addr = ent->address.addr_high;
+			addr = (addr << 32) + ent->address.addr_low;
 			di->ops = uart_ns8250_ops;
-			di->bas.iobase = (ent->address.addr_high << 32) +
-				ent->address.addr_low;
-			di->bas.bst = IA64_BUS_SPACE_IO;
+			di->bas.chan = 0;
 			di->bas.bst = (ent->address.addr_space == 0)
 			    ? IA64_BUS_SPACE_MEM : IA64_BUS_SPACE_IO;
-			if (bus_space_map(di->bas.bst, di->bas.iobase, 8, 0,
-					  &di->bas.bsh) != 0)
+			if (bus_space_map(di->bas.bst, addr, 8, 0,
+			    &di->bas.bsh) != 0)
 				continue;
 			di->bas.regshft = 0;
 			di->bas.rclk = ent->pclock << 4;
@@ -124,7 +125,7 @@ uart_cpu_getdev(int devtype, struct uart_devinfo *di)
 		 * ns8250 and successors on i386.
 		 */
 		di->ops = uart_ns8250_ops;
-		di->bas.iobase = ivar;
+		di->bas.chan = 0;
 		di->bas.bst = IA64_BUS_SPACE_IO;
 		if (bus_space_map(di->bas.bst, ivar, 8, 0, &di->bas.bsh) != 0)
 			continue;
diff --git a/sys/dev/uart/uart_cpu_pc98.c b/sys/dev/uart/uart_cpu_pc98.c
index 11c6e91c941c..4005a90dfd2d 100644
--- a/sys/dev/uart/uart_cpu_pc98.c
+++ b/sys/dev/uart/uart_cpu_pc98.c
@@ -40,7 +40,7 @@ int
 uart_cpu_eqres(struct uart_bas *b1, struct uart_bas *b2)
 {
 
-	return ((b1->iobase == b2->iobase && b1->bst == b2->bst) ? 1 : 0);
+	return (0);		/* XXX */
 }
 
 int
@@ -80,7 +80,7 @@ uart_cpu_getdev(int devtype, struct uart_devinfo *di)
 			di->ops = uart_ns8250_ops;
 		else
 			di->ops = uart_i8251_ops;
-		di->bas.iobase = ivar;
+		di->bas.chan = 0;
 		di->bas.bst = I386_BUS_SPACE_IO;
 		if (bus_space_map(di->bas.bst, ivar, 8, 0, &di->bas.bsh) != 0)
 			continue;
diff --git a/sys/dev/uart/uart_cpu_sparc64.c b/sys/dev/uart/uart_cpu_sparc64.c
index 5b8b1c62abc5..b99bc7101c28 100644
--- a/sys/dev/uart/uart_cpu_sparc64.c
+++ b/sys/dev/uart/uart_cpu_sparc64.c
@@ -55,7 +55,7 @@ uart_cpu_channel(char *dev)
 	if (len < 2 || alias[len - 2] != ':' || alias[len - 1] < 'a' ||
 	    alias[len - 1] > 'b')
 		return (0);
-	return (alias[len - 1] - 'a');
+	return (alias[len - 1] - 'a' + 1);
 }
 
 int
@@ -71,7 +71,7 @@ uart_cpu_getdev(int devtype, struct uart_devinfo *di)
 	char buf[32], dev[32], compat[32];
 	phandle_t input, options, output;
 	bus_addr_t addr;
-	int baud, bits, ch, error, space, stop;
+	int baud, bits, error, space, stop;
 	char flag, par;
 
 	/*
@@ -123,20 +123,21 @@ uart_cpu_getdev(int devtype, struct uart_devinfo *di)
 	di->bas.rclk = 0;
 	if (!strcmp(buf, "se")) {
 		di->ops = uart_sab82532_ops;
-		addr += 64 * uart_cpu_channel(dev);
+		di->bas.chan = uart_cpu_channel(dev);
+		addr += 64 * (di->bas.chan - 1);
 	} else if (!strcmp(buf, "zs")) {
 		di->ops = uart_z8530_ops;
+		di->bas.chan = uart_cpu_channel(dev);
 		di->bas.regshft = 1;
-		ch = uart_cpu_channel(dev);
-		addr += 4 - 4 * ch;
+		addr += 4 - 4 * (di->bas.chan - 1);
 	} else if (!strcmp(buf, "su") || !strcmp(buf, "su_pnp") ||
-	    !strcmp(compat, "su") || !strcmp(compat, "su16550"))
+	    !strcmp(compat, "su") || !strcmp(compat, "su16550")) {
 		di->ops = uart_ns8250_ops;
-	else
+		di->bas.chan = 0;
+	} else
 		return (ENXIO);
 
 	/* Fill in the device info. */
-	di->bas.iobase = addr;
 	di->bas.bst = &bst_store[devtype];
 	di->bas.bsh = sparc64_fake_bustag(space, addr, di->bas.bst);
 
diff --git a/sys/dev/uart/uart_dev_sab82532.c b/sys/dev/uart/uart_dev_sab82532.c
index b9e781f5f1e7..72c297bb4da8 100644
--- a/sys/dev/uart/uart_dev_sab82532.c
+++ b/sys/dev/uart/uart_dev_sab82532.c
@@ -42,9 +42,6 @@ __FBSDID("$FreeBSD$");
 
 #define	DEFAULT_RCLK	29491200
 
-#define	IS_CHANNEL_A(bas)	(((bas)->iobase & 0x40) == 0x00)
-#define	IS_CHANNEL_B(bas)	(((bas)->iobase & 0x40) == 0x40)
-
 /*
  * NOTE: To allow us to read the baudrate divisor from the chip, we
  * copy the value written to the write-only BGR register to an unused
@@ -219,7 +216,14 @@ sab82532_init(struct uart_bas *bas, int baudrate, int databits, int stopbits,
 	uart_barrier(bas);
 	/* Set DTR. */
 	pvr = uart_getreg(bas, SAB_PVR);
-	pvr &= IS_CHANNEL_A(bas) ? ~SAB_PVR_DTR_A : ~SAB_PVR_DTR_B;
+	switch (bas->chan) {
+	case 1:
+		pvr &= ~SAB_PVR_DTR_A;
+		break;
+	case 2:
+		pvr &= ~SAB_PVR_DTR_B;
+		break;
+	}
 	uart_setreg(bas, SAB_PVR, pvr | SAB_PVR_MAGIC);
 	uart_barrier(bas);
 
@@ -268,7 +272,14 @@ sab82532_term(struct uart_bas *bas)
 	uint8_t pvr;
 
 	pvr = uart_getreg(bas, SAB_PVR);
-	pvr |= IS_CHANNEL_A(bas) ? SAB_PVR_DTR_A : SAB_PVR_DTR_B;
+	switch (bas->chan) {
+	case 1:
+		pvr |= SAB_PVR_DTR_A;
+		break;
+	case 2:
+		pvr |= SAB_PVR_DTR_B;
+		break;
+	}
 	uart_setreg(bas, SAB_PVR, pvr);
 	uart_barrier(bas);
 }
@@ -448,7 +459,14 @@ sab82532_bus_getsig(struct uart_softc *sc)
 		vstr = uart_getreg(bas, SAB_VSTR);
 		SIGCHG(vstr & SAB_VSTR_CD, sig, UART_SIG_DCD, UART_SIG_DDCD);
 		pvr = uart_getreg(bas, SAB_PVR);
-		pvr &= (IS_CHANNEL_A(bas)) ? SAB_PVR_DSR_A : SAB_PVR_DSR_B;
+		switch (bas->chan) {
+		case 1:
+			pvr &= SAB_PVR_DSR_A;
+			break;
+		case 2:
+			pvr &= SAB_PVR_DSR_B;
+			break;
+		}
 		SIGCHG(~pvr, sig, UART_SIG_DSR, UART_SIG_DDSR);
 		mtx_unlock_spin(&sc->sc_hwmtx);
 		new = sig & ~UART_SIGMASK_DELTA;
@@ -558,15 +576,15 @@ static int
 sab82532_bus_probe(struct uart_softc *sc)
 {
 	char buf[80];
-	const char *ch, *vstr;
+	const char *vstr;
 	int error;
+	char ch;
 
 	error = sab82532_probe(&sc->sc_bas);
 	if (error)
 		return (error);
 
-	/* Assume the address range is naturally aligned. */
-	ch = IS_CHANNEL_A(&sc->sc_bas) ? "A" : "B";
+	ch = sc->sc_bas.chan - 1 + 'A';
 
 	switch (uart_getreg(&sc->sc_bas, SAB_VSTR) & SAB_VSTR_VMASK) {
 	case SAB_VSTR_V_1:
@@ -585,7 +603,7 @@ sab82532_bus_probe(struct uart_softc *sc)
 		break;
 	}
 
-	snprintf(buf, sizeof(buf), "SAB 82532 %s, channel %s", vstr, ch);
+	snprintf(buf, sizeof(buf), "SAB 82532 %s, channel %c", vstr, ch);
 	device_set_desc_copy(sc->sc_dev, buf);
 	return (0);
 }
@@ -650,10 +668,20 @@ sab82532_bus_setsig(struct uart_softc *sc, int sig)
 	mtx_lock_spin(&sc->sc_hwmtx);
 	/* Set DTR pin. */
 	pvr = uart_getreg(bas, SAB_PVR);
-	if (new & UART_SIG_DTR)
-		pvr &= (IS_CHANNEL_A(bas)) ? ~SAB_PVR_DTR_A : ~SAB_PVR_DTR_B;
-	else
-		pvr |= (IS_CHANNEL_A(bas)) ? SAB_PVR_DTR_A : SAB_PVR_DTR_B;
+	switch (bas->chan) {
+	case 1:
+		if (new & UART_SIG_DTR)
+			pvr &= ~SAB_PVR_DTR_A;
+		else
+			pvr |= SAB_PVR_DTR_A;
+		break;
+	case 2:
+		if (new & UART_SIG_DTR)
+			pvr &= ~SAB_PVR_DTR_B;
+		else
+			pvr |= SAB_PVR_DTR_B;
+		break;
+	}
 	uart_setreg(bas, SAB_PVR, pvr);
 
 	/* Set RTS pin. */
diff --git a/sys/dev/uart/uart_dev_z8530.c b/sys/dev/uart/uart_dev_z8530.c
index 30d8ed8ede7e..25bdca7df30e 100644
--- a/sys/dev/uart/uart_dev_z8530.c
+++ b/sys/dev/uart/uart_dev_z8530.c
@@ -42,9 +42,6 @@ __FBSDID("$FreeBSD$");
 
 #define	DEFAULT_RCLK	307200
 
-#define	IS_CHANNEL_A(bas)	(((bas)->iobase & 7) != 0)
-#define	IS_CHANNEL_B(bas)	(((bas)->iobase & 7) == 0)
-
 /* Multiplexed I/O. */
 static __inline void
 uart_setmreg(struct uart_bas *bas, int reg, int val)
@@ -144,14 +141,22 @@ static int
 z8530_setup(struct uart_bas *bas, int baudrate, int databits, int stopbits,
     int parity)
 {
-	uint8_t tpc;
+	uint8_t mic, tpc;
 
 	if (bas->rclk == 0)
 		bas->rclk = DEFAULT_RCLK;
 
 	/* Assume we don't need to perform a full hardware reset. */
-	uart_setmreg(bas, WR_MIC, ((IS_CHANNEL_A(bas)) ? MIC_CRA : MIC_CRB) |
-	    MIC_MIE | MIC_NV);
+	mic = MIC_MIE | MIC_NV;
+	switch (bas->chan) {
+	case 1:
+		mic |= MIC_CRA;
+		break;
+	case 2:
+		mic |= MIC_CRB;
+		break;
+	}
+	uart_setmreg(bas, WR_MIC, mic);
 	uart_barrier(bas);
 	/* Set clock sources and enable BRG. */
 	uart_setmreg(bas, WR_CMC, CMC_RC_BRG | CMC_TC_BRG);
@@ -433,17 +438,16 @@ static int
 z8530_bus_probe(struct uart_softc *sc)
 {
 	char buf[80];
-	const char *ch;
 	int error;
+	char ch;
 
 	error = z8530_probe(&sc->sc_bas);
 	if (error)
 		return (error);
 
-	/* Assume the address range is naturally aligned. */
-	ch = IS_CHANNEL_A(&sc->sc_bas) ? "A" : "B";
+	ch = sc->sc_bas.chan - 1 + 'A';
 
-	snprintf(buf, sizeof(buf), "z8530, channel %s", ch);
+	snprintf(buf, sizeof(buf), "z8530, channel %c", ch);
 	device_set_desc_copy(sc->sc_dev, buf);
 	return (0);
 }