Rework how the nexus(4) device works on x86 to better handle the idea of

different "platforms" on x86 machines.  The existing code already handles
having two platforms: ACPI and legacy.  However, the existing approach was
rather hardcoded and difficult to extend.  These changes take the approach
that each x86 hardware platform should provide its own nexus(4) driver (it
can inherit most of its behavior from the default legacy nexus(4) driver)
which is responsible for probing for the platform and performing
appropriate platform-specific setup during attach (such as adding a
platform-specific bus device).  This does mean changing the x86 platform
busses to no longer use an identify routine for probing, but to move that
logic into their matching nexus(4) driver instead.
- Make the default nexus(4) driver in nexus.c on i386 and amd64 handle the
  legacy platform.  It's probe routine now returns BUS_PROBE_GENERIC so it
  can be overriden.
- Expose a nexus_init_resources() routine which initializes the various
  resource managers so that subclassed nexus(4) drivers can invoke it from
  their attach routine.
- The legacy nexus(4) driver explicitly adds a legacy0 device in its
  attach routine.
- The ACPI driver no longer contains an new-bus identify method.  Instead
  it exposes a public function (acpi_identify()) which is a probe routine
  that the MD nexus(4) drivers can use to probe for ACPI.  All of the
  probe logic in acpi_probe() is now moved into acpi_identify() and
  acpi_probe() is just a stub.
- On i386 and amd64, an ACPI-specific nexus(4) driver checks for ACPI via
  acpi_identify() and claims the nexus0 device if the probe succeeds.  It
  then explicitly adds an acpi0 device in its attach routine.
- The legacy(4) driver no longer knows anything about the acpi0 device.
- On ia64 if acpi_identify() fails you basically end up with no devices.
  This matches the previous behavior where the old acpi_identify() would
  fail to add an acpi0 device again leaving you with no devices.

Discussed with:	imp
Silence on:	arch@

11 files changed, 270 insertions, 121 deletions

diff --git a/sys/amd64/acpica/acpi_machdep.c b/sys/amd64/acpica/acpi_machdep.c
index 5201ad7..e9e9235 100644
--- a/sys/amd64/acpica/acpi_machdep.c
+++ b/sys/amd64/acpica/acpi_machdep.c
@@ -29,10 +29,14 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/bus.h>
+#include <sys/kernel.h>
+#include <sys/module.h>
 
 #include <contrib/dev/acpica/acpi.h>
 #include <dev/acpica/acpivar.h>
 
+#include <machine/nexusvar.h>
+
 static int intr_model = ACPI_INTR_PIC;
 
 int
@@ -67,3 +71,43 @@ acpi_cpu_c1()
 {
 	__asm __volatile("sti; hlt");
 }
+
+/*
+ * ACPI nexus(4) driver.
+ */
+static int
+nexus_acpi_probe(device_t dev)
+{
+	int error;
+
+	error = acpi_identify();
+	if (error)
+		return (error);
+
+	return (BUS_PROBE_DEFAULT);
+}
+
+static int
+nexus_acpi_attach(device_t dev)
+{
+
+	nexus_init_resources();
+	bus_generic_probe(dev);
+	if (BUS_ADD_CHILD(dev, 10, "acpi", 0) == NULL)
+		panic("failed to add acpi0 device");
+
+	return (bus_generic_attach(dev));
+}
+
+static device_method_t nexus_acpi_methods[] = {
+	/* Device interface */
+	DEVMETHOD(device_probe,		nexus_acpi_probe),
+	DEVMETHOD(device_attach,	nexus_acpi_attach),
+
+	{ 0, 0 }
+};
+
+DEFINE_CLASS_1(nexus, nexus_acpi_driver, nexus_acpi_methods, 1, nexus_driver);
+static devclass_t nexus_devclass;
+
+DRIVER_MODULE(nexus_acpi, root, nexus_acpi_driver, nexus_devclass, 0, 0);
diff --git a/sys/amd64/amd64/legacy.c b/sys/amd64/amd64/legacy.c
index 65dd27c..9793c02 100644
--- a/sys/amd64/amd64/legacy.c
+++ b/sys/amd64/amd64/legacy.c
@@ -57,7 +57,6 @@ struct legacy_device {
 
 #define DEVTOAT(dev)	((struct legacy_device *)device_get_ivars(dev))
 
-static void legacy_identify(driver_t *driver, device_t parent);
 static	int legacy_probe(device_t);
 static	int legacy_attach(device_t);
 static	int legacy_print_child(device_t, device_t);
@@ -68,7 +67,6 @@ static	int legacy_write_ivar(device_t, device_t, int, uintptr_t);
 
 static device_method_t legacy_methods[] = {
 	/* Device interface */
-	DEVMETHOD(device_identify,	legacy_identify),
 	DEVMETHOD(device_probe,		legacy_probe),
 	DEVMETHOD(device_attach,	legacy_attach),
 	DEVMETHOD(device_detach,	bus_generic_detach),
@@ -100,29 +98,10 @@ static devclass_t legacy_devclass;
 
 DRIVER_MODULE(legacy, nexus, legacy_driver, legacy_devclass, 0, 0);
 
-static void
-legacy_identify(driver_t *driver, device_t parent)
-{
-
-	/*
-	 * Add child device with order of 11 so it gets probed
-	 * after ACPI (which is at order 10).
-	 */
-	if (BUS_ADD_CHILD(parent, 11, "legacy", 0) == NULL)
-		panic("legacy: could not attach");
-}
-
 static int
 legacy_probe(device_t dev)
 {
-	device_t acpi;
 
-	/*
-	 * Fail to probe if ACPI is ok.
-	 */
-	acpi = devclass_get_device(devclass_find("acpi"), 0);
-	if (acpi != NULL && device_is_alive(acpi))
-		return (ENXIO);
 	device_set_desc(dev, "legacy system");
 	device_quiet(dev);
 	return (0);
diff --git a/sys/amd64/amd64/nexus.c b/sys/amd64/amd64/nexus.c
index 54d9e5f..de47d7d 100644
--- a/sys/amd64/amd64/nexus.c
+++ b/sys/amd64/amd64/nexus.c
@@ -61,6 +61,7 @@ __FBSDID("$FreeBSD$");
 #include <machine/pmap.h>
 
 #include <machine/metadata.h>
+#include <machine/nexusvar.h>
 #include <machine/resource.h>
 #include <machine/pc/bios.h>
 
@@ -73,13 +74,10 @@ __FBSDID("$FreeBSD$");
 #include <sys/rtprio.h>
 
 static MALLOC_DEFINE(M_NEXUSDEV, "nexusdev", "Nexus device");
-struct nexus_device {
-	struct resource_list	nx_resources;
-};
 
 #define DEVTONX(dev)	((struct nexus_device *)device_get_ivars(dev))
 
-static struct rman irq_rman, drq_rman, port_rman, mem_rman;
+struct rman irq_rman, drq_rman, port_rman, mem_rman;
 
 static	int nexus_probe(device_t);
 static	int nexus_attach(device_t);
@@ -146,11 +144,7 @@ static device_method_t nexus_methods[] = {
 	{ 0, 0 }
 };
 
-static driver_t nexus_driver = {
-	"nexus",
-	nexus_methods,
-	1,			/* no softc */
-};
+DEFINE_CLASS_0(nexus, nexus_driver, nexus_methods, 1);
 static devclass_t nexus_devclass;
 
 DRIVER_MODULE(nexus, root, nexus_driver, nexus_devclass, 0, 0);
@@ -158,9 +152,15 @@ DRIVER_MODULE(nexus, root, nexus_driver, nexus_devclass, 0, 0);
 static int
 nexus_probe(device_t dev)
 {
-	int irq;
 
 	device_quiet(dev);	/* suppress attach message for neatness */
+	return (BUS_PROBE_GENERIC);
+}
+  
+void
+nexus_init_resources(void)
+{
+	int irq;
 
 	/* 
 	 * XXX working notes:
@@ -185,7 +185,7 @@ nexus_probe(device_t dev)
 	irq_rman.rm_descr = "Interrupt request lines";
 	irq_rman.rm_end = NUM_IO_INTS - 1;
 	if (rman_init(&irq_rman))
-		panic("nexus_probe irq_rman");
+		panic("nexus_init_resources irq_rman");
 
 	/*
 	 * We search for regions of existing IRQs and add those to the IRQ
@@ -194,7 +194,7 @@ nexus_probe(device_t dev)
 	for (irq = 0; irq < NUM_IO_INTS; irq++)
 		if (intr_lookup_source(irq) != NULL)
 			if (rman_manage_region(&irq_rman, irq, irq) != 0)
-				panic("nexus_probe irq_rman add");
+				panic("nexus_init_resources irq_rman add");
 
 	/*
 	 * ISA DMA on PCI systems is implemented in the ISA part of each
@@ -209,7 +209,7 @@ nexus_probe(device_t dev)
 	if (rman_init(&drq_rman)
 	    || rman_manage_region(&drq_rman,
 				  drq_rman.rm_start, drq_rman.rm_end))
-		panic("nexus_probe drq_rman");
+		panic("nexus_init_resources drq_rman");
 
 	/*
 	 * However, IO ports and Memory truely are global at this level,
@@ -222,7 +222,7 @@ nexus_probe(device_t dev)
 	port_rman.rm_descr = "I/O ports";
 	if (rman_init(&port_rman)
 	    || rman_manage_region(&port_rman, 0, 0xffff))
-		panic("nexus_probe port_rman");
+		panic("nexus_init_resources port_rman");
 
 	mem_rman.rm_start = 0;
 	mem_rman.rm_end = ~0u;
@@ -230,16 +230,23 @@ nexus_probe(device_t dev)
 	mem_rman.rm_descr = "I/O memory addresses";
 	if (rman_init(&mem_rman)
 	    || rman_manage_region(&mem_rman, 0, ~0))
-		panic("nexus_probe mem_rman");
-
-	return 0;
+		panic("nexus_init_resources mem_rman");
 }
 
 static int
 nexus_attach(device_t dev)
 {
 
+	nexus_init_resources();
 	bus_generic_probe(dev);
+
+	/*
+	 * Explicitly add the legacy0 device here.  Other platform
+	 * types (such as ACPI), use their own nexus(4) subclass
+	 * driver to override this routine and add their own root bus.
+	 */
+	if (BUS_ADD_CHILD(dev, 10, "legacy", 0) == NULL)
+		panic("legacy: could not attach");
 	bus_generic_attach(dev);
 	return 0;
 }
diff --git a/sys/amd64/include/nexusvar.h b/sys/amd64/include/nexusvar.h
new file mode 100644
index 0000000..c39a686
--- /dev/null
+++ b/sys/amd64/include/nexusvar.h
@@ -0,0 +1,45 @@
+/*-
+ * Copyright 1998 Massachusetts Institute of Technology
+ *
+ * Permission to use, copy, modify, and distribute this software and
+ * its documentation for any purpose and without fee is hereby
+ * granted, provided that both the above copyright notice and this
+ * permission notice appear in all copies, that both the above
+ * copyright notice and this permission notice appear in all
+ * supporting documentation, and that the name of M.I.T. not be used
+ * in advertising or publicity pertaining to distribution of the
+ * software without specific, written prior permission.  M.I.T. makes
+ * no representations about the suitability of this software for any
+ * purpose.  It is provided "as is" without express or implied
+ * warranty.
+ *
+ * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''.  M.I.T. DISCLAIMS
+ * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
+ * SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef _MACHINE_NEXUSVAR_H_
+#define	_MACHINE_NEXUSVAR_H_
+
+struct nexus_device {
+	struct resource_list	nx_resources;
+};
+
+DECLARE_CLASS(nexus_driver);
+
+extern struct rman irq_rman, drq_rman, port_rman, mem_rman;
+
+void	nexus_init_resources(void);
+
+#endif /* !_MACHINE_NEXUSVAR_H_ */
diff --git a/sys/dev/acpica/acpi.c b/sys/dev/acpica/acpi.c
index 44a9012..da26b8a 100644
--- a/sys/dev/acpica/acpi.c
+++ b/sys/dev/acpica/acpi.c
@@ -91,7 +91,6 @@ struct mtx	acpi_mutex;
 int		acpi_quirks;
 
 static int	acpi_modevent(struct module *mod, int event, void *junk);
-static void	acpi_identify(driver_t *driver, device_t parent);
 static int	acpi_probe(device_t dev);
 static int	acpi_attach(device_t dev);
 static int	acpi_suspend(device_t dev);
@@ -156,7 +155,6 @@ static int	acpi_child_pnpinfo_str_method(device_t acdev, device_t child,
 
 static device_method_t acpi_methods[] = {
     /* Device interface */
-    DEVMETHOD(device_identify,		acpi_identify),
     DEVMETHOD(device_probe,		acpi_probe),
     DEVMETHOD(device_attach,		acpi_attach),
     DEVMETHOD(device_shutdown,		acpi_shutdown),
@@ -219,6 +217,9 @@ static struct rman acpi_rman_io, acpi_rman_mem;
 static const char* sleep_state_names[] = {
     "S0", "S1", "S2", "S3", "S4", "S5", "NONE"};
 
+/* Holds the description of the acpi0 device. */
+static char acpi_desc[ACPI_OEM_ID_SIZE + ACPI_OEM_TABLE_ID_SIZE + 2];
+
 SYSCTL_NODE(_debug, OID_AUTO, acpi, CTLFLAG_RD, NULL, "ACPI debugging");
 static char acpi_ca_version[12];
 SYSCTL_STRING(_debug_acpi, OID_AUTO, acpi_ca_version, CTLFLAG_RD,
@@ -316,64 +317,41 @@ acpi_Startup(void)
 }
 
 /*
- * Detect ACPI, perform early initialisation
+ * Detect ACPI and perform early initialisation.
  */
-static void
-acpi_identify(driver_t *driver, device_t parent)
+int
+acpi_identify(void)
 {
-    device_t	child;
+    ACPI_TABLE_RSDP	*rsdp;
+    ACPI_TABLE_HEADER	*rsdt;
+    ACPI_PHYSICAL_ADDRESS paddr;
+    struct sbuf		sb;
 
     ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
 
     if (!cold)
-	return_VOID;
+	return (ENXIO);
 
     /* Check that we haven't been disabled with a hint. */
     if (resource_disabled("acpi", 0))
-	return_VOID;
-
-    /* Make sure we're not being doubly invoked. */
-    if (device_find_child(parent, "acpi", 0) != NULL)
-	return_VOID;
+	return (ENXIO);
 
-    snprintf(acpi_ca_version, sizeof(acpi_ca_version), "%x", ACPI_CA_VERSION);
+    /* Check for other PM systems. */
+    if (power_pm_get_type() != POWER_PM_TYPE_NONE &&
+	power_pm_get_type() != POWER_PM_TYPE_ACPI) {
+	printf("ACPI identify failed, other PM system enabled.\n");
+	return (ENXIO);
+    }
 
     /* Initialize root tables. */
     if (ACPI_FAILURE(acpi_Startup())) {
 	printf("ACPI: Try disabling either ACPI or apic support.\n");
-	return_VOID;
-    }
-
-    /* Attach the actual ACPI device. */
-    if ((child = BUS_ADD_CHILD(parent, 10, "acpi", 0)) == NULL) {
-	device_printf(parent, "device_identify failed\n");
-	return_VOID;
-    }
-}
-
-/*
- * Fetch some descriptive data from ACPI to put in our attach message.
- */
-static int
-acpi_probe(device_t dev)
-{
-    ACPI_TABLE_RSDP	*rsdp;
-    ACPI_TABLE_HEADER	*rsdt;
-    ACPI_PHYSICAL_ADDRESS paddr;
-    char		buf[ACPI_OEM_ID_SIZE + ACPI_OEM_TABLE_ID_SIZE + 2];
-    struct sbuf		sb;
-
-    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
-
-    if (power_pm_get_type() != POWER_PM_TYPE_NONE &&
-	power_pm_get_type() != POWER_PM_TYPE_ACPI) {
-	device_printf(dev, "probe failed, other PM system enabled.\n");
-	return_VALUE (ENXIO);
+	return (ENXIO);
     }
 
     if ((paddr = AcpiOsGetRootPointer()) == 0 ||
 	(rsdp = AcpiOsMapMemory(paddr, sizeof(ACPI_TABLE_RSDP))) == NULL)
-	return_VALUE (ENXIO);
+	return (ENXIO);
     if (rsdp->Revision > 1 && rsdp->XsdtPhysicalAddress != 0)
 	paddr = (ACPI_PHYSICAL_ADDRESS)rsdp->XsdtPhysicalAddress;
     else
@@ -381,18 +359,33 @@ acpi_probe(device_t dev)
     AcpiOsUnmapMemory(rsdp, sizeof(ACPI_TABLE_RSDP));
 
     if ((rsdt = AcpiOsMapMemory(paddr, sizeof(ACPI_TABLE_HEADER))) == NULL)
-	return_VALUE (ENXIO);
-    sbuf_new(&sb, buf, sizeof(buf), SBUF_FIXEDLEN);
+	return (ENXIO);
+    sbuf_new(&sb, acpi_desc, sizeof(acpi_desc), SBUF_FIXEDLEN);
     sbuf_bcat(&sb, rsdt->OemId, ACPI_OEM_ID_SIZE);
     sbuf_trim(&sb);
     sbuf_putc(&sb, ' ');
     sbuf_bcat(&sb, rsdt->OemTableId, ACPI_OEM_TABLE_ID_SIZE);
     sbuf_trim(&sb);
     sbuf_finish(&sb);
-    device_set_desc_copy(dev, sbuf_data(&sb));
     sbuf_delete(&sb);
     AcpiOsUnmapMemory(rsdt, sizeof(ACPI_TABLE_HEADER));
 
+    snprintf(acpi_ca_version, sizeof(acpi_ca_version), "%x", ACPI_CA_VERSION);
+
+    return (0);
+}
+
+/*
+ * Fetch some descriptive data from ACPI to put in our attach message.
+ */
+static int
+acpi_probe(device_t dev)
+{
+
+    ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
+
+    device_set_desc(dev, acpi_desc);
+
     return_VALUE (0);
 }
 
diff --git a/sys/dev/acpica/acpivar.h b/sys/dev/acpica/acpivar.h
index 35bd66d..a5ac2de 100644
--- a/sys/dev/acpica/acpivar.h
+++ b/sys/dev/acpica/acpivar.h
@@ -364,6 +364,7 @@ struct acpi_parse_resource_set {
 
 extern struct	acpi_parse_resource_set acpi_res_parse_set;
 
+int		acpi_identify(void);
 void		acpi_config_intr(device_t dev, ACPI_RESOURCE *res);
 ACPI_STATUS	acpi_lookup_irq_resource(device_t dev, int rid,
 		    struct resource *res, ACPI_RESOURCE *acpi_res);
diff --git a/sys/i386/acpica/acpi_machdep.c b/sys/i386/acpica/acpi_machdep.c
index 4010690..db78988 100644
--- a/sys/i386/acpica/acpi_machdep.c
+++ b/sys/i386/acpica/acpi_machdep.c
@@ -34,6 +34,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/fcntl.h>
 #include <sys/kernel.h>
 #include <sys/malloc.h>
+#include <sys/module.h>
 #include <sys/poll.h>
 #include <sys/sysctl.h>
 #include <sys/uio.h>
@@ -44,6 +45,8 @@ __FBSDID("$FreeBSD$");
 #include <dev/acpica/acpivar.h>
 #include <dev/acpica/acpiio.h>
 
+#include <machine/nexusvar.h>
+
 /*
  * APM driver emulation 
  */
@@ -549,3 +552,43 @@ acpi_cpu_c1()
 {
 	__asm __volatile("sti; hlt");
 }
+
+/*
+ * ACPI nexus(4) driver.
+ */
+static int
+nexus_acpi_probe(device_t dev)
+{
+	int error;
+
+	error = acpi_identify();
+	if (error)
+		return (error);
+
+	return (BUS_PROBE_DEFAULT);
+}
+
+static int
+nexus_acpi_attach(device_t dev)
+{
+
+	nexus_init_resources();
+	bus_generic_probe(dev);
+	if (BUS_ADD_CHILD(dev, 10, "acpi", 0) == NULL)
+		panic("failed to add acpi0 device");
+
+	return (bus_generic_attach(dev));
+}
+
+static device_method_t nexus_acpi_methods[] = {
+	/* Device interface */
+	DEVMETHOD(device_probe,		nexus_acpi_probe),
+	DEVMETHOD(device_attach,	nexus_acpi_attach),
+
+	{ 0, 0 }
+};
+
+DEFINE_CLASS_1(nexus, nexus_acpi_driver, nexus_acpi_methods, 1, nexus_driver);
+static devclass_t nexus_devclass;
+
+DRIVER_MODULE(nexus_acpi, root, nexus_acpi_driver, nexus_devclass, 0, 0);
diff --git a/sys/i386/i386/legacy.c b/sys/i386/i386/legacy.c
index c3c52f5..5300488 100644
--- a/sys/i386/i386/legacy.c
+++ b/sys/i386/i386/legacy.c
@@ -62,7 +62,6 @@ struct legacy_device {
 
 #define DEVTOAT(dev)	((struct legacy_device *)device_get_ivars(dev))
 
-static void legacy_identify(driver_t *driver, device_t parent);
 static	int legacy_probe(device_t);
 static	int legacy_attach(device_t);
 static	int legacy_print_child(device_t, device_t);
@@ -73,7 +72,6 @@ static	int legacy_write_ivar(device_t, device_t, int, uintptr_t);
 
 static device_method_t legacy_methods[] = {
 	/* Device interface */
-	DEVMETHOD(device_identify,	legacy_identify),
 	DEVMETHOD(device_probe,		legacy_probe),
 	DEVMETHOD(device_attach,	legacy_attach),
 	DEVMETHOD(device_detach,	bus_generic_detach),
@@ -105,29 +103,10 @@ static devclass_t legacy_devclass;
 
 DRIVER_MODULE(legacy, nexus, legacy_driver, legacy_devclass, 0, 0);
 
-static void
-legacy_identify(driver_t *driver, device_t parent)
-{
-
-	/*
-	 * Add child device with order of 11 so it gets probed
-	 * after ACPI (which is at order 10).
-	 */
-	if (BUS_ADD_CHILD(parent, 11, "legacy", 0) == NULL)
-		panic("legacy: could not attach");
-}
-
 static int
 legacy_probe(device_t dev)
 {
-	device_t acpi;
 
-	/*
-	 * Fail to probe if ACPI is ok.
-	 */
-	acpi = devclass_get_device(devclass_find("acpi"), 0);
-	if (acpi != NULL && device_is_alive(acpi))
-		return (ENXIO);
 	device_set_desc(dev, "legacy system");
 	device_quiet(dev);
 	return (0);
diff --git a/sys/i386/i386/nexus.c b/sys/i386/i386/nexus.c
index f5fa4e0..0c09c34 100644
--- a/sys/i386/i386/nexus.c
+++ b/sys/i386/i386/nexus.c
@@ -60,6 +60,7 @@ __FBSDID("$FreeBSD$");
 #include <vm/pmap.h>
 #include <machine/pmap.h>
 
+#include <machine/nexusvar.h>
 #include <machine/resource.h>
 
 #ifdef DEV_APIC
@@ -77,13 +78,10 @@ __FBSDID("$FreeBSD$");
 #include <sys/rtprio.h>
 
 static MALLOC_DEFINE(M_NEXUSDEV, "nexusdev", "Nexus device");
-struct nexus_device {
-	struct resource_list	nx_resources;
-};
 
 #define DEVTONX(dev)	((struct nexus_device *)device_get_ivars(dev))
 
-static struct rman irq_rman, drq_rman, port_rman, mem_rman;
+struct rman irq_rman, drq_rman, port_rman, mem_rman;
 
 static	int nexus_probe(device_t);
 static	int nexus_attach(device_t);
@@ -154,11 +152,7 @@ static device_method_t nexus_methods[] = {
 	{ 0, 0 }
 };
 
-static driver_t nexus_driver = {
-	"nexus",
-	nexus_methods,
-	1,			/* no softc */
-};
+DEFINE_CLASS_0(nexus, nexus_driver, nexus_methods, 1);
 static devclass_t nexus_devclass;
 
 DRIVER_MODULE(nexus, root, nexus_driver, nexus_devclass, 0, 0);
@@ -166,9 +160,15 @@ DRIVER_MODULE(nexus, root, nexus_driver, nexus_devclass, 0, 0);
 static int
 nexus_probe(device_t dev)
 {
-	int irq;
 
 	device_quiet(dev);	/* suppress attach message for neatness */
+	return (BUS_PROBE_GENERIC);
+}
+
+void
+nexus_init_resources(void)
+{
+	int irq;
 
 	/*
 	 * XXX working notes:
@@ -193,7 +193,7 @@ nexus_probe(device_t dev)
 	irq_rman.rm_descr = "Interrupt request lines";
 	irq_rman.rm_end = NUM_IO_INTS - 1;
 	if (rman_init(&irq_rman))
-		panic("nexus_probe irq_rman");
+		panic("nexus_init_resources irq_rman");
 
 	/*
 	 * We search for regions of existing IRQs and add those to the IRQ
@@ -202,7 +202,7 @@ nexus_probe(device_t dev)
 	for (irq = 0; irq < NUM_IO_INTS; irq++)
 		if (intr_lookup_source(irq) != NULL)
 			if (rman_manage_region(&irq_rman, irq, irq) != 0)
-				panic("nexus_probe irq_rman add");
+				panic("nexus_init_resources irq_rman add");
 
 	/*
 	 * ISA DMA on PCI systems is implemented in the ISA part of each
@@ -221,7 +221,7 @@ nexus_probe(device_t dev)
 	if (rman_init(&drq_rman)
 	    || rman_manage_region(&drq_rman,
 				  drq_rman.rm_start, drq_rman.rm_end))
-		panic("nexus_probe drq_rman");
+		panic("nexus_init_resources drq_rman");
 
 	/*
 	 * However, IO ports and Memory truely are global at this level,
@@ -234,7 +234,7 @@ nexus_probe(device_t dev)
 	port_rman.rm_descr = "I/O ports";
 	if (rman_init(&port_rman)
 	    || rman_manage_region(&port_rman, 0, 0xffff))
-		panic("nexus_probe port_rman");
+		panic("nexus_init_resources port_rman");
 
 	mem_rman.rm_start = 0;
 	mem_rman.rm_end = ~0u;
@@ -242,16 +242,23 @@ nexus_probe(device_t dev)
 	mem_rman.rm_descr = "I/O memory addresses";
 	if (rman_init(&mem_rman)
 	    || rman_manage_region(&mem_rman, 0, ~0))
-		panic("nexus_probe mem_rman");
-
-	return 0;
+		panic("nexus_init_resources mem_rman");
 }
 
 static int
 nexus_attach(device_t dev)
 {
 
+	nexus_init_resources();
 	bus_generic_probe(dev);
+
+	/*
+	 * Explicitly add the legacy0 device here.  Other platform
+	 * types (such as ACPI), use their own nexus(4) subclass
+	 * driver to override this routine and add their own root bus.
+	 */
+	if (BUS_ADD_CHILD(dev, 10, "legacy", 0) == NULL)
+		panic("legacy: could not attach");
 	bus_generic_attach(dev);
 	return 0;
 }
diff --git a/sys/i386/include/nexusvar.h b/sys/i386/include/nexusvar.h
new file mode 100644
index 0000000..c39a686
--- /dev/null
+++ b/sys/i386/include/nexusvar.h
@@ -0,0 +1,45 @@
+/*-
+ * Copyright 1998 Massachusetts Institute of Technology
+ *
+ * Permission to use, copy, modify, and distribute this software and
+ * its documentation for any purpose and without fee is hereby
+ * granted, provided that both the above copyright notice and this
+ * permission notice appear in all copies, that both the above
+ * copyright notice and this permission notice appear in all
+ * supporting documentation, and that the name of M.I.T. not be used
+ * in advertising or publicity pertaining to distribution of the
+ * software without specific, written prior permission.  M.I.T. makes
+ * no representations about the suitability of this software for any
+ * purpose.  It is provided "as is" without express or implied
+ * warranty.
+ *
+ * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''.  M.I.T. DISCLAIMS
+ * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
+ * SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef _MACHINE_NEXUSVAR_H_
+#define	_MACHINE_NEXUSVAR_H_
+
+struct nexus_device {
+	struct resource_list	nx_resources;
+};
+
+DECLARE_CLASS(nexus_driver);
+
+extern struct rman irq_rman, drq_rman, port_rman, mem_rman;
+
+void	nexus_init_resources(void);
+
+#endif /* !_MACHINE_NEXUSVAR_H_ */
diff --git a/sys/ia64/ia64/nexus.c b/sys/ia64/ia64/nexus.c
index ac184b4..fad54de 100644
--- a/sys/ia64/ia64/nexus.c
+++ b/sys/ia64/ia64/nexus.c
@@ -60,6 +60,9 @@
 #include <machine/sapicvar.h>
 #include <machine/vmparam.h>
 
+#include <contrib/dev/acpica/acpi.h>
+#include <dev/acpica/acpivar.h>
+
 #include <isa/isareg.h>
 #include <sys/rtprio.h>
 
@@ -217,12 +220,15 @@ nexus_probe(device_t dev)
 static int
 nexus_attach(device_t dev)
 {
+
 	/*
 	 * Mask the legacy PICs - we will use the I/O SAPIC for interrupt.
 	 */
 	outb(IO_ICU1+1, 0xff);
 	outb(IO_ICU2+1, 0xff);
 
+	if (acpi_identify() == 0)
+		BUS_ADD_CHILD(dev, 10, "acpi", 0);
 	bus_generic_attach(dev);
 	return 0;
 }