Implement a PCI bus rescan method.

Rescanning a PCI bus uses the following steps:
- Fetch the current set of child devices and save it in the 'devlist'
  array.
- Allocate a parallel array 'unchanged' initalized with NULL pointers.
- Scan the bus checking each slot (and each function on slots with a
  multifunction device).
- If a valid function is found, look for a matching device in the 'devlist'
  array.  If a device is found, save the pointer in the 'unchanged' array.
  If a device is not found, add a new device.
- After the scan has finished, walk the 'devlist' array deleting any
  devices that do not have a matching pointer in the 'unchanged' array.
- Finally, fetch an updated set of child devices and explicitly attach any
  devices that are not present in the 'unchanged' array.

This builds on the previous changes to move subclass data management into
pci_alloc_devinfo(), pci_child_added(), and bus_child_deleted().

Subclasses of the PCI bus use custom rescan logic explicitly override the
rescan method to disable rescans.

Differential Revision:	https://reviews.freebsd.org/D6018

sys/dev/cardbus/cardbus.c

@@ -346,6 +346,7 @@ static device_method_t cardbus_methods[] = {
 	DEVMETHOD(bus_get_dma_tag,	bus_generic_get_dma_tag),
 	DEVMETHOD(bus_read_ivar,	cardbus_read_ivar),
 	DEVMETHOD(bus_driver_added,	cardbus_driver_added),
+	DEVMETHOD(bus_rescan,		kobj_error_method),
 
 	/* Card Interface */
 	DEVMETHOD(card_attach_card,	cardbus_attach_card),

sys/dev/pci/pci.c

@@ -168,6 +168,7 @@ static device_method_t pci_methods[] = {
 	DEVMETHOD(bus_remap_intr,	pci_remap_intr_method),
 	DEVMETHOD(bus_suspend_child,	pci_suspend_child),
 	DEVMETHOD(bus_resume_child,	pci_resume_child),
+	DEVMETHOD(bus_rescan,		pci_rescan_method),
 
 	/* PCI interface */
 	DEVMETHOD(pci_read_config,	pci_read_config_method),
@@ -3917,6 +3918,103 @@ pci_add_children(device_t dev, int domain, int busno)
 #undef REG
 }
 
+int
+pci_rescan_method(device_t dev)
+{
+#define	REG(n, w)	PCIB_READ_CONFIG(pcib, busno, s, f, n, w)
+	device_t pcib = device_get_parent(dev);
+	struct pci_softc *sc;
+	device_t child, *devlist, *unchanged;
+	int devcount, error, i, j, maxslots, oldcount;
+	int busno, domain, s, f, pcifunchigh;
+	uint8_t hdrtype;
+
+	/* No need to check for ARI on a rescan. */
+	error = device_get_children(dev, &devlist, &devcount);
+	if (error)
+		return (error);
+	if (devcount != 0) {
+		unchanged = malloc(devcount * sizeof(device_t), M_TEMP,
+		    M_NOWAIT | M_ZERO);
+		if (unchanged == NULL) {
+			free(devlist, M_TEMP);
+			return (ENOMEM);
+		}
+	} else
+		unchanged = NULL;
+
+	sc = device_get_softc(dev);
+	domain = pcib_get_domain(dev);
+	busno = pcib_get_bus(dev);
+	maxslots = PCIB_MAXSLOTS(pcib);
+	for (s = 0; s <= maxslots; s++) {
+		/* If function 0 is not present, skip to the next slot. */
+		f = 0;
+		if (REG(PCIR_VENDOR, 2) == 0xffff)
+			continue;
+		pcifunchigh = 0;
+		hdrtype = REG(PCIR_HDRTYPE, 1);
+		if ((hdrtype & PCIM_HDRTYPE) > PCI_MAXHDRTYPE)
+			continue;
+		if (hdrtype & PCIM_MFDEV)
+			pcifunchigh = PCIB_MAXFUNCS(pcib);
+		for (f = 0; f <= pcifunchigh; f++) {
+			if (REG(PCIR_VENDOR, 2) == 0xfff)
+				continue;
+
+			/*
+			 * Found a valid function.  Check if a
+			 * device_t for this device already exists.
+			 */
+			for (i = 0; i < devcount; i++) {
+				child = devlist[i];
+				if (child == NULL)
+					continue;
+				if (pci_get_slot(child) == s &&
+				    pci_get_function(child) == f) {
+					unchanged[i] = child;
+					goto next_func;
+				}
+			}
+
+			pci_identify_function(pcib, dev, domain, busno, s, f);
+		next_func:;
+		}
+	}
+
+	/* Remove devices that are no longer present. */
+	for (i = 0; i < devcount; i++) {
+		if (unchanged[i] != NULL)
+			continue;
+		device_delete_child(dev, devlist[i]);
+	}
+
+	free(devlist, M_TEMP);
+	oldcount = devcount;
+
+	/* Try to attach the devices just added. */
+	error = device_get_children(dev, &devlist, &devcount);
+	if (error) {
+		free(unchanged, M_TEMP);
+		return (error);
+	}
+
+	for (i = 0; i < devcount; i++) {
+		for (j = 0; j < oldcount; j++) {
+			if (devlist[i] == unchanged[j])
+				goto next_device;
+		}
+
+		device_probe_and_attach(devlist[i]);
+	next_device:;
+	}
+
+	free(unchanged, M_TEMP);
+	free(devlist, M_TEMP);
+	return (0);
+#undef REG
+}
+
 #ifdef PCI_IOV
 device_t
 pci_add_iov_child(device_t bus, device_t pf, uint16_t rid, uint16_t vid,

sys/dev/pci/pci_private.h

@@ -57,6 +57,7 @@ void		pci_add_resources(device_t bus, device_t dev, int force,
 void		pci_add_resources_ea(device_t bus, device_t dev, int alloc_iov);
 struct pci_devinfo *pci_alloc_devinfo_method(device_t dev);
 int		pci_attach_common(device_t dev);
+int		pci_rescan_method(device_t dev);
 void		pci_driver_added(device_t dev, driver_t *driver);
 int		pci_ea_is_enabled(device_t dev, int rid);
 int		pci_print_child(device_t dev, device_t child);

sys/mips/nlm/xlp_pci.c

@@ -154,6 +154,7 @@ static device_method_t xlp_pci_methods[] = {
 	/* Device interface */
 	DEVMETHOD(device_probe,		xlp_pci_probe),
 	DEVMETHOD(device_attach,	xlp_pci_attach),
+	DEVMETHOD(bus_rescan,		kobj_error_method),
 	DEVMETHOD_END
 };
 

sys/powerpc/ofw/ofw_pcibus.c

@@ -77,6 +77,7 @@ static device_method_t ofw_pcibus_methods[] = {
 	/* Bus interface */
 	DEVMETHOD(bus_child_deleted,	ofw_pcibus_child_deleted),
 	DEVMETHOD(bus_child_pnpinfo_str, ofw_pcibus_child_pnpinfo_str_method),
+	DEVMETHOD(bus_rescan,		kobj_error_method),
 
 	/* PCI interface */
 	DEVMETHOD(pci_alloc_devinfo,	ofw_pcibus_alloc_devinfo),

sys/sparc64/pci/ofw_pcibus.c

@@ -81,6 +81,7 @@ static device_method_t ofw_pcibus_methods[] = {
 	/* Bus interface */
 	DEVMETHOD(bus_child_deleted,	ofw_pcibus_child_deleted),
 	DEVMETHOD(bus_child_pnpinfo_str, ofw_pcibus_pnpinfo_str),
+	DEVMETHOD(bus_rescan,		kobj_error_method),
 
 	/* PCI interface */
 	DEVMETHOD(pci_alloc_devinfo,	ofw_pcibus_alloc_devinfo),