xen/pcifront: move xenstore config scanning into sub-function

pcifront_try_connect() and pcifront_attach_devices() share a large
chunk of duplicated code for reading the config information from
Xenstore, which only differs regarding calling pcifront_rescan_root()
or pcifront_scan_root().

Put that code into a new sub-function. It is fine to always call
pcifront_rescan_root() from that common function, as it will fallback
to pcifront_scan_root() if the domain/bus combination isn't known
yet (and pcifront_scan_root() should never be called for an already
known domain/bus combination anyway). In order to avoid duplicate
messages for the fallback case move the check for domain/bus not known
to the beginning of pcifront_rescan_root().

While at it fix the error reporting in case the root-xx node had the
wrong format.

As the return value of pcifront_try_connect() and
pcifront_attach_devices() are not used anywhere make those functions
return void. As an additional bonus this removes the dubious return
of -EFAULT in case of an unexpected driver state.
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jason Andryuk <jandryuk@gmail.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

drivers/pci/xen-pcifront.c

@@ -521,24 +521,14 @@ static int pcifront_rescan_root(struct pcifront_device *pdev,
 	int err;
 	struct pci_bus *b;
 
-#ifndef CONFIG_PCI_DOMAINS
-	if (domain != 0) {
-		dev_err(&pdev->xdev->dev,
-			"PCI Root in non-zero PCI Domain! domain=%d\n", domain);
-		dev_err(&pdev->xdev->dev,
-			"Please compile with CONFIG_PCI_DOMAINS\n");
-		return -EINVAL;
-	}
-#endif
-
-	dev_info(&pdev->xdev->dev, "Rescanning PCI Frontend Bus %04x:%02x\n",
-		 domain, bus);
-
 	b = pci_find_bus(domain, bus);
 	if (!b)
 		/* If the bus is unknown, create it. */
 		return pcifront_scan_root(pdev, domain, bus);
 
+	dev_info(&pdev->xdev->dev, "Rescanning PCI Frontend Bus %04x:%02x\n",
+		 domain, bus);
+
 	err = pcifront_scan_bus(pdev, domain, bus, b);
 
 	/* Claim resources before going "live" with our devices */
@@ -819,76 +809,73 @@ static int pcifront_publish_info(struct pcifront_device *pdev)
 	return err;
 }
 
-static int pcifront_try_connect(struct pcifront_device *pdev)
+static void pcifront_connect(struct pcifront_device *pdev)
 {
-	int err = -EFAULT;
+	int err;
 	int i, num_roots, len;
 	char str[64];
 	unsigned int domain, bus;
 
-
-	/* Only connect once */
-	if (xenbus_read_driver_state(pdev->xdev->nodename) !=
-	    XenbusStateInitialised)
-		goto out;
-
-	err = pcifront_connect_and_init_dma(pdev);
-	if (err && err != -EEXIST) {
-		xenbus_dev_fatal(pdev->xdev, err,
-				 "Error setting up PCI Frontend");
-		goto out;
-	}
-
 	err = xenbus_scanf(XBT_NIL, pdev->xdev->otherend,
 			   "root_num", "%d", &num_roots);
 	if (err == -ENOENT) {
 		xenbus_dev_error(pdev->xdev, err,
 				 "No PCI Roots found, trying 0000:00");
-		err = pcifront_scan_root(pdev, 0, 0);
+		err = pcifront_rescan_root(pdev, 0, 0);
 		if (err) {
 			xenbus_dev_fatal(pdev->xdev, err,
 					 "Error scanning PCI root 0000:00");
-			goto out;
+			return;
 		}
 		num_roots = 0;
 	} else if (err != 1) {
-		if (err == 0)
-			err = -EINVAL;
-		xenbus_dev_fatal(pdev->xdev, err,
+		xenbus_dev_fatal(pdev->xdev, err >= 0 ? -EINVAL : err,
 				 "Error reading number of PCI roots");
-		goto out;
+		return;
 	}
 
 	for (i = 0; i < num_roots; i++) {
 		len = snprintf(str, sizeof(str), "root-%d", i);
-		if (unlikely(len >= (sizeof(str) - 1))) {
-			err = -ENOMEM;
-			goto out;
-		}
+		if (unlikely(len >= (sizeof(str) - 1)))
+			return;
 
 		err = xenbus_scanf(XBT_NIL, pdev->xdev->otherend, str,
 				   "%x:%x", &domain, &bus);
 		if (err != 2) {
-			if (err >= 0)
-				err = -EINVAL;
-			xenbus_dev_fatal(pdev->xdev, err,
+			xenbus_dev_fatal(pdev->xdev, err >= 0 ? -EINVAL : err,
 					 "Error reading PCI root %d", i);
-			goto out;
+			return;
 		}
 
-		err = pcifront_scan_root(pdev, domain, bus);
+		err = pcifront_rescan_root(pdev, domain, bus);
 		if (err) {
 			xenbus_dev_fatal(pdev->xdev, err,
 					 "Error scanning PCI root %04x:%02x",
 					 domain, bus);
-			goto out;
+			return;
 		}
 	}
 
-	err = xenbus_switch_state(pdev->xdev, XenbusStateConnected);
+	xenbus_switch_state(pdev->xdev, XenbusStateConnected);
+}
 
-out:
-	return err;
+static void pcifront_try_connect(struct pcifront_device *pdev)
+{
+	int err;
+
+	/* Only connect once */
+	if (xenbus_read_driver_state(pdev->xdev->nodename) !=
+	    XenbusStateInitialised)
+		return;
+
+	err = pcifront_connect_and_init_dma(pdev);
+	if (err && err != -EEXIST) {
+		xenbus_dev_fatal(pdev->xdev, err,
+				 "Error setting up PCI Frontend");
+		return;
+	}
+
+	pcifront_connect(pdev);
 }
 
 static int pcifront_try_disconnect(struct pcifront_device *pdev)
@@ -914,67 +901,11 @@ static int pcifront_try_disconnect(struct pcifront_device *pdev)
 	return err;
 }
 
-static int pcifront_attach_devices(struct pcifront_device *pdev)
+static void pcifront_attach_devices(struct pcifront_device *pdev)
 {
-	int err = -EFAULT;
-	int i, num_roots, len;
-	unsigned int domain, bus;
-	char str[64];
-
-	if (xenbus_read_driver_state(pdev->xdev->nodename) !=
+	if (xenbus_read_driver_state(pdev->xdev->nodename) ==
 	    XenbusStateReconfiguring)
-		goto out;
-
-	err = xenbus_scanf(XBT_NIL, pdev->xdev->otherend,
-			   "root_num", "%d", &num_roots);
-	if (err == -ENOENT) {
-		xenbus_dev_error(pdev->xdev, err,
-				 "No PCI Roots found, trying 0000:00");
-		err = pcifront_rescan_root(pdev, 0, 0);
-		if (err) {
-			xenbus_dev_fatal(pdev->xdev, err,
-					 "Error scanning PCI root 0000:00");
-			goto out;
-		}
-		num_roots = 0;
-	} else if (err != 1) {
-		if (err == 0)
-			err = -EINVAL;
-		xenbus_dev_fatal(pdev->xdev, err,
-				 "Error reading number of PCI roots");
-		goto out;
-	}
-
-	for (i = 0; i < num_roots; i++) {
-		len = snprintf(str, sizeof(str), "root-%d", i);
-		if (unlikely(len >= (sizeof(str) - 1))) {
-			err = -ENOMEM;
-			goto out;
-		}
-
-		err = xenbus_scanf(XBT_NIL, pdev->xdev->otherend, str,
-				   "%x:%x", &domain, &bus);
-		if (err != 2) {
-			if (err >= 0)
-				err = -EINVAL;
-			xenbus_dev_fatal(pdev->xdev, err,
-					 "Error reading PCI root %d", i);
-			goto out;
-		}
-
-		err = pcifront_rescan_root(pdev, domain, bus);
-		if (err) {
-			xenbus_dev_fatal(pdev->xdev, err,
-					 "Error scanning PCI root %04x:%02x",
-					 domain, bus);
-			goto out;
-		}
-	}
-
-	xenbus_switch_state(pdev->xdev, XenbusStateConnected);
-
-out:
-	return err;
+		pcifront_connect(pdev);
 }
 
 static int pcifront_detach_devices(struct pcifront_device *pdev)