--- 1ac0c93603c903a1d7a39f1efb10530936a2f4e1
+++ aa8688d25e848457d81797d11d07700abc5bf0b0
@@ -954,6 +954,7 @@ static ssize_t vga_arb_write(struct file
 		}
 
 	} else if (strncmp(curr_pos, "target ", 7) == 0) {
+		struct pci_bus *pbus;
 		unsigned int domain, bus, devfn;
 		struct vga_device *vgadev;
 
@@ -961,7 +962,7 @@ static ssize_t vga_arb_write(struct file
 		remaining -= 7;
 		pr_devel("client 0x%p called 'target'\n", priv);
 		/* if target is default */
-		if (!strncmp(buf, "default", 7))
+		if (!strncmp(curr_pos, "default", 7))
 			pdev = pci_dev_get(vga_default_device());
 		else {
 			if (!vga_pci_str_to_vars(curr_pos, remaining,
@@ -969,18 +970,31 @@ static ssize_t vga_arb_write(struct file
 				ret_val = -EPROTO;
 				goto done;
 			}
+			pr_devel("vgaarb: %s ==> %x:%x:%x.%x\n", curr_pos,
+				domain, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
 
-			pdev = pci_get_bus_and_slot(bus, devfn);
+			pbus = pci_find_bus(domain, bus);
+			pr_devel("vgaarb: pbus %p\n", pbus);
+			if (pbus == NULL) {
+				pr_err("vgaarb: invalid PCI domain and/or bus address %x:%x\n",
+					domain, bus);
+				ret_val = -ENODEV;
+				goto done;
+			}
+			pdev = pci_get_slot(pbus, devfn);
+			pr_devel("vgaarb: pdev %p\n", pdev);
 			if (!pdev) {
-				pr_info("vgaarb: invalid PCI address!\n");
+				pr_err("vgaarb: invalid PCI address %x:%x\n",
+					bus, devfn);
 				ret_val = -ENODEV;
 				goto done;
 			}
 		}
 
 		vgadev = vgadev_find(pdev);
+		pr_devel("vgaarb: vgadev %p\n", vgadev);
 		if (vgadev == NULL) {
-			pr_info("vgaarb: this pci device is not a vga device\n");
+			pr_err("vgaarb: this pci device is not a vga device\n");
 			pci_dev_put(pdev);
 			ret_val = -ENODEV;
 			goto done;
@@ -998,7 +1012,8 @@ static ssize_t vga_arb_write(struct file
 			}
 		}
 		if (i == MAX_USER_CARDS) {
-			pr_err("vgaarb: maximum user cards number reached!\n");
+			pr_err("vgaarb: maximum user cards (%d) number reached!\n",
+				MAX_USER_CARDS);
 			pci_dev_put(pdev);
 			/* XXX: which value to return? */
 			ret_val =  -ENOMEM;