ACPI / PCI: Make PCI root driver use struct acpi_scan_handler

Make the ACPI PCI root bridge driver use struct acpi_scan_handler
for representing the object used to enumerate the PCI busses under
PCI host bridges found in the ACPI namespace (and to tear down data
structures representing the bus and devices on it before
unregistering the host bridges' ACPI device nodes).

This simplifies the code slightly and reduces the kernel's memory
footprint by avoiding the registration of a struct device_driver
object with the driver core and creation of its sysfs directory
which is unnecessary.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>
Acked-by: Toshi Kani <toshi.kani@hp.com>

drivers/acpi/internal.h

@@ -25,6 +25,7 @@
 
 int init_acpi_device_notify(void);
 int acpi_scan_init(void);
+void acpi_pci_root_init(void);
 int acpi_sysfs_init(void);
 void acpi_csrt_init(void);
 
@@ -86,7 +87,6 @@ struct acpi_ec {
 
 extern struct acpi_ec *first_ec;
 
-int acpi_pci_root_init(void);
 int acpi_ec_init(void);
 int acpi_ec_ecdt_probe(void);
 int acpi_boot_ec_enable(void);

drivers/acpi/pci_root.c

@@ -45,8 +45,9 @@
 ACPI_MODULE_NAME("pci_root");
 #define ACPI_PCI_ROOT_CLASS		"pci_bridge"
 #define ACPI_PCI_ROOT_DEVICE_NAME	"PCI Root Bridge"
-static int acpi_pci_root_add(struct acpi_device *device);
-static int acpi_pci_root_remove(struct acpi_device *device);
+static int acpi_pci_root_add(struct acpi_device *device,
+			     const struct acpi_device_id *not_used);
+static void acpi_pci_root_remove(struct acpi_device *device);
 
 #define ACPI_PCIE_REQ_SUPPORT (OSC_EXT_PCI_CONFIG_SUPPORT \
 				| OSC_ACTIVE_STATE_PWR_SUPPORT \
@@ -57,16 +58,11 @@ static const struct acpi_device_id root_device_ids[] = {
 	{"PNP0A03", 0},
 	{"", 0},
 };
-MODULE_DEVICE_TABLE(acpi, root_device_ids);
 
-static struct acpi_driver acpi_pci_root_driver = {
-	.name = "pci_root",
-	.class = ACPI_PCI_ROOT_CLASS,
+static struct acpi_scan_handler pci_root_handler = {
 	.ids = root_device_ids,
-	.ops = {
-		.add = acpi_pci_root_add,
-		.remove = acpi_pci_root_remove,
-		},
+	.attach = acpi_pci_root_add,
+	.detach = acpi_pci_root_remove,
 };
 
 /* Lock to protect both acpi_pci_roots and acpi_pci_drivers lists */
@@ -428,7 +424,8 @@ acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 *mask, u32 req)
 }
 EXPORT_SYMBOL(acpi_pci_osc_control_set);
 
-static int acpi_pci_root_add(struct acpi_device *device)
+static int acpi_pci_root_add(struct acpi_device *device,
+			     const struct acpi_device_id *not_used)
 {
 	unsigned long long segment, bus;
 	acpi_status status;
@@ -614,7 +611,7 @@ static int acpi_pci_root_add(struct acpi_device *device)
 		pci_enable_bridges(root->bus);
 
 	pci_bus_add_devices(root->bus);
-	return 0;
+	return 1;
 
 out_del_root:
 	mutex_lock(&acpi_pci_root_lock);
@@ -627,7 +624,7 @@ static int acpi_pci_root_add(struct acpi_device *device)
 	return result;
 }
 
-static int acpi_pci_root_remove(struct acpi_device *device)
+static void acpi_pci_root_remove(struct acpi_device *device)
 {
 	acpi_status status;
 	acpi_handle handle;
@@ -655,19 +652,14 @@ static int acpi_pci_root_remove(struct acpi_device *device)
 	list_del(&root->node);
 	mutex_unlock(&acpi_pci_root_lock);
 	kfree(root);
-	return 0;
 }
 
-int __init acpi_pci_root_init(void)
+void __init acpi_pci_root_init(void)
 {
 	acpi_hest_init();
 
-	if (acpi_pci_disabled)
-		return 0;
-
-	pci_acpi_crs_quirks();
-	if (acpi_bus_register_driver(&acpi_pci_root_driver) < 0)
-		return -ENODEV;
-
-	return 0;
+	if (!acpi_pci_disabled) {
+		pci_acpi_crs_quirks();
+		acpi_scan_add_handler(&pci_root_handler);
+	}
 }