ACPI / scan: Use direct recurrence for device hierarchy walks

Rework acpi_bus_trim() and acpi_bus_device_attach(), which is
renamed as acpi_bus_attach(), to walk the list of each device
object's children directly and call themselves recursively for
each child instead of using acpi_walk_namespace().  This
simplifies the code quite a bit and avoids the overhead of
callbacks and the ACPICA's internal processing which are not
really necessary for these two routines.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 45 insertions, 75 deletions

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index cf773c918102..311904c720b1 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -1909,54 +1909,40 @@ static int acpi_scan_attach_handler(struct acpi_device *device)
         return ret;
 }
 
-static acpi_status acpi_bus_device_attach(acpi_handle handle, u32 lvl_not_used,
-                                          void *not_used, void **ret_not_used)
+static void acpi_bus_attach(struct acpi_device *device)
 {
-        struct acpi_device *device;
-        unsigned long long sta;
+        struct acpi_device *child;
         int ret;
 
-        /*
-         * Ignore errors ignored by acpi_bus_check_add() to avoid terminating
-         * namespace walks prematurely.
-         */
-        if (acpi_bus_type_and_status(handle, &ret, &sta))
-                return AE_OK;
-
-        if (acpi_bus_get_device(handle, &device))
-                return AE_CTRL_DEPTH;
-
-        acpi_set_device_status(device, sta);
+        acpi_bus_get_status(device);
         /* Skip devices that are not present. */
-        if (!acpi_device_is_present(device))
-                goto err;
-
+        if (!acpi_device_is_present(device)) {
+                device->flags.visited = false;
+                return;
+        }
         if (device->handler)
-                return AE_OK;
+                goto ok;
 
         if (!device->flags.initialized) {
                 acpi_bus_update_power(device, NULL);
                 device->flags.initialized = true;
         }
+        device->flags.visited = false;
         ret = acpi_scan_attach_handler(device);
         if (ret < 0)
-                goto err;
+                return;
 
         device->flags.match_driver = true;
-        if (ret > 0)
-                goto ok;
-
-        ret = device_attach(&device->dev);
-        if (ret < 0)
-                goto err;
-
- ok:
+        if (!ret) {
+                ret = device_attach(&device->dev);
+                if (ret < 0)
+                        return;
+        }
         device->flags.visited = true;
-        return AE_OK;
 
- err:
-        device->flags.visited = false;
-        return AE_CTRL_DEPTH;
+ ok:
+        list_for_each_entry(child, &device->children, node)
+                acpi_bus_attach(child);
 }
 
 /**
@@ -1976,64 +1962,48 @@ static acpi_status acpi_bus_device_attach(acpi_handle handle, u32 lvl_not_used,
 int acpi_bus_scan(acpi_handle handle)
 {
         void *device = NULL;
-        int error = 0;
 
         if (ACPI_SUCCESS(acpi_bus_check_add(handle, 0, NULL, &device)))
                 acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX,
                                     acpi_bus_check_add, NULL, NULL, &device);
 
-        if (!device)
-                error = -ENODEV;
-        else if (ACPI_SUCCESS(acpi_bus_device_attach(handle, 0, NULL, NULL)))
-                acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX,
-                                    acpi_bus_device_attach, NULL, NULL, NULL);
-
-        return error;
-}
-EXPORT_SYMBOL(acpi_bus_scan);
-
-static acpi_status acpi_bus_device_detach(acpi_handle handle, u32 lvl_not_used,
-                                          void *not_used, void **ret_not_used)
-{
-        struct acpi_device *device = NULL;
-
-        if (!acpi_bus_get_device(handle, &device)) {
-                struct acpi_scan_handler *dev_handler = device->handler;
-
-                if (dev_handler) {
-                        if (dev_handler->detach)
-                                dev_handler->detach(device);
-
-                        device->handler = NULL;
-                } else {
-                        device_release_driver(&device->dev);
-                }
-                /*
-                 * Most likely, the device is going away, so put it into D3cold
-                 * before that.
-                 */
-                acpi_device_set_power(device, ACPI_STATE_D3_COLD);
-                device->flags.initialized = false;
-                device->flags.visited = false;
+        if (device) {
+                acpi_bus_attach(device);
+                return 0;
         }
-        return AE_OK;
+        return -ENODEV;
 }
+EXPORT_SYMBOL(acpi_bus_scan);
 
 /**
- * acpi_bus_trim - Remove ACPI device node and all of its descendants
- * @start: Root of the ACPI device nodes subtree to remove.
+ * acpi_bus_trim - Detach scan handlers and drivers from ACPI device objects.
+ * @adev: Root of the ACPI namespace scope to walk.
  *
  * Must be called under acpi_scan_lock.
  */
-void acpi_bus_trim(struct acpi_device *start)
+void acpi_bus_trim(struct acpi_device *adev)
 {
+        struct acpi_scan_handler *handler = adev->handler;
+        struct acpi_device *child;
+
+        list_for_each_entry_reverse(child, &adev->children, node)
+                acpi_bus_trim(child);
+
+        if (handler) {
+                if (handler->detach)
+                        handler->detach(adev);
+
+                adev->handler = NULL;
+        } else {
+                device_release_driver(&adev->dev);
+        }
         /*
-         * Execute acpi_bus_device_detach() as a post-order callback to detach
-         * all ACPI drivers from the device nodes being removed.
+         * Most likely, the device is going away, so put it into D3cold before
+         * that.
          */
-        acpi_walk_namespace(ACPI_TYPE_ANY, start->handle, ACPI_UINT32_MAX, NULL,
-                            acpi_bus_device_detach, NULL, NULL);
-        acpi_bus_device_detach(start->handle, 0, NULL, NULL);
+        acpi_device_set_power(adev, ACPI_STATE_D3_COLD);
+        adev->flags.initialized = false;
+        adev->flags.visited = false;
 }
 EXPORT_SYMBOL_GPL(acpi_bus_trim);