ACPI / scan: Add acpi_device objects for all device nodes in the namespace

Modify the ACPI namespace scanning code to register a struct
acpi_device object for every namespace node representing a device,
processor and so on, even if the device represented by that namespace
node is reported to be not present and not functional by _STA.

There are multiple reasons to do that.  First of all, it avoids
quite a lot of overhead when struct acpi_device objects are
deleted every time acpi_bus_trim() is run and then added again
by a subsequent acpi_bus_scan() for the same scope, although the
namespace objects they correspond to stay in memory all the time
(which always is the case on a vast majority of systems).

Second, it will allow user space to see that there are namespace
nodes representing devices that are not present at the moment and may
be added to the system.  It will also allow user space to evaluate
_SUN for those nodes to check what physical slots the "missing"
devices may be put into and it will make sense to add a sysfs
attribute for _STA evaluation after this change (that will be
useful for thermal management on some systems).

Next, it will help to consolidate the ACPI hotplug handling among
subsystems by making it possible to store hotplug-related information
in struct acpi_device objects in a standard common way.

Finally, it will help to avoid a race condition related to the
deletion of ACPI namespace nodes.  Namely, namespace nodes may be
deleted as a result of a table unload triggered by _EJ0 or _DCK.
If a hotplug notification for one of those nodes is triggered
right before the deletion and it executes a hotplug callback
via acpi_hotplug_execute(), the ACPI handle passed to that
callback may be stale when the callback actually runs.  One way
to work around that is to always pass struct acpi_device pointers
to hotplug callbacks after doing a get_device() on the objects in
question which eliminates the use-after-free possibility (the ACPI
handles in those objects are invalidated by acpi_scan_drop_device(),
so they will trigger ACPICA errors on attempts to use them).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>

1 files changed, 51 insertions, 56 deletions

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index ad2522015e5..bc52192785f 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -259,7 +259,6 @@ static int acpi_scan_hot_remove(struct acpi_device *device)
 
 	acpi_bus_trim(device);
 
-	/* Device node has been unregistered. */
 	put_device(&device->dev);
 	device = NULL;
 
@@ -328,7 +327,7 @@ void acpi_bus_device_eject(void *data, u32 ost_src)
 static void acpi_scan_bus_device_check(void *data, u32 ost_source)
 {
 	acpi_handle handle = data;
-	struct acpi_device *device = NULL;
+	struct acpi_device *device;
 	u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE;
 	int error;
 
@@ -336,8 +335,9 @@ static void acpi_scan_bus_device_check(void *data, u32 ost_source)
 	mutex_lock(&acpi_scan_lock);
 
 	if (ost_source != ACPI_NOTIFY_BUS_CHECK) {
+		device = NULL;
 		acpi_bus_get_device(handle, &device);
-		if (device) {
+		if (acpi_device_enumerated(device)) {
 			dev_warn(&device->dev, "Attempt to re-insert\n");
 			goto out;
 		}
@@ -347,9 +347,10 @@ static void acpi_scan_bus_device_check(void *data, u32 ost_source)
 		acpi_handle_warn(handle, "Namespace scan failure\n");
 		goto out;
 	}
-	error = acpi_bus_get_device(handle, &device);
-	if (error) {
-		acpi_handle_warn(handle, "Missing device node object\n");
+	device = NULL;
+	acpi_bus_get_device(handle, &device);
+	if (!acpi_device_enumerated(device)) {
+		acpi_handle_warn(handle, "Device not enumerated\n");
 		goto out;
 	}
 	ost_code = ACPI_OST_SC_SUCCESS;
@@ -1111,20 +1112,6 @@ int acpi_device_add(struct acpi_device *device,
 	return result;
 }
 
-static void acpi_device_unregister(struct acpi_device *device)
-{
-	acpi_detach_data(device->handle, acpi_scan_drop_device);
-	acpi_device_del(device);
-	/*
-	 * Transition the device to D3cold to drop the reference counts of all
-	 * power resources the device depends on and turn off the ones that have
-	 * no more references.
-	 */
-	acpi_device_set_power(device, ACPI_STATE_D3_COLD);
-	device->handle = NULL;
-	put_device(&device->dev);
-}
-
 /* --------------------------------------------------------------------------
                                  Driver Management
    -------------------------------------------------------------------------- */
@@ -1703,6 +1690,8 @@ void acpi_init_device_object(struct acpi_device *device, acpi_handle handle,
 	acpi_set_pnp_ids(handle, &device->pnp, type);
 	acpi_bus_get_flags(device);
 	device->flags.match_driver = false;
+	device->flags.initialized = true;
+	device->flags.visited = false;
 	device_initialize(&device->dev);
 	dev_set_uevent_suppress(&device->dev, true);
 }
@@ -1787,6 +1776,15 @@ static int acpi_bus_type_and_status(acpi_handle handle, int *type,
 	return 0;
 }
 
+bool acpi_device_is_present(struct acpi_device *adev)
+{
+	if (adev->status.present || adev->status.functional)
+		return true;
+
+	adev->flags.initialized = false;
+	return false;
+}
+
 static bool acpi_scan_handler_matching(struct acpi_scan_handler *handler,
 				       char *idstr,
 				       const struct acpi_device_id **matchid)
@@ -1880,18 +1878,6 @@ static acpi_status acpi_bus_check_add(acpi_handle handle, u32 lvl_not_used,
 
 	acpi_scan_init_hotplug(handle, type);
 
-	if (!(sta & ACPI_STA_DEVICE_PRESENT) &&
-	    !(sta & ACPI_STA_DEVICE_FUNCTIONING)) {
-		struct acpi_device_wakeup wakeup;
-
-		if (acpi_has_method(handle, "_PRW")) {
-			acpi_bus_extract_wakeup_device_power_package(handle,
-								     &wakeup);
-			acpi_power_resources_list_free(&wakeup.resources);
-		}
-		return AE_CTRL_DEPTH;
-	}
-
 	acpi_add_single_object(&device, handle, type, sta);
 	if (!device)
 		return AE_CTRL_DEPTH;
@@ -1930,32 +1916,50 @@ static acpi_status acpi_bus_device_attach(acpi_handle handle, u32 lvl_not_used,
 					  void *not_used, void **ret_not_used)
 {
 	struct acpi_device *device;
-	unsigned long long sta_not_used;
+	unsigned long long sta;
 	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_not_used))
+	if (acpi_bus_type_and_status(handle, &ret, &sta))
 		return AE_OK;
 
 	if (acpi_bus_get_device(handle, &device))
 		return AE_CTRL_DEPTH;
 
+	STRUCT_TO_INT(device->status) = sta;
+	/* Skip devices that are not present. */
+	if (!acpi_device_is_present(device))
+		goto err;
+
 	if (device->handler)
 		return AE_OK;
 
+	if (!device->flags.initialized) {
+		acpi_bus_update_power(device, NULL);
+		device->flags.initialized = true;
+	}
 	ret = acpi_scan_attach_handler(device);
 	if (ret < 0)
-		return AE_CTRL_DEPTH;
+		goto err;
 
 	device->flags.match_driver = true;
 	if (ret > 0)
-		return AE_OK;
+		goto ok;
 
 	ret = device_attach(&device->dev);
-	return ret >= 0 ? AE_OK : AE_CTRL_DEPTH;
+	if (ret < 0)
+		goto err;
+
+ ok:
+	device->flags.visited = true;
+	return AE_OK;
+
+ err:
+	device->flags.visited = false;
+	return AE_CTRL_DEPTH;
 }
 
 /**
@@ -2007,21 +2011,17 @@ static acpi_status acpi_bus_device_detach(acpi_handle handle, u32 lvl_not_used,
 		} 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;
 	}
 	return AE_OK;
 }
 
-static acpi_status acpi_bus_remove(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))
-		acpi_device_unregister(device);
-
-	return AE_OK;
-}
-
 /**
  * acpi_bus_trim - Remove ACPI device node and all of its descendants
  * @start: Root of the ACPI device nodes subtree to remove.
@@ -2037,13 +2037,6 @@ void acpi_bus_trim(struct acpi_device *start)
 	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);
-	/*
-	 * Execute acpi_bus_remove() as a post-order callback to remove device
-	 * nodes in the given namespace scope.
-	 */
-	acpi_walk_namespace(ACPI_TYPE_ANY, start->handle, ACPI_UINT32_MAX, NULL,
-			    acpi_bus_remove, NULL, NULL);
-	acpi_bus_remove(start->handle, 0, NULL, NULL);
 }
 EXPORT_SYMBOL_GPL(acpi_bus_trim);
 
@@ -2121,7 +2114,9 @@ int __init acpi_scan_init(void)
 
 	result = acpi_bus_scan_fixed();
 	if (result) {
-		acpi_device_unregister(acpi_root);
+		acpi_detach_data(acpi_root->handle, acpi_scan_drop_device);
+		acpi_device_del(acpi_root);
+		put_device(&acpi_root->dev);
 		goto out;
 	}