linux-kernel - [PATCH 1/2] ACPI: Allow ACPI handles of devices to be initialized in advance

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Date:	Sun, 18 Nov 2012 22:12:52 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jean Delvare <khali@...ux-fr.org>, ben-linux@...ff.org,
	w.sang@...gutronix.de, linux-kernel@...r.kernel.org,
	lenb@...nel.org, rafael.j.wysocki@...el.com,
	broonie@...nsource.wolfsonmicro.com, grant.likely@...retlab.ca,
	linus.walleij@...aro.org, mathias.nyman@...ux.intel.com,
	linux-acpi@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH 1/2] ACPI: Allow ACPI handles of devices to be initialized in advance

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Currently, the ACPI handles of devices are initialized from within
device_add(), by acpi_bind_one() called from acpi_platform_notify()
which first uses the .find_device() routine provided by the device's
bus type to find the matching device node in the ACPI namespace.
This is a source of some computational overhead and, moreover, the
correctness of the result depends on the implementation of
.find_device() which is known to fail occasionally for some bus types
(e.g. PCI).  In some cases, however, the corresponding ACPI device
node is known already before calling device_add() for the given
struct device object and the whole .find_device() dance in
acpi_platform_notify() is then simply unnecessary.

For this reason, make it possible to initialize the ACPI handles of
devices before calling device_add() for them.  Modify
acpi_platform_notify() to call acpi_bind_one() in advance to check
the device's existing ACPI handle and skip the .find_device()
search if that is successful.  Change acpi_bind_one() accordingly.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/acpi/glue.c |   42 +++++++++++++++++++++++++++++++++---------
 1 file changed, 33 insertions(+), 9 deletions(-)

Index: linux/drivers/acpi/glue.c
===================================================================
--- linux.orig/drivers/acpi/glue.c
+++ linux/drivers/acpi/glue.c
@@ -135,41 +135,54 @@ static int acpi_bind_one(struct device *
 	int retval = -EINVAL;
 
 	if (dev->acpi_handle) {
-		dev_warn(dev, "Drivers changed 'acpi_handle'\n");
-		return -EINVAL;
+		if (handle) {
+			dev_warn(dev, "ACPI handle is already set\n");
+			return -EINVAL;
+		} else {
+			handle = dev->acpi_handle;
+		}
 	}
+	if (!handle)
+		return -EINVAL;
 
 	get_device(dev);
 	status = acpi_bus_get_device(handle, &acpi_dev);
 	if (ACPI_FAILURE(status))
 		goto err;
 
-	physical_node = kzalloc(sizeof(struct acpi_device_physical_node),
-		GFP_KERNEL);
+	physical_node = kzalloc(sizeof(*physical_node), GFP_KERNEL);
 	if (!physical_node) {
 		retval = -ENOMEM;
 		goto err;
 	}
 
 	mutex_lock(&acpi_dev->physical_node_lock);
+
+	/* Sanity check. */
+	list_for_each_entry(physical_node, &acpi_dev->physical_node_list, node)
+		if (physical_node->dev == dev) {
+			dev_warn(dev, "Already associated with ACPI node\n");
+			goto err_free;
+		}
+
 	/* allocate physical node id according to physical_node_id_bitmap */
 	physical_node->node_id =
 		find_first_zero_bit(acpi_dev->physical_node_id_bitmap,
 		ACPI_MAX_PHYSICAL_NODE);
 	if (physical_node->node_id >= ACPI_MAX_PHYSICAL_NODE) {
 		retval = -ENOSPC;
-		mutex_unlock(&acpi_dev->physical_node_lock);
-		kfree(physical_node);
-		goto err;
+		goto err_free;
 	}
 
 	set_bit(physical_node->node_id, acpi_dev->physical_node_id_bitmap);
 	physical_node->dev = dev;
 	list_add_tail(&physical_node->node, &acpi_dev->physical_node_list);
 	acpi_dev->physical_node_count++;
+
 	mutex_unlock(&acpi_dev->physical_node_lock);
 
-	dev->acpi_handle = handle;
+	if (!dev->acpi_handle)
+		dev->acpi_handle = handle;
 
 	if (!physical_node->node_id)
 		strcpy(physical_node_name, PHYSICAL_NODE_STRING);
@@ -187,8 +200,14 @@ static int acpi_bind_one(struct device *
 	return 0;
 
  err:
+	dev->acpi_handle = NULL;
 	put_device(dev);
 	return retval;
+
+ err_free:
+	mutex_unlock(&acpi_dev->physical_node_lock);
+	kfree(physical_node);
+	goto err;
 }
 
 static int acpi_unbind_one(struct device *dev)
@@ -247,6 +266,10 @@ static int acpi_platform_notify(struct d
 	acpi_handle handle;
 	int ret = -EINVAL;
 
+	ret = acpi_bind_one(dev, NULL);
+	if (!ret)
+		goto out;
+
 	if (!dev->bus || !dev->parent) {
 		/* bridge devices genernally haven't bus or parent */
 		ret = acpi_find_bridge_device(dev, &handle);
@@ -260,10 +283,11 @@ static int acpi_platform_notify(struct d
 	}
 	if ((ret = type->find_device(dev, &handle)) != 0)
 		DBG("Can't get handler for %s\n", dev_name(dev));
-      end:
+ end:
 	if (!ret)
 		acpi_bind_one(dev, handle);
 
+ out:
 #if ACPI_GLUE_DEBUG
 	if (!ret) {
 		struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };

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