[Devel] PATCH 4/4] driver core: Implement shadow directory support for device classes.

[Eric W. Biederman]

This patch enables shadowing on every class directory if struct class
has shadow_ops.

In addition device_del and device_rename were modified to use
sysfs_delete_link and sysfs_rename_link respectively to ensure when
these operations happen on devices whos classes have shadow operations
that they work properly.

Signed-off-by: Eric W. Biederman <ebiederm at xmission.com>
---
 drivers/base/class.c   |   30 ++++++++++++++++++++++++++----
 drivers/base/core.c    |   45 ++++++++++++++++++++++++---------------------
 include/linux/device.h |    2 ++
 3 files changed, 52 insertions(+), 25 deletions(-)

diff --git a/drivers/base/class.c b/drivers/base/class.c
index 4d22226..c981f75 100644
--- a/drivers/base/class.c
+++ b/drivers/base/class.c
@@ -134,6 +134,17 @@ static void remove_class_attrs(struct class * cls)
 	}
 }
 
+static int class_setup_shadowing(struct class *cls)
+{
+	const struct shadow_dir_operations *shadow_ops;
+
+	shadow_ops = cls->shadow_ops;
+	if (!shadow_ops)
+		return 0;
+
+	return sysfs_enable_shadowing(&cls->subsys.kobj, shadow_ops);
+}
+
 int class_register(struct class * cls)
 {
 	int error;
@@ -152,11 +163,22 @@ int class_register(struct class * cls)
 	subsys_set_kset(cls, class_subsys);
 
 	error = subsystem_register(&cls->subsys);
-	if (!error) {
-		error = add_class_attrs(class_get(cls));
-		class_put(cls);
-	}
+	if (error)
+		goto out;
+
+	error = class_setup_shadowing(cls);
+	if (error)
+		goto out_unregister;
+
+	error = add_class_attrs(cls);
+	if (error)
+		goto out_unregister;
+
+out:
 	return error;
+out_unregister:
+	subsystem_unregister(&cls->subsys);
+	goto out;
 }
 
 void class_unregister(struct class * cls)
diff --git a/drivers/base/core.c b/drivers/base/core.c
index c7543bc..b1a5241 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -622,8 +622,14 @@ static struct kobject * get_device_parent(struct device *dev,
 			return kobj;
 
 		/* or create a new class-directory at the parent device */
-		return kobject_kset_add_dir(&dev->class->class_dirs,
+		kobj = kobject_kset_add_dir(&dev->class->class_dirs,
 					    parent_kobj, dev->class->name);
+
+		/* If we created a new class-directory setup shadowing */
+		if (kobj && dev->class->shadow_ops)
+			sysfs_enable_shadowing(kobj, dev->class->shadow_ops);
+
+		return kobj;
 	}
 
 	if (parent)
@@ -920,8 +926,8 @@ void device_del(struct device * dev)
 		/* If this is not a "fake" compatible device, remove the
 		 * symlink from the class to the device. */
 		if (dev->kobj.parent != &dev->class->subsys.kobj)
-			sysfs_remove_link(&dev->class->subsys.kobj,
-					  dev->bus_id);
+			sysfs_delete_link(&dev->class->subsys.kobj,
+					  &dev->kobj, dev->bus_id);
 		if (parent) {
 #ifdef CONFIG_SYSFS_DEPRECATED
 			char *class_name = make_class_name(dev->class->name,
@@ -1219,6 +1225,13 @@ int device_rename(struct device *dev, char *new_name)
 	strlcpy(old_device_name, dev->bus_id, BUS_ID_SIZE);
 	strlcpy(dev->bus_id, new_name, BUS_ID_SIZE);
 
+	if (dev->class && (dev->kobj.parent != &dev->class->subsys.kobj)) {
+		error = sysfs_rename_link(&dev->class->subsys.kobj,
+			&dev->kobj, old_device_name, new_name);
+		if (error)
+			goto out;
+	}
+
 	error = kobject_rename(&dev->kobj, new_name);
 	if (error) {
 		strlcpy(dev->bus_id, old_device_name, BUS_ID_SIZE);
@@ -1227,27 +1240,17 @@ int device_rename(struct device *dev, char *new_name)
 
 #ifdef CONFIG_SYSFS_DEPRECATED
 	if (old_class_name) {
+		error = -ENOMEM;
 		new_class_name = make_class_name(dev->class->name, &dev->kobj);
-		if (new_class_name) {
-			error = sysfs_create_link(&dev->parent->kobj,
-						  &dev->kobj, new_class_name);
-			if (error)
-				goto out;
-			sysfs_remove_link(&dev->parent->kobj, old_class_name);
-		}
-	}
-#endif
+		if (!new_class_name)
+			goto out;
 
-	if (dev->class) {
-		sysfs_remove_link(&dev->class->subsys.kobj, old_device_name);
-		error = sysfs_create_link(&dev->class->subsys.kobj, &dev->kobj,
-					  dev->bus_id);
-		if (error) {
-			/* Uh... how to unravel this if restoring can fail? */
-			dev_err(dev, "%s: sysfs_create_symlink failed (%d)\n",
-				__FUNCTION__, error);
-		}
+		error = sysfs_rename_link(&dev->parent->kobj, &dev->kobj,
+					  old_class_name, new_class_name);
+		if (error)
+			goto out;
 	}
+#endif
 out:
 	put_device(dev);
 
diff --git a/include/linux/device.h b/include/linux/device.h
index be2debe..918dfa3 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -200,6 +200,8 @@ struct class {
 
 	int	(*suspend)(struct device *, pm_message_t state);
 	int	(*resume)(struct device *);
+
+	const struct shadow_dir_operations *shadow_ops;
 };
 
 extern int __must_check class_register(struct class *);
-- 
1.5.1.1.181.g2de0

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