[PATCH 1/3] sysfs: introduce a sysfs_create_file_uevent new API

[Bryan Wu <bryan.wu@canonical.com>]

Send a uevent notification whenever a new sysfs file is created to allow
userspace processes such as udev to modify permissions on the new files.

This new API function helps to do this.

Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
---
 fs/sysfs/file.c       | 28 ++++++++++++++++++++++++++++
 include/linux/sysfs.h | 13 +++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 00012e3..5a22d13 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -576,6 +576,34 @@ int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
 
 }
 
+/**
+ *	sysfs_create_file_uevent - create an attribute file for an object
+					and send a uevent to userspace.
+ *	@kobj:	object we're creating for.
+ *	@attr:	attribute descriptor.
+ *	@desc:  description about the uevent.
+ *	@action: kobject uevent action type.
+ */
+
+int sysfs_create_file_uevent(struct kobject *kobj, const struct attribute *attr,
+			const char *desc, enum kobject_action action)
+{
+	int err = 0;
+	char *envp[2];
+
+	BUG_ON(!kobj || !kobj->sd || !attr || !desc);
+
+	err = sysfs_add_file(kobj->sd, attr, SYSFS_KOBJ_ATTR);
+
+	if (desc) {
+		envp[0] = desc;
+		envp[1] = NULL;
+		kobject_uevent_env(kobj, action, envp);
+	}
+
+	return err;
+}
+
 int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
 {
 	int err = 0;
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 381f06d..0054d41 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -22,6 +22,7 @@
 struct kobject;
 struct module;
 enum kobj_ns_type;
+enum kobject_action;
 
 struct attribute {
 	const char		*name;
@@ -142,6 +143,10 @@ int __must_check sysfs_move_dir(struct kobject *kobj,
 
 int __must_check sysfs_create_file(struct kobject *kobj,
 				   const struct attribute *attr);
+int __must_check sysfs_create_file_uevent(struct kobject * kobj,
+				const struct attribute * attr,
+				const char * desc,
+				enum kobject_action action);
 int __must_check sysfs_create_files(struct kobject *kobj,
 				   const struct attribute **attr);
 int __must_check sysfs_chmod_file(struct kobject *kobj,
@@ -226,6 +231,14 @@ static inline int sysfs_create_file(struct kobject *kobj,
 	return 0;
 }
 
+static inline int sysfs_create_file_uevent(struct kobject * kobj,
+					const struct attribute * attr,
+					const char *desc,
+					enum kobject_action action)
+{
+	return 0;
+}
+
 static inline int sysfs_create_files(struct kobject *kobj,
 				    const struct attribute **attr)
 {
-- 
1.7.11.1