sysfs: marry api with struct kobject.

This works on obviating the need for a separate data type to describe a sysfs
directory (which was renamed from struct driver_dir_entry to struct sysfs_dir).

All sysfs creation and removal functions now take a struct kobject, instead
of a struct sysfs_dir. This kobject is embedded in ->d_fsdata of the directory.

sysfs_create_dir() takes only 1 parameter now: the object that we're creating
the directory for. The parent dentry is derived by looking at the object's 
parent. 

sysfs_create_file() takes the object as the first parameter, and the attribute
as the second, which makes more sense from an API perspective. 

sysfs_remove_file() now takes an attribute as a second parameter, to be 
consistent with the creation function.

sysfs_remove_link() is created, which is basically the old sysfs_remove_file().
(symlinks don't have an attribute associated with them; only a name, which was
prohibiting the previous change). 

open() and close() look for a kobject now, and do refcounting directly on the
object. Because of that, we don't need the ->open() and ->close() callbacks
in struct sysfs_ops, so they've been removed. 

read() and write() also now look for a kobject now. 

The comments have been updated, too. 

fs/sysfs/inode.c

@@ -33,7 +33,7 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/backing-dev.h>
-#include <linux/sysfs.h>
+#include <linux/kobject.h>
 
 #include <asm/uaccess.h>
 
@@ -154,30 +154,35 @@ static int sysfs_unlink(struct inode *dir, struct dentry *dentry)
 }
 
 /**
- * sysfs_read_file - "read" data from a file.
- * @file:	file pointer
- * @buf:	buffer to fill
- * @count:	number of bytes to read
- * @ppos:	starting offset in file
+ *	sysfs_read_file - read an attribute. 
+ *	@file:	file pointer.
+ *	@buf:	buffer to fill.
+ *	@count:	number of bytes to read.
+ *	@ppos:	starting offset in file.
+ *
+ *	Userspace wants to read an attribute file. The attribute descriptor
+ *	is in the file's ->d_fsdata. The target object is in the directory's
+ *	->d_fsdata. 
  *
- * Userspace wants data from a file. It is up to the creator of the file to
- * provide that data.
- * There is a struct device_attribute embedded in file->private_data. We
- * obtain that and check if the read callback is implemented. If so, we call
- * it, passing the data field of the file entry.
- * Said callback is responsible for filling the buffer and returning the number
- * of bytes it put in it. We update @ppos correctly.
+ *	We allocate a %PAGE_SIZE buffer, and pass it to the object's ->show()
+ *	method (along with the object). We loop doing this until @count is 
+ *	satisfied, or ->show() returns %0. 
  */
+
 static ssize_t
 sysfs_read_file(struct file *file, char *buf, size_t count, loff_t *ppos)
 {
 	struct attribute * attr = file->f_dentry->d_fsdata;
-	struct driver_dir_entry * dir;
+	struct sysfs_ops * ops = NULL;
+	struct kobject * kobj;
 	unsigned char *page;
 	ssize_t retval = 0;
 
-	dir = file->f_dentry->d_parent->d_fsdata;
-	if (!dir->ops->show)
+	kobj = file->f_dentry->d_parent->d_fsdata;
+	if (kobj)
+		ops = kobj->dir.ops;
+
+	if (!ops || !ops->show)
 		return 0;
 
 	if (count > PAGE_SIZE)
@@ -190,7 +195,7 @@ sysfs_read_file(struct file *file, char *buf, size_t count, loff_t *ppos)
 	while (count > 0) {
 		ssize_t len;
 
-		len = dir->ops->show(dir,attr,page,count,*ppos);
+		len = ops->show(kobj,attr,page,count,*ppos);
 
 		if (len <= 0) {
 			if (len < 0)
@@ -214,27 +219,32 @@ sysfs_read_file(struct file *file, char *buf, size_t count, loff_t *ppos)
 }
 
 /**
- * sysfs_write_file - "write" to a file
+ *	sysfs_write_file - write an attribute.
  *	@file:	file pointer
  *	@buf:	data to write
  *	@count:	number of bytes
  *	@ppos:	starting offset
  *
- * Similarly to sysfs_read_file, we act essentially as a bit pipe.
- * We check for a "write" callback in file->private_data, and pass
- * @buffer, @count, @ppos, and the file entry's data to the callback.
- * The number of bytes written is returned, and we handle updating
- * @ppos properly.
+ *	Identical to sysfs_read_file(), though going the opposite direction.
+ *	We allocate a %PAGE_SIZE buffer and copy in the userspace buffer. We
+ *	pass that to the object's ->store() method until we reach @count or 
+ *	->store() returns %0 or less.
  */
+
 static ssize_t
 sysfs_write_file(struct file *file, const char *buf, size_t count, loff_t *ppos)
 {
 	struct attribute * attr = file->f_dentry->d_fsdata;
-	struct driver_dir_entry * dir;
+	struct sysfs_ops * ops = NULL;
+	struct kobject * kobj;
 	ssize_t retval = 0;
 	char * page;
 
-	dir = file->f_dentry->d_parent->d_fsdata;
+	kobj = file->f_dentry->d_parent->d_fsdata;
+	if (kobj)
+		ops = kobj->dir.ops;
+	if (!ops || !ops->store)
+		return 0;
 
 	page = (char *)__get_free_page(GFP_KERNEL);
 	if (!page)
@@ -249,7 +259,7 @@ sysfs_write_file(struct file *file, const char *buf, size_t count, loff_t *ppos)
 	while (count > 0) {
 		ssize_t len;
 
-		len = dir->ops->store(dir,attr,page + retval,count,*ppos);
+		len = ops->store(kobj,attr,page + retval,count,*ppos);
 
 		if (len <= 0) {
 			if (len < 0)
@@ -268,29 +278,24 @@ sysfs_write_file(struct file *file, const char *buf, size_t count, loff_t *ppos)
 
 static int sysfs_open_file(struct inode * inode, struct file * filp)
 {
-	struct driver_dir_entry * dir;
+	struct kobject * kobj;
 	int error = 0;
 
-	dir = (struct driver_dir_entry *)filp->f_dentry->d_parent->d_fsdata;
-	if (dir) {
+	kobj = filp->f_dentry->d_parent->d_fsdata;
+	if ((kobj = kobject_get(kobj))) {
 		struct attribute * attr = filp->f_dentry->d_fsdata;
-		if (attr && dir->ops) {
-			if (dir->ops->open)
-				error = dir->ops->open(dir);
-			goto Done;
-		}
-	}
+		if (!attr)
+			error = -EINVAL;
+	} else
 		error = -EINVAL;
- Done:
 	return error;
 }
 
 static int sysfs_release(struct inode * inode, struct file * filp)
 {
-	struct driver_dir_entry * dir;
-	dir = (struct driver_dir_entry *)filp->f_dentry->d_parent->d_fsdata;
-	if (dir->ops->close)
-		dir->ops->close(dir);
+	struct kobject * kobj = filp->f_dentry->d_parent->d_fsdata;
+	if (kobj) 
+		kobject_put(kobj);
 	return 0;
 }
 
@@ -371,6 +376,7 @@ static int __init sysfs_init(void)
 
 core_initcall(sysfs_init);
 
+
 static struct dentry * get_dentry(struct dentry * parent, const char * name)
 {
 	struct qstr qstr;
@@ -381,137 +387,160 @@ static struct dentry * get_dentry(struct dentry * parent, const char * name)
 	return lookup_hash(&qstr,parent);
 }
 
+
 /**
- * sysfs_create_dir - create a directory in the filesystem
- * @entry:	directory entry
- * @parent:	parent directory entry
+ *	sysfs_create_dir - create a directory for an object.
+ *	@parent:	parent parent object.
+ *	@kobj:		object we're creating directory for. 
  */
-int
-sysfs_create_dir(struct driver_dir_entry * entry,
-		    struct driver_dir_entry * parent)
+
+int sysfs_create_dir(struct kobject * kobj)
 {
 	struct dentry * dentry = NULL;
-	struct dentry * parent_dentry;
+	struct dentry * parent;
 	int error = 0;
 
-	if (!entry)
+	if (!kobj)
 		return -EINVAL;
 
-	parent_dentry = parent ? parent->dentry : NULL;
-
-	if (!parent_dentry)
-		if (sysfs_mount && sysfs_mount->mnt_sb)
-			parent_dentry = sysfs_mount->mnt_sb->s_root;
-
-	if (!parent_dentry)
+	if (kobj->parent)
+		parent = kobj->parent->dir.dentry;
+	else if (sysfs_mount && sysfs_mount->mnt_sb)
+		parent = sysfs_mount->mnt_sb->s_root;
+	else
 		return -EFAULT;
 
-	down(&parent_dentry->d_inode->i_sem);
-	dentry = get_dentry(parent_dentry,entry->name);
+	down(&parent->d_inode->i_sem);
+	dentry = get_dentry(parent,kobj->name);
 	if (!IS_ERR(dentry)) {
-		dentry->d_fsdata = (void *) entry;
-		entry->dentry = dentry;
-		error = sysfs_mkdir(parent_dentry->d_inode,dentry,entry->mode);
+		dentry->d_fsdata = (void *)kobj;
+		kobj->dir.dentry = dentry;
+		error = sysfs_mkdir(parent->d_inode,dentry,
+				    (S_IFDIR| S_IRWXU | S_IRUGO | S_IXUGO));
 	} else
 		error = PTR_ERR(dentry);
-	up(&parent_dentry->d_inode->i_sem);
+	up(&parent->d_inode->i_sem);
 
 	return error;
 }
 
+
 /**
- * sysfs_create_file - create a file
- * @entry:	structure describing the file
- * @parent:	directory to create it in
+ *	sysfs_create_file - create an attribute file for an object.
+ *	@kobj:	object we're creating for. 
+ *	@attr:	atrribute descriptor.
  */
-int
-sysfs_create_file(struct attribute * entry,
-		     struct driver_dir_entry * parent)
+
+int sysfs_create_file(struct kobject * kobj, struct attribute * attr)
 {
 	struct dentry * dentry;
+	struct dentry * parent;
 	int error = 0;
 
-	if (!entry || !parent)
+	if (!kobj || !attr)
 		return -EINVAL;
 
-	if (!parent->dentry)
-		return -EINVAL;
+	if (kobj->parent)
+		parent = kobj->parent->dir.dentry;
+	else
+		return -ENOENT;
 
-	down(&parent->dentry->d_inode->i_sem);
-	dentry = get_dentry(parent->dentry,entry->name);
+	down(&parent->d_inode->i_sem);
+	dentry = get_dentry(parent,attr->name);
 	if (!IS_ERR(dentry)) {
-		dentry->d_fsdata = (void *)entry;
-		error = sysfs_create(parent->dentry->d_inode,dentry,entry->mode);
+		dentry->d_fsdata = (void *)attr;
+		error = sysfs_create(parent->d_inode,dentry,attr->mode);
 	} else
 		error = PTR_ERR(dentry);
-	up(&parent->dentry->d_inode->i_sem);
+	up(&parent->d_inode->i_sem);
 	return error;
 }
 
+
 /**
  *	sysfs_create_symlink - make a symlink
- * @parent:	directory we're creating in 
- * @entry:	entry describing link
- * @target:	place we're symlinking to
- * 
+ *	@kobj:	object who's directory we're creating in. 
+ *	@name:	name of the symlink.
+ *	@target:	path we're pointing to.
  */
-int sysfs_create_symlink(struct driver_dir_entry * parent, 
-			    char * name, char * target)
+
+int sysfs_create_link(struct kobject * kobj, char * name, char * target)
 {
 	struct dentry * dentry;
-	int error = 0;
+	int error;
 
-	if (!parent || !parent->dentry)
-		return -EINVAL;
+	if (kobj) {
+		struct dentry * parent = kobj->dir.dentry;
 
-	down(&parent->dentry->d_inode->i_sem);
-	dentry = get_dentry(parent->dentry,name);
+		down(&parent->d_inode->i_sem);
+		dentry = get_dentry(parent,name);
 		if (!IS_ERR(dentry))
-		error = sysfs_symlink(parent->dentry->d_inode,dentry,target);
+			error = sysfs_symlink(parent->d_inode,dentry,target);
 		else
 			error = PTR_ERR(dentry);
-	up(&parent->dentry->d_inode->i_sem);
+		up(&parent->d_inode->i_sem);
+	} else
+		error = -EINVAL;
 	return error;
 }
 
+
+static void hash_and_remove(struct dentry * dir, const char * name)
+{
+	struct dentry * victim;
+
+	down(&dir->d_inode->i_sem);
+	victim = get_dentry(dir,name);
+	if (!IS_ERR(victim)) {
+		/* make sure dentry is really there */
+		if (victim->d_inode && 
+		    (victim->d_parent->d_inode == dir->d_inode)) {
+			sysfs_unlink(dir->d_inode,victim);
+		}
+	}
+	up(&dir->d_inode->i_sem);
+}
+
+
 /**
- * sysfs_remove_file - exported file removal
- * @dir:	directory the file supposedly resides in
- * @name:	name of the file
+ *	sysfs_remove_file - remove an object attribute.
+ *	@kobj:	object we're acting for.
+ *	@attr:	attribute descriptor.
  *
- * Try and find the file in the dir's list.
- * If it's there, call __remove_file() (above) for the dentry.
+ *	Hash the attribute name and kill the victim.
  */
-void sysfs_remove_file(struct driver_dir_entry * dir, const char * name)
+
+void sysfs_remove_file(struct kobject * kobj, struct attribute * attr)
 {
-	struct dentry * dentry;
+	hash_and_remove(kobj->dir.dentry,attr->name);
+}
 
-	if (!dir->dentry)
-		return;
 
-	down(&dir->dentry->d_inode->i_sem);
-	dentry = get_dentry(dir->dentry,name);
-	if (!IS_ERR(dentry)) {
-		/* make sure dentry is really there */
-		if (dentry->d_inode && 
-		    (dentry->d_parent->d_inode == dir->dentry->d_inode)) {
-			sysfs_unlink(dir->dentry->d_inode,dentry);
-		}
-	}
-	up(&dir->dentry->d_inode->i_sem);
+/**
+ *	sysfs_remove_link - remove symlink in object's directory.
+ *	@kobj:	object we're acting for.
+ *	@name:	name of the symlink to remove.
+ */
+
+void sysfs_remove_link(struct kobject * kobj, char * name)
+{
+	hash_and_remove(kobj->dir.dentry,name);
 }
 
+
 /**
- * sysfs_remove_dir - exportable directory removal
- * @dir:	directory to remove
+ *	sysfs_remove_dir - remove an object's directory.
+ *	@kobj:	object. 
  *
- * To make sure we don't orphan anyone, first remove
- * all the children in the list, then do clean up the directory.
+ *	The only thing special about this is that we remove any files in 
+ *	the directory before we remove the directory, and we've inlined
+ *	what used to be sysfs_rmdir() below, instead of calling separately.
  */
-void sysfs_remove_dir(struct driver_dir_entry * dir)
+
+void sysfs_remove_dir(struct kobject * kobj)
 {
 	struct list_head * node, * next;
-	struct dentry * dentry = dir->dentry;
+	struct dentry * dentry = kobj->dir.dentry;
 	struct dentry * parent;
 
 	if (!dentry)
@@ -542,8 +571,9 @@ void sysfs_remove_dir(struct driver_dir_entry * dir)
 }
 
 EXPORT_SYMBOL(sysfs_create_file);
-EXPORT_SYMBOL(sysfs_create_symlink);
-EXPORT_SYMBOL(sysfs_create_dir);
 EXPORT_SYMBOL(sysfs_remove_file);
+EXPORT_SYMBOL(sysfs_create_link);
+EXPORT_SYMBOL(sysfs_remove_link);
+EXPORT_SYMBOL(sysfs_create_dir);
 EXPORT_SYMBOL(sysfs_remove_dir);
 MODULE_LICENSE("GPL");

include/linux/kobject.h

@@ -16,6 +16,7 @@ struct kobject {
 	atomic_t		refcount;
 	struct list_head	entry;
 	struct kobject		* parent;
+	struct sysfs_dir	dir;
 };
 
 extern void kobject_init(struct kobject *);

include/linux/sysfs.h

@@ -11,18 +11,15 @@
 
 struct driver_dir_entry;
 struct attribute;
+struct kobject;
 
 struct sysfs_ops {
-	int	(*open)(struct driver_dir_entry *);
-	int	(*close)(struct driver_dir_entry *);
-	ssize_t	(*show)(struct driver_dir_entry *, struct attribute *,char *, size_t, loff_t);
-	ssize_t	(*store)(struct driver_dir_entry *,struct attribute *,const char *, size_t, loff_t);
+	ssize_t	(*show)(struct kobject *, struct attribute *,char *, size_t, loff_t);
+	ssize_t	(*store)(struct kobject *,struct attribute *,const char *, size_t, loff_t);
 };
 
-struct driver_dir_entry {
-	char			* name;
+struct sysfs_dir {
 	struct dentry		* dentry;
-	mode_t			mode;
 	struct sysfs_ops	* ops;
 };
 
@@ -32,20 +29,21 @@ struct attribute {
 };
 
 extern int
-sysfs_create_dir(struct driver_dir_entry *, struct driver_dir_entry *);
+sysfs_create_dir(struct kobject *);
 
 extern void
-sysfs_remove_dir(struct driver_dir_entry * entry);
+sysfs_remove_dir(struct kobject *);
 
 extern int
-sysfs_create_file(struct attribute * attr,
-		     struct driver_dir_entry * parent);
+sysfs_create_file(struct kobject *, struct attribute *);
+
+extern void
+sysfs_remove_file(struct kobject *, struct attribute *);
 
 extern int 
-sysfs_create_symlink(struct driver_dir_entry * parent, 
-			char * name, char * target);
+sysfs_create_link(struct kobject * kobj, char * name, char * target);
 
 extern void
-sysfs_remove_file(struct driver_dir_entry *, const char * name);
+sysfs_remove_link(struct kobject *, char * name);
 
 #endif /* _SYSFS_H_ */