+static int sysfs_dir_open(struct inode *inode, struct file *file)
+{
+ struct dentry * dentry = file->f_dentry;
+ struct sysfs_dirent * parent_sd = dentry->d_fsdata;
+
+ mutex_lock(&dentry->d_inode->i_mutex);
+ file->private_data = sysfs_new_dirent(parent_sd, NULL);
+ mutex_unlock(&dentry->d_inode->i_mutex);
+
+ return file->private_data ? 0 : -ENOMEM;
+
+}
+
+static int sysfs_dir_close(struct inode *inode, struct file *file)
+{
+ struct dentry * dentry = file->f_dentry;
+ struct sysfs_dirent * cursor = file->private_data;
+
+ mutex_lock(&dentry->d_inode->i_mutex);
+ list_del_init(&cursor->s_sibling);
+ mutex_unlock(&dentry->d_inode->i_mutex);
+
+ release_sysfs_dirent(cursor);
+
+ return 0;
+}
+
+/* Relationship between s_mode and the DT_xxx types */
+static inline unsigned char dt_type(struct sysfs_dirent *sd)
+{
+ return (sd->s_mode >> 12) & 15;
+}
+
+static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
+{
+ struct dentry *dentry = filp->f_dentry;
+ struct sysfs_dirent * parent_sd = dentry->d_fsdata;
+ struct sysfs_dirent *cursor = filp->private_data;
+ struct list_head *p, *q = &cursor->s_sibling;
+ ino_t ino;
+ int i = filp->f_pos;
+
+ switch (i) {
+ case 0:
+ ino = dentry->d_inode->i_ino;
+ if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
+ break;
+ filp->f_pos++;
+ i++;
+ /* fallthrough */
+ case 1:
+ ino = parent_ino(dentry);
+ if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
+ break;
+ filp->f_pos++;
+ i++;
+ /* fallthrough */
+ default:
+ if (filp->f_pos == 2) {
+ list_del(q);
+ list_add(q, &parent_sd->s_children);
+ }
+ for (p=q->next; p!= &parent_sd->s_children; p=p->next) {
+ struct sysfs_dirent *next;
+ const char * name;
+ int len;
+
+ next = list_entry(p, struct sysfs_dirent,
+ s_sibling);
+ if (!next->s_element)
+ continue;
+
+ name = sysfs_get_name(next);
+ len = strlen(name);
+ if (next->s_dentry)
+ ino = next->s_dentry->d_inode->i_ino;
+ else
+ ino = iunique(sysfs_sb, 2);
+
+ if (filldir(dirent, name, len, filp->f_pos, ino,
+ dt_type(next)) < 0)
+ return 0;
+
+ list_del(q);
+ list_add(q, p);
+ p = q;
+ filp->f_pos++;
+ }
+ }
+ return 0;
+}
+
+static loff_t sysfs_dir_lseek(struct file * file, loff_t offset, int origin)
+{
+ struct dentry * dentry = file->f_dentry;
+
+ mutex_lock(&dentry->d_inode->i_mutex);
+ switch (origin) {
+ case 1:
+ offset += file->f_pos;
+ case 0:
+ if (offset >= 0)
+ break;
+ default:
+ mutex_unlock(&file->f_dentry->d_inode->i_mutex);
+ return -EINVAL;
+ }
+ if (offset != file->f_pos) {
+ file->f_pos = offset;
+ if (file->f_pos >= 2) {
+ struct sysfs_dirent *sd = dentry->d_fsdata;
+ struct sysfs_dirent *cursor = file->private_data;
+ struct list_head *p;
+ loff_t n = file->f_pos - 2;
+
+ list_del(&cursor->s_sibling);
+ p = sd->s_children.next;
+ while (n && p != &sd->s_children) {
+ struct sysfs_dirent *next;
+ next = list_entry(p, struct sysfs_dirent,
+ s_sibling);
+ if (next->s_element)
+ n--;
+ p = p->next;
+ }
+ list_add_tail(&cursor->s_sibling, p);
+ }
+ }
+ mutex_unlock(&dentry->d_inode->i_mutex);
+ return offset;
+}