2 * symlink.c - operations for sysfs symlinks.
6 #include <linux/mount.h>
7 #include <linux/module.h>
8 #include <linux/kobject.h>
9 #include <linux/namei.h>
10 #include <asm/semaphore.h>
14 static int object_depth(struct kobject * kobj)
16 struct kobject * p = kobj;
18 do { depth++; } while ((p = p->parent));
22 static int object_path_length(struct kobject * kobj)
24 struct kobject * p = kobj;
27 length += strlen(kobject_name(p)) + 1;
33 static void fill_object_path(struct kobject * kobj, char * buffer, int length)
38 for (p = kobj; p; p = p->parent) {
39 int cur = strlen(kobject_name(p));
41 /* back up enough to print this bus id with '/' */
43 strncpy(buffer + length,kobject_name(p),cur);
44 *(buffer + --length) = '/';
48 static int sysfs_add_link(struct dentry * parent, const char * name, struct kobject * target)
50 struct sysfs_dirent * parent_sd = parent->d_fsdata;
51 struct sysfs_dirent * sd;
53 sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK);
57 sd->s_elem.symlink.target_kobj = kobject_get(target);
58 sysfs_attach_dirent(sd, parent_sd, NULL);
63 * sysfs_create_link - create symlink between two objects.
64 * @kobj: object whose directory we're creating the link in.
65 * @target: object we're pointing to.
66 * @name: name of the symlink.
68 int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char * name)
70 struct dentry *dentry = NULL;
76 if (sysfs_mount && sysfs_mount->mnt_sb)
77 dentry = sysfs_mount->mnt_sb->s_root;
79 dentry = kobj->dentry;
84 mutex_lock(&dentry->d_inode->i_mutex);
85 if (!sysfs_dirent_exist(dentry->d_fsdata, name))
86 error = sysfs_add_link(dentry, name, target);
87 mutex_unlock(&dentry->d_inode->i_mutex);
93 * sysfs_remove_link - remove symlink in object's directory.
94 * @kobj: object we're acting for.
95 * @name: name of the symlink to remove.
98 void sysfs_remove_link(struct kobject * kobj, const char * name)
100 sysfs_hash_and_remove(kobj->dentry,name);
103 static int sysfs_get_target_path(struct kobject * kobj, struct kobject * target,
109 depth = object_depth(kobj);
110 size = object_path_length(target) + depth * 3 - 1;
112 return -ENAMETOOLONG;
114 pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size);
116 for (s = path; depth--; s += 3)
119 fill_object_path(target, path, size);
120 pr_debug("%s: path = '%s'\n", __FUNCTION__, path);
125 static int sysfs_getlink(struct dentry *dentry, char * path)
127 struct kobject *kobj, *target_kobj;
130 kobj = sysfs_get_kobject(dentry->d_parent);
134 target_kobj = sysfs_get_kobject(dentry);
140 down_read(&sysfs_rename_sem);
141 error = sysfs_get_target_path(kobj, target_kobj, path);
142 up_read(&sysfs_rename_sem);
145 kobject_put(target_kobj);
150 static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
153 unsigned long page = get_zeroed_page(GFP_KERNEL);
155 error = sysfs_getlink(dentry, (char *) page);
156 nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
160 static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
162 char *page = nd_get_link(nd);
164 free_page((unsigned long)page);
167 const struct inode_operations sysfs_symlink_inode_operations = {
168 .readlink = generic_readlink,
169 .follow_link = sysfs_follow_link,
170 .put_link = sysfs_put_link,
174 EXPORT_SYMBOL_GPL(sysfs_create_link);
175 EXPORT_SYMBOL_GPL(sysfs_remove_link);