2 * symlink.c - operations for sysfs symlinks.
6 #include <linux/module.h>
7 #include <linux/kobject.h>
8 #include <linux/namei.h>
12 static int object_depth(struct kobject * kobj)
14 struct kobject * p = kobj;
16 do { depth++; } while ((p = p->parent));
20 static int object_path_length(struct kobject * kobj)
22 struct kobject * p = kobj;
25 length += strlen(kobject_name(p)) + 1;
31 static void fill_object_path(struct kobject * kobj, char * buffer, int length)
36 for (p = kobj; p; p = p->parent) {
37 int cur = strlen(kobject_name(p));
39 /* back up enough to print this bus id with '/' */
41 strncpy(buffer + length,kobject_name(p),cur);
42 *(buffer + --length) = '/';
46 static int sysfs_add_link(struct dentry * parent, const char * name, struct kobject * target)
48 struct sysfs_dirent * parent_sd = parent->d_fsdata;
49 struct sysfs_symlink * sl;
53 sl = kmalloc(sizeof(*sl), GFP_KERNEL);
57 sl->link_name = kmalloc(strlen(name) + 1, GFP_KERNEL);
61 strcpy(sl->link_name, name);
62 sl->target_kobj = kobject_get(target);
64 error = sysfs_make_dirent(parent_sd, NULL, sl, S_IFLNK|S_IRWXUGO,
77 * sysfs_create_link - create symlink between two objects.
78 * @kobj: object whose directory we're creating the link in.
79 * @target: object we're pointing to.
80 * @name: name of the symlink.
82 int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char * name)
84 struct dentry * dentry = kobj->dentry;
87 BUG_ON(!kobj || !kobj->dentry || !name);
89 mutex_lock(&dentry->d_inode->i_mutex);
90 if (!sysfs_dirent_exist(dentry->d_fsdata, name))
91 error = sysfs_add_link(dentry, name, target);
92 mutex_unlock(&dentry->d_inode->i_mutex);
98 * sysfs_remove_link - remove symlink in object's directory.
99 * @kobj: object we're acting for.
100 * @name: name of the symlink to remove.
103 void sysfs_remove_link(struct kobject * kobj, const char * name)
105 sysfs_hash_and_remove(kobj->dentry,name);
108 static int sysfs_get_target_path(struct kobject * kobj, struct kobject * target,
114 depth = object_depth(kobj);
115 size = object_path_length(target) + depth * 3 - 1;
117 return -ENAMETOOLONG;
119 pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size);
121 for (s = path; depth--; s += 3)
124 fill_object_path(target, path, size);
125 pr_debug("%s: path = '%s'\n", __FUNCTION__, path);
130 static int sysfs_getlink(struct dentry *dentry, char * path)
132 struct kobject *kobj, *target_kobj;
135 kobj = sysfs_get_kobject(dentry->d_parent);
139 target_kobj = sysfs_get_kobject(dentry);
145 down_read(&sysfs_rename_sem);
146 error = sysfs_get_target_path(kobj, target_kobj, path);
147 up_read(&sysfs_rename_sem);
150 kobject_put(target_kobj);
155 static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
158 unsigned long page = get_zeroed_page(GFP_KERNEL);
160 error = sysfs_getlink(dentry, (char *) page);
161 nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
165 static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
167 char *page = nd_get_link(nd);
169 free_page((unsigned long)page);
172 struct inode_operations sysfs_symlink_inode_operations = {
173 .readlink = generic_readlink,
174 .follow_link = sysfs_follow_link,
175 .put_link = sysfs_put_link,
179 EXPORT_SYMBOL_GPL(sysfs_create_link);
180 EXPORT_SYMBOL_GPL(sysfs_remove_link);