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_symlink * sl;
55 sl = kzalloc(sizeof(*sl), GFP_KERNEL);
59 sl->link_name = kmalloc(strlen(name) + 1, GFP_KERNEL);
63 strcpy(sl->link_name, name);
64 sl->target_kobj = kobject_get(target);
66 error = sysfs_make_dirent(parent_sd, NULL, sl, S_IFLNK|S_IRWXUGO,
75 kobject_put(sl->target_kobj);
83 * sysfs_create_link - create symlink between two objects.
84 * @kobj: object whose directory we're creating the link in.
85 * @target: object we're pointing to.
86 * @name: name of the symlink.
88 int sysfs_create_link(struct kobject * kobj, struct kobject * target, const char * name)
90 struct dentry *dentry = NULL;
96 if (sysfs_mount && sysfs_mount->mnt_sb)
97 dentry = sysfs_mount->mnt_sb->s_root;
99 dentry = kobj->dentry;
104 mutex_lock(&dentry->d_inode->i_mutex);
105 if (!sysfs_dirent_exist(dentry->d_fsdata, name))
106 error = sysfs_add_link(dentry, name, target);
107 mutex_unlock(&dentry->d_inode->i_mutex);
113 * sysfs_remove_link - remove symlink in object's directory.
114 * @kobj: object we're acting for.
115 * @name: name of the symlink to remove.
118 void sysfs_remove_link(struct kobject * kobj, const char * name)
120 sysfs_hash_and_remove(kobj->dentry,name);
123 static int sysfs_get_target_path(struct kobject * kobj, struct kobject * target,
129 depth = object_depth(kobj);
130 size = object_path_length(target) + depth * 3 - 1;
132 return -ENAMETOOLONG;
134 pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size);
136 for (s = path; depth--; s += 3)
139 fill_object_path(target, path, size);
140 pr_debug("%s: path = '%s'\n", __FUNCTION__, path);
145 static int sysfs_getlink(struct dentry *dentry, char * path)
147 struct kobject *kobj, *target_kobj;
150 kobj = sysfs_get_kobject(dentry->d_parent);
154 target_kobj = sysfs_get_kobject(dentry);
160 down_read(&sysfs_rename_sem);
161 error = sysfs_get_target_path(kobj, target_kobj, path);
162 up_read(&sysfs_rename_sem);
165 kobject_put(target_kobj);
170 static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
173 unsigned long page = get_zeroed_page(GFP_KERNEL);
175 error = sysfs_getlink(dentry, (char *) page);
176 nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
180 static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
182 char *page = nd_get_link(nd);
184 free_page((unsigned long)page);
187 const struct inode_operations sysfs_symlink_inode_operations = {
188 .readlink = generic_readlink,
189 .follow_link = sysfs_follow_link,
190 .put_link = sysfs_put_link,
194 EXPORT_SYMBOL_GPL(sysfs_create_link);
195 EXPORT_SYMBOL_GPL(sysfs_remove_link);