[PATCH] w1: Added w1_reset_select_slave() - Resets the bus and then selects the slave by
[linux-2.6/verdex.git] / fs / sysfs / symlink.c
blobde402fa915f2778e010d20bfeca2c6ebc05f6ddd
1 /*
2 * symlink.c - operations for sysfs symlinks.
3 */
5 #include <linux/fs.h>
6 #include <linux/module.h>
7 #include <linux/kobject.h>
8 #include <linux/namei.h>
10 #include "sysfs.h"
12 static int object_depth(struct kobject * kobj)
14 struct kobject * p = kobj;
15 int depth = 0;
16 do { depth++; } while ((p = p->parent));
17 return depth;
20 static int object_path_length(struct kobject * kobj)
22 struct kobject * p = kobj;
23 int length = 1;
24 do {
25 length += strlen(kobject_name(p)) + 1;
26 p = p->parent;
27 } while (p);
28 return length;
31 static void fill_object_path(struct kobject * kobj, char * buffer, int length)
33 struct kobject * p;
35 --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 '/' */
40 length -= cur;
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;
50 int error = 0;
52 error = -ENOMEM;
53 sl = kmalloc(sizeof(*sl), GFP_KERNEL);
54 if (!sl)
55 goto exit1;
57 sl->link_name = kmalloc(strlen(name) + 1, GFP_KERNEL);
58 if (!sl->link_name)
59 goto exit2;
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,
65 SYSFS_KOBJ_LINK);
66 if (!error)
67 return 0;
69 kfree(sl->link_name);
70 exit2:
71 kfree(sl);
72 exit1:
73 return error;
76 /**
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;
85 int error = 0;
87 BUG_ON(!kobj || !kobj->dentry || !name);
89 down(&dentry->d_inode->i_sem);
90 error = sysfs_add_link(dentry, name, target);
91 up(&dentry->d_inode->i_sem);
92 return error;
96 /**
97 * sysfs_remove_link - remove symlink in object's directory.
98 * @kobj: object we're acting for.
99 * @name: name of the symlink to remove.
102 void sysfs_remove_link(struct kobject * kobj, const char * name)
104 sysfs_hash_and_remove(kobj->dentry,name);
107 static int sysfs_get_target_path(struct kobject * kobj, struct kobject * target,
108 char *path)
110 char * s;
111 int depth, size;
113 depth = object_depth(kobj);
114 size = object_path_length(target) + depth * 3 - 1;
115 if (size > PATH_MAX)
116 return -ENAMETOOLONG;
118 pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size);
120 for (s = path; depth--; s += 3)
121 strcpy(s,"../");
123 fill_object_path(target, path, size);
124 pr_debug("%s: path = '%s'\n", __FUNCTION__, path);
126 return 0;
129 static int sysfs_getlink(struct dentry *dentry, char * path)
131 struct kobject *kobj, *target_kobj;
132 int error = 0;
134 kobj = sysfs_get_kobject(dentry->d_parent);
135 if (!kobj)
136 return -EINVAL;
138 target_kobj = sysfs_get_kobject(dentry);
139 if (!target_kobj) {
140 kobject_put(kobj);
141 return -EINVAL;
144 down_read(&sysfs_rename_sem);
145 error = sysfs_get_target_path(kobj, target_kobj, path);
146 up_read(&sysfs_rename_sem);
148 kobject_put(kobj);
149 kobject_put(target_kobj);
150 return error;
154 static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
156 int error = -ENOMEM;
157 unsigned long page = get_zeroed_page(GFP_KERNEL);
158 if (page)
159 error = sysfs_getlink(dentry, (char *) page);
160 nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
161 return NULL;
164 static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
166 char *page = nd_get_link(nd);
167 if (!IS_ERR(page))
168 free_page((unsigned long)page);
171 struct inode_operations sysfs_symlink_inode_operations = {
172 .readlink = generic_readlink,
173 .follow_link = sysfs_follow_link,
174 .put_link = sysfs_put_link,
178 EXPORT_SYMBOL_GPL(sysfs_create_link);
179 EXPORT_SYMBOL_GPL(sysfs_remove_link);