fs/sysfs/symlink.c

   1 /*
   2  * symlink.c - operations for sysfs symlinks.
   3  */
   4
   5 #include <linux/fs.h>
   6 #include <linux/module.h>
   7 #include <linux/kobject.h>
   8
   9 #include "sysfs.h"
  10
  11
  12 static int init_symlink(struct inode * inode)
  13 {
  14         inode->i_op = &page_symlink_inode_operations;
  15         return 0;
  16 }
  17
  18 static int sysfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
  19 {
  20         int error;
  21
  22         error = sysfs_create(dentry, S_IFLNK|S_IRWXUGO, init_symlink);
  23         if (!error) {
  24                 int l = strlen(symname)+1;
  25                 error = page_symlink(dentry->d_inode, symname, l);
  26                 if (error)
  27                         iput(dentry->d_inode);
  28         }
  29         return error;
  30 }
  31
  32 static int object_depth(struct kobject * kobj)
  33 {
  34         struct kobject * p = kobj;
  35         int depth = 0;
  36         do { depth++; } while ((p = p->parent));
  37         return depth;
  38 }
  39
  40 static int object_path_length(struct kobject * kobj)
  41 {
  42         struct kobject * p = kobj;
  43         int length = 1;
  44         do {
  45                 length += strlen(kobject_name(p)) + 1;
  46                 p = p->parent;
  47         } while (p);
  48         return length;
  49 }
  50
  51 static void fill_object_path(struct kobject * kobj, char * buffer, int length)
  52 {
  53         struct kobject * p;
  54
  55         --length;
  56         for (p = kobj; p; p = p->parent) {
  57                 int cur = strlen(kobject_name(p));
  58
  59                 /* back up enough to print this bus id with '/' */
  60                 length -= cur;
  61                 strncpy(buffer + length,kobject_name(p),cur);
  62                 *(buffer + --length) = '/';
  63         }
  64 }
  65
  66 /**
  67  *      sysfs_create_link - create symlink between two objects.
  68  *      @kobj:  object whose directory we're creating the link in.
  69  *      @target:        object we're pointing to.
  70  *      @name:          name of the symlink.
  71  */
  72 int sysfs_create_link(struct kobject * kobj, struct kobject * target, char * name)
  73 {
  74         struct dentry * dentry = kobj->dentry;
  75         struct dentry * d;
  76         int error = 0;
  77         int size;
  78         int depth;
  79         char * path;
  80         char * s;
  81
  82         depth = object_depth(kobj);
  83         size = object_path_length(target) + depth * 3 - 1;
  84         if (size > PATH_MAX)
  85                 return -ENAMETOOLONG;
  86         pr_debug("%s: depth = %d, size = %d\n",__FUNCTION__,depth,size);
  87
  88         path = kmalloc(size,GFP_KERNEL);
  89         if (!path)
  90                 return -ENOMEM;
  91         memset(path,0,size);
  92
  93         for (s = path; depth--; s += 3)
  94                 strcpy(s,"../");
  95
  96         fill_object_path(target,path,size);
  97         pr_debug("%s: path = '%s'\n",__FUNCTION__,path);
  98
  99         down(&dentry->d_inode->i_sem);
 100         d = sysfs_get_dentry(dentry,name);
 101         if (!IS_ERR(d))
 102                 error = sysfs_symlink(dentry->d_inode,d,path);
 103         else
 104                 error = PTR_ERR(d);
 105         dput(d);
 106         up(&dentry->d_inode->i_sem);
 107         kfree(path);
 108         return error;
 109 }
 110
 111
 112 /**
 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.
 116  */
 117
 118 void sysfs_remove_link(struct kobject * kobj, char * name)
 119 {
 120         sysfs_hash_and_remove(kobj->dentry,name);
 121 }
 122
 123
 124 EXPORT_SYMBOL(sysfs_create_link);
 125 EXPORT_SYMBOL(sysfs_remove_link);
 126