/*
  * Device file system interface to the TPM
+ *
+ * It's assured that the chip will be opened just once,
+ * by the check of is_open variable, which is protected
+ * by driver_lock.
  */
 int tpm_open(struct inode *inode, struct file *file)
 {
        int rc = 0, minor = iminor(inode);
        struct tpm_chip *chip = NULL, *pos;
 
-       lock_kernel();
        spin_lock(&driver_lock);
 
        list_for_each_entry(pos, &tpm_chip_list, list) {
        if (chip->data_buffer == NULL) {
                chip->num_opens--;
                put_device(chip->dev);
-               unlock_kernel();
                return -ENOMEM;
        }
 
        atomic_set(&chip->data_pending, 0);
 
        file->private_data = chip;
-       unlock_kernel();
        return 0;
 
 err_out:
        spin_unlock(&driver_lock);
-       unlock_kernel();
        return rc;
 }
 EXPORT_SYMBOL_GPL(tpm_open);