text: /*
   * Copyright (C) 2004 IBM Corporation
   * Authors:
   * Leendert van Doorn <leendert@watson.ibm.com>
   * Dave Safford <safford@watson.ibm.com>
   * Reiner Sailer <sailer@watson.ibm.com>
   * Kylene Hall <kjhall@us.ibm.com>
   *
   * Copyright (C) 2013 Obsidian Research Corp
   * Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
   *
   * Device file system interface to the TPM
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License as
   * published by the Free Software Foundation, version 2 of the
   * License.
   *
   */
  #include <linux/slab.h>
  #include <linux/uaccess.h>
  #include "tpm.h"
  
  struct file_priv {
  	struct tpm_chip *chip;
  
  	/* Data passed to and from the tpm via the read/write calls */
  	atomic_t data_pending;
  	struct mutex buffer_mutex;
  
  	struct timer_list user_read_timer;      /* user needs to claim result */
  	struct work_struct work;
  
  	u8 data_buffer[TPM_BUFSIZE];
  };
  
  static void user_reader_timeout(unsigned long ptr)
  {
  	struct file_priv *priv = (struct file_priv *)ptr;
  
  	schedule_work(&priv->work);
  }
  
  static void timeout_work(struct work_struct *work)
  {
  	struct file_priv *priv = container_of(work, struct file_priv, work);
  
  	mutex_lock(&priv->buffer_mutex);
  	atomic_set(&priv->data_pending, 0);
  	memset(priv->data_buffer, 0, sizeof(priv->data_buffer));
  	mutex_unlock(&priv->buffer_mutex);
  }
  
  static int tpm_open(struct inode *inode, struct file *file)
  {
  	struct tpm_chip *chip =
  		container_of(inode->i_cdev, struct tpm_chip, cdev);
  	struct file_priv *priv;
  
  	/* It's assured that the chip will be opened just once,
  	 * by the check of is_open variable, which is protected
  	 * by driver_lock. */
  	if (test_and_set_bit(0, &chip->is_open)) {
  		dev_dbg(chip->pdev, "Another process owns this TPM\n");
  		return -EBUSY;
  	}
  
  	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
  	if (priv == NULL) {
  		clear_bit(0, &chip->is_open);
  		return -ENOMEM;
  	}
  
  	priv->chip = chip;
  	atomic_set(&priv->data_pending, 0);
  	mutex_init(&priv->buffer_mutex);
  	setup_timer(&priv->user_read_timer, user_reader_timeout,
  			(unsigned long)priv);
  	INIT_WORK(&priv->work, timeout_work);
  
  	file->private_data = priv;
  	get_device(chip->pdev);
  	return 0;
  }
  
  static ssize_t tpm_read(struct file *file, char __user *buf,
  			size_t size, loff_t *off)
  {
  	struct file_priv *priv = file->private_data;
  	ssize_t ret_size;
  	int rc;
  
  	del_singleshot_timer_sync(&priv->user_read_timer);
  	flush_work(&priv->work);
  	ret_size = atomic_read(&priv->data_pending);
  	if (ret_size > 0) {	/* relay data */
  		ssize_t orig_ret_size = ret_size;
  		if (size < ret_size)
  			ret_size = size;
  
  		mutex_lock(&priv->buffer_mutex);
  		rc = copy_to_user(buf, priv->data_buffer, ret_size);
  		memset(priv->data_buffer, 0, orig_ret_size);
  		if (rc)
  			ret_size = -EFAULT;
  
  		mutex_unlock(&priv->buffer_mutex);
  	}
  
  	atomic_set(&priv->data_pending, 0);
  
  	return ret_size;
  }
  
  static ssize_t tpm_write(struct file *file, const char __user *buf,
  			 size_t size, loff_t *off)
  {
  	struct file_priv *priv = file->private_data;
  	size_t in_size = size;
  	ssize_t out_size;
  
  	/* cannot perform a write until the read has cleared
  	   either via tpm_read or a user_read_timer timeout.
  	   This also prevents splitted buffered writes from blocking here.
  	*/
  	if (atomic_read(&priv->data_pending) != 0)
  		return -EBUSY;
  
  	if (in_size > TPM_BUFSIZE)
  		return -E2BIG;
  
  	mutex_lock(&priv->buffer_mutex);
  
  	if (copy_from_user
  	    (priv->data_buffer, (void __user *) buf, in_size)) {
  		mutex_unlock(&priv->buffer_mutex);
  		return -EFAULT;
  	}
  
  	/* atomic tpm command send and result receive */
  	out_size = tpm_transmit(priv->chip, priv->data_buffer,
  				sizeof(priv->data_buffer));
  	if (out_size < 0) {
  		mutex_unlock(&priv->buffer_mutex);
  		return out_size;
  	}
  
  	atomic_set(&priv->data_pending, out_size);
  	mutex_unlock(&priv->buffer_mutex);
  
  	/* Set a timeout by which the reader must come claim the result */
  	mod_timer(&priv->user_read_timer, jiffies + (60 * HZ));
  
  	return in_size;
  }
  
  /*
   * Called on file close
   */
  static int tpm_release(struct inode *inode, struct file *file)
  {
  	struct file_priv *priv = file->private_data;
  
  	del_singleshot_timer_sync(&priv->user_read_timer);
  	flush_work(&priv->work);
  	file->private_data = NULL;
  	atomic_set(&priv->data_pending, 0);
  	clear_bit(0, &priv->chip->is_open);
  	put_device(priv->chip->pdev);
  	kfree(priv);
  	return 0;
  }
  
  const struct file_operations tpm_fops = {
  	.owner = THIS_MODULE,
  	.llseek = no_llseek,
  	.open = tpm_open,
  	.read = tpm_read,
  	.write = tpm_write,
  	.release = tpm_release,
  };
  
  
  