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serio_raw.c

/*
 * Raw serio device providing access to a raw byte stream from underlying
 * serio port. Closely emulates behavior of pre-2.6 /dev/psaux device
 *
 * Copyright (c) 2004 Dmitry Torokhov
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 */

#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/module.h>
#include <linux/serio.h>
#include <linux/init.h>
#include <linux/major.h>
#include <linux/device.h>
#include <linux/miscdevice.h>
#include <linux/wait.h>
#include <linux/mutex.h>

#define DRIVER_DESC     "Raw serio driver"

MODULE_AUTHOR("Dmitry Torokhov <dtor@mail.ru>");
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");

#define SERIO_RAW_QUEUE_LEN   64
struct serio_raw {
      unsigned char queue[SERIO_RAW_QUEUE_LEN];
      unsigned int tail, head;

      char name[16];
      unsigned int refcnt;
      struct serio *serio;
      struct miscdevice dev;
      wait_queue_head_t wait;
      struct list_head list;
      struct list_head node;
};

struct serio_raw_list {
      struct fasync_struct *fasync;
      struct serio_raw *serio_raw;
      struct list_head node;
};

static DEFINE_MUTEX(serio_raw_mutex);
static LIST_HEAD(serio_raw_list);
static unsigned int serio_raw_no;

/*********************************************************************
 *             Interface with userspace (file operations)            *
 *********************************************************************/

static int serio_raw_fasync(int fd, struct file *file, int on)
{
      struct serio_raw_list *list = file->private_data;
      int retval;

      retval = fasync_helper(fd, file, on, &list->fasync);
      return retval < 0 ? retval : 0;
}

static struct serio_raw *serio_raw_locate(int minor)
{
      struct serio_raw *serio_raw;

      list_for_each_entry(serio_raw, &serio_raw_list, node) {
            if (serio_raw->dev.minor == minor)
                  return serio_raw;
      }

      return NULL;
}

static int serio_raw_open(struct inode *inode, struct file *file)
{
      struct serio_raw *serio_raw;
      struct serio_raw_list *list;
      int retval = 0;

      retval = mutex_lock_interruptible(&serio_raw_mutex);
      if (retval)
            return retval;

      if (!(serio_raw = serio_raw_locate(iminor(inode)))) {
            retval = -ENODEV;
            goto out;
      }

      if (!serio_raw->serio) {
            retval = -ENODEV;
            goto out;
      }

      if (!(list = kzalloc(sizeof(struct serio_raw_list), GFP_KERNEL))) {
            retval = -ENOMEM;
            goto out;
      }

      list->serio_raw = serio_raw;
      file->private_data = list;

      serio_raw->refcnt++;
      list_add_tail(&list->node, &serio_raw->list);

out:
      mutex_unlock(&serio_raw_mutex);
      return retval;
}

static int serio_raw_cleanup(struct serio_raw *serio_raw)
{
      if (--serio_raw->refcnt == 0) {
            misc_deregister(&serio_raw->dev);
            list_del_init(&serio_raw->node);
            kfree(serio_raw);

            return 1;
      }

      return 0;
}

static int serio_raw_release(struct inode *inode, struct file *file)
{
      struct serio_raw_list *list = file->private_data;
      struct serio_raw *serio_raw = list->serio_raw;

      mutex_lock(&serio_raw_mutex);

      serio_raw_fasync(-1, file, 0);
      serio_raw_cleanup(serio_raw);

      mutex_unlock(&serio_raw_mutex);
      return 0;
}

static int serio_raw_fetch_byte(struct serio_raw *serio_raw, char *c)
{
      unsigned long flags;
      int empty;

      spin_lock_irqsave(&serio_raw->serio->lock, flags);

      empty = serio_raw->head == serio_raw->tail;
      if (!empty) {
            *c = serio_raw->queue[serio_raw->tail];
            serio_raw->tail = (serio_raw->tail + 1) % SERIO_RAW_QUEUE_LEN;
      }

      spin_unlock_irqrestore(&serio_raw->serio->lock, flags);

      return !empty;
}

static ssize_t serio_raw_read(struct file *file, char __user *buffer, size_t count, loff_t *ppos)
{
      struct serio_raw_list *list = file->private_data;
      struct serio_raw *serio_raw = list->serio_raw;
      char uninitialized_var(c);
      ssize_t retval = 0;

      if (!serio_raw->serio)
            return -ENODEV;

      if (serio_raw->head == serio_raw->tail && (file->f_flags & O_NONBLOCK))
            return -EAGAIN;

      retval = wait_event_interruptible(list->serio_raw->wait,
                                serio_raw->head != serio_raw->tail || !serio_raw->serio);
      if (retval)
            return retval;

      if (!serio_raw->serio)
            return -ENODEV;

      while (retval < count && serio_raw_fetch_byte(serio_raw, &c)) {
            if (put_user(c, buffer++))
                  return -EFAULT;
            retval++;
      }

      return retval;
}

static ssize_t serio_raw_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos)
{
      struct serio_raw_list *list = file->private_data;
      ssize_t written = 0;
      int retval;
      unsigned char c;

      retval = mutex_lock_interruptible(&serio_raw_mutex);
      if (retval)
            return retval;

      if (!list->serio_raw->serio) {
            retval = -ENODEV;
            goto out;
      }

      if (count > 32)
            count = 32;

      while (count--) {
            if (get_user(c, buffer++)) {
                  retval = -EFAULT;
                  goto out;
            }
            if (serio_write(list->serio_raw->serio, c)) {
                  retval = -EIO;
                  goto out;
            }
            written++;
      };

out:
      mutex_unlock(&serio_raw_mutex);
      return written;
}

static unsigned int serio_raw_poll(struct file *file, poll_table *wait)
{
      struct serio_raw_list *list = file->private_data;

      poll_wait(file, &list->serio_raw->wait, wait);

      if (list->serio_raw->head != list->serio_raw->tail)
            return POLLIN | POLLRDNORM;

      return 0;
}

static const struct file_operations serio_raw_fops = {
      .owner =    THIS_MODULE,
      .open =           serio_raw_open,
      .release =  serio_raw_release,
      .read =           serio_raw_read,
      .write =    serio_raw_write,
      .poll =           serio_raw_poll,
      .fasync =   serio_raw_fasync,
};


/*********************************************************************
 *                   Interface with serio port                     *
 *********************************************************************/

static irqreturn_t serio_raw_interrupt(struct serio *serio, unsigned char data,
                              unsigned int dfl)
{
      struct serio_raw *serio_raw = serio_get_drvdata(serio);
      struct serio_raw_list *list;
      unsigned int head = serio_raw->head;

      /* we are holding serio->lock here so we are prootected */
      serio_raw->queue[head] = data;
      head = (head + 1) % SERIO_RAW_QUEUE_LEN;
      if (likely(head != serio_raw->tail)) {
            serio_raw->head = head;
            list_for_each_entry(list, &serio_raw->list, node)
                  kill_fasync(&list->fasync, SIGIO, POLL_IN);
            wake_up_interruptible(&serio_raw->wait);
      }

      return IRQ_HANDLED;
}

static int serio_raw_connect(struct serio *serio, struct serio_driver *drv)
{
      struct serio_raw *serio_raw;
      int err;

      if (!(serio_raw = kzalloc(sizeof(struct serio_raw), GFP_KERNEL))) {
            printk(KERN_ERR "serio_raw.c: can't allocate memory for a device\n");
            return -ENOMEM;
      }

      mutex_lock(&serio_raw_mutex);

      snprintf(serio_raw->name, sizeof(serio_raw->name), "serio_raw%d", serio_raw_no++);
      serio_raw->refcnt = 1;
      serio_raw->serio = serio;
      INIT_LIST_HEAD(&serio_raw->list);
      init_waitqueue_head(&serio_raw->wait);

      serio_set_drvdata(serio, serio_raw);

      err = serio_open(serio, drv);
      if (err)
            goto out_free;

      list_add_tail(&serio_raw->node, &serio_raw_list);

      serio_raw->dev.minor = PSMOUSE_MINOR;
      serio_raw->dev.name = serio_raw->name;
      serio_raw->dev.parent = &serio->dev;
      serio_raw->dev.fops = &serio_raw_fops;

      err = misc_register(&serio_raw->dev);
      if (err) {
            serio_raw->dev.minor = MISC_DYNAMIC_MINOR;
            err = misc_register(&serio_raw->dev);
      }

      if (err) {
            printk(KERN_INFO "serio_raw: failed to register raw access device for %s\n",
                  serio->phys);
            goto out_close;
      }

      printk(KERN_INFO "serio_raw: raw access enabled on %s (%s, minor %d)\n",
            serio->phys, serio_raw->name, serio_raw->dev.minor);
      goto out;

out_close:
      serio_close(serio);
      list_del_init(&serio_raw->node);
out_free:
      serio_set_drvdata(serio, NULL);
      kfree(serio_raw);
out:
      mutex_unlock(&serio_raw_mutex);
      return err;
}

static int serio_raw_reconnect(struct serio *serio)
{
      struct serio_raw *serio_raw = serio_get_drvdata(serio);
      struct serio_driver *drv = serio->drv;

      if (!drv || !serio_raw) {
            printk(KERN_DEBUG "serio_raw: reconnect request, but serio is disconnected, ignoring...\n");
            return -1;
      }

      /*
       * Nothing needs to be done here, we just need this method to
       * keep the same device.
       */
      return 0;
}

static void serio_raw_disconnect(struct serio *serio)
{
      struct serio_raw *serio_raw;

      mutex_lock(&serio_raw_mutex);

      serio_raw = serio_get_drvdata(serio);

      serio_close(serio);
      serio_set_drvdata(serio, NULL);

      serio_raw->serio = NULL;
      if (!serio_raw_cleanup(serio_raw))
            wake_up_interruptible(&serio_raw->wait);

      mutex_unlock(&serio_raw_mutex);
}

static struct serio_device_id serio_raw_serio_ids[] = {
      {
            .type = SERIO_8042,
            .proto      = SERIO_ANY,
            .id   = SERIO_ANY,
            .extra      = SERIO_ANY,
      },
      { 0 }
};

MODULE_DEVICE_TABLE(serio, serio_raw_serio_ids);

static struct serio_driver serio_raw_drv = {
      .driver           = {
            .name = "serio_raw",
      },
      .description      = DRIVER_DESC,
      .id_table   = serio_raw_serio_ids,
      .interrupt  = serio_raw_interrupt,
      .connect    = serio_raw_connect,
      .reconnect  = serio_raw_reconnect,
      .disconnect = serio_raw_disconnect,
      .manual_bind      = 1,
};

static int __init serio_raw_init(void)
{
      return serio_register_driver(&serio_raw_drv);
}

static void __exit serio_raw_exit(void)
{
      serio_unregister_driver(&serio_raw_drv);
}

module_init(serio_raw_init);
module_exit(serio_raw_exit);

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