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serport.c

/*
 * Input device TTY line discipline
 *
 * Copyright (c) 1999-2002 Vojtech Pavlik
 *
 * This is a module that converts a tty line into a much simpler
 * 'serial io port' abstraction that the input device drivers use.
 */

/*
 * 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 <asm/uaccess.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/serio.h>
#include <linux/tty.h>

MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
MODULE_DESCRIPTION("Input device TTY line discipline");
MODULE_LICENSE("GPL");
MODULE_ALIAS_LDISC(N_MOUSE);

#define SERPORT_BUSY    1
#define SERPORT_ACTIVE  2
#define SERPORT_DEAD    3

struct serport {
      struct tty_struct *tty;
      wait_queue_head_t wait;
      struct serio *serio;
      struct serio_device_id id;
      spinlock_t lock;
      unsigned long flags;
};

/*
 * Callback functions from the serio code.
 */

static int serport_serio_write(struct serio *serio, unsigned char data)
{
      struct serport *serport = serio->port_data;
      return -(serport->tty->driver->write(serport->tty, &data, 1) != 1);
}

static int serport_serio_open(struct serio *serio)
{
      struct serport *serport = serio->port_data;
      unsigned long flags;

      spin_lock_irqsave(&serport->lock, flags);
      set_bit(SERPORT_ACTIVE, &serport->flags);
      spin_unlock_irqrestore(&serport->lock, flags);

      return 0;
}


static void serport_serio_close(struct serio *serio)
{
      struct serport *serport = serio->port_data;
      unsigned long flags;

      spin_lock_irqsave(&serport->lock, flags);
      clear_bit(SERPORT_ACTIVE, &serport->flags);
      set_bit(SERPORT_DEAD, &serport->flags);
      spin_unlock_irqrestore(&serport->lock, flags);

      wake_up_interruptible(&serport->wait);
}

/*
 * serport_ldisc_open() is the routine that is called upon setting our line
 * discipline on a tty. It prepares the serio struct.
 */

static int serport_ldisc_open(struct tty_struct *tty)
{
      struct serport *serport;

      if (!capable(CAP_SYS_ADMIN))
            return -EPERM;

      serport = kzalloc(sizeof(struct serport), GFP_KERNEL);
      if (!serport)
            return -ENOMEM;

      serport->tty = tty;
      spin_lock_init(&serport->lock);
      init_waitqueue_head(&serport->wait);

      tty->disc_data = serport;
      tty->receive_room = 256;
      set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);

      return 0;
}

/*
 * serport_ldisc_close() is the opposite of serport_ldisc_open()
 */

static void serport_ldisc_close(struct tty_struct *tty)
{
      struct serport *serport = (struct serport *) tty->disc_data;

      kfree(serport);
}

/*
 * serport_ldisc_receive() is called by the low level tty driver when characters
 * are ready for us. We forward the characters, one by one to the 'interrupt'
 * routine.
 */

static void serport_ldisc_receive(struct tty_struct *tty, const unsigned char *cp, char *fp, int count)
{
      struct serport *serport = (struct serport*) tty->disc_data;
      unsigned long flags;
      int i;

      spin_lock_irqsave(&serport->lock, flags);

      if (!test_bit(SERPORT_ACTIVE, &serport->flags))
            goto out;

      for (i = 0; i < count; i++)
            serio_interrupt(serport->serio, cp[i], 0);

out:
      spin_unlock_irqrestore(&serport->lock, flags);
}

/*
 * serport_ldisc_read() just waits indefinitely if everything goes well.
 * However, when the serio driver closes the serio port, it finishes,
 * returning 0 characters.
 */

static ssize_t serport_ldisc_read(struct tty_struct * tty, struct file * file, unsigned char __user * buf, size_t nr)
{
      struct serport *serport = (struct serport*) tty->disc_data;
      struct serio *serio;
      char name[64];

      if (test_and_set_bit(SERPORT_BUSY, &serport->flags))
            return -EBUSY;

      serport->serio = serio = kzalloc(sizeof(struct serio), GFP_KERNEL);
      if (!serio)
            return -ENOMEM;

      strlcpy(serio->name, "Serial port", sizeof(serio->name));
      snprintf(serio->phys, sizeof(serio->phys), "%s/serio0", tty_name(tty, name));
      serio->id = serport->id;
      serio->id.type = SERIO_RS232;
      serio->write = serport_serio_write;
      serio->open = serport_serio_open;
      serio->close = serport_serio_close;
      serio->port_data = serport;

      serio_register_port(serport->serio);
      printk(KERN_INFO "serio: Serial port %s\n", tty_name(tty, name));

      wait_event_interruptible(serport->wait, test_bit(SERPORT_DEAD, &serport->flags));
      serio_unregister_port(serport->serio);
      serport->serio = NULL;

      clear_bit(SERPORT_DEAD, &serport->flags);
      clear_bit(SERPORT_BUSY, &serport->flags);

      return 0;
}

/*
 * serport_ldisc_ioctl() allows to set the port protocol, and device ID
 */

static int serport_ldisc_ioctl(struct tty_struct * tty, struct file * file, unsigned int cmd, unsigned long arg)
{
      struct serport *serport = (struct serport*) tty->disc_data;
      unsigned long type;

      if (cmd == SPIOCSTYPE) {
            if (get_user(type, (unsigned long __user *) arg))
                  return -EFAULT;

            serport->id.proto = type & 0x000000ff;
            serport->id.id      = (type & 0x0000ff00) >> 8;
            serport->id.extra = (type & 0x00ff0000) >> 16;

            return 0;
      }

      return -EINVAL;
}

static void serport_ldisc_write_wakeup(struct tty_struct * tty)
{
      struct serport *serport = (struct serport *) tty->disc_data;
      unsigned long flags;

      spin_lock_irqsave(&serport->lock, flags);
      if (test_bit(SERPORT_ACTIVE, &serport->flags))
            serio_drv_write_wakeup(serport->serio);
      spin_unlock_irqrestore(&serport->lock, flags);
}

/*
 * The line discipline structure.
 */

static struct tty_ldisc serport_ldisc = {
      .owner =    THIS_MODULE,
      .name =           "input",
      .open =           serport_ldisc_open,
      .close =    serport_ldisc_close,
      .read =           serport_ldisc_read,
      .ioctl =    serport_ldisc_ioctl,
      .receive_buf =    serport_ldisc_receive,
      .write_wakeup =   serport_ldisc_write_wakeup
};

/*
 * The functions for insering/removing us as a module.
 */

static int __init serport_init(void)
{
      int retval;
      retval = tty_register_ldisc(N_MOUSE, &serport_ldisc);
      if (retval)
            printk(KERN_ERR "serport.c: Error registering line discipline.\n");

      return  retval;
}

static void __exit serport_exit(void)
{
      tty_unregister_ldisc(N_MOUSE);
}

module_init(serport_init);
module_exit(serport_exit);

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