irtty-sir.c

Go to the documentation of this file.

/*********************************************************************
 *                
 * Filename:      irtty-sir.c
 * Version:       2.0
 * Description:   IrDA line discipline implementation
 * Status:        Experimental.
 * Author:        Dag Brattli <[email protected]>
 * Created at:    Tue Dec  9 21:18:38 1997
 * Modified at:   Sun Oct 27 22:13:30 2002
 * Modified by:   Martin Diehl <[email protected]>
 * Sources:       slip.c by Laurence Culhane,   <[email protected]>
 *                          Fred N. van Kempen, <[email protected]>
 * 
 *     Copyright (c) 1998-2000 Dag Brattli,
 *     Copyright (c) 2002 Martin Diehl,
 *     All Rights Reserved.
 *      
 *     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; either version 2 of 
 *     the License, or (at your option) any later version.
 *  
 *     Neither Dag Brattli nor University of Tromsø admit liability nor
 *     provide warranty for any of this software. This material is 
 *     provided "AS-IS" and at no charge.
 *     
 ********************************************************************/    

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/tty.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <linux/delay.h>
#include <linux/mutex.h>

#include <net/irda/irda.h>
#include <net/irda/irda_device.h>

#include "sir-dev.h"
#include "irtty-sir.h"

static int qos_mtt_bits = 0x03;      /* 5 ms or more */

module_param(qos_mtt_bits, int, 0);
MODULE_PARM_DESC(qos_mtt_bits, "Minimum Turn Time");

/* ------------------------------------------------------- */

/* device configuration callbacks always invoked with irda-thread context */

/* find out, how many chars we have in buffers below us
 * this is allowed to lie, i.e. return less chars than we
 * actually have. The returned value is used to determine
 * how long the irdathread should wait before doing the
 * real blocking wait_until_sent()
 */

static int irtty_chars_in_buffer(struct sir_dev *dev)
{
    struct sirtty_cb *priv = dev->priv;

    IRDA_ASSERT(priv != NULL, return -1;);
    IRDA_ASSERT(priv->magic == IRTTY_MAGIC, return -1;);

    return tty_chars_in_buffer(priv->tty);
}

/* Wait (sleep) until underlaying hardware finished transmission
 * i.e. hardware buffers are drained
 * this must block and not return before all characters are really sent
 *
 * If the tty sits on top of a 16550A-like uart, there are typically
 * up to 16 bytes in the fifo - f.e. 9600 bps 8N1 needs 16.7 msec
 *
 * With usbserial the uart-fifo is basically replaced by the converter's
 * outgoing endpoint buffer, which can usually hold 64 bytes (at least).
 * With pl2303 it appears we are safe with 60msec here.
 *
 * I really wish all serial drivers would provide
 * correct implementation of wait_until_sent()
 */

#define USBSERIAL_TX_DONE_DELAY 60

static void irtty_wait_until_sent(struct sir_dev *dev)
{
    struct sirtty_cb *priv = dev->priv;
    struct tty_struct *tty;

    IRDA_ASSERT(priv != NULL, return;);
    IRDA_ASSERT(priv->magic == IRTTY_MAGIC, return;);

    tty = priv->tty;
    if (tty->ops->wait_until_sent) {
        tty->ops->wait_until_sent(tty, msecs_to_jiffies(100));
    }
    else {
        msleep(USBSERIAL_TX_DONE_DELAY);
    }
}

/* 
 *  Function irtty_change_speed (dev, speed)
 *
 *    Change the speed of the serial port.
 *
 * This may sleep in set_termios (usbserial driver f.e.) and must
 * not be called from interrupt/timer/tasklet therefore.
 * All such invocations are deferred to kIrDAd now so we can sleep there.
 */

static int irtty_change_speed(struct sir_dev *dev, unsigned speed)
{
    struct sirtty_cb *priv = dev->priv;
    struct tty_struct *tty;
        struct ktermios old_termios;
    int cflag;

    IRDA_ASSERT(priv != NULL, return -1;);
    IRDA_ASSERT(priv->magic == IRTTY_MAGIC, return -1;);

    tty = priv->tty;

    mutex_lock(&tty->termios_mutex);
    old_termios = tty->termios;
    cflag = tty->termios.c_cflag;
    tty_encode_baud_rate(tty, speed, speed);
    if (tty->ops->set_termios)
        tty->ops->set_termios(tty, &old_termios);
    priv->io.speed = speed;
    mutex_unlock(&tty->termios_mutex);

    return 0;
}

/*
 * Function irtty_set_dtr_rts (dev, dtr, rts)
 *
 *    This function can be used by dongles etc. to set or reset the status
 *    of the dtr and rts lines
 */

static int irtty_set_dtr_rts(struct sir_dev *dev, int dtr, int rts)
{
    struct sirtty_cb *priv = dev->priv;
    int set = 0;
    int clear = 0;

    IRDA_ASSERT(priv != NULL, return -1;);
    IRDA_ASSERT(priv->magic == IRTTY_MAGIC, return -1;);

    if (rts)
        set |= TIOCM_RTS;
    else
        clear |= TIOCM_RTS;
    if (dtr)
        set |= TIOCM_DTR;
    else
        clear |= TIOCM_DTR;

    /*
     * We can't use ioctl() because it expects a non-null file structure,
     * and we don't have that here.
     * This function is not yet defined for all tty driver, so
     * let's be careful... Jean II
     */
    IRDA_ASSERT(priv->tty->ops->tiocmset != NULL, return -1;);
    priv->tty->ops->tiocmset(priv->tty, set, clear);

    return 0;
}

/* ------------------------------------------------------- */

/* called from sir_dev when there is more data to send
 * context is either netdev->hard_xmit or some transmit-completion bh
 * i.e. we are under spinlock here and must not sleep.
 */

static int irtty_do_write(struct sir_dev *dev, const unsigned char *ptr, size_t len)
{
    struct sirtty_cb *priv = dev->priv;
    struct tty_struct *tty;
    int writelen;

    IRDA_ASSERT(priv != NULL, return -1;);
    IRDA_ASSERT(priv->magic == IRTTY_MAGIC, return -1;);

    tty = priv->tty;
    if (!tty->ops->write)
        return 0;
    set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
    writelen = tty_write_room(tty);
    if (writelen > len)
        writelen = len;
    return tty->ops->write(tty, ptr, writelen);
}

/* ------------------------------------------------------- */

/* irda line discipline callbacks */

/* 
 *  Function irtty_receive_buf( tty, cp, count)
 *
 *    Handle the 'receiver data ready' interrupt.  This function is called
 *    by the 'tty_io' module in the kernel when a block of IrDA data has
 *    been received, which can now be decapsulated and delivered for
 *    further processing 
 *
 * calling context depends on underlying driver and tty->low_latency!
 * for example (low_latency: 1 / 0):
 * serial.c:    uart-interrupt / softint
 * usbserial:   urb-complete-interrupt / softint
 */

static void irtty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
                  char *fp, int count) 
{
    struct sir_dev *dev;
    struct sirtty_cb *priv = tty->disc_data;
    int i;

    IRDA_ASSERT(priv != NULL, return;);
    IRDA_ASSERT(priv->magic == IRTTY_MAGIC, return;);

    if (unlikely(count==0))     /* yes, this happens */
        return;

    dev = priv->dev;
    if (!dev) {
        IRDA_WARNING("%s(), not ready yet!\n", __func__);
        return;
    }

    for (i = 0; i < count; i++) {
        /* 
         *  Characters received with a parity error, etc?
         */
        if (fp && *fp++) { 
            IRDA_DEBUG(0, "Framing or parity error!\n");
            sirdev_receive(dev, NULL, 0);   /* notify sir_dev (updating stats) */
            return;
        }
    }

    sirdev_receive(dev, cp, count);
}

/*
 * Function irtty_write_wakeup (tty)
 *
 *    Called by the driver when there's room for more data.  If we have
 *    more packets to send, we send them here.
 *
 */
static void irtty_write_wakeup(struct tty_struct *tty) 
{
    struct sirtty_cb *priv = tty->disc_data;

    IRDA_ASSERT(priv != NULL, return;);
    IRDA_ASSERT(priv->magic == IRTTY_MAGIC, return;);

    clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
    if (priv->dev)
        sirdev_write_complete(priv->dev);
}

/* ------------------------------------------------------- */

/*
 * Function irtty_stop_receiver (tty, stop)
 *
 */

static inline void irtty_stop_receiver(struct tty_struct *tty, int stop)
{
    struct ktermios old_termios;
    int cflag;

    mutex_lock(&tty->termios_mutex);
    old_termios = tty->termios;
    cflag = tty->termios.c_cflag;
    
    if (stop)
        cflag &= ~CREAD;
    else
        cflag |= CREAD;

    tty->termios.c_cflag = cflag;
    if (tty->ops->set_termios)
        tty->ops->set_termios(tty, &old_termios);
    mutex_unlock(&tty->termios_mutex);
}

/*****************************************************************/

/* serialize ldisc open/close with sir_dev */
static DEFINE_MUTEX(irtty_mutex);

/* notifier from sir_dev when irda% device gets opened (ifup) */

static int irtty_start_dev(struct sir_dev *dev)
{
    struct sirtty_cb *priv;
    struct tty_struct *tty;

    /* serialize with ldisc open/close */
    mutex_lock(&irtty_mutex);

    priv = dev->priv;
    if (unlikely(!priv || priv->magic!=IRTTY_MAGIC)) {
        mutex_unlock(&irtty_mutex);
        return -ESTALE;
    }

    tty = priv->tty;

    if (tty->ops->start)
        tty->ops->start(tty);
    /* Make sure we can receive more data */
    irtty_stop_receiver(tty, FALSE);

    mutex_unlock(&irtty_mutex);
    return 0;
}

/* notifier from sir_dev when irda% device gets closed (ifdown) */

static int irtty_stop_dev(struct sir_dev *dev)
{
    struct sirtty_cb *priv;
    struct tty_struct *tty;

    /* serialize with ldisc open/close */
    mutex_lock(&irtty_mutex);

    priv = dev->priv;
    if (unlikely(!priv || priv->magic!=IRTTY_MAGIC)) {
        mutex_unlock(&irtty_mutex);
        return -ESTALE;
    }

    tty = priv->tty;

    /* Make sure we don't receive more data */
    irtty_stop_receiver(tty, TRUE);
    if (tty->ops->stop)
        tty->ops->stop(tty);

    mutex_unlock(&irtty_mutex);

    return 0;
}

/* ------------------------------------------------------- */

static struct sir_driver sir_tty_drv = {
    .owner          = THIS_MODULE,
    .driver_name        = "sir_tty",
    .start_dev      = irtty_start_dev,
    .stop_dev       = irtty_stop_dev,
    .do_write       = irtty_do_write,
    .chars_in_buffer    = irtty_chars_in_buffer,
    .wait_until_sent    = irtty_wait_until_sent,
    .set_speed      = irtty_change_speed,
    .set_dtr_rts        = irtty_set_dtr_rts,
};

/* ------------------------------------------------------- */

/*
 * Function irtty_ioctl (tty, file, cmd, arg)
 *
 *     The Swiss army knife of system calls :-)
 *
 */
static int irtty_ioctl(struct tty_struct *tty, struct file *file, unsigned int cmd, unsigned long arg)
{
    struct irtty_info { char name[6]; } info;
    struct sir_dev *dev;
    struct sirtty_cb *priv = tty->disc_data;
    int err = 0;

    IRDA_ASSERT(priv != NULL, return -ENODEV;);
    IRDA_ASSERT(priv->magic == IRTTY_MAGIC, return -EBADR;);

    IRDA_DEBUG(3, "%s(cmd=0x%X)\n", __func__, cmd);

    dev = priv->dev;
    IRDA_ASSERT(dev != NULL, return -1;);

    switch (cmd) {
    case IRTTY_IOCTDONGLE:
        /* this call blocks for completion */
        err = sirdev_set_dongle(dev, (IRDA_DONGLE) arg);
        break;

    case IRTTY_IOCGET:
        IRDA_ASSERT(dev->netdev != NULL, return -1;);

        memset(&info, 0, sizeof(info)); 
        strncpy(info.name, dev->netdev->name, sizeof(info.name)-1);

        if (copy_to_user((void __user *)arg, &info, sizeof(info)))
            err = -EFAULT;
        break;
    default:
        err = tty_mode_ioctl(tty, file, cmd, arg);
        break;
    }
    return err;
}


/* 
 *  Function irtty_open(tty)
 *
 *    This function is called by the TTY module when the IrDA line
 *    discipline is called for.  Because we are sure the tty line exists,
 *    we only have to link it to a free IrDA channel.  
 */
static int irtty_open(struct tty_struct *tty) 
{
    struct sir_dev *dev;
    struct sirtty_cb *priv;
    int ret = 0;

    /* Module stuff handled via irda_ldisc.owner - Jean II */

    /* First make sure we're not already connected. */
    if (tty->disc_data != NULL) {
        priv = tty->disc_data;
        if (priv && priv->magic == IRTTY_MAGIC) {
            ret = -EEXIST;
            goto out;
        }
        tty->disc_data = NULL;      /* ### */
    }

    /* stop the underlying  driver */
    irtty_stop_receiver(tty, TRUE);
    if (tty->ops->stop)
        tty->ops->stop(tty);

    tty_driver_flush_buffer(tty);
    
    /* apply mtt override */
    sir_tty_drv.qos_mtt_bits = qos_mtt_bits;

    /* get a sir device instance for this driver */
    dev = sirdev_get_instance(&sir_tty_drv, tty->name);
    if (!dev) {
        ret = -ENODEV;
        goto out;
    }

    /* allocate private device info block */
    priv = kzalloc(sizeof(*priv), GFP_KERNEL);
    if (!priv) {
        ret = -ENOMEM;
        goto out_put;
    }

    priv->magic = IRTTY_MAGIC;
    priv->tty = tty;
    priv->dev = dev;

    /* serialize with start_dev - in case we were racing with ifup */
    mutex_lock(&irtty_mutex);

    dev->priv = priv;
    tty->disc_data = priv;
    tty->receive_room = 65536;

    mutex_unlock(&irtty_mutex);

    IRDA_DEBUG(0, "%s - %s: irda line discipline opened\n", __func__, tty->name);

    return 0;

out_put:
    sirdev_put_instance(dev);
out:
    return ret;
}

/* 
 *  Function irtty_close (tty)
 *
 *    Close down a IrDA channel. This means flushing out any pending queues,
 *    and then restoring the TTY line discipline to what it was before it got
 *    hooked to IrDA (which usually is TTY again).  
 */
static void irtty_close(struct tty_struct *tty) 
{
    struct sirtty_cb *priv = tty->disc_data;

    IRDA_ASSERT(priv != NULL, return;);
    IRDA_ASSERT(priv->magic == IRTTY_MAGIC, return;);

    /* Hm, with a dongle attached the dongle driver wants
     * to close the dongle - which requires the use of
     * some tty write and/or termios or ioctl operations.
     * Are we allowed to call those when already requested
     * to shutdown the ldisc?
     * If not, we should somehow mark the dev being staled.
     * Question remains, how to close the dongle in this case...
     * For now let's assume we are granted to issue tty driver calls
     * until we return here from the ldisc close. I'm just wondering
     * how this behaves with hotpluggable serial hardware like
     * rs232-pcmcia card or usb-serial...
     *
     * priv->tty = NULL?;
     */

    /* we are dead now */
    tty->disc_data = NULL;

    sirdev_put_instance(priv->dev);

    /* Stop tty */
    irtty_stop_receiver(tty, TRUE);
    clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
    if (tty->ops->stop)
        tty->ops->stop(tty);

    kfree(priv);

    IRDA_DEBUG(0, "%s - %s: irda line discipline closed\n", __func__, tty->name);
}

/* ------------------------------------------------------- */

static struct tty_ldisc_ops irda_ldisc = {
    .magic      = TTY_LDISC_MAGIC,
    .name       = "irda",
    .flags      = 0,
    .open       = irtty_open,
    .close      = irtty_close,
    .read       = NULL,
    .write      = NULL,
    .ioctl      = irtty_ioctl,
    .poll       = NULL,
    .receive_buf    = irtty_receive_buf,
    .write_wakeup   = irtty_write_wakeup,
    .owner      = THIS_MODULE,
};

/* ------------------------------------------------------- */

static int __init irtty_sir_init(void)
{
    int err;

    if ((err = tty_register_ldisc(N_IRDA, &irda_ldisc)) != 0)
        IRDA_ERROR("IrDA: can't register line discipline (err = %d)\n",
               err);
    return err;
}

static void __exit irtty_sir_cleanup(void) 
{
    int err;

    if ((err = tty_unregister_ldisc(N_IRDA))) {
        IRDA_ERROR("%s(), can't unregister line discipline (err = %d)\n",
               __func__, err);
    }
}

module_init(irtty_sir_init);
module_exit(irtty_sir_cleanup);

MODULE_AUTHOR("Dag Brattli <[email protected]>");
MODULE_DESCRIPTION("IrDA TTY device driver");
MODULE_ALIAS_LDISC(N_IRDA);
MODULE_LICENSE("GPL");