slcan.c

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/*
 * slcan.c - serial line CAN interface driver (using tty line discipline)
 *
 * This file is derived from linux/drivers/net/slip/slip.c
 *
 * slip.c Authors  : Laurence Culhane <[email protected]>
 *                   Fred N. van Kempen <[email protected]>
 * slcan.c Author  : Oliver Hartkopp <[email protected]>
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307. You can also get it
 * at http://www.gnu.org/licenses/gpl.html
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 *
 */

#include <linux/module.h>
#include <linux/moduleparam.h>

#include <linux/uaccess.h>
#include <linux/bitops.h>
#include <linux/string.h>
#include <linux/tty.h>
#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/can.h>

static __initconst const char banner[] =
    KERN_INFO "slcan: serial line CAN interface driver\n";

MODULE_ALIAS_LDISC(N_SLCAN);
MODULE_DESCRIPTION("serial line CAN interface");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Oliver Hartkopp <[email protected]>");

#define SLCAN_MAGIC 0x53CA

static int maxdev = 10;     /* MAX number of SLCAN channels;
                   This can be overridden with
                   insmod slcan.ko maxdev=nnn   */
module_param(maxdev, int, 0);
MODULE_PARM_DESC(maxdev, "Maximum number of slcan interfaces");

/* maximum rx buffer len: extended CAN frame with timestamp */
#define SLC_MTU (sizeof("T1111222281122334455667788EA5F\r")+1)

struct slcan {
    int         magic;

    /* Various fields. */
    struct tty_struct   *tty;       /* ptr to TTY structure      */
    struct net_device   *dev;       /* easy for intr handling    */
    spinlock_t      lock;

    /* These are pointers to the malloc()ed frame buffers. */
    unsigned char       rbuff[SLC_MTU]; /* receiver buffer       */
    int         rcount;         /* received chars counter    */
    unsigned char       xbuff[SLC_MTU]; /* transmitter buffer        */
    unsigned char       *xhead;         /* pointer to next XMIT byte */
    int         xleft;          /* bytes left in XMIT queue  */

    unsigned long       flags;      /* Flag values/ mode etc     */
#define SLF_INUSE       0       /* Channel in use            */
#define SLF_ERROR       1               /* Parity, etc. error        */
};

static struct net_device **slcan_devs;

 /************************************************************************
  *         SLCAN ENCAPSULATION FORMAT           *
  ************************************************************************/

/*
 * A CAN frame has a can_id (11 bit standard frame format OR 29 bit extended
 * frame format) a data length code (can_dlc) which can be from 0 to 8
 * and up to <can_dlc> data bytes as payload.
 * Additionally a CAN frame may become a remote transmission frame if the
 * RTR-bit is set. This causes another ECU to send a CAN frame with the
 * given can_id.
 *
 * The SLCAN ASCII representation of these different frame types is:
 * <type> <id> <dlc> <data>*
 *
 * Extended frames (29 bit) are defined by capital characters in the type.
 * RTR frames are defined as 'r' types - normal frames have 't' type:
 * t => 11 bit data frame
 * r => 11 bit RTR frame
 * T => 29 bit data frame
 * R => 29 bit RTR frame
 *
 * The <id> is 3 (standard) or 8 (extended) bytes in ASCII Hex (base64).
 * The <dlc> is a one byte ASCII number ('0' - '8')
 * The <data> section has at much ASCII Hex bytes as defined by the <dlc>
 *
 * Examples:
 *
 * t1230 : can_id 0x123, can_dlc 0, no data
 * t4563112233 : can_id 0x456, can_dlc 3, data 0x11 0x22 0x33
 * T12ABCDEF2AA55 : extended can_id 0x12ABCDEF, can_dlc 2, data 0xAA 0x55
 * r1230 : can_id 0x123, can_dlc 0, no data, remote transmission request
 *
 */

 /************************************************************************
  *         STANDARD SLCAN DECAPSULATION             *
  ************************************************************************/

/* Send one completely decapsulated can_frame to the network layer */
static void slc_bump(struct slcan *sl)
{
    struct sk_buff *skb;
    struct can_frame cf;
    int i, dlc_pos, tmp;
    unsigned long ultmp;
    char cmd = sl->rbuff[0];

    if ((cmd != 't') && (cmd != 'T') && (cmd != 'r') && (cmd != 'R'))
        return;

    if (cmd & 0x20) /* tiny chars 'r' 't' => standard frame format */
        dlc_pos = 4; /* dlc position tiiid */
    else
        dlc_pos = 9; /* dlc position Tiiiiiiiid */

    if (!((sl->rbuff[dlc_pos] >= '0') && (sl->rbuff[dlc_pos] < '9')))
        return;

    cf.can_dlc = sl->rbuff[dlc_pos] - '0'; /* get can_dlc from ASCII val */

    sl->rbuff[dlc_pos] = 0; /* terminate can_id string */

    if (strict_strtoul(sl->rbuff+1, 16, &ultmp))
        return;

    cf.can_id = ultmp;

    if (!(cmd & 0x20)) /* NO tiny chars => extended frame format */
        cf.can_id |= CAN_EFF_FLAG;

    if ((cmd | 0x20) == 'r') /* RTR frame */
        cf.can_id |= CAN_RTR_FLAG;

    *(u64 *) (&cf.data) = 0; /* clear payload */

    for (i = 0, dlc_pos++; i < cf.can_dlc; i++) {
        tmp = hex_to_bin(sl->rbuff[dlc_pos++]);
        if (tmp < 0)
            return;
        cf.data[i] = (tmp << 4);
        tmp = hex_to_bin(sl->rbuff[dlc_pos++]);
        if (tmp < 0)
            return;
        cf.data[i] |= tmp;
    }

    skb = dev_alloc_skb(sizeof(struct can_frame));
    if (!skb)
        return;

    skb->dev = sl->dev;
    skb->protocol = htons(ETH_P_CAN);
    skb->pkt_type = PACKET_BROADCAST;
    skb->ip_summed = CHECKSUM_UNNECESSARY;
    memcpy(skb_put(skb, sizeof(struct can_frame)),
           &cf, sizeof(struct can_frame));
    netif_rx_ni(skb);

    sl->dev->stats.rx_packets++;
    sl->dev->stats.rx_bytes += cf.can_dlc;
}

/* parse tty input stream */
static void slcan_unesc(struct slcan *sl, unsigned char s)
{

    if ((s == '\r') || (s == '\a')) { /* CR or BEL ends the pdu */
        if (!test_and_clear_bit(SLF_ERROR, &sl->flags) &&
            (sl->rcount > 4))  {
            slc_bump(sl);
        }
        sl->rcount = 0;
    } else {
        if (!test_bit(SLF_ERROR, &sl->flags))  {
            if (sl->rcount < SLC_MTU)  {
                sl->rbuff[sl->rcount++] = s;
                return;
            } else {
                sl->dev->stats.rx_over_errors++;
                set_bit(SLF_ERROR, &sl->flags);
            }
        }
    }
}

 /************************************************************************
  *         STANDARD SLCAN ENCAPSULATION             *
  ************************************************************************/

/* Encapsulate one can_frame and stuff into a TTY queue. */
static void slc_encaps(struct slcan *sl, struct can_frame *cf)
{
    int actual, idx, i;
    char cmd;

    if (cf->can_id & CAN_RTR_FLAG)
        cmd = 'R'; /* becomes 'r' in standard frame format */
    else
        cmd = 'T'; /* becomes 't' in standard frame format */

    if (cf->can_id & CAN_EFF_FLAG)
        sprintf(sl->xbuff, "%c%08X%d", cmd,
            cf->can_id & CAN_EFF_MASK, cf->can_dlc);
    else
        sprintf(sl->xbuff, "%c%03X%d", cmd | 0x20,
            cf->can_id & CAN_SFF_MASK, cf->can_dlc);

    idx = strlen(sl->xbuff);

    for (i = 0; i < cf->can_dlc; i++)
        sprintf(&sl->xbuff[idx + 2*i], "%02X", cf->data[i]);

    strcat(sl->xbuff, "\r"); /* add terminating character */

    /* Order of next two lines is *very* important.
     * When we are sending a little amount of data,
     * the transfer may be completed inside the ops->write()
     * routine, because it's running with interrupts enabled.
     * In this case we *never* got WRITE_WAKEUP event,
     * if we did not request it before write operation.
     *       14 Oct 1994  Dmitry Gorodchanin.
     */
    set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
    actual = sl->tty->ops->write(sl->tty, sl->xbuff, strlen(sl->xbuff));
    sl->xleft = strlen(sl->xbuff) - actual;
    sl->xhead = sl->xbuff + actual;
    sl->dev->stats.tx_bytes += cf->can_dlc;
}

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

    /* First make sure we're connected. */
    if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
        return;

    if (sl->xleft <= 0)  {
        /* Now serial buffer is almost free & we can start
         * transmission of another packet */
        sl->dev->stats.tx_packets++;
        clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
        netif_wake_queue(sl->dev);
        return;
    }

    actual = tty->ops->write(tty, sl->xhead, sl->xleft);
    sl->xleft -= actual;
    sl->xhead += actual;
}

/* Send a can_frame to a TTY queue. */
static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
{
    struct slcan *sl = netdev_priv(dev);

    if (skb->len != sizeof(struct can_frame))
        goto out;

    spin_lock(&sl->lock);
    if (!netif_running(dev))  {
        spin_unlock(&sl->lock);
        printk(KERN_WARNING "%s: xmit: iface is down\n", dev->name);
        goto out;
    }
    if (sl->tty == NULL) {
        spin_unlock(&sl->lock);
        goto out;
    }

    netif_stop_queue(sl->dev);
    slc_encaps(sl, (struct can_frame *) skb->data); /* encaps & send */
    spin_unlock(&sl->lock);

out:
    kfree_skb(skb);
    return NETDEV_TX_OK;
}


/******************************************
 *   Routines looking at netdevice side.
 ******************************************/

/* Netdevice UP -> DOWN routine */
static int slc_close(struct net_device *dev)
{
    struct slcan *sl = netdev_priv(dev);

    spin_lock_bh(&sl->lock);
    if (sl->tty) {
        /* TTY discipline is running. */
        clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
    }
    netif_stop_queue(dev);
    sl->rcount   = 0;
    sl->xleft    = 0;
    spin_unlock_bh(&sl->lock);

    return 0;
}

/* Netdevice DOWN -> UP routine */
static int slc_open(struct net_device *dev)
{
    struct slcan *sl = netdev_priv(dev);

    if (sl->tty == NULL)
        return -ENODEV;

    sl->flags &= (1 << SLF_INUSE);
    netif_start_queue(dev);
    return 0;
}

/* Hook the destructor so we can free slcan devs at the right point in time */
static void slc_free_netdev(struct net_device *dev)
{
    int i = dev->base_addr;
    free_netdev(dev);
    slcan_devs[i] = NULL;
}

static const struct net_device_ops slc_netdev_ops = {
    .ndo_open               = slc_open,
    .ndo_stop               = slc_close,
    .ndo_start_xmit         = slc_xmit,
};

static void slc_setup(struct net_device *dev)
{
    dev->netdev_ops     = &slc_netdev_ops;
    dev->destructor     = slc_free_netdev;

    dev->hard_header_len    = 0;
    dev->addr_len       = 0;
    dev->tx_queue_len   = 10;

    dev->mtu        = sizeof(struct can_frame);
    dev->type       = ARPHRD_CAN;

    /* New-style flags. */
    dev->flags      = IFF_NOARP;
    dev->features           = NETIF_F_HW_CSUM;
}

/******************************************
  Routines looking at TTY side.
 ******************************************/

/*
 * Handle the 'receiver data ready' interrupt.
 * This function is called by the 'tty_io' module in the kernel when
 * a block of SLCAN data has been received, which can now be decapsulated
 * and sent on to some IP layer for further processing. This will not
 * be re-entered while running but other ldisc functions may be called
 * in parallel
 */

static void slcan_receive_buf(struct tty_struct *tty,
                  const unsigned char *cp, char *fp, int count)
{
    struct slcan *sl = (struct slcan *) tty->disc_data;

    if (!sl || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev))
        return;

    /* Read the characters out of the buffer */
    while (count--) {
        if (fp && *fp++) {
            if (!test_and_set_bit(SLF_ERROR, &sl->flags))
                sl->dev->stats.rx_errors++;
            cp++;
            continue;
        }
        slcan_unesc(sl, *cp++);
    }
}

/************************************
 *  slcan_open helper routines.
 ************************************/

/* Collect hanged up channels */
static void slc_sync(void)
{
    int i;
    struct net_device *dev;
    struct slcan      *sl;

    for (i = 0; i < maxdev; i++) {
        dev = slcan_devs[i];
        if (dev == NULL)
            break;

        sl = netdev_priv(dev);
        if (sl->tty)
            continue;
        if (dev->flags & IFF_UP)
            dev_close(dev);
    }
}

/* Find a free SLCAN channel, and link in this `tty' line. */
static struct slcan *slc_alloc(dev_t line)
{
    int i;
    char name[IFNAMSIZ];
    struct net_device *dev = NULL;
    struct slcan       *sl;

    for (i = 0; i < maxdev; i++) {
        dev = slcan_devs[i];
        if (dev == NULL)
            break;

    }

    /* Sorry, too many, all slots in use */
    if (i >= maxdev)
        return NULL;

    sprintf(name, "slcan%d", i);
    dev = alloc_netdev(sizeof(*sl), name, slc_setup);
    if (!dev)
        return NULL;

    dev->base_addr  = i;
    sl = netdev_priv(dev);

    /* Initialize channel control data */
    sl->magic = SLCAN_MAGIC;
    sl->dev = dev;
    spin_lock_init(&sl->lock);
    slcan_devs[i] = dev;

    return sl;
}

/*
 * Open the high-level part of the SLCAN channel.
 * This function is called by the TTY module when the
 * SLCAN line discipline is called for.  Because we are
 * sure the tty line exists, we only have to link it to
 * a free SLCAN channel...
 *
 * Called in process context serialized from other ldisc calls.
 */

static int slcan_open(struct tty_struct *tty)
{
    struct slcan *sl;
    int err;

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

    if (tty->ops->write == NULL)
        return -EOPNOTSUPP;

    /* RTnetlink lock is misused here to serialize concurrent
       opens of slcan channels. There are better ways, but it is
       the simplest one.
     */
    rtnl_lock();

    /* Collect hanged up channels. */
    slc_sync();

    sl = tty->disc_data;

    err = -EEXIST;
    /* First make sure we're not already connected. */
    if (sl && sl->magic == SLCAN_MAGIC)
        goto err_exit;

    /* OK.  Find a free SLCAN channel to use. */
    err = -ENFILE;
    sl = slc_alloc(tty_devnum(tty));
    if (sl == NULL)
        goto err_exit;

    sl->tty = tty;
    tty->disc_data = sl;

    if (!test_bit(SLF_INUSE, &sl->flags)) {
        /* Perform the low-level SLCAN initialization. */
        sl->rcount   = 0;
        sl->xleft    = 0;

        set_bit(SLF_INUSE, &sl->flags);

        err = register_netdevice(sl->dev);
        if (err)
            goto err_free_chan;
    }

    /* Done.  We have linked the TTY line to a channel. */
    rtnl_unlock();
    tty->receive_room = 65536;  /* We don't flow control */

    /* TTY layer expects 0 on success */
    return 0;

err_free_chan:
    sl->tty = NULL;
    tty->disc_data = NULL;
    clear_bit(SLF_INUSE, &sl->flags);

err_exit:
    rtnl_unlock();

    /* Count references from TTY module */
    return err;
}

/*
 * Close down a SLCAN channel.
 * This means flushing out any pending queues, and then returning. This
 * call is serialized against other ldisc functions.
 *
 * We also use this method for a hangup event.
 */

static void slcan_close(struct tty_struct *tty)
{
    struct slcan *sl = (struct slcan *) tty->disc_data;

    /* First make sure we're connected. */
    if (!sl || sl->magic != SLCAN_MAGIC || sl->tty != tty)
        return;

    tty->disc_data = NULL;
    sl->tty = NULL;

    /* Flush network side */
    unregister_netdev(sl->dev);
    /* This will complete via sl_free_netdev */
}

static int slcan_hangup(struct tty_struct *tty)
{
    slcan_close(tty);
    return 0;
}

/* Perform I/O control on an active SLCAN channel. */
static int slcan_ioctl(struct tty_struct *tty, struct file *file,
               unsigned int cmd, unsigned long arg)
{
    struct slcan *sl = (struct slcan *) tty->disc_data;
    unsigned int tmp;

    /* First make sure we're connected. */
    if (!sl || sl->magic != SLCAN_MAGIC)
        return -EINVAL;

    switch (cmd) {
    case SIOCGIFNAME:
        tmp = strlen(sl->dev->name) + 1;
        if (copy_to_user((void __user *)arg, sl->dev->name, tmp))
            return -EFAULT;
        return 0;

    case SIOCSIFHWADDR:
        return -EINVAL;

    default:
        return tty_mode_ioctl(tty, file, cmd, arg);
    }
}

static struct tty_ldisc_ops slc_ldisc = {
    .owner      = THIS_MODULE,
    .magic      = TTY_LDISC_MAGIC,
    .name       = "slcan",
    .open       = slcan_open,
    .close      = slcan_close,
    .hangup     = slcan_hangup,
    .ioctl      = slcan_ioctl,
    .receive_buf    = slcan_receive_buf,
    .write_wakeup   = slcan_write_wakeup,
};

static int __init slcan_init(void)
{
    int status;

    if (maxdev < 4)
        maxdev = 4; /* Sanity */

    printk(banner);
    printk(KERN_INFO "slcan: %d dynamic interface channels.\n", maxdev);

    slcan_devs = kzalloc(sizeof(struct net_device *)*maxdev, GFP_KERNEL);
    if (!slcan_devs)
        return -ENOMEM;

    /* Fill in our line protocol discipline, and register it */
    status = tty_register_ldisc(N_SLCAN, &slc_ldisc);
    if (status)  {
        printk(KERN_ERR "slcan: can't register line discipline\n");
        kfree(slcan_devs);
    }
    return status;
}

static void __exit slcan_exit(void)
{
    int i;
    struct net_device *dev;
    struct slcan *sl;
    unsigned long timeout = jiffies + HZ;
    int busy = 0;

    if (slcan_devs == NULL)
        return;

    /* First of all: check for active disciplines and hangup them.
     */
    do {
        if (busy)
            msleep_interruptible(100);

        busy = 0;
        for (i = 0; i < maxdev; i++) {
            dev = slcan_devs[i];
            if (!dev)
                continue;
            sl = netdev_priv(dev);
            spin_lock_bh(&sl->lock);
            if (sl->tty) {
                busy++;
                tty_hangup(sl->tty);
            }
            spin_unlock_bh(&sl->lock);
        }
    } while (busy && time_before(jiffies, timeout));

    /* FIXME: hangup is async so we should wait when doing this second
       phase */

    for (i = 0; i < maxdev; i++) {
        dev = slcan_devs[i];
        if (!dev)
            continue;
        slcan_devs[i] = NULL;

        sl = netdev_priv(dev);
        if (sl->tty) {
            printk(KERN_ERR "%s: tty discipline still running\n",
                   dev->name);
            /* Intentionally leak the control block. */
            dev->destructor = NULL;
        }

        unregister_netdev(dev);
    }

    kfree(slcan_devs);
    slcan_devs = NULL;

    i = tty_unregister_ldisc(N_SLCAN);
    if (i)
        printk(KERN_ERR "slcan: can't unregister ldisc (err %d)\n", i);
}

module_init(slcan_init);
module_exit(slcan_exit);