--- /dev/null
+/*
+ * sllin.c - serial line LIN interface driver (using tty line discipline)
+ *
+ * This file is derived from linux/drivers/net/slip.c
+ *
+ * slip.c Authors : Laurence Culhane <loz@holmes.demon.co.uk>
+ * Fred N. van Kempen <waltje@uwalt.nl.mugnet.org>
+ * sllin.c Author : Oliver Hartkopp <socketcan@hartkopp.net>
+ *
+ * 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.
+ *
+ * Send feedback to <socketcan-users@lists.berlios.de>
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+
+#include <asm/system.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/can.h>
+
+/* Should be in include/linux/tty.h */
+#define N_SLLIN 25
+
+static __initdata const char banner[] =
+ KERN_INFO "sllin: serial line LIN interface driver\n";
+
+MODULE_ALIAS_LDISC(N_SLLIN);
+MODULE_DESCRIPTION("serial line LIN interface");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Oliver Hartkopp <socketcan@hartkopp.net>");
+
+#define SLLIN_MAGIC 0x53CA
+
+static int maxdev = 10; /* MAX number of SLLIN channels;
+ This can be overridden with
+ insmod sllin.ko maxdev=nnn */
+module_param(maxdev, int, 0);
+MODULE_PARM_DESC(maxdev, "Maximum number of sllin interfaces");
+
+/* maximum rx buffer len: extended CAN frame with timestamp */
+#define SLC_MTU (sizeof("T1111222281122334455667788EA5F\r")+1)
+
+struct sllin {
+ 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 */
+
+ unsigned char leased;
+ dev_t line;
+ pid_t pid;
+};
+
+static struct net_device **sllin_devs;
+
+
+static int sltty_change_speed(struct tty_struct *tty, unsigned speed)
+{
+ struct ktermios old_termios;
+ int cflag;
+
+ 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;
+}
+
+
+/* Send one completely decapsulated can_frame to the network layer */
+static void sll_bump(struct sllin *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 = asc2nibble(sl->rbuff[dlc_pos++]);
+// if (tmp > 0x0F)
+// return;
+// cf.data[i] = (tmp << 4);
+// tmp = asc2nibble(sl->rbuff[dlc_pos++]);
+// if (tmp > 0x0F)
+// 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(skb);
+//
+// sl->dev->stats.rx_packets++;
+// sl->dev->stats.rx_bytes += cf.can_dlc;
+}
+
+/* parse tty input stream */
+static void sllin_unesc(struct sllin *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)) {
+ sll_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 SLLIN ENCAPSULATION *
+ ************************************************************************/
+
+/* Convert particular CAN frame into LIN frame and send it to TTY queue. */
+static void sll_encaps(struct sllin *sl, struct can_frame *cf)
+{
+ int actual, idx, i;
+ char lframe[16] = {0x00, 0x55}; /* Fake break, Sync byte */
+ struct tty_struct *tty = sl->tty;
+
+ pr_debug("sllin: %s() invoked\n", __FUNCTION__);
+
+ /* We do care only about SFF frames */
+ if (cf->can_id & CAN_EFF_FLAG)
+ return;
+
+ /* Send only header */
+ if (cf->can_id & CAN_RTR_FLAG) {
+ pr_debug("sllin: RTR CAN frame\n", __FUNCTION__);
+ lframe[2] = (u8)cf->can_id; /* Get one byte LIN ID */
+
+ sltty_change_speed(tty, 1200);
+ tty->ops->write(tty, &lframe[0], 1);
+ sltty_change_speed(tty, 2400);
+ tty->ops->write(tty, &lframe[1], 1);
+ tty->ops->write(tty, &lframe[2], 1);
+ } else {
+ pr_debug("sllin: non-RTR CAN frame\n", __FUNCTION__);
+ /* idx = strlen(sl->xbuff);
+
+ for (i = 0; i < cf->can_dlc; i++)
+ sprintf(&sl->xbuff[idx + 2*i], "%02X", cf->data[i]);
+
+ * 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 sllin_write_wakeup(struct tty_struct *tty)
+{
+ int actual;
+ struct sllin *sl = (struct sllin *) tty->disc_data;
+
+ /* First make sure we're connected. */
+ if (!sl || sl->magic != SLLIN_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 sll_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+ struct sllin *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);
+ sll_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 sll_close(struct net_device *dev)
+{
+ struct sllin *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 sll_open(struct net_device *dev)
+{
+ struct sllin *sl = netdev_priv(dev);
+
+ pr_debug("sllin: %s() invoked\n", __FUNCTION__);
+
+ if (sl->tty == NULL)
+ return -ENODEV;
+
+ sl->flags &= (1 << SLF_INUSE);
+ netif_start_queue(dev);
+ return 0;
+}
+
+/* Hook the destructor so we can free sllin devs at the right point in time */
+static void sll_free_netdev(struct net_device *dev)
+{
+ int i = dev->base_addr;
+ free_netdev(dev);
+ sllin_devs[i] = NULL;
+}
+
+static const struct net_device_ops sll_netdev_ops = {
+ .ndo_open = sll_open,
+ .ndo_stop = sll_close,
+ .ndo_start_xmit = sll_xmit,
+};
+
+static void sll_setup(struct net_device *dev)
+{
+ dev->netdev_ops = &sll_netdev_ops;
+ dev->destructor = sll_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_NO_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 SLLIN 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 sllin_receive_buf(struct tty_struct *tty,
+ const unsigned char *cp, char *fp, int count)
+{
+ struct sllin *sl = (struct sllin *) tty->disc_data;
+
+ if (!sl || sl->magic != SLLIN_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;
+ }
+ sllin_unesc(sl, *cp++);
+ }
+}
+
+/************************************
+ * sllin_open helper routines.
+ ************************************/
+
+/* Collect hanged up channels */
+static void sll_sync(void)
+{
+ int i;
+ struct net_device *dev;
+ struct sllin *sl;
+
+ for (i = 0; i < maxdev; i++) {
+ dev = sllin_devs[i];
+ if (dev == NULL)
+ break;
+
+ sl = netdev_priv(dev);
+ if (sl->tty || sl->leased)
+ continue;
+ if (dev->flags & IFF_UP)
+ dev_close(dev);
+ }
+}
+
+/* Find a free SLLIN channel, and link in this `tty' line. */
+static struct sllin *sll_alloc(dev_t line)
+{
+ int i;
+ struct net_device *dev = NULL;
+ struct sllin *sl;
+
+ if (sllin_devs == NULL)
+ return NULL; /* Master array missing ! */
+
+ for (i = 0; i < maxdev; i++) {
+ dev = sllin_devs[i];
+ if (dev == NULL)
+ break;
+
+ }
+
+ /* Sorry, too many, all slots in use */
+ if (i >= maxdev)
+ return NULL;
+
+ if (dev) {
+ sl = netdev_priv(dev);
+ if (test_bit(SLF_INUSE, &sl->flags)) {
+ unregister_netdevice(dev);
+ dev = NULL;
+ sllin_devs[i] = NULL;
+ }
+ }
+
+ if (!dev) {
+ char name[IFNAMSIZ];
+ sprintf(name, "sllin%d", i);
+
+ dev = alloc_netdev(sizeof(*sl), name, sll_setup);
+ if (!dev)
+ return NULL;
+ dev->base_addr = i;
+ }
+
+ sl = netdev_priv(dev);
+
+ /* Initialize channel control data */
+ sl->magic = SLLIN_MAGIC;
+ sl->dev = dev;
+ spin_lock_init(&sl->lock);
+ sllin_devs[i] = dev;
+
+ return sl;
+}
+
+/*
+ * Open the high-level part of the SLLIN channel.
+ * This function is called by the TTY module when the
+ * SLLIN line discipline is called for. Because we are
+ * sure the tty line exists, we only have to link it to
+ * a free SLLIN channel...
+ *
+ * Called in process context serialized from other ldisc calls.
+ */
+
+static int sllin_open(struct tty_struct *tty)
+{
+ struct sllin *sl;
+ int err;
+ pr_debug("sllin: %s() invoked\n", __FUNCTION__);
+
+ if (!capable(CAP_NET_ADMIN))
+ return -EPERM;
+
+ if (tty->ops->write == NULL)
+ return -EOPNOTSUPP;
+
+ /* RTnetlink lock is misused here to serialize concurrent
+ opens of sllin channels. There are better ways, but it is
+ the simplest one.
+ */
+ rtnl_lock();
+
+ /* Collect hanged up channels. */
+ sll_sync();
+
+ sl = tty->disc_data;
+
+ err = -EEXIST;
+ /* First make sure we're not already connected. */
+ if (sl && sl->magic == SLLIN_MAGIC)
+ goto err_exit;
+
+ /* OK. Find a free SLLIN channel to use. */
+ err = -ENFILE;
+ sl = sll_alloc(tty_devnum(tty));
+ if (sl == NULL)
+ goto err_exit;
+
+ sl->tty = tty;
+ tty->disc_data = sl;
+ sl->line = tty_devnum(tty);
+ sl->pid = current->pid;
+
+ if (!test_bit(SLF_INUSE, &sl->flags)) {
+ /* Perform the low-level SLLIN 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 SLLIN 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 sllin_close(struct tty_struct *tty)
+{
+ struct sllin *sl = (struct sllin *) tty->disc_data;
+
+ /* First make sure we're connected. */
+ if (!sl || sl->magic != SLLIN_MAGIC || sl->tty != tty)
+ return;
+
+ tty->disc_data = NULL;
+ sl->tty = NULL;
+ if (!sl->leased)
+ sl->line = 0;
+
+ /* Flush network side */
+ unregister_netdev(sl->dev);
+ /* This will complete via sl_free_netdev */
+}
+
+static int sllin_hangup(struct tty_struct *tty)
+{
+ sllin_close(tty);
+ return 0;
+}
+
+/* Perform I/O control on an active SLLIN channel. */
+static int sllin_ioctl(struct tty_struct *tty, struct file *file,
+ unsigned int cmd, unsigned long arg)
+{
+ struct sllin *sl = (struct sllin *) tty->disc_data;
+ unsigned int tmp;
+
+ /* First make sure we're connected. */
+ if (!sl || sl->magic != SLLIN_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 sll_ldisc = {
+ .owner = THIS_MODULE,
+ .magic = TTY_LDISC_MAGIC,
+ .name = "sllin",
+ .open = sllin_open,
+ .close = sllin_close,
+ .hangup = sllin_hangup,
+ .ioctl = sllin_ioctl,
+ .receive_buf = sllin_receive_buf,
+ .write_wakeup = sllin_write_wakeup,
+};
+
+static int __init sllin_init(void)
+{
+ int status;
+
+ if (maxdev < 4)
+ maxdev = 4; /* Sanity */
+
+ printk(banner);
+ printk(KERN_INFO "sllin: %d dynamic interface channels.\n", maxdev);
+
+ sllin_devs = kzalloc(sizeof(struct net_device *)*maxdev, GFP_KERNEL);
+ if (!sllin_devs) {
+ printk(KERN_ERR "sllin: can't allocate sllin device array!\n");
+ return -ENOMEM;
+ }
+
+ /* Fill in our line protocol discipline, and register it */
+ status = tty_register_ldisc(N_SLLIN, &sll_ldisc);
+ if (status) {
+ printk(KERN_ERR "sllin: can't register line discipline\n");
+ kfree(sllin_devs);
+ }
+ return status;
+}
+
+static void __exit sllin_exit(void)
+{
+ int i;
+ struct net_device *dev;
+ struct sllin *sl;
+ unsigned long timeout = jiffies + HZ;
+ int busy = 0;
+
+ if (sllin_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 = sllin_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 = sllin_devs[i];
+ if (!dev)
+ continue;
+ sllin_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(sllin_devs);
+ sllin_devs = NULL;
+
+ i = tty_unregister_ldisc(N_SLLIN);
+ if (i)
+ printk(KERN_ERR "sllin: can't unregister ldisc (err %d)\n", i);
+}
+
+module_init(sllin_init);
+module_exit(sllin_exit);
projects / linux-lin.git / commitdiff