bcm.c

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/*
 * bcm.c - Broadcast Manager to filter/send (cyclic) CAN content
 *
 * Copyright (c) 2002-2007 Volkswagen Group Electronic Research
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of Volkswagen nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * Alternatively, provided that this notice is retained in full, this
 * software may be distributed under the terms of the GNU General
 * Public License ("GPL") version 2, in which case the provisions of the
 * GPL apply INSTEAD OF those given above.
 *
 * The provided data structures and external interfaces from this code
 * are not restricted to be used by modules with a GPL compatible license.
 *
 * 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/init.h>
#include <linux/interrupt.h>
#include <linux/hrtimer.h>
#include <linux/list.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/uio.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/socket.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <linux/can.h>
#include <linux/can/core.h>
#include <linux/can/bcm.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <net/net_namespace.h>

/*
 * To send multiple CAN frame content within TX_SETUP or to filter
 * CAN messages with multiplex index within RX_SETUP, the number of
 * different filters is limited to 256 due to the one byte index value.
 */
#define MAX_NFRAMES 256

/* use of last_frames[index].can_dlc */
#define RX_RECV    0x40 /* received data for this element */
#define RX_THR     0x80 /* element not been sent due to throttle feature */
#define BCM_CAN_DLC_MASK 0x0F /* clean private flags in can_dlc by masking */

/* get best masking value for can_rx_register() for a given single can_id */
#define REGMASK(id) ((id & CAN_EFF_FLAG) ? \
             (CAN_EFF_MASK | CAN_EFF_FLAG | CAN_RTR_FLAG) : \
             (CAN_SFF_MASK | CAN_EFF_FLAG | CAN_RTR_FLAG))

#define CAN_BCM_VERSION CAN_VERSION
static __initconst const char banner[] = KERN_INFO
    "can: broadcast manager protocol (rev " CAN_BCM_VERSION " t)\n";

MODULE_DESCRIPTION("PF_CAN broadcast manager protocol");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Oliver Hartkopp <[email protected]>");
MODULE_ALIAS("can-proto-2");

/* easy access to can_frame payload */
static inline u64 GET_U64(const struct can_frame *cp)
{
    return *(u64 *)cp->data;
}

struct bcm_op {
    struct list_head list;
    int ifindex;
    canid_t can_id;
    u32 flags;
    unsigned long frames_abs, frames_filtered;
    struct timeval ival1, ival2;
    struct hrtimer timer, thrtimer;
    struct tasklet_struct tsklet, thrtsklet;
    ktime_t rx_stamp, kt_ival1, kt_ival2, kt_lastmsg;
    int rx_ifindex;
    u32 count;
    u32 nframes;
    u32 currframe;
    struct can_frame *frames;
    struct can_frame *last_frames;
    struct can_frame sframe;
    struct can_frame last_sframe;
    struct sock *sk;
    struct net_device *rx_reg_dev;
};

static struct proc_dir_entry *proc_dir;

struct bcm_sock {
    struct sock sk;
    int bound;
    int ifindex;
    struct notifier_block notifier;
    struct list_head rx_ops;
    struct list_head tx_ops;
    unsigned long dropped_usr_msgs;
    struct proc_dir_entry *bcm_proc_read;
    char procname [32]; /* inode number in decimal with \0 */
};

static inline struct bcm_sock *bcm_sk(const struct sock *sk)
{
    return (struct bcm_sock *)sk;
}

#define CFSIZ sizeof(struct can_frame)
#define OPSIZ sizeof(struct bcm_op)
#define MHSIZ sizeof(struct bcm_msg_head)

/*
 * procfs functions
 */
static char *bcm_proc_getifname(char *result, int ifindex)
{
    struct net_device *dev;

    if (!ifindex)
        return "any";

    rcu_read_lock();
    dev = dev_get_by_index_rcu(&init_net, ifindex);
    if (dev)
        strcpy(result, dev->name);
    else
        strcpy(result, "???");
    rcu_read_unlock();

    return result;
}

static int bcm_proc_show(struct seq_file *m, void *v)
{
    char ifname[IFNAMSIZ];
    struct sock *sk = (struct sock *)m->private;
    struct bcm_sock *bo = bcm_sk(sk);
    struct bcm_op *op;

    seq_printf(m, ">>> socket %pK", sk->sk_socket);
    seq_printf(m, " / sk %pK", sk);
    seq_printf(m, " / bo %pK", bo);
    seq_printf(m, " / dropped %lu", bo->dropped_usr_msgs);
    seq_printf(m, " / bound %s", bcm_proc_getifname(ifname, bo->ifindex));
    seq_printf(m, " <<<\n");

    list_for_each_entry(op, &bo->rx_ops, list) {

        unsigned long reduction;

        /* print only active entries & prevent division by zero */
        if (!op->frames_abs)
            continue;

        seq_printf(m, "rx_op: %03X %-5s ",
                op->can_id, bcm_proc_getifname(ifname, op->ifindex));
        seq_printf(m, "[%u]%c ", op->nframes,
                (op->flags & RX_CHECK_DLC)?'d':' ');
        if (op->kt_ival1.tv64)
            seq_printf(m, "timeo=%lld ",
                    (long long)
                    ktime_to_us(op->kt_ival1));

        if (op->kt_ival2.tv64)
            seq_printf(m, "thr=%lld ",
                    (long long)
                    ktime_to_us(op->kt_ival2));

        seq_printf(m, "# recv %ld (%ld) => reduction: ",
                op->frames_filtered, op->frames_abs);

        reduction = 100 - (op->frames_filtered * 100) / op->frames_abs;

        seq_printf(m, "%s%ld%%\n",
                (reduction == 100)?"near ":"", reduction);
    }

    list_for_each_entry(op, &bo->tx_ops, list) {

        seq_printf(m, "tx_op: %03X %s [%u] ",
                op->can_id,
                bcm_proc_getifname(ifname, op->ifindex),
                op->nframes);

        if (op->kt_ival1.tv64)
            seq_printf(m, "t1=%lld ",
                    (long long) ktime_to_us(op->kt_ival1));

        if (op->kt_ival2.tv64)
            seq_printf(m, "t2=%lld ",
                    (long long) ktime_to_us(op->kt_ival2));

        seq_printf(m, "# sent %ld\n", op->frames_abs);
    }
    seq_putc(m, '\n');
    return 0;
}

static int bcm_proc_open(struct inode *inode, struct file *file)
{
    return single_open(file, bcm_proc_show, PDE(inode)->data);
}

static const struct file_operations bcm_proc_fops = {
    .owner      = THIS_MODULE,
    .open       = bcm_proc_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = single_release,
};

/*
 * bcm_can_tx - send the (next) CAN frame to the appropriate CAN interface
 *              of the given bcm tx op
 */
static void bcm_can_tx(struct bcm_op *op)
{
    struct sk_buff *skb;
    struct net_device *dev;
    struct can_frame *cf = &op->frames[op->currframe];

    /* no target device? => exit */
    if (!op->ifindex)
        return;

    dev = dev_get_by_index(&init_net, op->ifindex);
    if (!dev) {
        /* RFC: should this bcm_op remove itself here? */
        return;
    }

    skb = alloc_skb(CFSIZ, gfp_any());
    if (!skb)
        goto out;

    memcpy(skb_put(skb, CFSIZ), cf, CFSIZ);

    /* send with loopback */
    skb->dev = dev;
    skb->sk = op->sk;
    can_send(skb, 1);

    /* update statistics */
    op->currframe++;
    op->frames_abs++;

    /* reached last frame? */
    if (op->currframe >= op->nframes)
        op->currframe = 0;
 out:
    dev_put(dev);
}

/*
 * bcm_send_to_user - send a BCM message to the userspace
 *                    (consisting of bcm_msg_head + x CAN frames)
 */
static void bcm_send_to_user(struct bcm_op *op, struct bcm_msg_head *head,
                 struct can_frame *frames, int has_timestamp)
{
    struct sk_buff *skb;
    struct can_frame *firstframe;
    struct sockaddr_can *addr;
    struct sock *sk = op->sk;
    unsigned int datalen = head->nframes * CFSIZ;
    int err;

    skb = alloc_skb(sizeof(*head) + datalen, gfp_any());
    if (!skb)
        return;

    memcpy(skb_put(skb, sizeof(*head)), head, sizeof(*head));

    if (head->nframes) {
        /* can_frames starting here */
        firstframe = (struct can_frame *)skb_tail_pointer(skb);

        memcpy(skb_put(skb, datalen), frames, datalen);

        /*
         * the BCM uses the can_dlc-element of the can_frame
         * structure for internal purposes. This is only
         * relevant for updates that are generated by the
         * BCM, where nframes is 1
         */
        if (head->nframes == 1)
            firstframe->can_dlc &= BCM_CAN_DLC_MASK;
    }

    if (has_timestamp) {
        /* restore rx timestamp */
        skb->tstamp = op->rx_stamp;
    }

    /*
     *  Put the datagram to the queue so that bcm_recvmsg() can
     *  get it from there.  We need to pass the interface index to
     *  bcm_recvmsg().  We pass a whole struct sockaddr_can in skb->cb
     *  containing the interface index.
     */

    BUILD_BUG_ON(sizeof(skb->cb) < sizeof(struct sockaddr_can));
    addr = (struct sockaddr_can *)skb->cb;
    memset(addr, 0, sizeof(*addr));
    addr->can_family  = AF_CAN;
    addr->can_ifindex = op->rx_ifindex;

    err = sock_queue_rcv_skb(sk, skb);
    if (err < 0) {
        struct bcm_sock *bo = bcm_sk(sk);

        kfree_skb(skb);
        /* don't care about overflows in this statistic */
        bo->dropped_usr_msgs++;
    }
}

static void bcm_tx_start_timer(struct bcm_op *op)
{
    if (op->kt_ival1.tv64 && op->count)
        hrtimer_start(&op->timer,
                  ktime_add(ktime_get(), op->kt_ival1),
                  HRTIMER_MODE_ABS);
    else if (op->kt_ival2.tv64)
        hrtimer_start(&op->timer,
                  ktime_add(ktime_get(), op->kt_ival2),
                  HRTIMER_MODE_ABS);
}

static void bcm_tx_timeout_tsklet(unsigned long data)
{
    struct bcm_op *op = (struct bcm_op *)data;
    struct bcm_msg_head msg_head;

    if (op->kt_ival1.tv64 && (op->count > 0)) {

        op->count--;
        if (!op->count && (op->flags & TX_COUNTEVT)) {

            /* create notification to user */
            msg_head.opcode  = TX_EXPIRED;
            msg_head.flags   = op->flags;
            msg_head.count   = op->count;
            msg_head.ival1   = op->ival1;
            msg_head.ival2   = op->ival2;
            msg_head.can_id  = op->can_id;
            msg_head.nframes = 0;

            bcm_send_to_user(op, &msg_head, NULL, 0);
        }
        bcm_can_tx(op);

    } else if (op->kt_ival2.tv64)
        bcm_can_tx(op);

    bcm_tx_start_timer(op);
}

/*
 * bcm_tx_timeout_handler - performs cyclic CAN frame transmissions
 */
static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
{
    struct bcm_op *op = container_of(hrtimer, struct bcm_op, timer);

    tasklet_schedule(&op->tsklet);

    return HRTIMER_NORESTART;
}

/*
 * bcm_rx_changed - create a RX_CHANGED notification due to changed content
 */
static void bcm_rx_changed(struct bcm_op *op, struct can_frame *data)
{
    struct bcm_msg_head head;

    /* update statistics */
    op->frames_filtered++;

    /* prevent statistics overflow */
    if (op->frames_filtered > ULONG_MAX/100)
        op->frames_filtered = op->frames_abs = 0;

    /* this element is not throttled anymore */
    data->can_dlc &= (BCM_CAN_DLC_MASK|RX_RECV);

    head.opcode  = RX_CHANGED;
    head.flags   = op->flags;
    head.count   = op->count;
    head.ival1   = op->ival1;
    head.ival2   = op->ival2;
    head.can_id  = op->can_id;
    head.nframes = 1;

    bcm_send_to_user(op, &head, data, 1);
}

/*
 * bcm_rx_update_and_send - process a detected relevant receive content change
 *                          1. update the last received data
 *                          2. send a notification to the user (if possible)
 */
static void bcm_rx_update_and_send(struct bcm_op *op,
                   struct can_frame *lastdata,
                   const struct can_frame *rxdata)
{
    memcpy(lastdata, rxdata, CFSIZ);

    /* mark as used and throttled by default */
    lastdata->can_dlc |= (RX_RECV|RX_THR);

    /* throtteling mode inactive ? */
    if (!op->kt_ival2.tv64) {
        /* send RX_CHANGED to the user immediately */
        bcm_rx_changed(op, lastdata);
        return;
    }

    /* with active throttling timer we are just done here */
    if (hrtimer_active(&op->thrtimer))
        return;

    /* first receiption with enabled throttling mode */
    if (!op->kt_lastmsg.tv64)
        goto rx_changed_settime;

    /* got a second frame inside a potential throttle period? */
    if (ktime_us_delta(ktime_get(), op->kt_lastmsg) <
        ktime_to_us(op->kt_ival2)) {
        /* do not send the saved data - only start throttle timer */
        hrtimer_start(&op->thrtimer,
                  ktime_add(op->kt_lastmsg, op->kt_ival2),
                  HRTIMER_MODE_ABS);
        return;
    }

    /* the gap was that big, that throttling was not needed here */
rx_changed_settime:
    bcm_rx_changed(op, lastdata);
    op->kt_lastmsg = ktime_get();
}

/*
 * bcm_rx_cmp_to_index - (bit)compares the currently received data to formerly
 *                       received data stored in op->last_frames[]
 */
static void bcm_rx_cmp_to_index(struct bcm_op *op, unsigned int index,
                const struct can_frame *rxdata)
{
    /*
     * no one uses the MSBs of can_dlc for comparation,
     * so we use it here to detect the first time of reception
     */

    if (!(op->last_frames[index].can_dlc & RX_RECV)) {
        /* received data for the first time => send update to user */
        bcm_rx_update_and_send(op, &op->last_frames[index], rxdata);
        return;
    }

    /* do a real check in can_frame data section */

    if ((GET_U64(&op->frames[index]) & GET_U64(rxdata)) !=
        (GET_U64(&op->frames[index]) & GET_U64(&op->last_frames[index]))) {
        bcm_rx_update_and_send(op, &op->last_frames[index], rxdata);
        return;
    }

    if (op->flags & RX_CHECK_DLC) {
        /* do a real check in can_frame dlc */
        if (rxdata->can_dlc != (op->last_frames[index].can_dlc &
                    BCM_CAN_DLC_MASK)) {
            bcm_rx_update_and_send(op, &op->last_frames[index],
                           rxdata);
            return;
        }
    }
}

/*
 * bcm_rx_starttimer - enable timeout monitoring for CAN frame receiption
 */
static void bcm_rx_starttimer(struct bcm_op *op)
{
    if (op->flags & RX_NO_AUTOTIMER)
        return;

    if (op->kt_ival1.tv64)
        hrtimer_start(&op->timer, op->kt_ival1, HRTIMER_MODE_REL);
}

static void bcm_rx_timeout_tsklet(unsigned long data)
{
    struct bcm_op *op = (struct bcm_op *)data;
    struct bcm_msg_head msg_head;

    /* create notification to user */
    msg_head.opcode  = RX_TIMEOUT;
    msg_head.flags   = op->flags;
    msg_head.count   = op->count;
    msg_head.ival1   = op->ival1;
    msg_head.ival2   = op->ival2;
    msg_head.can_id  = op->can_id;
    msg_head.nframes = 0;

    bcm_send_to_user(op, &msg_head, NULL, 0);
}

/*
 * bcm_rx_timeout_handler - when the (cyclic) CAN frame receiption timed out
 */
static enum hrtimer_restart bcm_rx_timeout_handler(struct hrtimer *hrtimer)
{
    struct bcm_op *op = container_of(hrtimer, struct bcm_op, timer);

    /* schedule before NET_RX_SOFTIRQ */
    tasklet_hi_schedule(&op->tsklet);

    /* no restart of the timer is done here! */

    /* if user wants to be informed, when cyclic CAN-Messages come back */
    if ((op->flags & RX_ANNOUNCE_RESUME) && op->last_frames) {
        /* clear received can_frames to indicate 'nothing received' */
        memset(op->last_frames, 0, op->nframes * CFSIZ);
    }

    return HRTIMER_NORESTART;
}

/*
 * bcm_rx_do_flush - helper for bcm_rx_thr_flush
 */
static inline int bcm_rx_do_flush(struct bcm_op *op, int update,
                  unsigned int index)
{
    if ((op->last_frames) && (op->last_frames[index].can_dlc & RX_THR)) {
        if (update)
            bcm_rx_changed(op, &op->last_frames[index]);
        return 1;
    }
    return 0;
}

/*
 * bcm_rx_thr_flush - Check for throttled data and send it to the userspace
 *
 * update == 0 : just check if throttled data is available  (any irq context)
 * update == 1 : check and send throttled data to userspace (soft_irq context)
 */
static int bcm_rx_thr_flush(struct bcm_op *op, int update)
{
    int updated = 0;

    if (op->nframes > 1) {
        unsigned int i;

        /* for MUX filter we start at index 1 */
        for (i = 1; i < op->nframes; i++)
            updated += bcm_rx_do_flush(op, update, i);

    } else {
        /* for RX_FILTER_ID and simple filter */
        updated += bcm_rx_do_flush(op, update, 0);
    }

    return updated;
}

static void bcm_rx_thr_tsklet(unsigned long data)
{
    struct bcm_op *op = (struct bcm_op *)data;

    /* push the changed data to the userspace */
    bcm_rx_thr_flush(op, 1);
}

/*
 * bcm_rx_thr_handler - the time for blocked content updates is over now:
 *                      Check for throttled data and send it to the userspace
 */
static enum hrtimer_restart bcm_rx_thr_handler(struct hrtimer *hrtimer)
{
    struct bcm_op *op = container_of(hrtimer, struct bcm_op, thrtimer);

    tasklet_schedule(&op->thrtsklet);

    if (bcm_rx_thr_flush(op, 0)) {
        hrtimer_forward(hrtimer, ktime_get(), op->kt_ival2);
        return HRTIMER_RESTART;
    } else {
        /* rearm throttle handling */
        op->kt_lastmsg = ktime_set(0, 0);
        return HRTIMER_NORESTART;
    }
}

/*
 * bcm_rx_handler - handle a CAN frame receiption
 */
static void bcm_rx_handler(struct sk_buff *skb, void *data)
{
    struct bcm_op *op = (struct bcm_op *)data;
    const struct can_frame *rxframe = (struct can_frame *)skb->data;
    unsigned int i;

    /* disable timeout */
    hrtimer_cancel(&op->timer);

    if (op->can_id != rxframe->can_id)
        return;

    /* save rx timestamp */
    op->rx_stamp = skb->tstamp;
    /* save originator for recvfrom() */
    op->rx_ifindex = skb->dev->ifindex;
    /* update statistics */
    op->frames_abs++;

    if (op->flags & RX_RTR_FRAME) {
        /* send reply for RTR-request (placed in op->frames[0]) */
        bcm_can_tx(op);
        return;
    }

    if (op->flags & RX_FILTER_ID) {
        /* the easiest case */
        bcm_rx_update_and_send(op, &op->last_frames[0], rxframe);
        goto rx_starttimer;
    }

    if (op->nframes == 1) {
        /* simple compare with index 0 */
        bcm_rx_cmp_to_index(op, 0, rxframe);
        goto rx_starttimer;
    }

    if (op->nframes > 1) {
        /*
         * multiplex compare
         *
         * find the first multiplex mask that fits.
         * Remark: The MUX-mask is stored in index 0
         */

        for (i = 1; i < op->nframes; i++) {
            if ((GET_U64(&op->frames[0]) & GET_U64(rxframe)) ==
                (GET_U64(&op->frames[0]) &
                 GET_U64(&op->frames[i]))) {
                bcm_rx_cmp_to_index(op, i, rxframe);
                break;
            }
        }
    }

rx_starttimer:
    bcm_rx_starttimer(op);
}

/*
 * helpers for bcm_op handling: find & delete bcm [rx|tx] op elements
 */
static struct bcm_op *bcm_find_op(struct list_head *ops, canid_t can_id,
                  int ifindex)
{
    struct bcm_op *op;

    list_for_each_entry(op, ops, list) {
        if ((op->can_id == can_id) && (op->ifindex == ifindex))
            return op;
    }

    return NULL;
}

static void bcm_remove_op(struct bcm_op *op)
{
    hrtimer_cancel(&op->timer);
    hrtimer_cancel(&op->thrtimer);

    if (op->tsklet.func)
        tasklet_kill(&op->tsklet);

    if (op->thrtsklet.func)
        tasklet_kill(&op->thrtsklet);

    if ((op->frames) && (op->frames != &op->sframe))
        kfree(op->frames);

    if ((op->last_frames) && (op->last_frames != &op->last_sframe))
        kfree(op->last_frames);

    kfree(op);
}

static void bcm_rx_unreg(struct net_device *dev, struct bcm_op *op)
{
    if (op->rx_reg_dev == dev) {
        can_rx_unregister(dev, op->can_id, REGMASK(op->can_id),
                  bcm_rx_handler, op);

        /* mark as removed subscription */
        op->rx_reg_dev = NULL;
    } else
        printk(KERN_ERR "can-bcm: bcm_rx_unreg: registered device "
               "mismatch %p %p\n", op->rx_reg_dev, dev);
}

/*
 * bcm_delete_rx_op - find and remove a rx op (returns number of removed ops)
 */
static int bcm_delete_rx_op(struct list_head *ops, canid_t can_id, int ifindex)
{
    struct bcm_op *op, *n;

    list_for_each_entry_safe(op, n, ops, list) {
        if ((op->can_id == can_id) && (op->ifindex == ifindex)) {

            /*
             * Don't care if we're bound or not (due to netdev
             * problems) can_rx_unregister() is always a save
             * thing to do here.
             */
            if (op->ifindex) {
                /*
                 * Only remove subscriptions that had not
                 * been removed due to NETDEV_UNREGISTER
                 * in bcm_notifier()
                 */
                if (op->rx_reg_dev) {
                    struct net_device *dev;

                    dev = dev_get_by_index(&init_net,
                                   op->ifindex);
                    if (dev) {
                        bcm_rx_unreg(dev, op);
                        dev_put(dev);
                    }
                }
            } else
                can_rx_unregister(NULL, op->can_id,
                          REGMASK(op->can_id),
                          bcm_rx_handler, op);

            list_del(&op->list);
            bcm_remove_op(op);
            return 1; /* done */
        }
    }

    return 0; /* not found */
}

/*
 * bcm_delete_tx_op - find and remove a tx op (returns number of removed ops)
 */
static int bcm_delete_tx_op(struct list_head *ops, canid_t can_id, int ifindex)
{
    struct bcm_op *op, *n;

    list_for_each_entry_safe(op, n, ops, list) {
        if ((op->can_id == can_id) && (op->ifindex == ifindex)) {
            list_del(&op->list);
            bcm_remove_op(op);
            return 1; /* done */
        }
    }

    return 0; /* not found */
}

/*
 * bcm_read_op - read out a bcm_op and send it to the user (for bcm_sendmsg)
 */
static int bcm_read_op(struct list_head *ops, struct bcm_msg_head *msg_head,
               int ifindex)
{
    struct bcm_op *op = bcm_find_op(ops, msg_head->can_id, ifindex);

    if (!op)
        return -EINVAL;

    /* put current values into msg_head */
    msg_head->flags   = op->flags;
    msg_head->count   = op->count;
    msg_head->ival1   = op->ival1;
    msg_head->ival2   = op->ival2;
    msg_head->nframes = op->nframes;

    bcm_send_to_user(op, msg_head, op->frames, 0);

    return MHSIZ;
}

/*
 * bcm_tx_setup - create or update a bcm tx op (for bcm_sendmsg)
 */
static int bcm_tx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
            int ifindex, struct sock *sk)
{
    struct bcm_sock *bo = bcm_sk(sk);
    struct bcm_op *op;
    unsigned int i;
    int err;

    /* we need a real device to send frames */
    if (!ifindex)
        return -ENODEV;

    /* check nframes boundaries - we need at least one can_frame */
    if (msg_head->nframes < 1 || msg_head->nframes > MAX_NFRAMES)
        return -EINVAL;

    /* check the given can_id */
    op = bcm_find_op(&bo->tx_ops, msg_head->can_id, ifindex);

    if (op) {
        /* update existing BCM operation */

        /*
         * Do we need more space for the can_frames than currently
         * allocated? -> This is a _really_ unusual use-case and
         * therefore (complexity / locking) it is not supported.
         */
        if (msg_head->nframes > op->nframes)
            return -E2BIG;

        /* update can_frames content */
        for (i = 0; i < msg_head->nframes; i++) {
            err = memcpy_fromiovec((u8 *)&op->frames[i],
                           msg->msg_iov, CFSIZ);

            if (op->frames[i].can_dlc > 8)
                err = -EINVAL;

            if (err < 0)
                return err;

            if (msg_head->flags & TX_CP_CAN_ID) {
                /* copy can_id into frame */
                op->frames[i].can_id = msg_head->can_id;
            }
        }

    } else {
        /* insert new BCM operation for the given can_id */

        op = kzalloc(OPSIZ, GFP_KERNEL);
        if (!op)
            return -ENOMEM;

        op->can_id    = msg_head->can_id;

        /* create array for can_frames and copy the data */
        if (msg_head->nframes > 1) {
            op->frames = kmalloc(msg_head->nframes * CFSIZ,
                         GFP_KERNEL);
            if (!op->frames) {
                kfree(op);
                return -ENOMEM;
            }
        } else
            op->frames = &op->sframe;

        for (i = 0; i < msg_head->nframes; i++) {
            err = memcpy_fromiovec((u8 *)&op->frames[i],
                           msg->msg_iov, CFSIZ);

            if (op->frames[i].can_dlc > 8)
                err = -EINVAL;

            if (err < 0) {
                if (op->frames != &op->sframe)
                    kfree(op->frames);
                kfree(op);
                return err;
            }

            if (msg_head->flags & TX_CP_CAN_ID) {
                /* copy can_id into frame */
                op->frames[i].can_id = msg_head->can_id;
            }
        }

        /* tx_ops never compare with previous received messages */
        op->last_frames = NULL;

        /* bcm_can_tx / bcm_tx_timeout_handler needs this */
        op->sk = sk;
        op->ifindex = ifindex;

        /* initialize uninitialized (kzalloc) structure */
        hrtimer_init(&op->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
        op->timer.function = bcm_tx_timeout_handler;

        /* initialize tasklet for tx countevent notification */
        tasklet_init(&op->tsklet, bcm_tx_timeout_tsklet,
                 (unsigned long) op);

        /* currently unused in tx_ops */
        hrtimer_init(&op->thrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);

        /* add this bcm_op to the list of the tx_ops */
        list_add(&op->list, &bo->tx_ops);

    } /* if ((op = bcm_find_op(&bo->tx_ops, msg_head->can_id, ifindex))) */

    if (op->nframes != msg_head->nframes) {
        op->nframes   = msg_head->nframes;
        /* start multiple frame transmission with index 0 */
        op->currframe = 0;
    }

    /* check flags */

    op->flags = msg_head->flags;

    if (op->flags & TX_RESET_MULTI_IDX) {
        /* start multiple frame transmission with index 0 */
        op->currframe = 0;
    }

    if (op->flags & SETTIMER) {
        /* set timer values */
        op->count = msg_head->count;
        op->ival1 = msg_head->ival1;
        op->ival2 = msg_head->ival2;
        op->kt_ival1 = timeval_to_ktime(msg_head->ival1);
        op->kt_ival2 = timeval_to_ktime(msg_head->ival2);

        /* disable an active timer due to zero values? */
        if (!op->kt_ival1.tv64 && !op->kt_ival2.tv64)
            hrtimer_cancel(&op->timer);
    }

    if (op->flags & STARTTIMER) {
        hrtimer_cancel(&op->timer);
        /* spec: send can_frame when starting timer */
        op->flags |= TX_ANNOUNCE;
    }

    if (op->flags & TX_ANNOUNCE) {
        bcm_can_tx(op);
        if (op->count)
            op->count--;
    }

    if (op->flags & STARTTIMER)
        bcm_tx_start_timer(op);

    return msg_head->nframes * CFSIZ + MHSIZ;
}

/*
 * bcm_rx_setup - create or update a bcm rx op (for bcm_sendmsg)
 */
static int bcm_rx_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
            int ifindex, struct sock *sk)
{
    struct bcm_sock *bo = bcm_sk(sk);
    struct bcm_op *op;
    int do_rx_register;
    int err = 0;

    if ((msg_head->flags & RX_FILTER_ID) || (!(msg_head->nframes))) {
        /* be robust against wrong usage ... */
        msg_head->flags |= RX_FILTER_ID;
        /* ignore trailing garbage */
        msg_head->nframes = 0;
    }

    /* the first element contains the mux-mask => MAX_NFRAMES + 1  */
    if (msg_head->nframes > MAX_NFRAMES + 1)
        return -EINVAL;

    if ((msg_head->flags & RX_RTR_FRAME) &&
        ((msg_head->nframes != 1) ||
         (!(msg_head->can_id & CAN_RTR_FLAG))))
        return -EINVAL;

    /* check the given can_id */
    op = bcm_find_op(&bo->rx_ops, msg_head->can_id, ifindex);
    if (op) {
        /* update existing BCM operation */

        /*
         * Do we need more space for the can_frames than currently
         * allocated? -> This is a _really_ unusual use-case and
         * therefore (complexity / locking) it is not supported.
         */
        if (msg_head->nframes > op->nframes)
            return -E2BIG;

        if (msg_head->nframes) {
            /* update can_frames content */
            err = memcpy_fromiovec((u8 *)op->frames,
                           msg->msg_iov,
                           msg_head->nframes * CFSIZ);
            if (err < 0)
                return err;

            /* clear last_frames to indicate 'nothing received' */
            memset(op->last_frames, 0, msg_head->nframes * CFSIZ);
        }

        op->nframes = msg_head->nframes;

        /* Only an update -> do not call can_rx_register() */
        do_rx_register = 0;

    } else {
        /* insert new BCM operation for the given can_id */
        op = kzalloc(OPSIZ, GFP_KERNEL);
        if (!op)
            return -ENOMEM;

        op->can_id    = msg_head->can_id;
        op->nframes   = msg_head->nframes;

        if (msg_head->nframes > 1) {
            /* create array for can_frames and copy the data */
            op->frames = kmalloc(msg_head->nframes * CFSIZ,
                         GFP_KERNEL);
            if (!op->frames) {
                kfree(op);
                return -ENOMEM;
            }

            /* create and init array for received can_frames */
            op->last_frames = kzalloc(msg_head->nframes * CFSIZ,
                          GFP_KERNEL);
            if (!op->last_frames) {
                kfree(op->frames);
                kfree(op);
                return -ENOMEM;
            }

        } else {
            op->frames = &op->sframe;
            op->last_frames = &op->last_sframe;
        }

        if (msg_head->nframes) {
            err = memcpy_fromiovec((u8 *)op->frames, msg->msg_iov,
                           msg_head->nframes * CFSIZ);
            if (err < 0) {
                if (op->frames != &op->sframe)
                    kfree(op->frames);
                if (op->last_frames != &op->last_sframe)
                    kfree(op->last_frames);
                kfree(op);
                return err;
            }
        }

        /* bcm_can_tx / bcm_tx_timeout_handler needs this */
        op->sk = sk;
        op->ifindex = ifindex;

        /* ifindex for timeout events w/o previous frame reception */
        op->rx_ifindex = ifindex;

        /* initialize uninitialized (kzalloc) structure */
        hrtimer_init(&op->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
        op->timer.function = bcm_rx_timeout_handler;

        /* initialize tasklet for rx timeout notification */
        tasklet_init(&op->tsklet, bcm_rx_timeout_tsklet,
                 (unsigned long) op);

        hrtimer_init(&op->thrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
        op->thrtimer.function = bcm_rx_thr_handler;

        /* initialize tasklet for rx throttle handling */
        tasklet_init(&op->thrtsklet, bcm_rx_thr_tsklet,
                 (unsigned long) op);

        /* add this bcm_op to the list of the rx_ops */
        list_add(&op->list, &bo->rx_ops);

        /* call can_rx_register() */
        do_rx_register = 1;

    } /* if ((op = bcm_find_op(&bo->rx_ops, msg_head->can_id, ifindex))) */

    /* check flags */
    op->flags = msg_head->flags;

    if (op->flags & RX_RTR_FRAME) {

        /* no timers in RTR-mode */
        hrtimer_cancel(&op->thrtimer);
        hrtimer_cancel(&op->timer);

        /*
         * funny feature in RX(!)_SETUP only for RTR-mode:
         * copy can_id into frame BUT without RTR-flag to
         * prevent a full-load-loopback-test ... ;-]
         */
        if ((op->flags & TX_CP_CAN_ID) ||
            (op->frames[0].can_id == op->can_id))
            op->frames[0].can_id = op->can_id & ~CAN_RTR_FLAG;

    } else {
        if (op->flags & SETTIMER) {

            /* set timer value */
            op->ival1 = msg_head->ival1;
            op->ival2 = msg_head->ival2;
            op->kt_ival1 = timeval_to_ktime(msg_head->ival1);
            op->kt_ival2 = timeval_to_ktime(msg_head->ival2);

            /* disable an active timer due to zero value? */
            if (!op->kt_ival1.tv64)
                hrtimer_cancel(&op->timer);

            /*
             * In any case cancel the throttle timer, flush
             * potentially blocked msgs and reset throttle handling
             */
            op->kt_lastmsg = ktime_set(0, 0);
            hrtimer_cancel(&op->thrtimer);
            bcm_rx_thr_flush(op, 1);
        }

        if ((op->flags & STARTTIMER) && op->kt_ival1.tv64)
            hrtimer_start(&op->timer, op->kt_ival1,
                      HRTIMER_MODE_REL);
    }

    /* now we can register for can_ids, if we added a new bcm_op */
    if (do_rx_register) {
        if (ifindex) {
            struct net_device *dev;

            dev = dev_get_by_index(&init_net, ifindex);
            if (dev) {
                err = can_rx_register(dev, op->can_id,
                              REGMASK(op->can_id),
                              bcm_rx_handler, op,
                              "bcm");

                op->rx_reg_dev = dev;
                dev_put(dev);
            }

        } else
            err = can_rx_register(NULL, op->can_id,
                          REGMASK(op->can_id),
                          bcm_rx_handler, op, "bcm");
        if (err) {
            /* this bcm rx op is broken -> remove it */
            list_del(&op->list);
            bcm_remove_op(op);
            return err;
        }
    }

    return msg_head->nframes * CFSIZ + MHSIZ;
}

/*
 * bcm_tx_send - send a single CAN frame to the CAN interface (for bcm_sendmsg)
 */
static int bcm_tx_send(struct msghdr *msg, int ifindex, struct sock *sk)
{
    struct sk_buff *skb;
    struct net_device *dev;
    int err;

    /* we need a real device to send frames */
    if (!ifindex)
        return -ENODEV;

    skb = alloc_skb(CFSIZ, GFP_KERNEL);

    if (!skb)
        return -ENOMEM;

    err = memcpy_fromiovec(skb_put(skb, CFSIZ), msg->msg_iov, CFSIZ);
    if (err < 0) {
        kfree_skb(skb);
        return err;
    }

    dev = dev_get_by_index(&init_net, ifindex);
    if (!dev) {
        kfree_skb(skb);
        return -ENODEV;
    }

    skb->dev = dev;
    skb->sk  = sk;
    err = can_send(skb, 1); /* send with loopback */
    dev_put(dev);

    if (err)
        return err;

    return CFSIZ + MHSIZ;
}

/*
 * bcm_sendmsg - process BCM commands (opcodes) from the userspace
 */
static int bcm_sendmsg(struct kiocb *iocb, struct socket *sock,
               struct msghdr *msg, size_t size)
{
    struct sock *sk = sock->sk;
    struct bcm_sock *bo = bcm_sk(sk);
    int ifindex = bo->ifindex; /* default ifindex for this bcm_op */
    struct bcm_msg_head msg_head;
    int ret; /* read bytes or error codes as return value */

    if (!bo->bound)
        return -ENOTCONN;

    /* check for valid message length from userspace */
    if (size < MHSIZ || (size - MHSIZ) % CFSIZ)
        return -EINVAL;

    /* check for alternative ifindex for this bcm_op */

    if (!ifindex && msg->msg_name) {
        /* no bound device as default => check msg_name */
        struct sockaddr_can *addr =
            (struct sockaddr_can *)msg->msg_name;

        if (msg->msg_namelen < sizeof(*addr))
            return -EINVAL;

        if (addr->can_family != AF_CAN)
            return -EINVAL;

        /* ifindex from sendto() */
        ifindex = addr->can_ifindex;

        if (ifindex) {
            struct net_device *dev;

            dev = dev_get_by_index(&init_net, ifindex);
            if (!dev)
                return -ENODEV;

            if (dev->type != ARPHRD_CAN) {
                dev_put(dev);
                return -ENODEV;
            }

            dev_put(dev);
        }
    }

    /* read message head information */

    ret = memcpy_fromiovec((u8 *)&msg_head, msg->msg_iov, MHSIZ);
    if (ret < 0)
        return ret;

    lock_sock(sk);

    switch (msg_head.opcode) {

    case TX_SETUP:
        ret = bcm_tx_setup(&msg_head, msg, ifindex, sk);
        break;

    case RX_SETUP:
        ret = bcm_rx_setup(&msg_head, msg, ifindex, sk);
        break;

    case TX_DELETE:
        if (bcm_delete_tx_op(&bo->tx_ops, msg_head.can_id, ifindex))
            ret = MHSIZ;
        else
            ret = -EINVAL;
        break;

    case RX_DELETE:
        if (bcm_delete_rx_op(&bo->rx_ops, msg_head.can_id, ifindex))
            ret = MHSIZ;
        else
            ret = -EINVAL;
        break;

    case TX_READ:
        /* reuse msg_head for the reply to TX_READ */
        msg_head.opcode  = TX_STATUS;
        ret = bcm_read_op(&bo->tx_ops, &msg_head, ifindex);
        break;

    case RX_READ:
        /* reuse msg_head for the reply to RX_READ */
        msg_head.opcode  = RX_STATUS;
        ret = bcm_read_op(&bo->rx_ops, &msg_head, ifindex);
        break;

    case TX_SEND:
        /* we need exactly one can_frame behind the msg head */
        if ((msg_head.nframes != 1) || (size != CFSIZ + MHSIZ))
            ret = -EINVAL;
        else
            ret = bcm_tx_send(msg, ifindex, sk);
        break;

    default:
        ret = -EINVAL;
        break;
    }

    release_sock(sk);

    return ret;
}

/*
 * notification handler for netdevice status changes
 */
static int bcm_notifier(struct notifier_block *nb, unsigned long msg,
            void *data)
{
    struct net_device *dev = (struct net_device *)data;
    struct bcm_sock *bo = container_of(nb, struct bcm_sock, notifier);
    struct sock *sk = &bo->sk;
    struct bcm_op *op;
    int notify_enodev = 0;

    if (!net_eq(dev_net(dev), &init_net))
        return NOTIFY_DONE;

    if (dev->type != ARPHRD_CAN)
        return NOTIFY_DONE;

    switch (msg) {

    case NETDEV_UNREGISTER:
        lock_sock(sk);

        /* remove device specific receive entries */
        list_for_each_entry(op, &bo->rx_ops, list)
            if (op->rx_reg_dev == dev)
                bcm_rx_unreg(dev, op);

        /* remove device reference, if this is our bound device */
        if (bo->bound && bo->ifindex == dev->ifindex) {
            bo->bound   = 0;
            bo->ifindex = 0;
            notify_enodev = 1;
        }

        release_sock(sk);

        if (notify_enodev) {
            sk->sk_err = ENODEV;
            if (!sock_flag(sk, SOCK_DEAD))
                sk->sk_error_report(sk);
        }
        break;

    case NETDEV_DOWN:
        if (bo->bound && bo->ifindex == dev->ifindex) {
            sk->sk_err = ENETDOWN;
            if (!sock_flag(sk, SOCK_DEAD))
                sk->sk_error_report(sk);
        }
    }

    return NOTIFY_DONE;
}

/*
 * initial settings for all BCM sockets to be set at socket creation time
 */
static int bcm_init(struct sock *sk)
{
    struct bcm_sock *bo = bcm_sk(sk);

    bo->bound            = 0;
    bo->ifindex          = 0;
    bo->dropped_usr_msgs = 0;
    bo->bcm_proc_read    = NULL;

    INIT_LIST_HEAD(&bo->tx_ops);
    INIT_LIST_HEAD(&bo->rx_ops);

    /* set notifier */
    bo->notifier.notifier_call = bcm_notifier;

    register_netdevice_notifier(&bo->notifier);

    return 0;
}

/*
 * standard socket functions
 */
static int bcm_release(struct socket *sock)
{
    struct sock *sk = sock->sk;
    struct bcm_sock *bo;
    struct bcm_op *op, *next;

    if (sk == NULL)
        return 0;

    bo = bcm_sk(sk);

    /* remove bcm_ops, timer, rx_unregister(), etc. */

    unregister_netdevice_notifier(&bo->notifier);

    lock_sock(sk);

    list_for_each_entry_safe(op, next, &bo->tx_ops, list)
        bcm_remove_op(op);

    list_for_each_entry_safe(op, next, &bo->rx_ops, list) {
        /*
         * Don't care if we're bound or not (due to netdev problems)
         * can_rx_unregister() is always a save thing to do here.
         */
        if (op->ifindex) {
            /*
             * Only remove subscriptions that had not
             * been removed due to NETDEV_UNREGISTER
             * in bcm_notifier()
             */
            if (op->rx_reg_dev) {
                struct net_device *dev;

                dev = dev_get_by_index(&init_net, op->ifindex);
                if (dev) {
                    bcm_rx_unreg(dev, op);
                    dev_put(dev);
                }
            }
        } else
            can_rx_unregister(NULL, op->can_id,
                      REGMASK(op->can_id),
                      bcm_rx_handler, op);

        bcm_remove_op(op);
    }

    /* remove procfs entry */
    if (proc_dir && bo->bcm_proc_read)
        remove_proc_entry(bo->procname, proc_dir);

    /* remove device reference */
    if (bo->bound) {
        bo->bound   = 0;
        bo->ifindex = 0;
    }

    sock_orphan(sk);
    sock->sk = NULL;

    release_sock(sk);
    sock_put(sk);

    return 0;
}

static int bcm_connect(struct socket *sock, struct sockaddr *uaddr, int len,
               int flags)
{
    struct sockaddr_can *addr = (struct sockaddr_can *)uaddr;
    struct sock *sk = sock->sk;
    struct bcm_sock *bo = bcm_sk(sk);

    if (len < sizeof(*addr))
        return -EINVAL;

    if (bo->bound)
        return -EISCONN;

    /* bind a device to this socket */
    if (addr->can_ifindex) {
        struct net_device *dev;

        dev = dev_get_by_index(&init_net, addr->can_ifindex);
        if (!dev)
            return -ENODEV;

        if (dev->type != ARPHRD_CAN) {
            dev_put(dev);
            return -ENODEV;
        }

        bo->ifindex = dev->ifindex;
        dev_put(dev);

    } else {
        /* no interface reference for ifindex = 0 ('any' CAN device) */
        bo->ifindex = 0;
    }

    bo->bound = 1;

    if (proc_dir) {
        /* unique socket address as filename */
        sprintf(bo->procname, "%lu", sock_i_ino(sk));
        bo->bcm_proc_read = proc_create_data(bo->procname, 0644,
                             proc_dir,
                             &bcm_proc_fops, sk);
    }

    return 0;
}

static int bcm_recvmsg(struct kiocb *iocb, struct socket *sock,
               struct msghdr *msg, size_t size, int flags)
{
    struct sock *sk = sock->sk;
    struct sk_buff *skb;
    int error = 0;
    int noblock;
    int err;

    noblock =  flags & MSG_DONTWAIT;
    flags   &= ~MSG_DONTWAIT;
    skb = skb_recv_datagram(sk, flags, noblock, &error);
    if (!skb)
        return error;

    if (skb->len < size)
        size = skb->len;

    err = memcpy_toiovec(msg->msg_iov, skb->data, size);
    if (err < 0) {
        skb_free_datagram(sk, skb);
        return err;
    }

    sock_recv_ts_and_drops(msg, sk, skb);

    if (msg->msg_name) {
        msg->msg_namelen = sizeof(struct sockaddr_can);
        memcpy(msg->msg_name, skb->cb, msg->msg_namelen);
    }

    skb_free_datagram(sk, skb);

    return size;
}

static const struct proto_ops bcm_ops = {
    .family        = PF_CAN,
    .release       = bcm_release,
    .bind          = sock_no_bind,
    .connect       = bcm_connect,
    .socketpair    = sock_no_socketpair,
    .accept        = sock_no_accept,
    .getname       = sock_no_getname,
    .poll          = datagram_poll,
    .ioctl         = can_ioctl, /* use can_ioctl() from af_can.c */
    .listen        = sock_no_listen,
    .shutdown      = sock_no_shutdown,
    .setsockopt    = sock_no_setsockopt,
    .getsockopt    = sock_no_getsockopt,
    .sendmsg       = bcm_sendmsg,
    .recvmsg       = bcm_recvmsg,
    .mmap          = sock_no_mmap,
    .sendpage      = sock_no_sendpage,
};

static struct proto bcm_proto __read_mostly = {
    .name       = "CAN_BCM",
    .owner      = THIS_MODULE,
    .obj_size   = sizeof(struct bcm_sock),
    .init       = bcm_init,
};

static const struct can_proto bcm_can_proto = {
    .type       = SOCK_DGRAM,
    .protocol   = CAN_BCM,
    .ops        = &bcm_ops,
    .prot       = &bcm_proto,
};

static int __init bcm_module_init(void)
{
    int err;

    printk(banner);

    err = can_proto_register(&bcm_can_proto);
    if (err < 0) {
        printk(KERN_ERR "can: registration of bcm protocol failed\n");
        return err;
    }

    /* create /proc/net/can-bcm directory */
    proc_dir = proc_mkdir("can-bcm", init_net.proc_net);
    return 0;
}

static void __exit bcm_module_exit(void)
{
    can_proto_unregister(&bcm_can_proto);

    if (proc_dir)
        proc_net_remove(&init_net, "can-bcm");
}

module_init(bcm_module_init);
module_exit(bcm_module_exit);