cgroup memory controller: document huge memory/cache overhead in Kconfig

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / net / can / bcm.c

/*
 * 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.
 *
 * Send feedback to <socketcan-users@lists.berlios.de>
 *
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/proc_fs.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 <net/sock.h>
#include <net/net_namespace.h>

/* 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_RTR_FLAG) | ((id & CAN_EFF_FLAG) ? \
                        (CAN_EFF_MASK | CAN_EFF_FLAG) : CAN_SFF_MASK))

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

MODULE_DESCRIPTION("PF_CAN broadcast manager protocol");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Oliver Hartkopp <oliver.hartkopp@volkswagen.de>");

/* 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;
        int flags;
        unsigned long j_ival1, j_ival2, j_lastmsg;
        unsigned long frames_abs, frames_filtered;
        struct timer_list timer, thrtimer;
        struct timeval ival1, ival2;
        ktime_t rx_stamp;
        int rx_ifindex;
        int count;
        int nframes;
        int 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 [9]; /* pointer printed in ASCII 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)

/*
 * rounded_tv2jif - calculate jiffies from timeval including optional up
 * @tv: pointer to timeval
 *
 * Description:
 * Unlike timeval_to_jiffies() provided in include/linux/jiffies.h, this
 * function is intentionally more relaxed on precise timer ticks to get
 * exact one jiffy for requested 1000us on a 1000HZ machine.
 * This code is to be removed when upgrading to kernel hrtimer.
 *
 * Return:
 *  calculated jiffies (max: ULONG_MAX)
 */
static unsigned long rounded_tv2jif(const struct timeval *tv)
{
        unsigned long sec  = tv->tv_sec;
        unsigned long usec = tv->tv_usec;
        unsigned long jif;

        if (sec > ULONG_MAX / HZ)
                return ULONG_MAX;

        /* round up to get at least the requested time */
        usec += 1000000 / HZ - 1;

        jif  = usec / (1000000 / HZ);

        if (sec * HZ > ULONG_MAX - jif)
                return ULONG_MAX;

        return jif + sec * HZ;
}

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

        if (!ifindex)
                return "any";

        /* no usage counting */
        dev = __dev_get_by_index(&init_net, ifindex);
        if (dev)
                return dev->name;

        return "???";
}

static int bcm_read_proc(char *page, char **start, off_t off,
                         int count, int *eof, void *data)
{
        int len = 0;
        struct sock *sk = (struct sock *)data;
        struct bcm_sock *bo = bcm_sk(sk);
        struct bcm_op *op;

        len += snprintf(page + len, PAGE_SIZE - len, ">>> socket %p",
                        sk->sk_socket);
        len += snprintf(page + len, PAGE_SIZE - len, " / sk %p", sk);
        len += snprintf(page + len, PAGE_SIZE - len, " / bo %p", bo);
        len += snprintf(page + len, PAGE_SIZE - len, " / dropped %lu",
                        bo->dropped_usr_msgs);
        len += snprintf(page + len, PAGE_SIZE - len, " / bound %s",
                        bcm_proc_getifname(bo->ifindex));
        len += snprintf(page + len, PAGE_SIZE - len, " <<<\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;

                len += snprintf(page + len, PAGE_SIZE - len,
                                "rx_op: %03X %-5s ",
                                op->can_id, bcm_proc_getifname(op->ifindex));
                len += snprintf(page + len, PAGE_SIZE - len, "[%d]%c ",
                                op->nframes,
                                (op->flags & RX_CHECK_DLC)?'d':' ');
                if (op->j_ival1)
                        len += snprintf(page + len, PAGE_SIZE - len,
                                        "timeo=%ld ", op->j_ival1);

                if (op->j_ival2)
                        len += snprintf(page + len, PAGE_SIZE - len,
                                        "thr=%ld ", op->j_ival2);

                len += snprintf(page + len, PAGE_SIZE - len,
                                "# recv %ld (%ld) => reduction: ",
                                op->frames_filtered, op->frames_abs);

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

                len += snprintf(page + len, PAGE_SIZE - len, "%s%ld%%\n",
                                (reduction == 100)?"near ":"", reduction);

                if (len > PAGE_SIZE - 200) {
                        /* mark output cut off */
                        len += snprintf(page + len, PAGE_SIZE - len, "(..)\n");
                        break;
                }
        }

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

                len += snprintf(page + len, PAGE_SIZE - len,
                                "tx_op: %03X %s [%d] ",
                                op->can_id, bcm_proc_getifname(op->ifindex),
                                op->nframes);
                if (op->j_ival1)
                        len += snprintf(page + len, PAGE_SIZE - len, "t1=%ld ",
                                        op->j_ival1);

                if (op->j_ival2)
                        len += snprintf(page + len, PAGE_SIZE - len, "t2=%ld ",
                                        op->j_ival2);

                len += snprintf(page + len, PAGE_SIZE - len, "# sent %ld\n",
                                op->frames_abs);

                if (len > PAGE_SIZE - 100) {
                        /* mark output cut off */
                        len += snprintf(page + len, PAGE_SIZE - len, "(..)\n");
                        break;
                }
        }

        len += snprintf(page + len, PAGE_SIZE - len, "\n");

        *eof = 1;
        return len;
}

/*
 * 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;
        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++;
        }
}

/*
 * bcm_tx_timeout_handler - performes cyclic CAN frame transmissions
 */
static void bcm_tx_timeout_handler(unsigned long data)
{
        struct bcm_op *op = (struct bcm_op *)data;

        if (op->j_ival1 && (op->count > 0)) {

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

                        /* 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);
                }
        }

        if (op->j_ival1 && (op->count > 0)) {

                /* send (next) frame */
                bcm_can_tx(op);
                mod_timer(&op->timer, jiffies + op->j_ival1);

        } else {
                if (op->j_ival2) {

                        /* send (next) frame */
                        bcm_can_tx(op);
                        mod_timer(&op->timer, jiffies + op->j_ival2);
                }
        }

        return;
}

/*
 * 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;

        op->j_lastmsg = jiffies;

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

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

        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,
                                   struct can_frame *rxdata)
{
        unsigned long nexttx = op->j_lastmsg + op->j_ival2;

        memcpy(lastdata, rxdata, CFSIZ);

        /* mark as used */
        lastdata->can_dlc |= RX_RECV;

        /* throttle bcm_rx_changed ? */
        if ((op->thrtimer.expires) ||
            ((op->j_ival2) && (nexttx > jiffies))) {
                /* we are already waiting OR we have to start waiting */

                /* mark as 'throttled' */
                lastdata->can_dlc |= RX_THR;

                if (!(op->thrtimer.expires)) {
                        /* start the timer only the first time */
                        mod_timer(&op->thrtimer, nexttx);
                }

        } else {
                /* send RX_CHANGED to the user immediately */
                bcm_rx_changed(op, rxdata);
        }
}

/*
 * 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, int index,
                                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->j_ival1)
                mod_timer(&op->timer, jiffies + op->j_ival1);
}

/*
 * bcm_rx_timeout_handler - when the (cyclic) CAN frame receiption timed out
 */
static void bcm_rx_timeout_handler(unsigned long data)
{
        struct bcm_op *op = (struct bcm_op *)data;
        struct bcm_msg_head msg_head;

        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);

        /* 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);
        }
}

/*
 * bcm_rx_thr_handler - the time for blocked content updates is over now:
 *                      Check for throttled data and send it to the userspace
 */
static void bcm_rx_thr_handler(unsigned long data)
{
        struct bcm_op *op = (struct bcm_op *)data;
        int i = 0;

        /* mark disabled / consumed timer */
        op->thrtimer.expires = 0;

        if (op->nframes > 1) {
                /* for MUX filter we start at index 1 */
                for (i = 1; i < op->nframes; i++) {
                        if ((op->last_frames) &&
                            (op->last_frames[i].can_dlc & RX_THR)) {
                                op->last_frames[i].can_dlc &= ~RX_THR;
                                bcm_rx_changed(op, &op->last_frames[i]);
                        }
                }

        } else {
                /* for RX_FILTER_ID and simple filter */
                if (op->last_frames && (op->last_frames[0].can_dlc & RX_THR)) {
                        op->last_frames[0].can_dlc &= ~RX_THR;
                        bcm_rx_changed(op, &op->last_frames[0]);
                }
        }
}

/*
 * 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;
        struct can_frame rxframe;
        int i;

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

        if (skb->len == sizeof(rxframe)) {
                memcpy(&rxframe, skb->data, sizeof(rxframe));
                /* save rx timestamp */
                op->rx_stamp = skb->tstamp;
                /* save originator for recvfrom() */
                op->rx_ifindex = skb->dev->ifindex;
                /* update statistics */
                op->frames_abs++;
                kfree_skb(skb);

        } else {
                kfree_skb(skb);
                return;
        }

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

        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);
                bcm_rx_starttimer(op);
                return;
        }

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

        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;
                        }
                }
                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)
{
        del_timer(&op->timer);
        del_timer(&op->thrtimer);

        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);

        return;
}

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;
        int i, err;

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

        /* we need at least one can_frame */
        if (msg_head->nframes < 1)
                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 (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 (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 */
                setup_timer(&op->timer, bcm_tx_timeout_handler,
                            (unsigned long)op);

                /* currently unused in tx_ops */
                init_timer(&op->thrtimer);

                /* 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->j_ival1 = rounded_tv2jif(&msg_head->ival1);
                op->j_ival2 = rounded_tv2jif(&msg_head->ival2);

                /* disable an active timer due to zero values? */
                if (!op->j_ival1 && !op->j_ival2)
                        del_timer(&op->timer);
        }

        if ((op->flags & STARTTIMER) &&
            ((op->j_ival1 && op->count) || op->j_ival2)) {

                /* spec: send can_frame when starting timer */
                op->flags |= TX_ANNOUNCE;

                if (op->j_ival1 && (op->count > 0)) {
                        /* op->count-- is done in bcm_tx_timeout_handler */
                        mod_timer(&op->timer, jiffies + op->j_ival1);
                } else
                        mod_timer(&op->timer, jiffies + op->j_ival2);
        }

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

        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;

                /* initialize uninitialized (kzalloc) structure */
                setup_timer(&op->timer, bcm_rx_timeout_handler,
                            (unsigned long)op);

                /* init throttle timer for RX_CHANGED */
                setup_timer(&op->thrtimer, bcm_rx_thr_handler,
                            (unsigned long)op);

                /* mark disabled timer */
                op->thrtimer.expires = 0;

                /* 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 */
                del_timer(&op->thrtimer);
                del_timer(&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->j_ival1 = rounded_tv2jif(&msg_head->ival1);
                        op->j_ival2 = rounded_tv2jif(&msg_head->ival2);

                        /* disable an active timer due to zero value? */
                        if (!op->j_ival1)
                                del_timer(&op->timer);

                        /* free currently blocked msgs ? */
                        if (op->thrtimer.expires) {
                                /* send blocked msgs hereafter */
                                mod_timer(&op->thrtimer, jiffies + 2);
                        }

                        /*
                         * if (op->j_ival2) is zero, no (new) throttling
                         * will happen. For details see functions
                         * bcm_rx_update_and_send() and bcm_rx_thr_handler()
                         */
                }

                if ((op->flags & STARTTIMER) && op->j_ival1)
                        mod_timer(&op->timer, jiffies + op->j_ival1);
        }

        /* 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;
        can_send(skb, 1); /* send with loopback */
        dev_put(dev);

        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 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 (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 at least one can_frame */
                if (msg_head.nframes < 1)
                        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 (dev->nd_net != &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 = bcm_sk(sk);
        struct bcm_op *op, *next;

        /* 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;
        }

        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 (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, "%p", sock);
                bo->bcm_proc_read = create_proc_read_entry(bo->procname, 0644,
                                                           proc_dir,
                                                           bcm_read_proc, 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_timestamp(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 struct proto_ops bcm_ops __read_mostly = {
        .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         = NULL,          /* 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 struct can_proto bcm_can_proto __read_mostly = {
        .type       = SOCK_DGRAM,
        .protocol   = CAN_BCM,
        .capability = -1,
        .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);

        if (proc_dir)
                proc_dir->owner = THIS_MODULE;

        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);