/*
 * Copyright (C) 2005 Marc Kleine-Budde, Pengutronix
 * Copyright (C) 2006 Andrey Volkov, Varma Electronics
 * Copyright (C) 2008-2009 Wolfgang Grandegger <wg@grandegger.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the version 2 of the GNU General Public License
 * as published by the Free Software Foundation
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/netlink.h>
#include <net/rtnetlink.h>

#define MOD_DESC "CAN device driver interface"

MODULE_DESCRIPTION(MOD_DESC);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Wolfgang Grandegger <wg@grandegger.com>");

#ifdef CONFIG_CAN_CALC_BITTIMING
#define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */

/*
 * Bit-timing calculation derived from:
 *
 * Code based on LinCAN sources and H8S2638 project
 * Copyright 2004-2006 Pavel Pisa - DCE FELK CVUT cz
 * Copyright 2005      Stanislav Marek
 * email: pisa@cmp.felk.cvut.cz
 *
 * Calculates proper bit-timing parameters for a specified bit-rate
 * and sample-point, which can then be used to set the bit-timing
 * registers of the CAN controller. You can find more information
 * in the header file linux/can/netlink.h.
 */
static int can_update_spt(const struct can_bittiming_const *btc,
                          int sampl_pt, int tseg, int *tseg1, int *tseg2)
{
        *tseg2 = tseg + 1 - (sampl_pt * (tseg + 1)) / 1000;
        if (*tseg2 < btc->tseg2_min)
                *tseg2 = btc->tseg2_min;
        if (*tseg2 > btc->tseg2_max)
                *tseg2 = btc->tseg2_max;
        *tseg1 = tseg - *tseg2;
        if (*tseg1 > btc->tseg1_max) {
                *tseg1 = btc->tseg1_max;
                *tseg2 = tseg - *tseg1;
        }
        return 1000 * (tseg + 1 - *tseg2) / (tseg + 1);
}

static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt)
{
        struct can_priv *priv = netdev_priv(dev);
        const struct can_bittiming_const *btc = priv->bittiming_const;
        long rate, best_rate = 0;
        long best_error = 1000000000, error = 0;
        int best_tseg = 0, best_brp = 0, brp = 0;
        int tsegall, tseg = 0, tseg1 = 0, tseg2 = 0;
        int spt_error = 1000, spt = 0, sampl_pt;
        u64 v64;

        if (!priv->bittiming_const)
                return -ENOTSUPP;

        /* Use CIA recommended sample points */
        if (bt->sample_point) {
                sampl_pt = bt->sample_point;
        } else {
                if (bt->bitrate > 800000)
                        sampl_pt = 750;
                else if (bt->bitrate > 500000)
                        sampl_pt = 800;
                else
                        sampl_pt = 875;
        }

        /* tseg even = round down, odd = round up */
        for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1;
             tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) {
                tsegall = 1 + tseg / 2;
                /* Compute all possible tseg choices (tseg=tseg1+tseg2) */
                brp = priv->clock.freq / (tsegall * bt->bitrate) + tseg % 2;
                /* chose brp step which is possible in system */
                brp = (brp / btc->brp_inc) * btc->brp_inc;
                if ((brp < btc->brp_min) || (brp > btc->brp_max))
                        continue;
                rate = priv->clock.freq / (brp * tsegall);
                error = bt->bitrate - rate;
                /* tseg brp biterror */
                if (error < 0)
                        error = -error;
                if (error > best_error)
                        continue;
                best_error = error;
                if (error == 0) {
                        spt = can_update_spt(btc, sampl_pt, tseg / 2,
                                             &tseg1, &tseg2);
                        error = sampl_pt - spt;
                        if (error < 0)
                                error = -error;
                        if (error > spt_error)
                                continue;
                        spt_error = error;
                }
                best_tseg = tseg / 2;
                best_brp = brp;
                best_rate = rate;
                if (error == 0)
                        break;
        }

        if (best_error) {
                /* Error in one-tenth of a percent */
                error = (best_error * 1000) / bt->bitrate;
                if (error > CAN_CALC_MAX_ERROR) {
                        dev_err(dev->dev.parent,
                                "bitrate error %ld.%ld%% too high\n",
                                error / 10, error % 10);
                        return -EDOM;
                } else {
                        dev_warn(dev->dev.parent, "bitrate error %ld.%ld%%\n",
                                 error / 10, error % 10);
                }
        }

        /* real sample point */
        bt->sample_point = can_update_spt(btc, sampl_pt, best_tseg,
                                          &tseg1, &tseg2);

        v64 = (u64)best_brp * 1000000000UL;
        do_div(v64, priv->clock.freq);
        bt->tq = (u32)v64;
        bt->prop_seg = tseg1 / 2;
        bt->phase_seg1 = tseg1 - bt->prop_seg;
        bt->phase_seg2 = tseg2;
        bt->sjw = 1;
        bt->brp = best_brp;
        /* real bit-rate */
        bt->bitrate = priv->clock.freq / (bt->brp * (tseg1 + tseg2 + 1));

        return 0;
}
#else /* !CONFIG_CAN_CALC_BITTIMING */
static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt)
{
        dev_err(dev->dev.parent, "bit-timing calculation not available\n");
        return -EINVAL;
}
#endif /* CONFIG_CAN_CALC_BITTIMING */

/*
 * Checks the validity of the specified bit-timing parameters prop_seg,
 * phase_seg1, phase_seg2 and sjw and tries to determine the bitrate
 * prescaler value brp. You can find more information in the header
 * file linux/can/netlink.h.
 */
static int can_fixup_bittiming(struct net_device *dev, struct can_bittiming *bt)
{
        struct can_priv *priv = netdev_priv(dev);
        const struct can_bittiming_const *btc = priv->bittiming_const;
        int tseg1, alltseg;
        u64 brp64;

        if (!priv->bittiming_const)
                return -ENOTSUPP;

        tseg1 = bt->prop_seg + bt->phase_seg1;
        if (!bt->sjw)
                bt->sjw = 1;
        if (bt->sjw > btc->sjw_max ||
            tseg1 < btc->tseg1_min || tseg1 > btc->tseg1_max ||
            bt->phase_seg2 < btc->tseg2_min || bt->phase_seg2 > btc->tseg2_max)
                return -ERANGE;

        brp64 = (u64)priv->clock.freq * (u64)bt->tq;
        if (btc->brp_inc > 1)
                do_div(brp64, btc->brp_inc);
        brp64 += 500000000UL - 1;
        do_div(brp64, 1000000000UL); /* the practicable BRP */
        if (btc->brp_inc > 1)
                brp64 *= btc->brp_inc;
        bt->brp = (u32)brp64;

        if (bt->brp < btc->brp_min || bt->brp > btc->brp_max)
                return -EINVAL;

        alltseg = bt->prop_seg + bt->phase_seg1 + bt->phase_seg2 + 1;
        bt->bitrate = priv->clock.freq / (bt->brp * alltseg);
        bt->sample_point = ((tseg1 + 1) * 1000) / alltseg;

        return 0;
}

int can_get_bittiming(struct net_device *dev, struct can_bittiming *bt)
{
        struct can_priv *priv = netdev_priv(dev);
        int err;

        /* Check if the CAN device has bit-timing parameters */
        if (priv->bittiming_const) {

                /* Non-expert mode? Check if the bitrate has been pre-defined */
                if (!bt->tq)
                        /* Determine bit-timing parameters */
                        err = can_calc_bittiming(dev, bt);
                else
                        /* Check bit-timing params and calculate proper brp */
                        err = can_fixup_bittiming(dev, bt);
                if (err)
                        return err;
        }

        return 0;
}

/*
 * Local echo of CAN messages
 *
 * CAN network devices *should* support a local echo functionality
 * (see Documentation/networking/can.txt). To test the handling of CAN
 * interfaces that do not support the local echo both driver types are
 * implemented. In the case that the driver does not support the echo
 * the IFF_ECHO remains clear in dev->flags. This causes the PF_CAN core
 * to perform the echo as a fallback solution.
 */
static void can_flush_echo_skb(struct net_device *dev)
{
        struct can_priv *priv = netdev_priv(dev);
        struct net_device_stats *stats = &dev->stats;
        int i;

        for (i = 0; i < CAN_ECHO_SKB_MAX; i++) {
                if (priv->echo_skb[i]) {
                        kfree_skb(priv->echo_skb[i]);
                        priv->echo_skb[i] = NULL;
                        stats->tx_dropped++;
                        stats->tx_aborted_errors++;
                }
        }
}

/*
 * Put the skb on the stack to be looped backed locally lateron
 *
 * The function is typically called in the start_xmit function
 * of the device driver. The driver must protect access to
 * priv->echo_skb, if necessary.
 */
void can_put_echo_skb(struct sk_buff *skb, struct net_device *dev, int idx)
{
        struct can_priv *priv = netdev_priv(dev);

        /* check flag whether this packet has to be looped back */
        if (!(dev->flags & IFF_ECHO) || skb->pkt_type != PACKET_LOOPBACK) {
                kfree_skb(skb);
                return;
        }

        if (!priv->echo_skb[idx]) {
                struct sock *srcsk = skb->sk;

                if (atomic_read(&skb->users) != 1) {
                        struct sk_buff *old_skb = skb;

                        skb = skb_clone(old_skb, GFP_ATOMIC);
                        kfree_skb(old_skb);
                        if (!skb)
                                return;
                } else
                        skb_orphan(skb);

                skb->sk = srcsk;

                /* make settings for echo to reduce code in irq context */
                skb->protocol = htons(ETH_P_CAN);
                skb->pkt_type = PACKET_BROADCAST;
                skb->ip_summed = CHECKSUM_UNNECESSARY;
                skb->dev = dev;

                /* save this skb for tx interrupt echo handling */
                priv->echo_skb[idx] = skb;
        } else {
                /* locking problem with netif_stop_queue() ?? */
                dev_err(dev->dev.parent, "%s: BUG! echo_skb is occupied!\n",
                        __func__);
                kfree_skb(skb);
        }
}
EXPORT_SYMBOL_GPL(can_put_echo_skb);

/*
 * Get the skb from the stack and loop it back locally
 *
 * The function is typically called when the TX done interrupt
 * is handled in the device driver. The driver must protect
 * access to priv->echo_skb, if necessary.
 */
void can_get_echo_skb(struct net_device *dev, int idx)
{
        struct can_priv *priv = netdev_priv(dev);

        if (priv->echo_skb[idx]) {
                netif_rx(priv->echo_skb[idx]);
                priv->echo_skb[idx] = NULL;
        }
}
EXPORT_SYMBOL_GPL(can_get_echo_skb);

/*
  * Remove the skb from the stack and free it.
  *
  * The function is typically called when TX failed.
  */
void can_free_echo_skb(struct net_device *dev, int idx)
{
        struct can_priv *priv = netdev_priv(dev);

        if (priv->echo_skb[idx]) {
                kfree_skb(priv->echo_skb[idx]);
                priv->echo_skb[idx] = NULL;
        }
}
EXPORT_SYMBOL_GPL(can_free_echo_skb);

/*
 * CAN device restart for bus-off recovery
 */
void can_restart(unsigned long data)
{
        struct net_device *dev = (struct net_device *)data;
        struct can_priv *priv = netdev_priv(dev);
        struct net_device_stats *stats = &dev->stats;
        struct sk_buff *skb;
        struct can_frame *cf;
        int err;

        BUG_ON(netif_carrier_ok(dev));

        /*
         * No synchronization needed because the device is bus-off and
         * no messages can come in or go out.
         */
        can_flush_echo_skb(dev);

        /* send restart message upstream */
        skb = dev_alloc_skb(sizeof(struct can_frame));
        if (skb == NULL) {
                err = -ENOMEM;
                goto restart;
        }
        skb->dev = dev;
        skb->protocol = htons(ETH_P_CAN);
        cf = (struct can_frame *)skb_put(skb, sizeof(struct can_frame));
        memset(cf, 0, sizeof(struct can_frame));
        cf->can_id = CAN_ERR_FLAG | CAN_ERR_RESTARTED;
        cf->can_dlc = CAN_ERR_DLC;

        netif_rx(skb);

        stats->rx_packets++;
        stats->rx_bytes += cf->can_dlc;

restart:
        dev_dbg(dev->dev.parent, "restarted\n");
        priv->can_stats.restarts++;

        /* Now restart the device */
        err = priv->do_set_mode(dev, CAN_MODE_START);

        netif_carrier_on(dev);
        if (err)
                dev_err(dev->dev.parent, "Error %d during restart", err);
}

int can_restart_now(struct net_device *dev)
{
        struct can_priv *priv = netdev_priv(dev);

        /*
         * A manual restart is only permitted if automatic restart is
         * disabled and the device is in the bus-off state
         */
        if (priv->restart_ms)
                return -EINVAL;
        if (priv->state != CAN_STATE_BUS_OFF)
                return -EBUSY;

        /* Runs as soon as possible in the timer context */
        mod_timer(&priv->restart_timer, jiffies);

        return 0;
}

/*
 * CAN bus-off
 *
 * This functions should be called when the device goes bus-off to
 * tell the netif layer that no more packets can be sent or received.
 * If enabled, a timer is started to trigger bus-off recovery.
 */
void can_bus_off(struct net_device *dev)
{
        struct can_priv *priv = netdev_priv(dev);

        dev_dbg(dev->dev.parent, "bus-off\n");

        netif_carrier_off(dev);
        priv->can_stats.bus_off++;

        if (priv->restart_ms)
                mod_timer(&priv->restart_timer,
                          jiffies + (priv->restart_ms * HZ) / 1000);
}
EXPORT_SYMBOL_GPL(can_bus_off);

static void can_setup(struct net_device *dev)
{
        dev->type = ARPHRD_CAN;
        dev->mtu = sizeof(struct can_frame);
        dev->hard_header_len = 0;
        dev->addr_len = 0;
        dev->tx_queue_len = 10;

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

/*
 * Allocate and setup space for the CAN network device
 */
struct net_device *alloc_candev(int sizeof_priv)
{
        struct net_device *dev;
        struct can_priv *priv;

        dev = alloc_netdev(sizeof_priv, "can%d", can_setup);
        if (!dev)
                return NULL;

        priv = netdev_priv(dev);

        priv->state = CAN_STATE_STOPPED;

        init_timer(&priv->restart_timer);

        return dev;
}
EXPORT_SYMBOL_GPL(alloc_candev);

/*
 * Free space of the CAN network device
 */
void free_candev(struct net_device *dev)
{
        free_netdev(dev);
}
EXPORT_SYMBOL_GPL(free_candev);

/*
 * Common open function when the device gets opened.
 *
 * This function should be called in the open function of the device
 * driver.
 */
int open_candev(struct net_device *dev)
{
        struct can_priv *priv = netdev_priv(dev);

        if (!priv->bittiming.tq && !priv->bittiming.bitrate) {
                dev_err(dev->dev.parent, "bit-timing not yet defined\n");
                return -EINVAL;
        }

        /* Switch carrier on if device was stopped while in bus-off state */
        if (!netif_carrier_ok(dev))
                netif_carrier_on(dev);

        setup_timer(&priv->restart_timer, can_restart, (unsigned long)dev);

        return 0;
}
EXPORT_SYMBOL_GPL(open_candev);

/*
 * Common close function for cleanup before the device gets closed.
 *
 * This function should be called in the close function of the device
 * driver.
 */
void close_candev(struct net_device *dev)
{
        struct can_priv *priv = netdev_priv(dev);

        if (del_timer_sync(&priv->restart_timer))
                dev_put(dev);
        can_flush_echo_skb(dev);
}
EXPORT_SYMBOL_GPL(close_candev);

/*
 * CAN netlink interface
 */
static const struct nla_policy can_policy[IFLA_CAN_MAX + 1] = {
        [IFLA_CAN_STATE]        = { .type = NLA_U32 },
        [IFLA_CAN_CTRLMODE]     = { .len = sizeof(struct can_ctrlmode) },
        [IFLA_CAN_RESTART_MS]   = { .type = NLA_U32 },
        [IFLA_CAN_RESTART]      = { .type = NLA_U32 },
        [IFLA_CAN_BITTIMING]    = { .len = sizeof(struct can_bittiming) },
        [IFLA_CAN_BITTIMING_CONST]
                                = { .len = sizeof(struct can_bittiming_const) },
        [IFLA_CAN_CLOCK]        = { .len = sizeof(struct can_clock) },
};

static int can_changelink(struct net_device *dev,
                          struct nlattr *tb[], struct nlattr *data[])
{
        struct can_priv *priv = netdev_priv(dev);
        int err;

        /* We need synchronization with dev->stop() */
        ASSERT_RTNL();

        if (data[IFLA_CAN_CTRLMODE]) {
                struct can_ctrlmode *cm;

                /* Do not allow changing controller mode while running */
                if (dev->flags & IFF_UP)
                        return -EBUSY;
                cm = nla_data(data[IFLA_CAN_CTRLMODE]);
                priv->ctrlmode &= ~cm->mask;
                priv->ctrlmode |= cm->flags;
        }

        if (data[IFLA_CAN_BITTIMING]) {
                struct can_bittiming bt;

                /* Do not allow changing bittiming while running */
                if (dev->flags & IFF_UP)
                        return -EBUSY;
                memcpy(&bt, nla_data(data[IFLA_CAN_BITTIMING]), sizeof(bt));
                if ((!bt.bitrate && !bt.tq) || (bt.bitrate && bt.tq))
                        return -EINVAL;
                err = can_get_bittiming(dev, &bt);
                if (err)
                        return err;
                memcpy(&priv->bittiming, &bt, sizeof(bt));

                if (priv->do_set_bittiming) {
                        /* Finally, set the bit-timing registers */
                        err = priv->do_set_bittiming(dev);
                        if (err)
                                return err;
                }
        }

        if (data[IFLA_CAN_RESTART_MS]) {
                /* Do not allow changing restart delay while running */
                if (dev->flags & IFF_UP)
                        return -EBUSY;
                priv->restart_ms = nla_get_u32(data[IFLA_CAN_RESTART_MS]);
        }

        if (data[IFLA_CAN_RESTART]) {
                /* Do not allow a restart while not running */
                if (!(dev->flags & IFF_UP))
                        return -EINVAL;
                err = can_restart_now(dev);
                if (err)
                        return err;
        }

        return 0;
}

static size_t can_get_size(const struct net_device *dev)
{
        struct can_priv *priv = netdev_priv(dev);
        size_t size;

        size = nla_total_size(sizeof(u32));   /* IFLA_CAN_STATE */
        size += sizeof(struct can_ctrlmode);  /* IFLA_CAN_CTRLMODE */
        size += nla_total_size(sizeof(u32));  /* IFLA_CAN_RESTART_MS */
        size += sizeof(struct can_bittiming); /* IFLA_CAN_BITTIMING */
        size += sizeof(struct can_clock);     /* IFLA_CAN_CLOCK */
        if (priv->bittiming_const)            /* IFLA_CAN_BITTIMING_CONST */
                size += sizeof(struct can_bittiming_const);

        return size;
}

static int can_fill_info(struct sk_buff *skb, const struct net_device *dev)
{
        struct can_priv *priv = netdev_priv(dev);
        struct can_ctrlmode cm = {.flags = priv->ctrlmode};
        enum can_state state = priv->state;

        if (priv->do_get_state)
                priv->do_get_state(dev, &state);
        NLA_PUT_U32(skb, IFLA_CAN_STATE, state);
        NLA_PUT(skb, IFLA_CAN_CTRLMODE, sizeof(cm), &cm);
        NLA_PUT_U32(skb, IFLA_CAN_RESTART_MS, priv->restart_ms);
        NLA_PUT(skb, IFLA_CAN_BITTIMING,
                sizeof(priv->bittiming), &priv->bittiming);
        NLA_PUT(skb, IFLA_CAN_CLOCK, sizeof(cm), &priv->clock);
        if (priv->bittiming_const)
                NLA_PUT(skb, IFLA_CAN_BITTIMING_CONST,
                        sizeof(*priv->bittiming_const), priv->bittiming_const);

        return 0;

nla_put_failure:
        return -EMSGSIZE;
}

static size_t can_get_xstats_size(const struct net_device *dev)
{
        return sizeof(struct can_device_stats);
}

static int can_fill_xstats(struct sk_buff *skb, const struct net_device *dev)
{
        struct can_priv *priv = netdev_priv(dev);

        NLA_PUT(skb, IFLA_INFO_XSTATS,
                sizeof(priv->can_stats), &priv->can_stats);

        return 0;

nla_put_failure:
        return -EMSGSIZE;
}

static int can_newlink(struct net_device *dev,
                       struct nlattr *tb[], struct nlattr *data[])
{
        return -EOPNOTSUPP;
}

static struct rtnl_link_ops can_link_ops __read_mostly = {
        .kind           = "can",
        .maxtype        = IFLA_CAN_MAX,
        .policy         = can_policy,
        .setup          = can_setup,
        .newlink        = can_newlink,
        .changelink     = can_changelink,
        .get_size       = can_get_size,
        .fill_info      = can_fill_info,
        .get_xstats_size = can_get_xstats_size,
        .fill_xstats    = can_fill_xstats,
};

/*
 * Register the CAN network device
 */
int register_candev(struct net_device *dev)
{
        dev->rtnl_link_ops = &can_link_ops;
        return register_netdev(dev);
}
EXPORT_SYMBOL_GPL(register_candev);

/*
 * Unregister the CAN network device
 */
void unregister_candev(struct net_device *dev)
{
        unregister_netdev(dev);
}
EXPORT_SYMBOL_GPL(unregister_candev);

static __init int can_dev_init(void)
{
        int err;

        err = rtnl_link_register(&can_link_ops);
        if (!err)
                printk(KERN_INFO MOD_DESC "\n");

        return err;
}
module_init(can_dev_init);

static __exit void can_dev_exit(void)
{
        rtnl_link_unregister(&can_link_ops);
}
module_exit(can_dev_exit);

MODULE_ALIAS_RTNL_LINK("can");