can: CAN Network device driver and Netlink interface
The CAN network device driver interface provides a generic interface to
setup, configure and monitor CAN network devices. It exports a set of
common data structures and functions, which all real CAN network device
drivers should use. Please have a look to the SJA1000 or MSCAN driver
to understand how to use them. The name of the module is can-dev.ko.
Furthermore, it adds a Netlink interface allowing to configure the CAN
device using the program "ip" from the iproute2 utility suite.
For further information please check "Documentation/networking/can.txt"
Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: Oliver Hartkopp <oliver.hartkopp@volkswagen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
new file mode 100644
index 0000000..52b0e7d
--- /dev/null
+++ b/drivers/net/can/dev.c
@@ -0,0 +1,657 @@
+/*
+ * 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 ((dev->flags & IFF_ECHO) && priv->echo_skb[idx]) {
+ netif_rx(priv->echo_skb[idx]);
+ priv->echo_skb[idx] = NULL;
+ }
+}
+EXPORT_SYMBOL_GPL(can_get_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 out;
+ }
+ 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);
+
+ dev->last_rx = jiffies;
+ stats->rx_packets++;
+ stats->rx_bytes += cf->can_dlc;
+
+ dev_dbg(dev->dev.parent, "restarted\n");
+ priv->can_stats.restarts++;
+
+ /* Now restart the device */
+ err = priv->do_set_mode(dev, CAN_MODE_START);
+
+out:
+ 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;
+ }
+
+ setup_timer(&priv->restart_timer, can_restart, (unsigned long)dev);
+
+ return 0;
+}
+EXPORT_SYMBOL(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 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 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 struct rtnl_link_ops can_link_ops __read_mostly = {
+ .kind = "can",
+ .maxtype = IFLA_CAN_MAX,
+ .policy = can_policy,
+ .setup = can_setup,
+ .changelink = can_changelink,
+ .fill_info = can_fill_info,
+ .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");