/* * elmcan.c - ELM327 based CAN interface driver * (tty line discipline) * * This file is derived from linux/drivers/net/can/slcan.c * * elmcan.c Author : Max Staudt * slcan.c Author : Oliver Hartkopp * slip.c Authors : Laurence Culhane * Fred N. van Kempen * * SPDX-License-Identifier: GPL-2.0 * */ #define pr_fmt(fmt) "[elmcan] " fmt #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include MODULE_ALIAS_LDISC(N_ELMCAN); MODULE_DESCRIPTION("ELM327 based CAN interface"); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Max Staudt "); /* Line discipline ID number */ #ifndef N_ELMCAN #define N_ELMCAN 29 #endif #define ELM327_CAN_CONFIG_SEND_SFF 0x8000 #define ELM327_CAN_CONFIG_VARIABLE_DLC 0x4000 #define ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF 0x2000 #define ELM327_CAN_CONFIG_BAUDRATE_MULT_8_7 0x1000 #define ELM327_MAGIC_CHAR 'y' #define ELM327_MAGIC_STRING "y" #define ELM327_READY_CHAR '>' /* Bits in elm->cmds_todo */ enum ELM_TODO { ELM_TODO_CAN_DATA = 0, ELM_TODO_CANID_11BIT, ELM_TODO_CANID_29BIT_LOW, ELM_TODO_CANID_29BIT_HIGH, ELM_TODO_CAN_CONFIG, ELM_TODO_RESPONSES, ELM_TODO_SILENT_MONITOR, ELM_TODO_INIT }; struct elmcan { /* This must be the first member when using alloc_candev() */ struct can_priv can; /* TTY and netdev devices that we're bridging */ struct tty_struct *tty; struct net_device *dev; char ifname[IFNAMSIZ]; /* Per-channel lock */ spinlock_t lock; /* Keep track of how many things are using this struct. * Once it reaches 0, we are in the process of cleaning up, * and new operations will be cancelled immediately. * Use atomic_t rather than refcount_t because we deliberately * decrement to 0, and refcount_dec() spills a WARN_ONCE in * that case. */ atomic_t refcount; /* TTY TX helpers */ struct work_struct tx_work; /* Flushes TTY TX buffer */ unsigned char txbuf[32]; unsigned char *txhead; /* Pointer to next TX byte */ int txleft; /* Bytes left to TX */ /* TTY RX helpers */ unsigned char rxbuf[256]; int rxfill; /* State machine */ enum { ELM_NOTINIT = 0, ELM_GETMAGICCHAR, ELM_GETPROMPT, ELM_RECEIVING, } state; int drop_next_line; /* The CAN frame and config the ELM327 is sending/using, * or will send/use after finishing all cmds_todo */ struct can_frame can_frame; unsigned short can_config; unsigned long can_bitrate; unsigned char can_bitrate_divisor; int silent_monitoring; /* Things we have yet to send */ char **next_init_cmd; unsigned long cmds_todo; }; /* A lock for all tty->disc_data handled by this ldisc. * This is to prevent a case where tty->disc_data is set to NULL, * yet someone is still trying to dereference it. * Without this, we cannot do a clean shutdown. */ static DEFINE_SPINLOCK(elmcan_discdata_lock); static inline void elm327_panic(struct elmcan *elm); /************************************************************************ * ELM327: Transmission * * * * (all functions assume elm->lock taken) * ************************************************************************/ static void elm327_send(struct elmcan *elm, const void *buf, size_t len) { int actual; memcpy(elm->txbuf, buf, len); /* Order of next two lines is *very* important. * When we are sending a little amount of data, * the transfer may be completed inside the ops->write() * routine, because it's running with interrupts enabled. * In this case we *never* got WRITE_WAKEUP event, * if we did not request it before write operation. * 14 Oct 1994 Dmitry Gorodchanin. */ set_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags); actual = elm->tty->ops->write(elm->tty, elm->txbuf, len); if (actual < 0) { pr_err("Failed to write to tty for %s.\n", elm->dev->name); elm327_panic(elm); } elm->txleft = len - actual; elm->txhead = elm->txbuf + actual; } /* * Take the ELM327 out of almost any state and back into command mode * * Assumes elm->lock taken. */ static void elm327_kick_into_cmd_mode(struct elmcan *elm) { if (elm->state != ELM_GETMAGICCHAR && elm->state != ELM_GETPROMPT) { elm327_send(elm, ELM327_MAGIC_STRING, 1); elm->state = ELM_GETMAGICCHAR; elm->rxfill = 0; } } /* * Schedule a CAN frame, and any necessary config changes, * to be sent down the TTY. * * Assumes elm->lock taken. */ static void elm327_send_frame(struct elmcan *elm, struct can_frame *frame) { /* Schedule any necessary changes in ELM327's CAN configuration */ if (elm->can_frame.can_id != frame->can_id) { /* Set the new CAN ID for transmission. */ if ((frame->can_id & CAN_EFF_FLAG) ^ (elm->can_frame.can_id & CAN_EFF_FLAG)) { elm->can_config = (frame->can_id & CAN_EFF_FLAG ? 0 : ELM327_CAN_CONFIG_SEND_SFF) | ELM327_CAN_CONFIG_VARIABLE_DLC | ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF | elm->can_bitrate_divisor; set_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo); } if (frame->can_id & CAN_EFF_FLAG) { clear_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo); set_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo); set_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo); } else { set_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo); clear_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo); clear_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo); } } /* Schedule the CAN frame itself. */ elm->can_frame = *frame; set_bit(ELM_TODO_CAN_DATA, &elm->cmds_todo); elm327_kick_into_cmd_mode(elm); } /************************************************************************ * ELM327: Initialization sequence * * * * (assumes elm->lock taken) * ************************************************************************/ static char *elm327_init_script[] = { "AT WS\r", /* v1.0: Warm Start */ "AT PP FF OFF\r", /* v1.0: All Programmable Parameters Off */ "AT M0\r", /* v1.0: Memory Off */ "AT AL\r", /* v1.0: Allow Long messages */ "AT BI\r", /* v1.0: Bypass Initialization */ "AT CAF0\r", /* v1.0: CAN Auto Formatting Off */ "AT CFC0\r", /* v1.0: CAN Flow Control Off */ "AT CF 000\r", /* v1.0: Reset CAN ID Filter */ "AT CM 000\r", /* v1.0: Reset CAN ID Mask */ "AT E1\r", /* v1.0: Echo On */ "AT H1\r", /* v1.0: Headers On */ "AT L0\r", /* v1.0: Linefeeds Off */ "AT SH 7DF\r", /* v1.0: Set CAN sending ID to 0x7df */ "AT ST FF\r", /* v1.0: Set maximum Timeout for response after TX */ "AT AT0\r", /* v1.2: Adaptive Timing Off */ "AT D1\r", /* v1.3: Print DLC On */ "AT S1\r", /* v1.3: Spaces On */ "AT TP B\r", /* v1.0: Try Protocol B */ NULL }; static void elm327_init(struct elmcan *elm) { elm->state = ELM_NOTINIT; elm->can_frame.can_id = 0x7df; elm->rxfill = 0; elm->drop_next_line = 0; /* We can only set the bitrate as a fraction of 500000. * The bit timing constants in elmcan_bittiming_const will * limit the user to the right values. */ elm->can_bitrate_divisor = 500000 / elm->can.bittiming.bitrate; elm->can_config = ELM327_CAN_CONFIG_SEND_SFF | ELM327_CAN_CONFIG_VARIABLE_DLC | ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF | elm->can_bitrate_divisor; /* Configure ELM327 and then start monitoring */ elm->next_init_cmd = &elm327_init_script[0]; set_bit(ELM_TODO_INIT, &elm->cmds_todo); set_bit(ELM_TODO_SILENT_MONITOR, &elm->cmds_todo); set_bit(ELM_TODO_RESPONSES, &elm->cmds_todo); set_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo); elm327_kick_into_cmd_mode(elm); } /************************************************************************ * ELM327: Reception -> netdev glue * * * * (assumes elm->lock taken) * ************************************************************************/ static void elm327_feed_frame_to_netdev(struct elmcan *elm, const struct can_frame *frame) { struct can_frame *cf; struct sk_buff *skb; if (!netif_running(elm->dev)) { return; } skb = alloc_can_skb(elm->dev, &cf); if (!skb) return; memcpy(cf, frame, sizeof(struct can_frame)); elm->dev->stats.rx_packets++; elm->dev->stats.rx_bytes += frame->can_dlc; netif_rx_ni(skb); can_led_event(elm->dev, CAN_LED_EVENT_RX); } /************************************************************************ * ELM327: Panic handler * * * * (assumes elm->lock taken) * ************************************************************************/ static inline void elm327_panic(struct elmcan *elm) { struct can_frame frame = {0}; frame.can_id = CAN_ERR_FLAG | CAN_ERR_RESTARTED; frame.can_dlc = CAN_ERR_DLC; elm327_feed_frame_to_netdev(elm, &frame); pr_err("ELM327 misbehaved. Re-initializing.\n"); elm->can.can_stats.restarts++; elm327_init(elm); } /************************************************************************ * ELM327: Reception parser * * * * (assumes elm->lock taken) * ************************************************************************/ static void elm327_parse_error(struct elmcan *elm, int len) { struct can_frame frame = {0}; frame.can_id = CAN_ERR_FLAG; frame.can_dlc = CAN_ERR_DLC; switch(len) { case 17: if (!memcmp(elm->rxbuf, "UNABLE TO CONNECT", 17)) { pr_err("The ELM327 reported UNABLE TO CONNECT. Please check your setup.\n"); } break; case 11: if (!memcmp(elm->rxbuf, "BUFFER FULL", 11)) { /* This case will only happen if the last data * line was complete. * Otherwise, elm327_parse_frame() will emit the * error frame instead. */ frame.can_id |= CAN_ERR_CRTL; frame.data[1] = CAN_ERR_CRTL_RX_OVERFLOW; } break; case 9: if (!memcmp(elm->rxbuf, "BUS ERROR", 9)) { frame.can_id |= CAN_ERR_BUSERROR; } if (!memcmp(elm->rxbuf, "CAN ERROR", 9) || !memcmp(elm->rxbuf, "rxbuf, "BUS BUSY", 8)) { frame.can_id |= CAN_ERR_PROT; frame.data[2] = CAN_ERR_PROT_OVERLOAD; } if (!memcmp(elm->rxbuf, "FB ERROR", 8)) { frame.can_id |= CAN_ERR_PROT; frame.data[2] = CAN_ERR_PROT_TX; } break; case 5: if (!memcmp(elm->rxbuf, "ERR", 3)) { pr_err("The ELM327 reported an ERR%c%c. Please power it off and on again.\n", elm->rxbuf[3], elm->rxbuf[4]); frame.can_id |= CAN_ERR_CRTL; } break; default: /* Don't emit an error frame if we're unsure */ return; } elm327_feed_frame_to_netdev(elm, &frame); } static int elm327_parse_frame(struct elmcan *elm, int len) { struct can_frame frame = {0}; int hexlen; int datastart; int i; /* Find first non-hex and non-space character: * - In the simplest case, there is none. * - For RTR frames, 'R' is the first non-hex character. * - An error message may replace the end of the data line. */ for (hexlen = 0; hexlen <= len; hexlen++) { if (hex_to_bin(elm->rxbuf[hexlen]) < 0 && elm->rxbuf[hexlen] != ' ') { break; } } /* Use spaces in CAN ID to distinguish 29 or 11 bit address length. * No out-of-bounds access: * We use the fact that we can always read from elm->rxbuf. */ if (elm->rxbuf[2] == ' ' && elm->rxbuf[5] == ' ' && elm->rxbuf[8] == ' ' && elm->rxbuf[11] == ' ' && elm->rxbuf[13] == ' ') { frame.can_id = CAN_EFF_FLAG; datastart = 14; } else if (elm->rxbuf[3] == ' ' && elm->rxbuf[5] == ' ') { frame.can_id = 0; datastart = 6; } else { /* This is not a well-formatted data line. * Assume it's an error message. */ return 1; } if (hexlen < datastart) { /* The line is too short to be a valid frame hex dump. * Something interrupted the hex dump or it is invalid. */ return 1; } /* From here on all chars up to buf[hexlen] are hex or spaces, * at well-defined offsets. */ /* Read CAN data length */ frame.can_dlc = (hex_to_bin(elm->rxbuf[datastart - 2]) << 0); /* Read CAN ID */ if (frame.can_id & CAN_EFF_FLAG) { frame.can_id |= (hex_to_bin(elm->rxbuf[0]) << 28) | (hex_to_bin(elm->rxbuf[1]) << 24) | (hex_to_bin(elm->rxbuf[3]) << 20) | (hex_to_bin(elm->rxbuf[4]) << 16) | (hex_to_bin(elm->rxbuf[6]) << 12) | (hex_to_bin(elm->rxbuf[7]) << 8) | (hex_to_bin(elm->rxbuf[9]) << 4) | (hex_to_bin(elm->rxbuf[10]) << 0); } else { frame.can_id |= (hex_to_bin(elm->rxbuf[0]) << 8) | (hex_to_bin(elm->rxbuf[1]) << 4) | (hex_to_bin(elm->rxbuf[2]) << 0); } /* Check for RTR frame */ if (elm->rxfill >= hexlen + 3 && elm->rxbuf[hexlen + 0] == 'R' && elm->rxbuf[hexlen + 1] == 'T' && elm->rxbuf[hexlen + 2] == 'R') { frame.can_id |= CAN_RTR_FLAG; } /* Is the line long enough to hold the advertised payload? */ if (!(frame.can_id & CAN_RTR_FLAG) && (hexlen < frame.can_dlc * 3 + datastart)) { /* Incomplete frame. */ /* Probably the ELM327's RS232 TX buffer was full. * Emit an error frame and exit. */ frame.can_id = CAN_ERR_FLAG | CAN_ERR_CRTL; frame.can_dlc = CAN_ERR_DLC; frame.data[1] = CAN_ERR_CRTL_RX_OVERFLOW; elm327_feed_frame_to_netdev(elm, &frame); /* Signal failure to parse. * The line will be re-parsed as an error line, which will fail. * However, this will correctly drop the state machine back into * command mode. */ return 2; } /* Parse the data nibbles. */ for (i = 0; i < frame.can_dlc; i++) { frame.data[i] = (hex_to_bin(elm->rxbuf[datastart+3*i]) << 4) | (hex_to_bin(elm->rxbuf[datastart+3*i+1]) << 0); } /* Feed the frame to the network layer. */ elm327_feed_frame_to_netdev(elm, &frame); return 0; } static void elm327_parse_line(struct elmcan *elm, int len) { /* Skip empty lines */ if (!len) { return; } /* Skip echo lines */ if (elm->drop_next_line) { elm->drop_next_line = 0; return; } else if (elm->rxbuf[0] == 'A' && elm->rxbuf[1] == 'T') { return; } /* Regular parsing */ switch(elm->state) { case ELM_RECEIVING: if (elm327_parse_frame(elm, len)) { /* Parse an error line. */ elm327_parse_error(elm, len); /* After the error line, we expect a prompt. */ elm->state = ELM_GETPROMPT; } break; default: break; } } static void elm327_handle_prompt(struct elmcan *elm) { if (elm->cmds_todo) { struct can_frame *frame = &elm->can_frame; char txbuf[20]; if (test_bit(ELM_TODO_INIT, &elm->cmds_todo)) { elm327_send(elm, *elm->next_init_cmd, strlen(*elm->next_init_cmd)); elm->next_init_cmd++; if (!(*elm->next_init_cmd)) { clear_bit(ELM_TODO_INIT, &elm->cmds_todo); pr_info("%s: Initialization finished.\n", elm->dev->name); } /* Some chips are unreliable and need extra time after * init commands, as seen with a clone. * So let's do a dummy get-cmd-prompt dance. */ elm->state = ELM_NOTINIT; elm327_kick_into_cmd_mode(elm); } else if (test_and_clear_bit(ELM_TODO_SILENT_MONITOR, &elm->cmds_todo)) { snprintf(txbuf, sizeof(txbuf), "ATCSM%i\r", !(!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY))); } else if (test_and_clear_bit(ELM_TODO_RESPONSES, &elm->cmds_todo)) { snprintf(txbuf, sizeof(txbuf), "ATR%i\r", !(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)); } else if (test_and_clear_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo)) { snprintf(txbuf, sizeof(txbuf), "ATPB%04X\r", elm->can_config); } else if (test_and_clear_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo)) { snprintf(txbuf, sizeof(txbuf), "ATCP%02X\r", (frame->can_id & CAN_EFF_MASK) >> 24); } else if (test_and_clear_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo)) { snprintf(txbuf, sizeof(txbuf), "ATSH%06X\r", frame->can_id & CAN_EFF_MASK & ((1 << 24) - 1)); } else if (test_and_clear_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo)) { snprintf(txbuf, sizeof(txbuf), "ATSH%03X\r", frame->can_id & CAN_SFF_MASK); } else if (test_and_clear_bit(ELM_TODO_CAN_DATA, &elm->cmds_todo)) { if (frame->can_id & CAN_RTR_FLAG) { snprintf(txbuf, sizeof(txbuf), "ATRTR\r"); } else { int i; for (i = 0; i < frame->can_dlc; i++) { sprintf(&txbuf[2*i], "%02X", frame->data[i]); } sprintf(&txbuf[2*i], "\r"); } elm->drop_next_line = 1; elm->state = ELM_RECEIVING; } elm327_send(elm, txbuf, strlen(txbuf)); } else { /* Enter CAN monitor mode */ elm327_send(elm, "ATMA\r", 5); elm->state = ELM_RECEIVING; } } static void elm327_drop_bytes(struct elmcan *elm, int i) { memmove(&elm->rxbuf[0], &elm->rxbuf[i], sizeof(elm->rxbuf) - i); elm->rxfill -= i; } static void elm327_parse_rxbuf(struct elmcan *elm) { int len; switch (elm->state) { case ELM_NOTINIT: elm->rxfill = 0; return; case ELM_GETMAGICCHAR: { /* Wait for 'y' or '>' */ int i; for (i = 0; i < elm->rxfill; i++) { if (elm->rxbuf[i] == ELM327_MAGIC_CHAR) { elm327_send(elm, "\r", 1); elm->state = ELM_GETPROMPT; i++; break; } else if (elm->rxbuf[i] == ELM327_READY_CHAR) { elm327_send(elm, ELM327_MAGIC_STRING, 1); i++; break; } } elm327_drop_bytes(elm, i); return; } case ELM_GETPROMPT: /* Wait for '>' */ if (elm->rxbuf[elm->rxfill - 1] == ELM327_READY_CHAR) { elm327_handle_prompt(elm); } elm->rxfill = 0; return; case ELM_RECEIVING: /* Find delimiting feedback lines. */ for (len = 0; (len < elm->rxfill) && (elm->rxbuf[len] != '\r'); len++) { /* empty loop */ } if (len == sizeof(elm->rxbuf)) { /* Line exceeds buffer. It's probably all garbage. * Did we even connect at the right baud rate? */ pr_err("RX buffer overflow. Faulty ELM327 connected?\n"); elm327_panic(elm); } else if (len == elm->rxfill) { if (elm->state == ELM_RECEIVING && elm->rxbuf[elm->rxfill - 1] == ELM327_READY_CHAR) { /* The ELM327's AT ST response timeout ran out, * so we got a prompt. * Clear RX buffer and restart listening. */ elm->rxfill = 0; elm327_handle_prompt(elm); return; } else { /* We haven't received a full line yet. * Wait for more data. */ return; } } /* We have a full line to parse. */ elm327_parse_line(elm, len); /* Remove parsed data from RX buffer. */ elm327_drop_bytes(elm, len+1); /* More data to parse? */ if (elm->rxfill) { elm327_parse_rxbuf(elm); } } } /************************************************************************ * netdev * * * * (takes elm->lock) * ************************************************************************/ static int elmcan_netdev_init(struct net_device *dev) { struct elmcan *elm = netdev_priv(dev); /* Copy the interface name here, so the SIOCGIFNAME case in * elmcan_ldisc_ioctl() doesn't race against unregister_candev(). */ memcpy(elm->ifname, dev->name, IFNAMSIZ); return 0; } /* Netdevice DOWN -> UP routine */ static int elmcan_netdev_open(struct net_device *dev) { struct elmcan *elm = netdev_priv(dev); int err; spin_lock_bh(&elm->lock); if (elm->tty == NULL) { spin_unlock_bh(&elm->lock); return -ENODEV; } /* open_candev() checks for elm->can.bittiming.bitrate != 0 */ err = open_candev(dev); if (err) { spin_unlock_bh(&elm->lock); return err; } /* Initialize the ELM327 */ elm327_init(elm); spin_unlock_bh(&elm->lock); can_led_event(dev, CAN_LED_EVENT_OPEN); elm->can.state = CAN_STATE_ERROR_ACTIVE; netif_start_queue(dev); return 0; } /* Netdevice UP -> DOWN routine */ static int elmcan_netdev_close(struct net_device *dev) { struct elmcan *elm = netdev_priv(dev); spin_lock_bh(&elm->lock); if (elm->tty) { /* TTY discipline is running. */ /* Interrupt whatever we're doing right now */ elm327_send(elm, ELM327_MAGIC_STRING, 1); /* Clear the wakeup bit, as the netdev will be down and thus * the wakeup handler won't clear it */ clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags); spin_unlock_bh(&elm->lock); flush_work(&elm->tx_work); } else { spin_unlock_bh(&elm->lock); } elm->can.state = CAN_STATE_STOPPED; netif_stop_queue(dev); close_candev(dev); can_led_event(dev, CAN_LED_EVENT_STOP); return 0; } /* Send a can_frame to a TTY queue. */ static netdev_tx_t elmcan_netdev_start_xmit(struct sk_buff *skb, struct net_device *dev) { struct elmcan *elm = netdev_priv(dev); struct can_frame *frame = (struct can_frame *) skb->data; if (skb->len != sizeof(struct can_frame)) goto out; if (!netif_running(dev)) { pr_warn("%s: xmit: iface is down\n", dev->name); goto out; } /* BHs are already disabled, so no spin_lock_bh(). * See Documentation/networking/netdevices.txt */ spin_lock(&elm->lock); if (elm->tty == NULL || elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) { spin_unlock(&elm->lock); goto out; } netif_stop_queue(dev); elm327_send_frame(elm, frame); spin_unlock(&elm->lock); dev->stats.tx_packets++; dev->stats.tx_bytes += frame->can_dlc; can_led_event(dev, CAN_LED_EVENT_TX); out: kfree_skb(skb); return NETDEV_TX_OK; } static int elmcan_netdev_change_mtu(struct net_device *dev, int new_mtu) { return -EINVAL; } static const struct net_device_ops elmcan_netdev_ops = { .ndo_init = elmcan_netdev_init, .ndo_open = elmcan_netdev_open, .ndo_stop = elmcan_netdev_close, .ndo_start_xmit = elmcan_netdev_start_xmit, .ndo_change_mtu = elmcan_netdev_change_mtu, }; /************************************************************************ * Line discipline * * * * (takes elm->lock) * ************************************************************************/ /* * Get a reference to our struct, taking into account locks/refcounts. * This is to ensure ordering in case we are shutting down, and to ensure * there is a refcount at all (because tty->disc_data may be NULL). */ static struct elmcan* get_elm(struct tty_struct *tty) { struct elmcan *elm; bool got_ref; /* Lock all elmcan TTYs, so tty->disc_data can't become NULL * the moment before we increase the reference counter. */ spin_lock_bh(&elmcan_discdata_lock); elm = (struct elmcan *) tty->disc_data; if (!elm) { spin_unlock_bh(&elmcan_discdata_lock); return NULL; } got_ref = atomic_inc_not_zero(&elm->refcount); spin_unlock_bh(&elmcan_discdata_lock); if (!got_ref) { return NULL; } return elm; } static void put_elm(struct elmcan *elm) { atomic_dec(&elm->refcount); } /* * Handle the 'receiver data ready' interrupt. * This function is called by the 'tty_io' module in the kernel when * a block of ELM327 CAN data has been received, which can now be parsed * and sent on to some IP layer for further processing. This will not * be re-entered while running but other ldisc functions may be called * in parallel */ static void elmcan_ldisc_rx(struct tty_struct *tty, const unsigned char *cp, char *fp, int count) { struct elmcan *elm = get_elm(tty); if (!elm) return; /* Read the characters out of the buffer */ while (count-- && elm->rxfill < sizeof(elm->rxbuf)) { if (fp && *fp++) { pr_err("Error in received character stream. Check your wiring."); spin_lock_bh(&elm->lock); elm327_panic(elm); spin_unlock_bh(&elm->lock); put_elm(elm); return; } if (*cp != 0) { elm->rxbuf[elm->rxfill++] = *cp; } cp++; } if (count >= 0) { pr_err("Receive buffer overflowed. Bad chip or wiring?"); spin_lock_bh(&elm->lock); elm327_panic(elm); spin_unlock_bh(&elm->lock); put_elm(elm); return; } spin_lock_bh(&elm->lock); elm327_parse_rxbuf(elm); spin_unlock_bh(&elm->lock); put_elm(elm); } /* * Write out remaining transmit buffer. * Scheduled when TTY is writable. */ static void elmcan_ldisc_tx_worker(struct work_struct *work) { /* No need to use get_elm() here, as we'll always flush workers * befory destroying the elmcan object. */ struct elmcan *elm = container_of(work, struct elmcan, tx_work); ssize_t actual; spin_lock_bh(&elm->lock); /* First make sure we're connected. */ if (!elm->tty || !netif_running(elm->dev)) { spin_unlock_bh(&elm->lock); return; } if (elm->txleft <= 0) { /* Our TTY write buffer is empty: * We can start transmission of another packet */ clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags); spin_unlock_bh(&elm->lock); netif_wake_queue(elm->dev); return; } actual = elm->tty->ops->write(elm->tty, elm->txhead, elm->txleft); if (actual < 0) { pr_err("Failed to write to tty for %s.\n", elm->dev->name); elm327_panic(elm); } elm->txleft -= actual; elm->txhead += actual; spin_unlock_bh(&elm->lock); } /* * Called by the driver when there's room for more data. * Schedule the transmit. */ static void elmcan_ldisc_tx_wakeup(struct tty_struct *tty) { struct elmcan *elm = get_elm(tty); if (!elm) return; schedule_work(&elm->tx_work); put_elm(elm); } /* Some fake bit timings to allow bitrate setting */ static const struct can_bittiming_const elmcan_bittiming_const = { .name = "elmcan", .tseg1_min = 1, .tseg1_max = 1, .tseg2_min = 0, .tseg2_max = 0, .sjw_max = 1, .brp_min = 1, .brp_max = 500, .brp_inc = 1, }; /* * Open the high-level part of the elmcan channel. * This function is called by the TTY module when the * elmcan line discipline is called for. * * Called in process context serialized from other ldisc calls. */ static int elmcan_ldisc_open(struct tty_struct *tty) { struct net_device *dev; struct elmcan *elm; int err; if (!capable(CAP_NET_ADMIN)) return -EPERM; if (!tty->ops->write) return -EOPNOTSUPP; /* OK. Find a free elmcan channel to use. */ dev = alloc_candev(sizeof(struct elmcan), 0); if (!dev) return -ENFILE; elm = netdev_priv(dev); /* Configure TTY interface */ tty->receive_room = 65536; /* We don't flow control */ elm->txleft = 0; /* Clear TTY TX buffer */ spin_lock_init(&elm->lock); atomic_set(&elm->refcount, 1); INIT_WORK(&elm->tx_work, elmcan_ldisc_tx_worker); /* Configure CAN metadata */ elm->can.state = CAN_STATE_STOPPED; elm->can.clock.freq = 1000000; elm->can.bittiming_const = &elmcan_bittiming_const; elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY; /* Configure netlink interface */ elm->dev = dev; dev->netdev_ops = &elmcan_netdev_ops; /* Mark ldisc channel as alive */ elm->tty = tty; tty->disc_data = elm; devm_can_led_init(elm->dev); /* Let 'er rip */ err = register_candev(elm->dev); if (err) { free_candev(elm->dev); return err; } netdev_info(elm->dev, "elmcan on %s.\n", tty->name); return 0; } /* * Close down an elmcan channel. * This means flushing out any pending queues, and then returning. * This call is serialized against other ldisc functions: * Once this is called, no other ldisc function of ours is entered. * * We also use this function for a hangup event. */ static void elmcan_ldisc_close(struct tty_struct *tty) { /* Use get_elm() to synchronize against other users */ struct elmcan *elm = get_elm(tty); if (!elm) return; /* Tear down network side. * unregister_netdev() calls .ndo_stop() so we don't have to. */ unregister_candev(elm->dev); /* Decrease the refcount twice, once for our own get_elm(), * and once to remove the count of 1 that we set in _open(). * Once it reaches 0, we can safely destroy it. */ put_elm(elm); put_elm(elm); /* Spin until refcount reaches 0 */ while(atomic_read(&elm->refcount) > 0) msleep(1); /* At this point, all ldisc calls to us will be no-ops. * Since the refcount is 0, they are bailing immediately. */ /* Mark channel as dead */ spin_lock_bh(&elm->lock); tty->disc_data = NULL; elm->tty = NULL; spin_unlock_bh(&elm->lock); /* Flush TTY side */ flush_work(&elm->tx_work); netdev_info(elm->dev, "elmcan off %s.\n", tty->name); /* Free our memory */ free_candev(elm->dev); } static int elmcan_ldisc_hangup(struct tty_struct *tty) { elmcan_ldisc_close(tty); return 0; } /* Perform I/O control on an active elmcan channel. */ static int elmcan_ldisc_ioctl(struct tty_struct *tty, struct file *file, unsigned int cmd, unsigned long arg) { struct elmcan *elm = get_elm(tty); unsigned int tmp; /* First make sure we're connected. */ if (!elm) return -EINVAL; switch (cmd) { case SIOCGIFNAME: tmp = strlen(elm->ifname) + 1; if (copy_to_user((void __user *)arg, elm->ifname, tmp)) { put_elm(elm); return -EFAULT; } put_elm(elm); return 0; case SIOCSIFHWADDR: put_elm(elm); return -EINVAL; default: put_elm(elm); return tty_mode_ioctl(tty, file, cmd, arg); } } static struct tty_ldisc_ops elmcan_ldisc = { .owner = THIS_MODULE, .magic = TTY_LDISC_MAGIC, .name = "elmcan", .receive_buf = elmcan_ldisc_rx, .write_wakeup = elmcan_ldisc_tx_wakeup, .open = elmcan_ldisc_open, .close = elmcan_ldisc_close, .hangup = elmcan_ldisc_hangup, .ioctl = elmcan_ldisc_ioctl, }; /************************************************************************ * Module init/exit * ************************************************************************/ static int __init elmcan_init(void) { int status; pr_info("ELM327 based best-effort CAN interface driver\n"); pr_info("This device is severely limited as a CAN interface, see documentation.\n"); /* Fill in our line protocol discipline, and register it */ status = tty_register_ldisc(N_ELMCAN, &elmcan_ldisc); if (status) { pr_err("can't register line discipline\n"); } return status; } static void __exit elmcan_exit(void) { /* This will only be called when all channels have been closed by * userspace - tty_ldisc.c takes care of the module's refcount. */ int status; status = tty_unregister_ldisc(N_ELMCAN); if (status) { pr_err("Can't unregister line discipline (error: %d)\n", status); } } module_init(elmcan_init); module_exit(elmcan_exit);