diff options
Diffstat (limited to 'module/can327.c')
| -rw-r--r-- | module/can327.c | 1210 |
1 files changed, 1210 insertions, 0 deletions
diff --git a/module/can327.c b/module/can327.c new file mode 100644 index 0000000..75d1ec5 --- /dev/null +++ b/module/can327.c @@ -0,0 +1,1210 @@ +// SPDX-License-Identifier: GPL-2.0 +/* ELM327 based CAN interface driver (tty line discipline) + * + * This driver started as a derivative of linux/drivers/net/can/slcan.c + * and my thanks go to the original authors for their inspiration. + * + * can327.c Author : Max Staudt <max-linux@enpas.org> + * slcan.c Author : Oliver Hartkopp <socketcan@hartkopp.net> + * slip.c Authors : Laurence Culhane <loz@holmes.demon.co.uk> + * Fred N. van Kempen <waltje@uwalt.nl.mugnet.org> + */ + +#define pr_fmt(fmt) "can327: " fmt + +#include <linux/init.h> +#include <linux/module.h> +#include <linux/moduleparam.h> + +#include <linux/atomic.h> +#include <linux/bitops.h> +#include <linux/ctype.h> +#include <linux/delay.h> +#include <linux/errno.h> +#include <linux/if_ether.h> +#include <linux/kernel.h> +#include <linux/list.h> +#include <linux/lockdep.h> +#include <linux/netdevice.h> +#include <linux/skbuff.h> +#include <linux/spinlock.h> +#include <linux/string.h> +#include <linux/tty.h> +#include <linux/tty_ldisc.h> +#include <linux/version.h> +#include <linux/workqueue.h> + +#include <uapi/linux/tty.h> + +#include <linux/can.h> +#include <linux/can/dev.h> +#include <linux/can/error.h> +#include <linux/can/led.h> +#include <linux/can/rx-offload.h> + +/* Line discipline ID number. + * Starting with Linux v5.18-rc1, N_DEVELOPMENT is defined as 29: + * https://github.com/torvalds/linux/commit/c2faf737abfb10f88f2d2612d573e9edc3c42c37 + */ +#ifndef N_DEVELOPMENT +#define N_DEVELOPMENT 29 +#endif + +/* Compatibility for Linux < 5.11 */ +#if LINUX_VERSION_CODE < KERNEL_VERSION(5,11,0) +#define len can_dlc +#endif + +#define ELM327_NAPI_WEIGHT 4 + +#define ELM327_SIZE_RXBUF 224 +#define ELM327_SIZE_TXBUF 32 + +#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_DUMMY_CHAR 'y' +#define ELM327_DUMMY_STRING "y" +#define ELM327_READY_CHAR '>' + +/* Bits in elm->cmds_todo */ +enum elm327_to_to_do_bits { + ELM327_TX_DO_CAN_DATA = 0, + ELM327_TX_DO_CANID_11BIT, + ELM327_TX_DO_CANID_29BIT_LOW, + ELM327_TX_DO_CANID_29BIT_HIGH, + ELM327_TX_DO_CAN_CONFIG_PART2, + ELM327_TX_DO_CAN_CONFIG, + ELM327_TX_DO_RESPONSES, + ELM327_TX_DO_SILENT_MONITOR, + ELM327_TX_DO_INIT +}; + +struct can327 { + /* This must be the first member when using alloc_candev() */ + struct can_priv can; + + struct can_rx_offload offload; + + /* TTY buffers */ + u8 rxbuf[ELM327_SIZE_RXBUF]; + u8 txbuf[ELM327_SIZE_TXBUF] ____cacheline_aligned; + + /* Per-channel lock */ + spinlock_t lock; + + /* TTY and netdev devices that we're bridging */ + struct tty_struct *tty; + struct net_device *dev; + + /* TTY buffer accounting */ + struct work_struct tx_work; /* Flushes TTY TX buffer */ + u8 *txhead; /* Next TX byte */ + size_t txleft; /* Bytes left to TX */ + int rxfill; /* Bytes already RX'd in buffer */ + + /* State machine */ + enum { + ELM327_STATE_NOTINIT = 0, + ELM327_STATE_GETDUMMYCHAR, + ELM327_STATE_GETPROMPT, + ELM327_STATE_RECEIVING, + } state; + + /* Things we have yet to send */ + char **next_init_cmd; + unsigned long cmds_todo; + + /* The CAN frame and config the ELM327 is sending/using, + * or will send/use after finishing all cmds_todo + */ + struct can_frame can_frame_to_send; + u16 can_config; + u8 can_bitrate_divisor; + + /* Parser state */ + bool drop_next_line; + + /* Stop the channel on UART side hardware failure, e.g. stray + * characters or neverending lines. This may be caused by bad + * UART wiring, a bad ELM327, a bad UART bridge... + * Once this is true, nothing will be sent to the TTY. + */ + bool uart_side_failure; +}; + +static inline void elm327_uart_side_failure(struct can327 *elm); + +static void elm327_send(struct can327 *elm, const void *buf, size_t len) +{ + int written; + + lockdep_assert_held(&elm->lock); + + if (elm->uart_side_failure) + return; + + 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); + written = elm->tty->ops->write(elm->tty, elm->txbuf, len); + if (written < 0) { + netdev_err(elm->dev, + "Failed to write to tty %s.\n", + elm->tty->name); + elm327_uart_side_failure(elm); + return; + } + + elm->txleft = len - written; + elm->txhead = elm->txbuf + written; +} + +/* Take the ELM327 out of almost any state and back into command mode. + * We send ELM327_DUMMY_CHAR which will either abort any running + * operation, or be echoed back to us in case we're already in command + * mode. + */ +static void elm327_kick_into_cmd_mode(struct can327 *elm) +{ + lockdep_assert_held(&elm->lock); + + if (elm->state != ELM327_STATE_GETDUMMYCHAR && + elm->state != ELM327_STATE_GETPROMPT) { + elm327_send(elm, ELM327_DUMMY_STRING, 1); + + elm->state = ELM327_STATE_GETDUMMYCHAR; + } +} + +/* Schedule a CAN frame and necessary config changes to be sent to the TTY. */ +static void elm327_send_frame(struct can327 *elm, struct can_frame *frame) +{ + lockdep_assert_held(&elm->lock); + + /* Schedule any necessary changes in ELM327's CAN configuration */ + if (elm->can_frame_to_send.can_id != frame->can_id) { + /* Set the new CAN ID for transmission. */ + if ((frame->can_id & CAN_EFF_FLAG) ^ + (elm->can_frame_to_send.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(ELM327_TX_DO_CAN_CONFIG, &elm->cmds_todo); + } + + if (frame->can_id & CAN_EFF_FLAG) { + clear_bit(ELM327_TX_DO_CANID_11BIT, &elm->cmds_todo); + set_bit(ELM327_TX_DO_CANID_29BIT_LOW, &elm->cmds_todo); + set_bit(ELM327_TX_DO_CANID_29BIT_HIGH, &elm->cmds_todo); + } else { + set_bit(ELM327_TX_DO_CANID_11BIT, &elm->cmds_todo); + clear_bit(ELM327_TX_DO_CANID_29BIT_LOW, &elm->cmds_todo); + clear_bit(ELM327_TX_DO_CANID_29BIT_HIGH, &elm->cmds_todo); + } + } + + /* Schedule the CAN frame itself. */ + elm->can_frame_to_send = *frame; + set_bit(ELM327_TX_DO_CAN_DATA, &elm->cmds_todo); + + elm327_kick_into_cmd_mode(elm); +} + +/* ELM327 initialisation sequence. + * The line length is limited by the buffer in elm327_handle_prompt(). + */ +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 Initialisation */ + "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 can327 *elm) +{ + lockdep_assert_held(&elm->lock); + + elm->state = ELM327_STATE_NOTINIT; + elm->can_frame_to_send.can_id = 0x7df; /* ELM327 HW default */ + elm->rxfill = 0; + elm->drop_next_line = 0; + + /* We can only set the bitrate as a fraction of 500000. + * The bit timing constants in can327_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(ELM327_TX_DO_INIT, &elm->cmds_todo); + set_bit(ELM327_TX_DO_SILENT_MONITOR, &elm->cmds_todo); + set_bit(ELM327_TX_DO_RESPONSES, &elm->cmds_todo); + set_bit(ELM327_TX_DO_CAN_CONFIG, &elm->cmds_todo); + + elm327_kick_into_cmd_mode(elm); +} + +static void elm327_feed_frame_to_netdev(struct can327 *elm, + struct sk_buff *skb) +{ + lockdep_assert_held(&elm->lock); + + if (!netif_running(elm->dev)) + return; + + /* Queue for NAPI pickup. + * rx-offload will update stats and LEDs for us. + */ + if (can_rx_offload_queue_tail(&elm->offload, skb)) + elm->dev->stats.rx_fifo_errors++; + +#if LINUX_VERSION_CODE >= KERNEL_VERSION(5,15,0) + /* Wake NAPI */ + can_rx_offload_irq_finish(&elm->offload); +#endif +} + +/* Called when we're out of ideas and just want it all to end. */ +static inline void elm327_uart_side_failure(struct can327 *elm) +{ + struct can_frame *frame; + struct sk_buff *skb; + + lockdep_assert_held(&elm->lock); + + elm->uart_side_failure = true; + + clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags); + + elm->can.can_stats.bus_off++; + netif_stop_queue(elm->dev); + elm->can.state = CAN_STATE_BUS_OFF; + can_bus_off(elm->dev); + + netdev_err(elm->dev, "ELM327 misbehaved. Blocking further communication.\n"); + + skb = alloc_can_err_skb(elm->dev, &frame); + if (!skb) + return; + + frame->can_id |= CAN_ERR_BUSOFF; + elm327_feed_frame_to_netdev(elm, skb); +} + +/* Compare buffer to string length, then compare buffer to fixed string. + * This ensures two things: + * - It flags cases where the fixed string is only the start of the + * buffer, rather than exactly all of it. + * - It avoids byte comparisons in case the length doesn't match. + * + * strncmp() cannot be used here because it accepts the following wrong case: + * strncmp("CAN ER", "CAN ERROR", 6); + * This must fail, hence this helper function. + */ +static inline int check_len_then_cmp(const u8 *mem, size_t mem_len, const char *str) +{ + size_t str_len = strlen(str); + + return (mem_len == str_len) && !memcmp(mem, str, str_len); +} + +static void elm327_parse_error(struct can327 *elm, size_t len) +{ + struct can_frame *frame; + struct sk_buff *skb; + + lockdep_assert_held(&elm->lock); + + skb = alloc_can_err_skb(elm->dev, &frame); + if (!skb) + /* It's okay to return here: + * The outer parsing loop will drop this UART buffer. + */ + return; + + /* Filter possible error messages based on length of RX'd line */ + if (check_len_then_cmp(elm->rxbuf, len, "UNABLE TO CONNECT")) { + netdev_err(elm->dev, + "ELM327 reported UNABLE TO CONNECT. Please check your setup.\n"); + } else if (check_len_then_cmp(elm->rxbuf, len, "BUFFER FULL")) { + /* This will only happen if the last data line was complete. + * Otherwise, elm327_parse_frame() will heuristically + * emit this kind of error frame instead. + */ + frame->can_id |= CAN_ERR_CRTL; + frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW; + } else if (check_len_then_cmp(elm->rxbuf, len, "BUS ERROR")) { + frame->can_id |= CAN_ERR_BUSERROR; + } else if (check_len_then_cmp(elm->rxbuf, len, "CAN ERROR")) { + frame->can_id |= CAN_ERR_PROT; + } else if (check_len_then_cmp(elm->rxbuf, len, "<RX ERROR")) { + frame->can_id |= CAN_ERR_PROT; + } else if (check_len_then_cmp(elm->rxbuf, len, "BUS BUSY")) { + frame->can_id |= CAN_ERR_PROT; + frame->data[2] = CAN_ERR_PROT_OVERLOAD; + } else if (check_len_then_cmp(elm->rxbuf, len, "FB ERROR")) { + frame->can_id |= CAN_ERR_PROT; + frame->data[2] = CAN_ERR_PROT_TX; + } else if (len == 5 && !memcmp(elm->rxbuf, "ERR", 3)) { + /* ERR is followed by two digits, hence line length 5 */ + netdev_err(elm->dev, "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; + } else { + /* Something else has happened. + * Maybe garbage on the UART line. + * Emit a generic error frame. + */ + } + + elm327_feed_frame_to_netdev(elm, skb); +} + +/* Parse CAN frames coming as ASCII from ELM327. + * They can be of various formats: + * + * 29-bit ID (EFF): 12 34 56 78 D PL PL PL PL PL PL PL PL + * 11-bit ID (!EFF): 123 D PL PL PL PL PL PL PL PL + * + * where D = DLC, PL = payload byte + * + * Instead of a payload, RTR indicates a remote request. + * + * We will use the spaces and line length to guess the format. + */ +static int elm327_parse_frame(struct can327 *elm, size_t len) +{ + struct can_frame *frame; + struct sk_buff *skb; + int hexlen; + int datastart; + int i; + + lockdep_assert_held(&elm->lock); + + skb = alloc_can_skb(elm->dev, &frame); + if (!skb) + return -ENOMEM; + + /* 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; + } + } + + /* Sanity check whether the line is really a clean hexdump, + * or terminated by an error message, or contains garbage. + */ + if (hexlen < len && + !isdigit(elm->rxbuf[hexlen]) && + !isupper(elm->rxbuf[hexlen]) && + '<' != elm->rxbuf[hexlen] && + ' ' != elm->rxbuf[hexlen]) { + /* The line is likely garbled anyway, so bail. + * The main code will restart listening. + */ + return -ENODATA; + } + + /* 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] == ' ') { + datastart = 6; + } else { + /* This is not a well-formatted data line. + * Assume it's an error message. + */ + return -ENODATA; + } + + 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 -ENODATA; + } + + /* From here on all chars up to buf[hexlen] are hex or spaces, + * at well-defined offsets. + */ + + /* Read CAN data length */ + frame->len = (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 && + !memcmp(&elm->rxbuf[hexlen], "RTR", 3)) { + frame->can_id |= CAN_RTR_FLAG; + } + + /* Is the line long enough to hold the advertised payload? + * Note: RTR frames have a DLC, but no actual payload. + */ + if (!(frame->can_id & CAN_RTR_FLAG) && + (hexlen < frame->len * 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->len = CAN_ERR_DLC; + frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW; + elm327_feed_frame_to_netdev(elm, skb); + + /* 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 -ENODATA; + } + + /* Parse the data nibbles. */ + for (i = 0; i < frame->len; i++) { + frame->data[i] = (hex_to_bin(elm->rxbuf[datastart + 3*i]) << 4) + | (hex_to_bin(elm->rxbuf[datastart + 3*i + 1])); + } + + /* Feed the frame to the network layer. */ + elm327_feed_frame_to_netdev(elm, skb); + + return 0; +} + +static void elm327_parse_line(struct can327 *elm, size_t len) +{ + lockdep_assert_held(&elm->lock); + + /* Skip empty lines */ + if (!len) + return; + + /* Skip echo lines */ + if (elm->drop_next_line) { + elm->drop_next_line = 0; + return; + } else if (!memcmp(elm->rxbuf, "AT", 2)) { + return; + } + + /* Regular parsing */ + if (elm->state == ELM327_STATE_RECEIVING && + elm327_parse_frame(elm, len)) { + /* Parse an error line. */ + elm327_parse_error(elm, len); + + /* Start afresh. */ + elm327_kick_into_cmd_mode(elm); + } +} + +static void elm327_handle_prompt(struct can327 *elm) +{ + struct can_frame *frame = &elm->can_frame_to_send; + /* Size this buffer for the largest ELM327 line we may generate, + * which is currently an 8 byte CAN frame's payload hexdump. + * Items in elm327_init_script must fit here, too! + */ + char local_txbuf[sizeof("0102030405060708\r")]; + + lockdep_assert_held(&elm->lock); + + if (!elm->cmds_todo) { + /* Enter CAN monitor mode */ + elm327_send(elm, "ATMA\r", 5); + elm->state = ELM327_STATE_RECEIVING; + + /* We will be in the default state once this command is + * sent, so enable the TX packet queue. + */ + netif_wake_queue(elm->dev); + + return; + } + + /* Reconfigure ELM327 step by step as indicated by elm->cmds_todo */ + if (test_bit(ELM327_TX_DO_INIT, &elm->cmds_todo)) { + snprintf(local_txbuf, sizeof(local_txbuf), + "%s", + *elm->next_init_cmd); + + elm->next_init_cmd++; + if (!(*elm->next_init_cmd)) { + clear_bit(ELM327_TX_DO_INIT, &elm->cmds_todo); + /* Init finished. */ + } + + } else if (test_and_clear_bit(ELM327_TX_DO_SILENT_MONITOR, &elm->cmds_todo)) { + snprintf(local_txbuf, sizeof(local_txbuf), + "ATCSM%i\r", + !(!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY))); + + } else if (test_and_clear_bit(ELM327_TX_DO_RESPONSES, &elm->cmds_todo)) { + snprintf(local_txbuf, sizeof(local_txbuf), + "ATR%i\r", + !(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)); + + } else if (test_and_clear_bit(ELM327_TX_DO_CAN_CONFIG, &elm->cmds_todo)) { + snprintf(local_txbuf, sizeof(local_txbuf), + "ATPC\r"); + set_bit(ELM327_TX_DO_CAN_CONFIG_PART2, &elm->cmds_todo); + + } else if (test_and_clear_bit(ELM327_TX_DO_CAN_CONFIG_PART2, &elm->cmds_todo)) { + snprintf(local_txbuf, sizeof(local_txbuf), + "ATPB%04X\r", + elm->can_config); + + } else if (test_and_clear_bit(ELM327_TX_DO_CANID_29BIT_HIGH, &elm->cmds_todo)) { + snprintf(local_txbuf, sizeof(local_txbuf), + "ATCP%02X\r", + (frame->can_id & CAN_EFF_MASK) >> 24); + + } else if (test_and_clear_bit(ELM327_TX_DO_CANID_29BIT_LOW, &elm->cmds_todo)) { + snprintf(local_txbuf, sizeof(local_txbuf), + "ATSH%06X\r", + frame->can_id & CAN_EFF_MASK & ((1 << 24) - 1)); + + } else if (test_and_clear_bit(ELM327_TX_DO_CANID_11BIT, &elm->cmds_todo)) { + snprintf(local_txbuf, sizeof(local_txbuf), + "ATSH%03X\r", + frame->can_id & CAN_SFF_MASK); + + } else if (test_and_clear_bit(ELM327_TX_DO_CAN_DATA, &elm->cmds_todo)) { + if (frame->can_id & CAN_RTR_FLAG) { + /* Send an RTR frame. Their DLC is fixed. + * Some chips don't send them at all. + */ + snprintf(local_txbuf, sizeof(local_txbuf), + "ATRTR\r"); + } else { + /* Send a regular CAN data frame */ + int i; + + for (i = 0; i < frame->len; i++) { + snprintf(&local_txbuf[2 * i], sizeof(local_txbuf), + "%02X", + frame->data[i]); + } + + snprintf(&local_txbuf[2 * i], sizeof(local_txbuf), + "\r"); + } + + elm->drop_next_line = 1; + elm->state = ELM327_STATE_RECEIVING; + + /* We will be in the default state once this command is + * sent, so enable the TX packet queue. + */ + netif_wake_queue(elm->dev); + } + + elm327_send(elm, local_txbuf, strlen(local_txbuf)); +} + +static bool elm327_is_ready_char(char c) +{ + /* Bits 0xc0 are sometimes set (randomly), hence the mask. + * Probably bad hardware. + */ + return (c & 0x3f) == ELM327_READY_CHAR; +} + +static void elm327_drop_bytes(struct can327 *elm, size_t i) +{ + lockdep_assert_held(&elm->lock); + + memmove(&elm->rxbuf[0], &elm->rxbuf[i], ELM327_SIZE_RXBUF - i); + elm->rxfill -= i; +} + +static void elm327_parse_rxbuf(struct can327 *elm) +{ + size_t len; + int i; + + lockdep_assert_held(&elm->lock); + + switch (elm->state) { + case ELM327_STATE_NOTINIT: + elm->rxfill = 0; + break; + + case ELM327_STATE_GETDUMMYCHAR: + { + /* Wait for 'y' or '>' */ + for (i = 0; i < elm->rxfill; i++) { + if (elm->rxbuf[i] == ELM327_DUMMY_CHAR) { + elm327_send(elm, "\r", 1); + elm->state = ELM327_STATE_GETPROMPT; + i++; + break; + } else if (elm327_is_ready_char(elm->rxbuf[i])) { + elm327_send(elm, ELM327_DUMMY_STRING, 1); + i++; + break; + } + } + + elm327_drop_bytes(elm, i); + + break; + } + + case ELM327_STATE_GETPROMPT: + /* Wait for '>' */ + if (elm327_is_ready_char(elm->rxbuf[elm->rxfill - 1])) + elm327_handle_prompt(elm); + + elm->rxfill = 0; + break; + + case ELM327_STATE_RECEIVING: + /* Find <CR> delimiting feedback lines. */ + for (len = 0; + (len < elm->rxfill) && (elm->rxbuf[len] != '\r'); + len++) { + /* empty loop */ + } + + if (len == ELM327_SIZE_RXBUF) { + /* Line exceeds buffer. It's probably all garbage. + * Did we even connect at the right baud rate? + */ + netdev_err(elm->dev, + "RX buffer overflow. Faulty ELM327 or UART?\n"); + elm327_uart_side_failure(elm); + break; + } else if (len == elm->rxfill) { + if (elm327_is_ready_char(elm->rxbuf[elm->rxfill - 1])) { + /* 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); + break; + } + + /* No <CR> found - we haven't received a full line yet. + * Wait for more data. + */ + break; + } + + /* 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); + } +} + +#if LINUX_VERSION_CODE < KERNEL_VERSION(5,10,0) +/* Dummy needed to use can_rx_offload */ +static struct sk_buff *can327_mailbox_read(struct can_rx_offload *offload, + unsigned int n, u32 *timestamp, + bool drop) +{ + WARN_ON_ONCE(1); /* This function is a dummy, so don't call it! */ + + return ERR_PTR(-ENOBUFS); +} +#endif + +static int can327_netdev_open(struct net_device *dev) +{ + struct can327 *elm = netdev_priv(dev); + int err; + + spin_lock_bh(&elm->lock); + + if (!elm->tty) { + spin_unlock_bh(&elm->lock); + return -ENODEV; + } + + if (elm->uart_side_failure) + netdev_warn(elm->dev, "Reopening netdev after a UART side fault has been detected.\n"); + + /* Clear TTY buffers */ + elm->rxfill = 0; + elm->txleft = 0; + + /* open_candev() checks for elm->can.bittiming.bitrate != 0 */ + err = open_candev(dev); + if (err) { + spin_unlock_bh(&elm->lock); + return err; + } + + elm327_init(elm); + spin_unlock_bh(&elm->lock); + +#if LINUX_VERSION_CODE < KERNEL_VERSION(5,10,0) + elm->offload.mailbox_read = can327_mailbox_read; + err = can_rx_offload_add_fifo(dev, &elm->offload, ELM327_NAPI_WEIGHT); +#else + err = can_rx_offload_add_manual(dev, &elm->offload, ELM327_NAPI_WEIGHT); +#endif + if (err) { + close_candev(dev); + return err; + } + + can_rx_offload_enable(&elm->offload); + + can_led_event(dev, CAN_LED_EVENT_OPEN); + elm->can.state = CAN_STATE_ERROR_ACTIVE; + netif_start_queue(dev); + + return 0; +} + +static int can327_netdev_close(struct net_device *dev) +{ + struct can327 *elm = netdev_priv(dev); + + /* Interrupt whatever the ELM327 is doing right now */ + spin_lock_bh(&elm->lock); + elm327_send(elm, ELM327_DUMMY_STRING, 1); + spin_unlock_bh(&elm->lock); + + netif_stop_queue(dev); + + /* Give UART one final chance to flush. */ + clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags); + flush_work(&elm->tx_work); + + can_rx_offload_disable(&elm->offload); + elm->can.state = CAN_STATE_STOPPED; + can_rx_offload_del(&elm->offload); + close_candev(dev); + can_led_event(dev, CAN_LED_EVENT_STOP); + + return 0; +} + +/* Send a can_frame to a TTY. */ +static netdev_tx_t can327_netdev_start_xmit(struct sk_buff *skb, + struct net_device *dev) +{ + struct can327 *elm = netdev_priv(dev); + struct can_frame *frame = (struct can_frame *)skb->data; + + if (can_dropped_invalid_skb(dev, skb)) + return NETDEV_TX_OK; + + /* BHs are already disabled, so no spin_lock_bh(). + * See Documentation/networking/netdevices.txt + */ + spin_lock(&elm->lock); + + /* We shouldn't get here after a hardware fault: + * can_bus_off() calls netif_carrier_off() + */ + WARN_ON_ONCE(elm->uart_side_failure); + + if (!elm->tty || + elm->uart_side_failure || + 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->len; + + can_led_event(dev, CAN_LED_EVENT_TX); + +out: + kfree_skb(skb); + return NETDEV_TX_OK; +} + +static const struct net_device_ops can327_netdev_ops = { + .ndo_open = can327_netdev_open, + .ndo_stop = can327_netdev_close, + .ndo_start_xmit = can327_netdev_start_xmit, + .ndo_change_mtu = can_change_mtu, +}; + +static bool can327_is_valid_rx_char(char c) +{ + return (isdigit(c) || + isupper(c) || + c == ELM327_DUMMY_CHAR || + c == ELM327_READY_CHAR || + c == '<' || + c == 'a' || + c == 'b' || + c == 'v' || + c == '.' || + c == '?' || + c == '\r' || + c == ' '); +} + +/* Handle incoming ELM327 ASCII data. + * This will not be re-entered while running, but other ldisc + * functions may be called in parallel. + */ +#if LINUX_VERSION_CODE < KERNEL_VERSION(5,14,0) +static void can327_ldisc_rx(struct tty_struct *tty, + const unsigned char *cp, char *fp, int count) +#else +static void can327_ldisc_rx(struct tty_struct *tty, + const unsigned char *cp, const char *fp, int count) +#endif +{ + struct can327 *elm = (struct can327 *)tty->disc_data; + + spin_lock_bh(&elm->lock); + + if (elm->uart_side_failure) + goto out; + + while (count-- && elm->rxfill < ELM327_SIZE_RXBUF) { + if (fp && *fp++) { + netdev_err(elm->dev, "Error in received character stream. Check your wiring."); + + elm327_uart_side_failure(elm); + + goto out; + } + + /* Ignore NUL characters, which the PIC microcontroller may + * inadvertently insert due to a known hardware bug. + * See ELM327 documentation, which refers to a Microchip PIC + * bug description. + */ + if (*cp != 0) { + /* Check for stray characters on the UART line. + * Likely caused by bad hardware. + */ + if (!can327_is_valid_rx_char(*cp)) { + netdev_err(elm->dev, + "Received illegal character %02x.\n", + *cp); + elm327_uart_side_failure(elm); + + goto out; + } + + elm->rxbuf[elm->rxfill++] = *cp; + } + + cp++; + } + + if (count >= 0) { + netdev_err(elm->dev, "Receive buffer overflowed. Bad chip or wiring?"); + + elm327_uart_side_failure(elm); + + goto out; + } + + elm327_parse_rxbuf(elm); + +out: + spin_unlock_bh(&elm->lock); +} + +/* Write out remaining transmit buffer. + * Scheduled when TTY is writable. + */ +static void can327_ldisc_tx_worker(struct work_struct *work) +{ + struct can327 *elm = container_of(work, struct can327, tx_work); + ssize_t written; + + if (elm->uart_side_failure) + return; + + spin_lock_bh(&elm->lock); + + if (elm->txleft) { + written = elm->tty->ops->write(elm->tty, elm->txhead, elm->txleft); + if (written < 0) { + netdev_err(elm->dev, + "Failed to write to tty %s.\n", + elm->tty->name); + elm327_uart_side_failure(elm); + spin_unlock_bh(&elm->lock); + return; + } + + elm->txleft -= written; + elm->txhead += written; + } + + if (!elm->txleft) { + clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags); + spin_unlock_bh(&elm->lock); + } else { + spin_unlock_bh(&elm->lock); + } +} + +/* Called by the driver when there's room for more data. */ +static void can327_ldisc_tx_wakeup(struct tty_struct *tty) +{ + struct can327 *elm = (struct can327 *)tty->disc_data; + + schedule_work(&elm->tx_work); +} + +/* ELM327 can only handle bitrates that are integer divisors of 500 kHz, + * or 7/8 of that. Divisors are 1 to 64. + * Currently we don't implement support for 7/8 rates. + */ +static const u32 can327_bitrate_const[64] = { + 7812, 7936, 8064, 8196, 8333, 8474, 8620, 8771, + 8928, 9090, 9259, 9433, 9615, 9803, 10000, 10204, + 10416, 10638, 10869, 11111, 11363, 11627, 11904, 12195, + 12500, 12820, 13157, 13513, 13888, 14285, 14705, 15151, + 15625, 16129, 16666, 17241, 17857, 18518, 19230, 20000, + 20833, 21739, 22727, 23809, 25000, 26315, 27777, 29411, + 31250, 33333, 35714, 38461, 41666, 45454, 50000, 55555, + 62500, 71428, 83333, 100000, 125000, 166666, 250000, 500000 +}; + +/* Dummy needed to use bitrate_const */ +static int can327_do_set_bittiming(struct net_device *netdev) +{ + return 0; +} + +static int can327_ldisc_open(struct tty_struct *tty) +{ + struct net_device *dev; + struct can327 *elm; + int err; + + if (!capable(CAP_NET_ADMIN)) + return -EPERM; + + if (!tty->ops->write) + return -EOPNOTSUPP; + + dev = alloc_candev(sizeof(struct can327), 0); + if (!dev) + return -ENFILE; + elm = netdev_priv(dev); + + /* Configure TTY interface */ + tty->receive_room = 65536; /* We don't flow control */ + spin_lock_init(&elm->lock); + INIT_WORK(&elm->tx_work, can327_ldisc_tx_worker); + + /* Configure CAN metadata */ + elm->can.bitrate_const = can327_bitrate_const; + elm->can.bitrate_const_cnt = ARRAY_SIZE(can327_bitrate_const); + elm->can.do_set_bittiming = can327_do_set_bittiming; + elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY; + + /* Configure netdev interface */ + elm->dev = dev; + dev->netdev_ops = &can327_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) + goto out_err; + + netdev_info(elm->dev, "can327 on %s.\n", tty->name); + + return 0; + +out_err: + free_candev(elm->dev); + return err; +} + +/* Close down a can327 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 can327_ldisc_close(struct tty_struct *tty) +{ + struct can327 *elm = (struct can327 *)tty->disc_data; + + /* unregister_netdev() calls .ndo_stop() so we don't have to. + * Our .ndo_stop() also flushes the TTY write wakeup handler, + * so we can safely set elm->tty = NULL after this. + */ + unregister_candev(elm->dev); + + /* Mark channel as dead */ + spin_lock_bh(&elm->lock); + tty->disc_data = NULL; + elm->tty = NULL; + spin_unlock_bh(&elm->lock); + + netdev_info(elm->dev, "can327 off %s.\n", tty->name); + + free_candev(elm->dev); +} + +static int can327_ldisc_ioctl(struct tty_struct *tty, +#if LINUX_VERSION_CODE < KERNEL_VERSION(5,17,0) + struct file *file, +#endif + unsigned int cmd, unsigned long arg) +{ + struct can327 *elm = (struct can327 *)tty->disc_data; + unsigned int tmp; + + switch (cmd) { + case SIOCGIFNAME: + tmp = strnlen(elm->dev->name, IFNAMSIZ - 1) + 1; + if (copy_to_user((void __user *)arg, elm->dev->name, tmp)) + return -EFAULT; + return 0; + + case SIOCSIFHWADDR: + return -EINVAL; + + default: +#if LINUX_VERSION_CODE < KERNEL_VERSION(5,16,0) + return tty_mode_ioctl(tty, file, cmd, arg); +#else + return tty_mode_ioctl(tty, cmd, arg); +#endif + } +} + +static struct tty_ldisc_ops can327_ldisc = { + .owner = THIS_MODULE, + .name = "can327", + .num = N_DEVELOPMENT, + .receive_buf = can327_ldisc_rx, + .write_wakeup = can327_ldisc_tx_wakeup, + .open = can327_ldisc_open, + .close = can327_ldisc_close, + .ioctl = can327_ldisc_ioctl, +}; + +static int __init can327_init(void) +{ + int status; + +#if LINUX_VERSION_CODE < KERNEL_VERSION(5,14,0) + status = tty_register_ldisc(N_DEVELOPMENT, &can327_ldisc); +#else + status = tty_register_ldisc(&can327_ldisc); +#endif + if (status) + pr_err("Can't register line discipline\n"); + + return status; +} + +static void __exit can327_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. + */ +#if LINUX_VERSION_CODE < KERNEL_VERSION(5,14,0) + int status; + + status = tty_unregister_ldisc(N_DEVELOPMENT); + if (status) + pr_err("Can't unregister line discipline (error: %d)\n", + status); +#else + tty_unregister_ldisc(&can327_ldisc); +#endif +} + +module_init(can327_init); +module_exit(can327_exit); + +MODULE_ALIAS_LDISC(N_DEVELOPMENT); +MODULE_DESCRIPTION("ELM327 based CAN interface"); +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Max Staudt <max-linux@enpas.org>"); |