-// 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.
- *
- * elmcan.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) "elmcan: " 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 elmcan {
- /* 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 elmcan *elm);
-
-static void elm327_send(struct elmcan *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 elmcan *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 elmcan *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 elmcan *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 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(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 elmcan *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 elmcan *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 elmcan *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 elmcan *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 elmcan *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 elmcan *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 elmcan *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 elmcan *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 *elmcan_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 elmcan_netdev_open(struct net_device *dev)
-{
- struct elmcan *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 = elmcan_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 elmcan_netdev_close(struct net_device *dev)
-{
- struct elmcan *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 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 (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 elmcan_netdev_ops = {
- .ndo_open = elmcan_netdev_open,
- .ndo_stop = elmcan_netdev_close,
- .ndo_start_xmit = elmcan_netdev_start_xmit,
- .ndo_change_mtu = can_change_mtu,
-};
-
-static bool elmcan_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 elmcan_ldisc_rx(struct tty_struct *tty,
- const unsigned char *cp, char *fp, int count)
-#else
-static void elmcan_ldisc_rx(struct tty_struct *tty,
- const unsigned char *cp, const char *fp, int count)
-#endif
-{
- struct elmcan *elm = (struct elmcan *)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 (!elmcan_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 elmcan_ldisc_tx_worker(struct work_struct *work)
-{
- struct elmcan *elm = container_of(work, struct elmcan, 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 elmcan_ldisc_tx_wakeup(struct tty_struct *tty)
-{
- struct elmcan *elm = (struct elmcan *)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 elmcan_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 elmcan_do_set_bittiming(struct net_device *netdev)
-{
- return 0;
-}
-
-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;
-
- 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 */
- spin_lock_init(&elm->lock);
- INIT_WORK(&elm->tx_work, elmcan_ldisc_tx_worker);
-
- /* Configure CAN metadata */
- elm->can.bitrate_const = elmcan_bitrate_const;
- elm->can.bitrate_const_cnt = ARRAY_SIZE(elmcan_bitrate_const);
- elm->can.do_set_bittiming = elmcan_do_set_bittiming;
- elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
-
- /* Configure netdev 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)
- goto out_err;
-
- netdev_info(elm->dev, "elmcan on %s.\n", tty->name);
-
- return 0;
-
-out_err:
- free_candev(elm->dev);
- return err;
-}
-
-/* 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)
-{
- struct elmcan *elm = (struct elmcan *)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, "elmcan off %s.\n", tty->name);
-
- free_candev(elm->dev);
-}
-
-static int elmcan_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 elmcan *elm = (struct elmcan *)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 elmcan_ldisc = {
- .owner = THIS_MODULE,
- .name = "elmcan",
- .num = N_DEVELOPMENT,
- .receive_buf = elmcan_ldisc_rx,
- .write_wakeup = elmcan_ldisc_tx_wakeup,
- .open = elmcan_ldisc_open,
- .close = elmcan_ldisc_close,
- .ioctl = elmcan_ldisc_ioctl,
-};
-
-static int __init elmcan_init(void)
-{
- int status;
-
-#if LINUX_VERSION_CODE < KERNEL_VERSION(5,14,0)
- status = tty_register_ldisc(N_DEVELOPMENT, &elmcan_ldisc);
-#else
- status = tty_register_ldisc(&elmcan_ldisc);
-#endif
- 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.
- */
-#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(&elmcan_ldisc);
-#endif
-}
-
-module_init(elmcan_init);
-module_exit(elmcan_exit);
-
-MODULE_ALIAS_LDISC(N_DEVELOPMENT);
-MODULE_DESCRIPTION("ELM327 based CAN interface");
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Max Staudt <max-linux@enpas.org>");
projects / elmcan.git / commitdiff