+// SPDX-License-Identifier: GPL-2.0
/*
* 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 <elmcan@enpas.org>
+ * 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>
*
- * SPDX-License-Identifier: GPL-2.0
- *
*/
#define pr_fmt(fmt) "[elmcan] " fmt
#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>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Max Staudt <max-linux@enpas.org>");
+/* If this is enabled, we'll try to make the best of the situation
+ * even if we receive unexpected characters on the line.
+ * No guarantees.
+ * Handle with care, it's likely your hardware is unreliable!
+ */
+static bool accept_flaky_uart;
+module_param_named(accept_flaky_uart, accept_flaky_uart, bool, 0444);
+MODULE_PARM_DESC(accept_flaky_uart, "Don't bail at the first invalid character. Behavior undefined.");
+
+
/* Line discipline ID number */
#ifndef N_ELMCAN
#define N_ELMCAN 29
#endif
+#define ELM327_SIZE_RXBUF 256
+#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
ELM_TODO_CANID_11BIT,
ELM_TODO_CANID_29BIT_LOW,
ELM_TODO_CANID_29BIT_HIGH,
+ ELM_TODO_CAN_CONFIG_PART2,
ELM_TODO_CAN_CONFIG,
ELM_TODO_RESPONSES,
ELM_TODO_SILENT_MONITOR,
/* TTY TX helpers */
struct work_struct tx_work; /* Flushes TTY TX buffer */
- unsigned char txbuf[32];
+ unsigned char *txbuf;
unsigned char *txhead; /* Pointer to next TX byte */
int txleft; /* Bytes left to TX */
/* TTY RX helpers */
- unsigned char rxbuf[256];
+ unsigned char *rxbuf;
int rxfill;
/* State machine */
int drop_next_line;
/* The CAN frame and config the ELM327 is sending/using,
- * or will send/use after finishing all cmds_todo */
+ * or will send/use after finishing all cmds_todo
+ */
struct can_frame can_frame;
unsigned short can_config;
unsigned long can_bitrate;
- /************************************************************************
- * ELM327: Transmission *
- * *
- * (all functions assume elm->lock taken) *
- ************************************************************************/
+ /***********************************************************************
+ * ELM327: Transmission *
+ * *
+ * (all functions assume elm->lock taken) *
+ ***********************************************************************/
static void elm327_send(struct elmcan *elm, const void *buf, size_t len)
{
int actual;
- if (elm->hw_failure) {
+ if (elm->hw_failure)
return;
- }
memcpy(elm->txbuf, buf, len);
set_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
actual = elm->tty->ops->write(elm->tty, elm->txbuf, len);
if (actual < 0) {
- netdev_err(elm->dev, "Failed to write to tty %s.\n", elm->tty->name);
+ netdev_err(elm->dev,
+ "Failed to write to tty %s.\n",
+ elm->tty->name);
elm327_hw_failure(elm);
return;
}
}
-/*
- * Take the ELM327 out of almost any state and back into command mode
- *
- * Assumes elm->lock taken.
+/* Take the ELM327 out of almost any state and back into command mode.
+ * We send ELM327_MAGIC_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)
{
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.
- */
+/* 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)
{
/* 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)
+ 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;
- /************************************************************************
- * ELM327: Initialization sequence *
- * *
- * (assumes elm->lock taken) *
- ************************************************************************/
+ /***********************************************************************
+ * ELM327: Initialization sequence *
+ * *
+ * (assumes elm->lock taken) *
+ ***********************************************************************/
static char *elm327_init_script[] = {
"AT WS\r", /* v1.0: Warm Start */
- /************************************************************************
- * ELM327: Reception -> netdev glue *
- * *
- * (assumes elm->lock taken) *
- ************************************************************************/
+ /***********************************************************************
+ * ELM327: Reception -> netdev glue *
+ * *
+ * (assumes elm->lock taken) *
+ ***********************************************************************/
-static void elm327_feed_frame_to_netdev(struct elmcan *elm, const struct can_frame *frame)
+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)) {
+ if (!netif_running(elm->dev))
return;
- }
skb = alloc_can_skb(elm->dev, &cf);
- /************************************************************************
- * ELM327: "Panic" handler *
- * *
- * (assumes elm->lock taken) *
- ************************************************************************/
+ /***********************************************************************
+ * ELM327: "Panic" handler *
+ * *
+ * (assumes elm->lock taken) *
+ ***********************************************************************/
/* Called when we're out of ideas and just want it all to end. */
static inline void elm327_hw_failure(struct elmcan *elm)
frame.data[7] = 'P';
elm327_feed_frame_to_netdev(elm, &frame);
- netdev_err(elm->dev, "ELM327 misbehaved. "
- "Blocking further communication.\n");
+ netdev_err(elm->dev, "ELM327 misbehaved. Blocking further communication.\n");
elm->hw_failure = true;
can_bus_off(elm->dev);
frame.can_id = CAN_ERR_FLAG;
frame.can_dlc = CAN_ERR_DLC;
- switch(len) {
- case 17:
- if (!memcmp(elm->rxbuf, "UNABLE TO CONNECT", 17)) {
- netdev_err(elm->dev, "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, "<RX ERROR", 9)) {
- frame.can_id |= CAN_ERR_PROT;
- }
- break;
- case 8:
- if (!memcmp(elm->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)) {
- netdev_err(elm->dev, "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;
+ switch (len) {
+ case 17:
+ if (!memcmp(elm->rxbuf, "UNABLE TO CONNECT", 17)) {
+ netdev_err(elm->dev,
+ "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 heuristically
+ * emit this 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))
+ frame.can_id |= CAN_ERR_PROT;
+ if (!memcmp(elm->rxbuf, "<RX ERROR", 9))
+ frame.can_id |= CAN_ERR_PROT;
+ break;
+ case 8:
+ if (!memcmp(elm->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)) {
+ netdev_err(elm->dev, "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);
}
+/* 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, int len)
{
struct can_frame frame;
}
}
+ /* If we accept stray characters coming in:
+ * Check for stray characters on a payload line.
+ * No idea what causes this.
+ */
+ if (accept_flaky_uart
+ && 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.
+ */
+ elm327_kick_into_cmd_mode(elm);
+ return 3;
+ }
+
/* 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.
/* Check for RTR frame */
if (elm->rxfill >= hexlen + 3
- && elm->rxbuf[hexlen + 0] == 'R'
- && elm->rxbuf[hexlen + 1] == 'T'
- && elm->rxbuf[hexlen + 2] == 'R') {
+ && !memcmp(&elm->rxbuf[hexlen], "RTR", 3)) {
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)) {
+ /* 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.can_dlc * 3 + datastart)) {
/* Incomplete frame. */
/* Probably the ELM327's RS232 TX buffer was full.
/* 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);
+ | (hex_to_bin(elm->rxbuf[datastart+3*i+1]) << 0);
}
/* Feed the frame to the network layer. */
static void elm327_parse_line(struct elmcan *elm, int len)
{
/* Skip empty lines */
- if (!len) {
+ if (!len)
return;
- }
/* Skip echo lines */
if (elm->drop_next_line) {
}
/* Regular parsing */
- switch(elm->state) {
- case ELM_RECEIVING:
- if (elm327_parse_frame(elm, len)) {
- /* Parse an error line. */
- elm327_parse_error(elm, len);
+ 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;
+ /* Start afresh. */
+ elm327_kick_into_cmd_mode(elm);
+ }
+ break;
+ default:
+ break;
}
}
-
static void elm327_handle_prompt(struct elmcan *elm)
{
- if (elm->cmds_todo) {
- struct can_frame *frame = &elm->can_frame;
- char local_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);
- netdev_info(elm->dev, "Initialization finished.\n");
- }
+ struct can_frame *frame = &elm->can_frame;
+ char local_txbuf[20];
- /* 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);
+ if (!elm->cmds_todo) {
+ /* Enter CAN monitor mode */
+ elm327_send(elm, "ATMA\r", 5);
+ elm->state = ELM_RECEIVING;
- return;
+ return;
+ }
+
+ /* Reconfigure ELM327 step by step as indicated by elm->cmds_todo */
+ if (test_bit(ELM_TODO_INIT, &elm->cmds_todo)) {
+ strcpy(local_txbuf, *elm->next_init_cmd);
- } else if (test_and_clear_bit(ELM_TODO_SILENT_MONITOR, &elm->cmds_todo)) {
- sprintf(local_txbuf, "ATCSM%i\r",
- !(!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)));
+ elm->next_init_cmd++;
+ if (!(*elm->next_init_cmd)) {
+ clear_bit(ELM_TODO_INIT, &elm->cmds_todo);
+ netdev_info(elm->dev, "Initialization finished.\n");
+ }
- } else if (test_and_clear_bit(ELM_TODO_RESPONSES, &elm->cmds_todo)) {
- sprintf(local_txbuf, "ATR%i\r",
- !(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
+ } else if (test_and_clear_bit(ELM_TODO_SILENT_MONITOR, &elm->cmds_todo)) {
+ sprintf(local_txbuf, "ATCSM%i\r",
+ !(!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY)));
- } else if (test_and_clear_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo)) {
- sprintf(local_txbuf, "ATPB%04X\r",
- elm->can_config);
+ } else if (test_and_clear_bit(ELM_TODO_RESPONSES, &elm->cmds_todo)) {
+ sprintf(local_txbuf, "ATR%i\r",
+ !(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
- } else if (test_and_clear_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo)) {
- sprintf(local_txbuf, "ATCP%02X\r",
- (frame->can_id & CAN_EFF_MASK) >> 24);
+ } else if (test_and_clear_bit(ELM_TODO_CAN_CONFIG, &elm->cmds_todo)) {
+ sprintf(local_txbuf, "ATPC\r");
+ set_bit(ELM_TODO_CAN_CONFIG_PART2, &elm->cmds_todo);
- } else if (test_and_clear_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo)) {
- sprintf(local_txbuf, "ATSH%06X\r",
- frame->can_id & CAN_EFF_MASK & ((1 << 24) - 1));
+ } else if (test_and_clear_bit(ELM_TODO_CAN_CONFIG_PART2, &elm->cmds_todo)) {
+ sprintf(local_txbuf, "ATPB%04X\r",
+ elm->can_config);
- } else if (test_and_clear_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo)) {
- sprintf(local_txbuf, "ATSH%03X\r",
- frame->can_id & CAN_SFF_MASK);
+ } else if (test_and_clear_bit(ELM_TODO_CANID_29BIT_HIGH, &elm->cmds_todo)) {
+ sprintf(local_txbuf, "ATCP%02X\r",
+ (frame->can_id & CAN_EFF_MASK) >> 24);
- } else if (test_and_clear_bit(ELM_TODO_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.
- */
- sprintf(local_txbuf, "ATRTR\r");
- } else {
- /* Send a regular CAN data frame */
- int i;
+ } else if (test_and_clear_bit(ELM_TODO_CANID_29BIT_LOW, &elm->cmds_todo)) {
+ sprintf(local_txbuf, "ATSH%06X\r",
+ frame->can_id & CAN_EFF_MASK & ((1 << 24) - 1));
- for (i = 0; i < frame->can_dlc; i++) {
- sprintf(&local_txbuf[2*i], "%02X",
- frame->data[i]);
- }
+ } else if (test_and_clear_bit(ELM_TODO_CANID_11BIT, &elm->cmds_todo)) {
+ sprintf(local_txbuf, "ATSH%03X\r",
+ frame->can_id & CAN_SFF_MASK);
- sprintf(&local_txbuf[2*i], "\r");
+ } else if (test_and_clear_bit(ELM_TODO_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.
+ */
+ sprintf(local_txbuf, "ATRTR\r");
+ } else {
+ /* Send a regular CAN data frame */
+ int i;
+
+ for (i = 0; i < frame->can_dlc; i++) {
+ sprintf(&local_txbuf[2*i], "%02X",
+ frame->data[i]);
}
- elm->drop_next_line = 1;
- elm->state = ELM_RECEIVING;
+ sprintf(&local_txbuf[2*i], "\r");
}
- elm327_send(elm, local_txbuf, strlen(local_txbuf));
- } else {
- /* Enter CAN monitor mode */
- elm327_send(elm, "ATMA\r", 5);
+ elm->drop_next_line = 1;
elm->state = ELM_RECEIVING;
}
+
+ 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, int i)
{
- memmove(&elm->rxbuf[0], &elm->rxbuf[i], sizeof(elm->rxbuf) - i);
+ memmove(&elm->rxbuf[0], &elm->rxbuf[i], ELM327_SIZE_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;
+ break;
case ELM_GETMAGICCHAR:
{
elm->state = ELM_GETPROMPT;
i++;
break;
- } else if (elm->rxbuf[i] == ELM327_READY_CHAR) {
+ } else if (elm327_is_ready_char(elm->rxbuf[i])) {
elm327_send(elm, ELM327_MAGIC_STRING, 1);
i++;
break;
elm327_drop_bytes(elm, i);
- return;
+ break;
}
case ELM_GETPROMPT:
/* Wait for '>' */
- if (elm->rxbuf[elm->rxfill - 1] == ELM327_READY_CHAR) {
+ if (elm327_is_ready_char(elm->rxbuf[elm->rxfill - 1]))
elm327_handle_prompt(elm);
- }
elm->rxfill = 0;
- return;
+ break;
case ELM_RECEIVING:
/* Find <CR> delimiting feedback lines. */
/* empty loop */
}
- if (len == sizeof(elm->rxbuf)) {
+ 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 connected?\n");
+ netdev_err(elm->dev,
+ "RX buffer overflow. Faulty ELM327 or UART?\n");
elm327_hw_failure(elm);
- return;
+ break;
} else if (len == elm->rxfill) {
- if (elm->state == ELM_RECEIVING
- && elm->rxbuf[elm->rxfill - 1] == ELM327_READY_CHAR) {
+ 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);
- return;
- } else {
- /* We haven't received a full line yet.
- * Wait for more data.
- */
- return;
+ 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_drop_bytes(elm, len+1);
/* More data to parse? */
- if (elm->rxfill) {
+ if (elm->rxfill)
elm327_parse_rxbuf(elm);
- }
}
}
- /************************************************************************
- * netdev *
- * *
- * (takes elm->lock) *
- ************************************************************************/
+ /***********************************************************************
+ * netdev *
+ * *
+ * (takes elm->lock) *
+ ***********************************************************************/
-/* Netdevice DOWN -> UP routine */
static int elmcan_netdev_open(struct net_device *dev)
{
struct elmcan *elm = netdev_priv(dev);
spin_lock_bh(&elm->lock);
if (elm->hw_failure) {
- netdev_err(elm->dev, "Refusing to open interface after "
- "a hardware fault has been detected.\n");
+ netdev_err(elm->dev, "Refusing to open interface after a hardware fault has been detected.\n");
spin_unlock_bh(&elm->lock);
return -EIO;
}
return err;
}
- /* Initialize the ELM327 */
elm327_init(elm);
spin_unlock_bh(&elm->lock);
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);
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)
+/* 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;
/* We shouldn't get here after a hardware fault:
* can_bus_off() calls netif_carrier_off()
*/
- BUG_ON(elm->hw_failure);
+ WARN_ON(elm->hw_failure);
if (elm->tty == NULL
+ || elm->hw_failure
|| elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {
spin_unlock(&elm->lock);
goto out;
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_open = elmcan_netdev_open,
.ndo_stop = elmcan_netdev_close,
.ndo_start_xmit = elmcan_netdev_start_xmit,
- .ndo_change_mtu = elmcan_netdev_change_mtu,
+ .ndo_change_mtu = can_change_mtu,
};
- /************************************************************************
- * Line discipline *
- * *
- * (takes elm->lock) *
- ************************************************************************/
+ /***********************************************************************
+ * Line discipline *
+ * *
+ * (takes elm->lock) *
+ ***********************************************************************/
-/*
- * Get a reference to our struct, taking into account locks/refcounts.
+/* 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).
+ * there is a refcount at all (otherwise tty->disc_data may be freed and
+ * before we increment the refcount).
+ * Use this for anything that can race against elmcan_ldisc_close().
*/
-static struct elmcan* get_elm(struct tty_struct *tty)
+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;
got_ref = atomic_inc_not_zero(&elm->refcount);
spin_unlock_bh(&elmcan_discdata_lock);
- if (!got_ref) {
+ if (!got_ref)
return NULL;
- }
return elm;
}
}
+static bool elmcan_is_valid_rx_char(char c)
+{
+ return (accept_flaky_uart
+ || isdigit(c)
+ || isupper(c)
+ || ELM327_MAGIC_CHAR == c
+ || ELM327_READY_CHAR == c
+ || '<' == c
+ || 'a' == c
+ || 'b' == c
+ || 'v' == c
+ || '.' == c
+ || '?' == c
+ || '\r' == c
+ || ' ' == c);
+}
-/*
- * 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
+/* Handle incoming ELM327 ASCII data.
+ * 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)
if (!elm)
return;
- /* Read the characters out of the buffer */
- while (count-- && elm->rxfill < sizeof(elm->rxbuf)) {
+ spin_lock_bh(&elm->lock);
+
+ if (elm->hw_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.");
- spin_lock_bh(&elm->lock);
elm327_hw_failure(elm);
- spin_unlock_bh(&elm->lock);
- put_elm(elm);
- return;
+ 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_hw_failure(elm);
+
+ goto out;
+ }
+
elm->rxbuf[elm->rxfill++] = *cp;
}
+
cp++;
}
if (count >= 0) {
netdev_err(elm->dev, "Receive buffer overflowed. Bad chip or wiring?");
- spin_lock_bh(&elm->lock);
elm327_hw_failure(elm);
- spin_unlock_bh(&elm->lock);
- put_elm(elm);
- return;
+ goto out;
}
- spin_lock_bh(&elm->lock);
elm327_parse_rxbuf(elm);
- spin_unlock_bh(&elm->lock);
+out:
+ spin_unlock_bh(&elm->lock);
put_elm(elm);
}
-/*
- * Write out remaining transmit buffer.
+
+/* 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.
+ * before destroying the elmcan object.
*/
struct elmcan *elm = container_of(work, struct elmcan, tx_work);
ssize_t actual;
if (elm->txleft <= 0) {
/* Our TTY write buffer is empty:
- * We can start transmission of another packet
+ * Allow netdev to hand us another packet
*/
clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
spin_unlock_bh(&elm->lock);
actual = elm->tty->ops->write(elm->tty, elm->txhead, elm->txleft);
if (actual < 0) {
- netdev_err(elm->dev, "Failed to write to tty %s.\n", elm->tty->name);
+ netdev_err(elm->dev,
+ "Failed to write to tty %s.\n",
+ elm->tty->name);
elm327_hw_failure(elm);
spin_unlock_bh(&elm->lock);
return;
spin_unlock_bh(&elm->lock);
}
-
-/*
- * Called by the driver when there's room for more data.
- * Schedule the transmit.
- */
+/* Called by the driver when there's room for more data. */
static void elmcan_ldisc_tx_wakeup(struct tty_struct *tty)
{
struct elmcan *elm = get_elm(tty);
}
-
-/* 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,
+/* 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
};
-/*
- * 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.
- */
+
+/* Dummy needed to use bitrate_const */
+static int elmcan_do_set_bittiming(struct net_device *netdev)
+{
+ (void)netdev;
+
+ return 0;
+}
+
+
static int elmcan_ldisc_open(struct tty_struct *tty)
{
struct net_device *dev;
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);
+ elm->rxbuf = kmalloc(ELM327_SIZE_RXBUF, GFP_KERNEL);
+ elm->txbuf = kmalloc(ELM327_SIZE_TXBUF, GFP_KERNEL);
+ if (!elm->rxbuf || !elm->txbuf) {
+ err = -ENOMEM;
+ goto out_err;
+ }
+
/* Configure TTY interface */
tty->receive_room = 65536; /* We don't flow control */
elm->txleft = 0; /* Clear TTY TX buffer */
/* Configure CAN metadata */
elm->can.state = CAN_STATE_STOPPED;
- elm->can.clock.freq = 1000000;
- elm->can.bittiming_const = &elmcan_bittiming_const;
+ 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 netlink interface */
/* Let 'er rip */
err = register_candev(elm->dev);
- if (err) {
- free_candev(elm->dev);
- return err;
- }
+ if (err)
+ goto out_err;
netdev_info(elm->dev, "elmcan on %s.\n", tty->name);
return 0;
+
+out_err:
+ if (elm->txbuf)
+ kfree(elm->txbuf);
+ if (elm->rxbuf)
+ kfree(elm->rxbuf);
+ free_candev(elm->dev);
+ return err;
}
-/*
- * Close down an elmcan channel.
+/* 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.
*/
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_netdev() calls .ndo_stop() so we don't have to. */
unregister_candev(elm->dev);
/* Decrease the refcount twice, once for our own get_elm(),
put_elm(elm);
put_elm(elm);
- /* Spin until refcount reaches 0 */
- while(atomic_read(&elm->refcount) > 0)
- msleep(1);
+ while (atomic_read(&elm->refcount) > 0)
+ msleep_interruptible(10);
- /* At this point, all ldisc calls to us will be no-ops.
- * Since the refcount is 0, they are bailing immediately.
- */
+ /* At this point, all ldisc calls to us have become no-ops. */
/* Mark channel as dead */
spin_lock_bh(&elm->lock);
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 */
+ kfree(elm->txbuf);
+ kfree(elm->rxbuf);
free_candev(elm->dev);
}
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)
{
switch (cmd) {
case SIOCGIFNAME:
- tmp = strlen(elm->dev->name) + 1;
+ tmp = strnlen(elm->dev->name, IFNAMSIZ - 1) + 1;
if (copy_to_user((void __user *)arg, elm->dev->name, tmp)) {
put_elm(elm);
return -EFAULT;
-
-
- /************************************************************************
- * 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) {
+ if (status)
pr_err("can't register line discipline\n");
- }
+
return status;
}
int status;
status = tty_unregister_ldisc(N_ELMCAN);
- if (status) {
- pr_err("Can't unregister line discipline (error: %d)\n", status);
- }
+ if (status)
+ pr_err("Can't unregister line discipline (error: %d)\n",
+ status);
}
module_init(elmcan_init);
projects / elmcan.git / blobdiff