// SPDX-License-Identifier: GPL-2.0
-/* elmcan.c - ELM327 based CAN interface driver
- * (tty line discipline)
+/* 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>
- *
- * This code barely bears any resemblance to slcan anymore, and whatever
- * may be left is Linux specific boilerplate anyway, however I am leaving
- * the GPL-2.0 identifier at the top just to be sure.
- *
- * Please feel free to use my own code, especially the ELM327 communication
- * logic, in accordance with SPDX-License-Identifier BSD-3-Clause to port
- * this driver to other systems.
- * - Max
- *
+ * and my thanks go to the original authors for their inspiration, even
+ * after almost none of their code is left.
*/
#define pr_fmt(fmt) "[elmcan] " fmt
#include <linux/can/led.h>
#include <linux/can/rx-offload.h>
-MODULE_ALIAS_LDISC(N_ELMCAN);
+MODULE_ALIAS_LDISC(N_DEVELOPMENT);
MODULE_DESCRIPTION("ELM327 based CAN interface");
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!
+/* Line discipline ID number.
+ * N_DEVELOPMENT will likely be defined from Linux 5.18 onwards:
+ * https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git/commit/?h=tty-next&id=c2faf737abfb10f88f2d2612d573e9edc3c42c37
*/
-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
+#ifndef N_DEVELOPMENT
+#define N_DEVELOPMENT 29
#endif
#define ELM327_NAPI_WEIGHT 4
#define ELM327_CAN_CONFIG_RECV_BOTH_SFF_EFF 0x2000
#define ELM327_CAN_CONFIG_BAUDRATE_MULT_8_7 0x1000
-#define ELM327_MAGIC_CHAR 'y'
-#define ELM327_MAGIC_STRING "y"
+#define ELM327_DUMMY_CHAR 'y'
+#define ELM327_DUMMY_STRING "y"
#define ELM327_READY_CHAR '>'
/* Bits in elm->cmds_todo */
/* State machine */
enum {
ELM_NOTINIT = 0,
- ELM_GETMAGICCHAR,
+ ELM_GETDUMMYCHAR,
ELM_GETPROMPT,
ELM_RECEIVING,
} state;
static inline void elm327_hw_failure(struct elmcan *elm);
- /***********************************************************************
- * ELM327: Transmission *
- * *
- * (all functions assume elm->lock taken) *
- ***********************************************************************/
-
+/* Assumes elm->lock taken. */
static void elm327_send(struct elmcan *elm, const void *buf, size_t len)
{
int actual;
}
/* Take the ELM327 out of almost any state and back into command mode.
- * We send ELM327_MAGIC_CHAR which will either abort any running
+ * 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.
+ *
+ * Assumes elm->lock taken.
*/
static void elm327_kick_into_cmd_mode(struct elmcan *elm)
{
- if (elm->state != ELM_GETMAGICCHAR && elm->state != ELM_GETPROMPT) {
- elm327_send(elm, ELM327_MAGIC_STRING, 1);
+ if (elm->state != ELM_GETDUMMYCHAR && elm->state != ELM_GETPROMPT) {
+ elm327_send(elm, ELM327_DUMMY_STRING, 1);
- elm->state = ELM_GETMAGICCHAR;
+ elm->state = ELM_GETDUMMYCHAR;
}
}
-/* Schedule a CAN frame and necessary config changes to be sent to the TTY. */
+/* Schedule a CAN frame and necessary config changes to be sent to the TTY.
+ *
+ * Assumes elm->lock taken.
+ */
static void elm327_send_frame(struct elmcan *elm, struct can_frame *frame)
{
/* Schedule any necessary changes in ELM327's CAN configuration */
elm327_kick_into_cmd_mode(elm);
}
- /***********************************************************************
- * 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 */
"AT PP FF OFF\r", /* v1.0: All Programmable Parameters Off */
elm327_kick_into_cmd_mode(elm);
}
- /***********************************************************************
- * ELM327: Reception -> netdev glue *
- * *
- * (assumes elm->lock taken) *
- ***********************************************************************/
-
+/* Assumes elm->lock taken. */
static void elm327_feed_frame_to_netdev(struct elmcan *elm,
const struct can_frame *frame)
{
#endif
}
- /***********************************************************************
- * ELM327: "Panic" handler *
- * *
- * (assumes elm->lock taken) *
- ***********************************************************************/
-
-/* Called when we're out of ideas and just want it all to end. */
+/* Called when we're out of ideas and just want it all to end.
+ * Assumes elm->lock taken.
+ */
static inline void elm327_hw_failure(struct elmcan *elm)
{
struct can_frame frame;
can_bus_off(elm->dev);
}
- /***********************************************************************
- * ELM327: Reception parser *
- * *
- * (assumes elm->lock taken) *
- ***********************************************************************/
+/* Compare a buffer to a fixed string */
+static inline int _memstrcmp(const u8 *mem, const char *str)
+{
+ return memcmp(mem, str, strlen(str));
+}
-static void elm327_parse_error(struct elmcan *elm, int len)
+/* 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.
+ */
+static inline int _len_memstrcmp(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);
+}
+
+/* Assumes elm->lock taken. */
+static void elm327_parse_error(struct elmcan *elm, size_t len)
{
struct can_frame frame;
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,
- "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, "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;
+ /* Filter possible error messages based on length of RX'd line */
+ if (!_len_memstrcmp(elm->rxbuf, len, "UNABLE TO CONNECT")) {
+ netdev_err(elm->dev,
+ "ELM327 reported UNABLE TO CONNECT. Please check your setup.\n");
+ } else if (!_len_memstrcmp(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 (!_len_memstrcmp(elm->rxbuf, len, "BUS ERROR")) {
+ frame.can_id |= CAN_ERR_BUSERROR;
+ } else if (!_len_memstrcmp(elm->rxbuf, len, "CAN ERROR")) {
+ frame.can_id |= CAN_ERR_PROT;
+ } else if (!_len_memstrcmp(elm->rxbuf, len, "<RX ERROR")) {
+ frame.can_id |= CAN_ERR_PROT;
+ } else if (!_len_memstrcmp(elm->rxbuf, len, "BUS BUSY")) {
+ frame.can_id |= CAN_ERR_PROT;
+ frame.data[2] = CAN_ERR_PROT_OVERLOAD;
+ } else if (!_len_memstrcmp(elm->rxbuf, len, "FB ERROR")) {
+ frame.can_id |= CAN_ERR_PROT;
+ frame.data[2] = CAN_ERR_PROT_TX;
+ } else if (len == 5 && !_memstrcmp(elm->rxbuf, "ERR")) {
+ /* 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, &frame);
* Instead of a payload, RTR indicates a remote request.
*
* We will use the spaces and line length to guess the format.
+ *
+ * Assumes elm->lock taken.
*/
-static int elm327_parse_frame(struct elmcan *elm, int len)
+static int elm327_parse_frame(struct elmcan *elm, size_t len)
{
struct can_frame frame;
int hexlen;
}
}
- /* If we accept stray characters coming in:
- * Check for stray characters on a payload line.
- * No idea what causes this.
+ /* Sanity check whether the line is really a clean hexdump,
+ * or terminated by an error message, or contains garbage.
*/
- if (accept_flaky_uart &&
- hexlen < len &&
+ if (hexlen < len &&
!isdigit(elm->rxbuf[hexlen]) &&
!isupper(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 -ENODATA;
}
/* Check for RTR frame */
if (elm->rxfill >= hexlen + 3 &&
- !memcmp(&elm->rxbuf[hexlen], "RTR", 3)) {
+ !_memstrcmp(&elm->rxbuf[hexlen], "RTR")) {
frame.can_id |= CAN_RTR_FLAG;
}
return 0;
}
-static void elm327_parse_line(struct elmcan *elm, int len)
+/* Assumes elm->lock taken. */
+static void elm327_parse_line(struct elmcan *elm, size_t len)
{
/* Skip empty lines */
if (!len)
if (elm->drop_next_line) {
elm->drop_next_line = 0;
return;
- } else if (elm->rxbuf[0] == 'A' && elm->rxbuf[1] == 'T') {
+ } else if (!_memstrcmp(elm->rxbuf, "AT")) {
return;
}
}
}
+/* Assumes elm->lock taken. */
static void elm327_handle_prompt(struct elmcan *elm)
{
struct can_frame *frame = &elm->can_frame;
elm->next_init_cmd++;
if (!(*elm->next_init_cmd)) {
clear_bit(TODO_INIT, &elm->cmds_todo);
- netdev_info(elm->dev, "Initialization finished.\n");
+ /* Init finished. */
}
} else if (test_and_clear_bit(TODO_SILENT_MONITOR, &elm->cmds_todo)) {
return (c & 0x3f) == ELM327_READY_CHAR;
}
-static void elm327_drop_bytes(struct elmcan *elm, int i)
+/* Assumes elm->lock taken. */
+static void elm327_drop_bytes(struct elmcan *elm, size_t i)
{
memmove(&elm->rxbuf[0], &elm->rxbuf[i], ELM327_SIZE_RXBUF - i);
elm->rxfill -= i;
}
+/* Assumes elm->lock taken. */
static void elm327_parse_rxbuf(struct elmcan *elm)
{
- int len;
+ size_t len;
switch (elm->state) {
case ELM_NOTINIT:
elm->rxfill = 0;
break;
- case ELM_GETMAGICCHAR:
+ case ELM_GETDUMMYCHAR:
{
/* Wait for 'y' or '>' */
int i;
for (i = 0; i < elm->rxfill; i++) {
- if (elm->rxbuf[i] == ELM327_MAGIC_CHAR) {
+ if (elm->rxbuf[i] == ELM327_DUMMY_CHAR) {
elm327_send(elm, "\r", 1);
elm->state = ELM_GETPROMPT;
i++;
break;
} else if (elm327_is_ready_char(elm->rxbuf[i])) {
- elm327_send(elm, ELM327_MAGIC_STRING, 1);
+ elm327_send(elm, ELM327_DUMMY_STRING, 1);
i++;
break;
}
}
}
- /***********************************************************************
- * netdev *
- * *
- * (takes elm->lock) *
- ***********************************************************************/
-
/* Dummy needed to use can_rx_offload */
static struct sk_buff *elmcan_mailbox_read(struct can_rx_offload *offload,
unsigned int n, u32 *timestamp,
spin_lock_bh(&elm->lock);
if (elm->tty) {
/* Interrupt whatever we're doing right now */
- elm327_send(elm, ELM327_MAGIC_STRING, 1);
+ elm327_send(elm, ELM327_DUMMY_STRING, 1);
/* Clear the wakeup bit, as the netdev will be down and thus
* the wakeup handler won't clear it
.ndo_change_mtu = can_change_mtu,
};
- /***********************************************************************
- * Line discipline *
- * *
- * (takes elm->lock) *
- ***********************************************************************/
-
/* Get a reference to our struct, taking into account locks/refcounts.
* This is to ensure ordering in case we are shutting down, and to ensure
* there is a refcount at all (otherwise tty->disc_data may be freed and
static bool elmcan_is_valid_rx_char(char c)
{
- return (accept_flaky_uart ||
- isdigit(c) ||
+ return (isdigit(c) ||
isupper(c) ||
- c == ELM327_MAGIC_CHAR ||
+ c == ELM327_DUMMY_CHAR ||
c == ELM327_READY_CHAR ||
c == '<' ||
c == 'a' ||
/* Dummy needed to use bitrate_const */
static int elmcan_do_set_bittiming(struct net_device *netdev)
{
- (void)netdev;
-
return 0;
}
elm->can.do_set_bittiming = elmcan_do_set_bittiming;
elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
- /* Configure netlink interface */
+ /* Configure netdev interface */
elm->dev = dev;
dev->netdev_ops = &elmcan_netdev_ops;
static struct tty_ldisc_ops elmcan_ldisc = {
.owner = THIS_MODULE,
.name = "elmcan",
- .num = N_ELMCAN,
+ .num = N_DEVELOPMENT,
.receive_buf = elmcan_ldisc_rx,
.write_wakeup = elmcan_ldisc_tx_wakeup,
.open = elmcan_ldisc_open,
{
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");
-
#if LINUX_VERSION_CODE < KERNEL_VERSION(5,14,0)
- status = tty_register_ldisc(N_ELMCAN, &elmcan_ldisc);
+ status = tty_register_ldisc(N_DEVELOPMENT, &elmcan_ldisc);
#else
status = tty_register_ldisc(&elmcan_ldisc);
#endif
#if LINUX_VERSION_CODE < KERNEL_VERSION(5,14,0)
int status;
- status = tty_unregister_ldisc(N_ELMCAN);
+ status = tty_unregister_ldisc(N_DEVELOPMENT);
if (status)
pr_err("Can't unregister line discipline (error: %d)\n",
status);
projects / elmcan.git / blobdiff