#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
can_bus_off(elm->dev);
}
+/* Compare a buffer to a fixed string */
+static int _memstrcmp(const u8 *mem, const char *str)
+{
+ return memcmp(mem, str, strlen(str));
+}
+
/* Assumes elm->lock taken. */
static void elm327_parse_error(struct elmcan *elm, int len)
{
frame.can_id = CAN_ERR_FLAG;
frame.can_dlc = CAN_ERR_DLC;
+ /* Filter possible error messages based on length of RX'd line */
switch (len) {
case 17:
- if (!memcmp(elm->rxbuf, "UNABLE TO CONNECT", 17)) {
+ if (!_memstrcmp(elm->rxbuf, "UNABLE TO CONNECT")) {
netdev_err(elm->dev,
"ELM327 reported UNABLE TO CONNECT. Please check your setup.\n");
}
break;
case 11:
- if (!memcmp(elm->rxbuf, "BUFFER FULL", 11)) {
+ if (!_memstrcmp(elm->rxbuf, "BUFFER FULL")) {
/* This case will only happen if the last data
* line was complete.
* Otherwise, elm327_parse_frame() will heuristically
}
break;
case 9:
- if (!memcmp(elm->rxbuf, "BUS ERROR", 9))
+ if (!_memstrcmp(elm->rxbuf, "BUS ERROR"))
frame.can_id |= CAN_ERR_BUSERROR;
- if (!memcmp(elm->rxbuf, "CAN ERROR", 9))
+ if (!_memstrcmp(elm->rxbuf, "CAN ERROR"))
frame.can_id |= CAN_ERR_PROT;
- if (!memcmp(elm->rxbuf, "<RX ERROR", 9))
+ if (!_memstrcmp(elm->rxbuf, "<RX ERROR"))
frame.can_id |= CAN_ERR_PROT;
break;
case 8:
- if (!memcmp(elm->rxbuf, "BUS BUSY", 8)) {
+ if (!_memstrcmp(elm->rxbuf, "BUS BUSY")) {
frame.can_id |= CAN_ERR_PROT;
frame.data[2] = CAN_ERR_PROT_OVERLOAD;
}
- if (!memcmp(elm->rxbuf, "FB ERROR", 8)) {
+ if (!_memstrcmp(elm->rxbuf, "FB ERROR")) {
frame.can_id |= CAN_ERR_PROT;
frame.data[2] = CAN_ERR_PROT_TX;
}
break;
- case 5:
- if (!memcmp(elm->rxbuf, "ERR", 3)) {
+ case 5: /* ERR is followed by two digits, hence line length 5 */
+ if (!_memstrcmp(elm->rxbuf, "ERR")) {
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;
+ /* Something else has happened.
+ * Maybe garbage on the UART line.
+ * Emit a generic error frame.
+ */
+ break;
}
elm327_feed_frame_to_netdev(elm, &frame);
}
}
- /* 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;
}
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;
}
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_READY_CHAR ||
/* Dummy needed to use bitrate_const */
static int elmcan_do_set_bittiming(struct net_device *netdev)
{
- (void)netdev;
-
return 0;
}
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