// 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 <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>
+/* 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, even
+ * after almost none of their code is left.
*/
#define pr_fmt(fmt) "[elmcan] " fmt
#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>
MODULE_ALIAS_LDISC(N_ELMCAN);
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!
- */
-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_NAPI_WEIGHT 4
+
#define ELM327_SIZE_RXBUF 256
#define ELM327_SIZE_TXBUF 32
/* This must be the first member when using alloc_candev() */
struct can_priv can;
+ struct can_rx_offload offload;
+
/* TTY and netdev devices that we're bridging */
struct tty_struct *tty;
struct net_device *dev;
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;
* 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.
+ *
+ * Assumes elm->lock taken.
*/
static void elm327_kick_into_cmd_mode(struct elmcan *elm)
{
}
}
-/* 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)
{
memcpy(cf, frame, sizeof(struct can_frame));
- elm->dev->stats.rx_packets++;
- elm->dev->stats.rx_bytes += frame->can_dlc;
- netif_rx_ni(skb);
+ /* 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++;
- can_led_event(elm->dev, CAN_LED_EVENT_RX);
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5,15,0)
+ /* Wake NAPI */
+ can_rx_offload_irq_finish(&elm->offload);
+#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 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)
{
struct can_frame frame;
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);
* 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)
{
}
}
- /* 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;
}
+/* Assumes elm->lock taken. */
static void elm327_parse_line(struct elmcan *elm, int len)
{
/* Skip empty lines */
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;
return (c & 0x3f) == ELM327_READY_CHAR;
}
+/* Assumes elm->lock taken. */
static void elm327_drop_bytes(struct elmcan *elm, int 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;
}
}
- /***********************************************************************
- * 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,
+ bool drop)
+{
+ WARN_ON_ONCE(1); /* This function is a dummy, so don't call it! */
+
+ return ERR_PTR(-ENOBUFS);
+}
static int elmcan_netdev_open(struct net_device *dev)
{
elm327_init(elm);
spin_unlock_bh(&elm->lock);
+ elm->offload.mailbox_read = elmcan_mailbox_read;
+ err = can_rx_offload_add_fifo(dev, &elm->offload, ELM327_NAPI_WEIGHT);
+ 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);
{
struct elmcan *elm = netdev_priv(dev);
+ netif_stop_queue(dev);
+
spin_lock_bh(&elm->lock);
if (elm->tty) {
/* Interrupt whatever we're doing right now */
spin_unlock_bh(&elm->lock);
}
+ can_rx_offload_disable(&elm->offload);
elm->can.state = CAN_STATE_STOPPED;
- netif_stop_queue(dev);
+ can_rx_offload_del(&elm->offload);
close_candev(dev);
can_led_event(dev, CAN_LED_EVENT_STOP);
/* We shouldn't get here after a hardware fault:
* can_bus_off() calls netif_carrier_off()
*/
- WARN_ON(elm->hw_failure);
+ WARN_ON_ONCE(elm->hw_failure);
if (!elm->tty ||
elm->hw_failure ||
.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_READY_CHAR ||
* 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 = get_elm(tty);
/* 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;
free_candev(elm->dev);
}
+#if LINUX_VERSION_CODE < KERNEL_VERSION(5,16,0)
static int elmcan_ldisc_hangup(struct tty_struct *tty)
+#else
+static void elmcan_ldisc_hangup(struct tty_struct *tty)
+#endif
{
elmcan_ldisc_close(tty);
+#if LINUX_VERSION_CODE < KERNEL_VERSION(5,16,0)
return 0;
+#endif
}
-static int elmcan_ldisc_ioctl(struct tty_struct *tty, struct file *file,
+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 = get_elm(tty);
default:
put_elm(elm);
+#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_ELMCAN,
.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);
+#else
+ status = tty_register_ldisc(&elmcan_ldisc);
+#endif
if (status)
pr_err("Can't register line discipline\n");
/* 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_ELMCAN);
if (status)
pr_err("Can't unregister line discipline (error: %d)\n",
status);
+#else
+ tty_unregister_ldisc(&elmcan_ldisc);
+#endif
}
module_init(elmcan_init);
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