/* 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.
+ * 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>
#include <linux/can/rx-offload.h>
/* 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
+ * 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
#define ELM327_NAPI_WEIGHT 4
-#define ELM327_SIZE_RXBUF 256
+#define ELM327_SIZE_RXBUF 224
#define ELM327_SIZE_TXBUF 32
#define ELM327_CAN_CONFIG_SEND_SFF 0x8000
#define ELM327_READY_CHAR '>'
/* Bits in elm->cmds_todo */
-enum ELM327_TX_DO_BITS {
+enum elm327_to_to_do_bits {
ELM327_TX_DO_CAN_DATA = 0,
ELM327_TX_DO_CANID_11BIT,
ELM327_TX_DO_CANID_29BIT_LOW,
struct can_rx_offload offload;
- /* TTY and netdev devices that we're bridging */
- struct tty_struct *tty;
- struct net_device *dev;
+ /* TTY buffers */
+ u8 rxbuf[ELM327_SIZE_RXBUF];
+ u8 txbuf[ELM327_SIZE_TXBUF] ____cacheline_aligned;
/* Per-channel lock */
spinlock_t lock;
- /* Stop the channel on hardware failure.
- * Once this is true, nothing will be sent to the TTY.
- */
- bool hw_failure;
-
- /* TTY TX helpers */
- struct work_struct tx_work; /* Flushes TTY TX buffer */
- u8 *txbuf; /* Pointer to our TX buffer */
- u8 *txhead; /* Pointer to next TX byte */
- unsigned txleft; /* Bytes left to TX */
+ /* TTY and netdev devices that we're bridging */
+ struct tty_struct *tty;
+ struct net_device *dev;
- /* TTY RX helpers */
- u8 rxbuf[ELM327_SIZE_RXBUF];
- int rxfill;
+ /* 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_RECEIVING,
} state;
- bool drop_next_line;
+ /* 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
u16 can_config;
u8 can_bitrate_divisor;
- /* Things we have yet to send */
- char **next_init_cmd;
- unsigned long cmds_todo;
+ /* 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_hw_failure(struct elmcan *elm);
+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);
+ lockdep_assert_held(&elm->lock);
- if (elm->hw_failure)
+ 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_hw_failure(elm);
+ elm327_uart_side_failure(elm);
return;
}
elm->txleft = len - written;
elm->txhead = elm->txbuf + written;
-
- if (!elm->txleft)
- netif_wake_queue(elm->dev);
- else
- set_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
}
/* Take the ELM327 out of almost any state and back into command mode.
*/
static void elm327_kick_into_cmd_mode(struct elmcan *elm)
{
- lockdep_assert_held(elm->lock);
+ lockdep_assert_held(&elm->lock);
if (elm->state != ELM327_STATE_GETDUMMYCHAR &&
elm->state != ELM327_STATE_GETPROMPT) {
/* 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);
+ 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) {
static void elm327_init(struct elmcan *elm)
{
- lockdep_assert_held(elm->lock);
+ lockdep_assert_held(&elm->lock);
elm->state = ELM327_STATE_NOTINIT;
elm->can_frame_to_send.can_id = 0x7df; /* ELM327 HW default */
static void elm327_feed_frame_to_netdev(struct elmcan *elm,
struct sk_buff *skb)
{
- lockdep_assert_held(elm->lock);
+ lockdep_assert_held(&elm->lock);
if (!netif_running(elm->dev))
return;
}
/* Called when we're out of ideas and just want it all to end. */
-static inline void elm327_hw_failure(struct elmcan *elm)
+static inline void elm327_uart_side_failure(struct elmcan *elm)
{
struct can_frame *frame;
struct sk_buff *skb;
- lockdep_assert_held(elm->lock);
+ lockdep_assert_held(&elm->lock);
- elm->hw_failure = true;
+ 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);
struct can_frame *frame;
struct sk_buff *skb;
- lockdep_assert_held(elm->lock);
+ lockdep_assert_held(&elm->lock);
skb = alloc_can_err_skb(elm->dev, &frame);
if (!skb)
int datastart;
int i;
- lockdep_assert_held(elm->lock);
+ lockdep_assert_held(&elm->lock);
skb = alloc_can_skb(elm->dev, &frame);
if (!skb)
static void elm327_parse_line(struct elmcan *elm, size_t len)
{
- lockdep_assert_held(elm->lock);
+ lockdep_assert_held(&elm->lock);
/* Skip empty lines */
if (!len)
}
/* Regular parsing */
- if (elm->state == ELM327_STATE_RECEIVING
- && elm327_parse_frame(elm, len)) {
+ if (elm->state == ELM327_STATE_RECEIVING &&
+ elm327_parse_frame(elm, len)) {
/* Parse an error line. */
elm327_parse_error(elm, len);
*/
char local_txbuf[sizeof("0102030405060708\r")];
- lockdep_assert_held(elm->lock);
+ 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);
+ "%s",
+ *elm->next_init_cmd);
elm->next_init_cmd++;
if (!(*elm->next_init_cmd)) {
} 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)));
+ "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));
+ "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");
+ "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);
+ "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);
+ "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));
+ "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);
+ "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) {
* Some chips don't send them at all.
*/
snprintf(local_txbuf, sizeof(local_txbuf),
- "ATRTR\r");
+ "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]);
+ "%02X",
+ frame->data[i]);
}
snprintf(&local_txbuf[2 * i], sizeof(local_txbuf),
- "\r");
+ "\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 void elm327_drop_bytes(struct elmcan *elm, size_t i)
{
- lockdep_assert_held(elm->lock);
+ lockdep_assert_held(&elm->lock);
memmove(&elm->rxbuf[0], &elm->rxbuf[i], ELM327_SIZE_RXBUF - i);
elm->rxfill -= i;
size_t len;
int i;
- lockdep_assert_held(elm->lock);
+ lockdep_assert_held(&elm->lock);
switch (elm->state) {
case ELM327_STATE_NOTINIT:
*/
netdev_err(elm->dev,
"RX buffer overflow. Faulty ELM327 or UART?\n");
- elm327_hw_failure(elm);
+ elm327_uart_side_failure(elm);
break;
} else if (len == elm->rxfill) {
if (elm327_is_ready_char(elm->rxbuf[elm->rxfill - 1])) {
int err;
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");
- spin_unlock_bh(&elm->lock);
- return -EIO;
- }
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) {
{
struct elmcan *elm = netdev_priv(dev);
- netif_stop_queue(dev);
-
+ /* Interrupt whatever the ELM327 is doing right now */
spin_lock_bh(&elm->lock);
- if (elm->tty) {
- /* Interrupt whatever we're doing right now */
- 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
- */
- clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
+ elm327_send(elm, ELM327_DUMMY_STRING, 1);
+ spin_unlock_bh(&elm->lock);
- spin_unlock_bh(&elm->lock);
+ netif_stop_queue(dev);
- flush_work(&elm->tx_work);
- } else {
- spin_unlock_bh(&elm->lock);
- }
+ /* 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;
/* We shouldn't get here after a hardware fault:
* can_bus_off() calls netif_carrier_off()
*/
- WARN_ON_ONCE(elm->hw_failure);
+ WARN_ON_ONCE(elm->uart_side_failure);
if (!elm->tty ||
- elm->hw_failure ||
+ elm->uart_side_failure ||
elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {
spin_unlock(&elm->lock);
goto out;
spin_lock_bh(&elm->lock);
- if (elm->hw_failure)
+ 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_hw_failure(elm);
+ elm327_uart_side_failure(elm);
goto out;
}
netdev_err(elm->dev,
"Received illegal character %02x.\n",
*cp);
- elm327_hw_failure(elm);
+ elm327_uart_side_failure(elm);
goto out;
}
if (count >= 0) {
netdev_err(elm->dev, "Receive buffer overflowed. Bad chip or wiring?");
- elm327_hw_failure(elm);
+ elm327_uart_side_failure(elm);
goto out;
}
struct elmcan *elm = container_of(work, struct elmcan, tx_work);
ssize_t written;
- if (elm->hw_failure)
+ if (elm->uart_side_failure)
return;
spin_lock_bh(&elm->lock);
netdev_err(elm->dev,
"Failed to write to tty %s.\n",
elm->tty->name);
- elm327_hw_failure(elm);
+ elm327_uart_side_failure(elm);
spin_unlock_bh(&elm->lock);
return;
- } else {
- elm->txleft -= written;
- elm->txhead += written;
}
+
+ elm->txleft -= written;
+ elm->txhead += written;
}
if (!elm->txleft) {
clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
spin_unlock_bh(&elm->lock);
- netif_wake_queue(elm->dev);
} else {
spin_unlock_bh(&elm->lock);
}
return -ENFILE;
elm = netdev_priv(dev);
- elm->txbuf = kmalloc(ELM327_SIZE_TXBUF, GFP_KERNEL);
- if (!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 */
spin_lock_init(&elm->lock);
INIT_WORK(&elm->tx_work, elmcan_ldisc_tx_worker);
return 0;
out_err:
- kfree(elm->txbuf);
free_candev(elm->dev);
return err;
}
{
struct elmcan *elm = (struct elmcan *)tty->disc_data;
- /* unregister_netdev() calls .ndo_stop() so we don't have to. */
+ /* 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);
- /* Ensure that our worker won't be rescheduled */
- clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
- flush_work(&elm->tx_work);
-
/* Mark channel as dead */
spin_lock_bh(&elm->lock);
tty->disc_data = NULL;
netdev_info(elm->dev, "elmcan off %s.\n", tty->name);
- kfree(elm->txbuf);
free_candev(elm->dev);
}
projects / elmcan.git / blobdiff