}
-/*
- * 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. */
static void elm327_kick_into_cmd_mode(struct elmcan *elm)
{
if (elm->state != ELM_GETMAGICCHAR && elm->state != ELM_GETPROMPT) {
}
-/*
- * 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 (!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.
+ * 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;
}
+/* 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;
/* 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? */
+ /* 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. */
}
}
-
static void elm327_handle_prompt(struct elmcan *elm)
{
struct can_frame *frame = &elm->can_frame;
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);
elm->rxfill -= i;
}
-
static void elm327_parse_rxbuf(struct elmcan *elm)
{
int len;
* (takes elm->lock) *
************************************************************************/
-/* Netdevice DOWN -> UP routine */
static int elmcan_netdev_open(struct net_device *dev)
{
struct elmcan *elm = netdev_priv(dev);
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. */
+/* Send a can_frame to a TTY. */
static netdev_tx_t elmcan_netdev_start_xmit(struct sk_buff *skb,
struct net_device *dev)
{
WARN_ON(elm->hw_failure);
if (elm->tty == NULL
+ || elm->hw_failure
|| elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {
spin_unlock(&elm->lock);
goto out;
* (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)
{
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;
}
-
-/*
- * 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)
return;
}
- /* Read the characters out of the buffer */
while (count-- && elm->rxfill < sizeof(elm->rxbuf)) {
if (fp && *fp++) {
netdev_err(elm->dev, "Error in received character stream. Check your wiring.");
*/
if (*cp != 0) {
/* Check for stray characters on the UART line.
- * No idea what causes this.
+ * Likely caused by bad hardware.
*/
if (!accept_flaky_uart
&& !isdigit(*cp)
&& '?' != *cp
&& '\r' != *cp
&& ' ' != *cp) {
- /* We've received an invalid character, so bail.
- * There's something wrong with the ELM327, or
- * with the UART line.
- */
netdev_err(elm->dev,
"Received illegal character %02x.\n",
*cp);
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);
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);
}
-
/* 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.
62500, 71428, 83333, 100000, 125000, 166666, 250000, 500000
};
-/* Dummy function to claim we're changing the bitrate.
- * We actually do this when opening the net device.
- */
+
+/* Dummy needed to use bitrate_const */
static int elmcan_do_set_bittiming(struct net_device *netdev)
{
return 0;
}
-/*
- * 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.
- */
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;
return 0;
}
-/*
- * 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_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 */
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)
{
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)
pr_err("can't register line discipline\n");
projects / elmcan.git / commitdiff