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linux-zen-desktop/drivers/net/can/can327.c

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// SPDX-License-Identifier: GPL-2.0
/* 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.
*
* can327.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>
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/init.h>
#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/lockdep.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/tty.h>
#include <linux/tty_ldisc.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/rx-offload.h>
#define CAN327_NAPI_WEIGHT 4
#define CAN327_SIZE_TXBUF 32
#define CAN327_SIZE_RXBUF 1024
#define CAN327_CAN_CONFIG_SEND_SFF 0x8000
#define CAN327_CAN_CONFIG_VARIABLE_DLC 0x4000
#define CAN327_CAN_CONFIG_RECV_BOTH_SFF_EFF 0x2000
#define CAN327_CAN_CONFIG_BAUDRATE_MULT_8_7 0x1000
#define CAN327_DUMMY_CHAR 'y'
#define CAN327_DUMMY_STRING "y"
#define CAN327_READY_CHAR '>'
/* Bits in elm->cmds_todo */
enum can327_tx_do {
CAN327_TX_DO_CAN_DATA = 0,
CAN327_TX_DO_CANID_11BIT,
CAN327_TX_DO_CANID_29BIT_LOW,
CAN327_TX_DO_CANID_29BIT_HIGH,
CAN327_TX_DO_CAN_CONFIG_PART2,
CAN327_TX_DO_CAN_CONFIG,
CAN327_TX_DO_RESPONSES,
CAN327_TX_DO_SILENT_MONITOR,
CAN327_TX_DO_INIT,
};
struct can327 {
/* This must be the first member when using alloc_candev() */
struct can_priv can;
struct can_rx_offload offload;
/* TTY buffers */
u8 txbuf[CAN327_SIZE_TXBUF];
u8 rxbuf[CAN327_SIZE_RXBUF];
/* Per-channel lock */
spinlock_t lock;
/* TTY and netdev devices that we're bridging */
struct tty_struct *tty;
struct net_device *dev;
/* 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 {
CAN327_STATE_NOTINIT = 0,
CAN327_STATE_GETDUMMYCHAR,
CAN327_STATE_GETPROMPT,
CAN327_STATE_RECEIVING,
} state;
/* 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
*/
struct can_frame can_frame_to_send;
u16 can_config;
u8 can_bitrate_divisor;
/* 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 can327_uart_side_failure(struct can327 *elm);
static void can327_send(struct can327 *elm, const void *buf, size_t len)
{
int written;
lockdep_assert_held(&elm->lock);
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);
can327_uart_side_failure(elm);
return;
}
elm->txleft = len - written;
elm->txhead = elm->txbuf + written;
}
/* Take the ELM327 out of almost any state and back into command mode.
* We send CAN327_DUMMY_CHAR which will either abort any running
* operation, or be echoed back to us in case we're already in command
* mode.
*/
static void can327_kick_into_cmd_mode(struct can327 *elm)
{
lockdep_assert_held(&elm->lock);
if (elm->state != CAN327_STATE_GETDUMMYCHAR &&
elm->state != CAN327_STATE_GETPROMPT) {
can327_send(elm, CAN327_DUMMY_STRING, 1);
elm->state = CAN327_STATE_GETDUMMYCHAR;
}
}
/* Schedule a CAN frame and necessary config changes to be sent to the TTY. */
static void can327_send_frame(struct can327 *elm, struct can_frame *frame)
{
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) {
/* Set the new CAN ID for transmission. */
if ((frame->can_id ^ elm->can_frame_to_send.can_id)
& CAN_EFF_FLAG) {
elm->can_config =
(frame->can_id & CAN_EFF_FLAG ? 0 : CAN327_CAN_CONFIG_SEND_SFF) |
CAN327_CAN_CONFIG_VARIABLE_DLC |
CAN327_CAN_CONFIG_RECV_BOTH_SFF_EFF |
elm->can_bitrate_divisor;
set_bit(CAN327_TX_DO_CAN_CONFIG, &elm->cmds_todo);
}
if (frame->can_id & CAN_EFF_FLAG) {
clear_bit(CAN327_TX_DO_CANID_11BIT, &elm->cmds_todo);
set_bit(CAN327_TX_DO_CANID_29BIT_LOW, &elm->cmds_todo);
set_bit(CAN327_TX_DO_CANID_29BIT_HIGH, &elm->cmds_todo);
} else {
set_bit(CAN327_TX_DO_CANID_11BIT, &elm->cmds_todo);
clear_bit(CAN327_TX_DO_CANID_29BIT_LOW,
&elm->cmds_todo);
clear_bit(CAN327_TX_DO_CANID_29BIT_HIGH,
&elm->cmds_todo);
}
}
/* Schedule the CAN frame itself. */
elm->can_frame_to_send = *frame;
set_bit(CAN327_TX_DO_CAN_DATA, &elm->cmds_todo);
can327_kick_into_cmd_mode(elm);
}
/* ELM327 initialisation sequence.
* The line length is limited by the buffer in can327_handle_prompt().
*/
static char *can327_init_script[] = {
"AT WS\r", /* v1.0: Warm Start */
"AT PP FF OFF\r", /* v1.0: All Programmable Parameters Off */
"AT M0\r", /* v1.0: Memory Off */
"AT AL\r", /* v1.0: Allow Long messages */
"AT BI\r", /* v1.0: Bypass Initialisation */
"AT CAF0\r", /* v1.0: CAN Auto Formatting Off */
"AT CFC0\r", /* v1.0: CAN Flow Control Off */
"AT CF 000\r", /* v1.0: Reset CAN ID Filter */
"AT CM 000\r", /* v1.0: Reset CAN ID Mask */
"AT E1\r", /* v1.0: Echo On */
"AT H1\r", /* v1.0: Headers On */
"AT L0\r", /* v1.0: Linefeeds Off */
"AT SH 7DF\r", /* v1.0: Set CAN sending ID to 0x7df */
"AT ST FF\r", /* v1.0: Set maximum Timeout for response after TX */
"AT AT0\r", /* v1.2: Adaptive Timing Off */
"AT D1\r", /* v1.3: Print DLC On */
"AT S1\r", /* v1.3: Spaces On */
"AT TP B\r", /* v1.0: Try Protocol B */
NULL
};
static void can327_init_device(struct can327 *elm)
{
lockdep_assert_held(&elm->lock);
elm->state = CAN327_STATE_NOTINIT;
elm->can_frame_to_send.can_id = 0x7df; /* ELM327 HW default */
elm->rxfill = 0;
elm->drop_next_line = 0;
/* We can only set the bitrate as a fraction of 500000.
* The bitrates listed in can327_bitrate_const will
* limit the user to the right values.
*/
elm->can_bitrate_divisor = 500000 / elm->can.bittiming.bitrate;
elm->can_config =
CAN327_CAN_CONFIG_SEND_SFF | CAN327_CAN_CONFIG_VARIABLE_DLC |
CAN327_CAN_CONFIG_RECV_BOTH_SFF_EFF | elm->can_bitrate_divisor;
/* Configure ELM327 and then start monitoring */
elm->next_init_cmd = &can327_init_script[0];
set_bit(CAN327_TX_DO_INIT, &elm->cmds_todo);
set_bit(CAN327_TX_DO_SILENT_MONITOR, &elm->cmds_todo);
set_bit(CAN327_TX_DO_RESPONSES, &elm->cmds_todo);
set_bit(CAN327_TX_DO_CAN_CONFIG, &elm->cmds_todo);
can327_kick_into_cmd_mode(elm);
}
static void can327_feed_frame_to_netdev(struct can327 *elm, struct sk_buff *skb)
{
lockdep_assert_held(&elm->lock);
if (!netif_running(elm->dev)) {
kfree_skb(skb);
return;
}
/* 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++;
/* Wake NAPI */
can_rx_offload_irq_finish(&elm->offload);
}
/* Called when we're out of ideas and just want it all to end. */
static inline void can327_uart_side_failure(struct can327 *elm)
{
struct can_frame *frame;
struct sk_buff *skb;
lockdep_assert_held(&elm->lock);
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);
elm->can.state = CAN_STATE_BUS_OFF;
can_bus_off(elm->dev);
netdev_err(elm->dev,
"ELM327 misbehaved. Blocking further communication.\n");
skb = alloc_can_err_skb(elm->dev, &frame);
if (!skb)
return;
frame->can_id |= CAN_ERR_BUSOFF;
can327_feed_frame_to_netdev(elm, skb);
}
/* Compares a byte buffer (non-NUL terminated) to the payload part of
* a string, and returns true iff the buffer (content *and* length) is
* exactly that string, without the terminating NUL byte.
*
* Example: If reference is "BUS ERROR", then this returns true iff nbytes == 9
* and !memcmp(buf, "BUS ERROR", 9).
*
* The reason to use strings is so we can easily include them in the C
* code, and to avoid hardcoding lengths.
*/
static inline bool can327_rxbuf_cmp(const u8 *buf, size_t nbytes,
const char *reference)
{
size_t ref_len = strlen(reference);
return (nbytes == ref_len) && !memcmp(buf, reference, ref_len);
}
static void can327_parse_error(struct can327 *elm, size_t len)
{
struct can_frame *frame;
struct sk_buff *skb;
lockdep_assert_held(&elm->lock);
skb = alloc_can_err_skb(elm->dev, &frame);
if (!skb)
/* It's okay to return here:
* The outer parsing loop will drop this UART buffer.
*/
return;
/* Filter possible error messages based on length of RX'd line */
if (can327_rxbuf_cmp(elm->rxbuf, len, "UNABLE TO CONNECT")) {
netdev_err(elm->dev,
"ELM327 reported UNABLE TO CONNECT. Please check your setup.\n");
} else if (can327_rxbuf_cmp(elm->rxbuf, len, "BUFFER FULL")) {
/* This will only happen if the last data line was complete.
* Otherwise, can327_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 (can327_rxbuf_cmp(elm->rxbuf, len, "BUS ERROR")) {
frame->can_id |= CAN_ERR_BUSERROR;
} else if (can327_rxbuf_cmp(elm->rxbuf, len, "CAN ERROR")) {
frame->can_id |= CAN_ERR_PROT;
} else if (can327_rxbuf_cmp(elm->rxbuf, len, "<RX ERROR")) {
frame->can_id |= CAN_ERR_PROT;
} else if (can327_rxbuf_cmp(elm->rxbuf, len, "BUS BUSY")) {
frame->can_id |= CAN_ERR_PROT;
frame->data[2] = CAN_ERR_PROT_OVERLOAD;
} else if (can327_rxbuf_cmp(elm->rxbuf, len, "FB ERROR")) {
frame->can_id |= CAN_ERR_PROT;
frame->data[2] = CAN_ERR_PROT_TX;
} else if (len == 5 && !memcmp(elm->rxbuf, "ERR", 3)) {
/* 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.
*/
}
can327_feed_frame_to_netdev(elm, skb);
}
/* 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 can327_parse_frame(struct can327 *elm, size_t len)
{
struct can_frame *frame;
struct sk_buff *skb;
int hexlen;
int datastart;
int i;
lockdep_assert_held(&elm->lock);
skb = alloc_can_skb(elm->dev, &frame);
if (!skb)
return -ENOMEM;
/* Find first non-hex and non-space character:
* - In the simplest case, there is none.
* - For RTR frames, 'R' is the first non-hex character.
* - An error message may replace the end of the data line.
*/
for (hexlen = 0; hexlen <= len; hexlen++) {
if (hex_to_bin(elm->rxbuf[hexlen]) < 0 &&
elm->rxbuf[hexlen] != ' ') {
break;
}
}
/* Sanity check whether the line is really a clean hexdump,
* or terminated by an error message, or contains garbage.
*/
if (hexlen < len && !isdigit(elm->rxbuf[hexlen]) &&
!isupper(elm->rxbuf[hexlen]) && '<' != elm->rxbuf[hexlen] &&
' ' != elm->rxbuf[hexlen]) {
/* The line is likely garbled anyway, so bail.
* The main code will restart listening.
*/
kfree_skb(skb);
return -ENODATA;
}
/* Use spaces in CAN ID to distinguish 29 or 11 bit address length.
* No out-of-bounds access:
* We use the fact that we can always read from elm->rxbuf.
*/
if (elm->rxbuf[2] == ' ' && elm->rxbuf[5] == ' ' &&
elm->rxbuf[8] == ' ' && elm->rxbuf[11] == ' ' &&
elm->rxbuf[13] == ' ') {
frame->can_id = CAN_EFF_FLAG;
datastart = 14;
} else if (elm->rxbuf[3] == ' ' && elm->rxbuf[5] == ' ') {
datastart = 6;
} else {
/* This is not a well-formatted data line.
* Assume it's an error message.
*/
kfree_skb(skb);
return -ENODATA;
}
if (hexlen < datastart) {
/* The line is too short to be a valid frame hex dump.
* Something interrupted the hex dump or it is invalid.
*/
kfree_skb(skb);
return -ENODATA;
}
/* From here on all chars up to buf[hexlen] are hex or spaces,
* at well-defined offsets.
*/
/* Read CAN data length */
frame->len = (hex_to_bin(elm->rxbuf[datastart - 2]) << 0);
/* Read CAN ID */
if (frame->can_id & CAN_EFF_FLAG) {
frame->can_id |= (hex_to_bin(elm->rxbuf[0]) << 28) |
(hex_to_bin(elm->rxbuf[1]) << 24) |
(hex_to_bin(elm->rxbuf[3]) << 20) |
(hex_to_bin(elm->rxbuf[4]) << 16) |
(hex_to_bin(elm->rxbuf[6]) << 12) |
(hex_to_bin(elm->rxbuf[7]) << 8) |
(hex_to_bin(elm->rxbuf[9]) << 4) |
(hex_to_bin(elm->rxbuf[10]) << 0);
} else {
frame->can_id |= (hex_to_bin(elm->rxbuf[0]) << 8) |
(hex_to_bin(elm->rxbuf[1]) << 4) |
(hex_to_bin(elm->rxbuf[2]) << 0);
}
/* Check for RTR frame */
if (elm->rxfill >= hexlen + 3 &&
!memcmp(&elm->rxbuf[hexlen], "RTR", 3)) {
frame->can_id |= CAN_RTR_FLAG;
}
/* 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->len * 3 + datastart)) {
/* Incomplete frame.
* Probably the ELM327's RS232 TX buffer was full.
* Emit an error frame and exit.
*/
frame->can_id = CAN_ERR_FLAG | CAN_ERR_CRTL;
frame->len = CAN_ERR_DLC;
frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
can327_feed_frame_to_netdev(elm, skb);
/* Signal failure to parse.
* The line will be re-parsed as an error line, which will fail.
* However, this will correctly drop the state machine back into
* command mode.
*/
return -ENODATA;
}
/* Parse the data nibbles. */
for (i = 0; i < frame->len; i++) {
frame->data[i] =
(hex_to_bin(elm->rxbuf[datastart + 3 * i]) << 4) |
(hex_to_bin(elm->rxbuf[datastart + 3 * i + 1]));
}
/* Feed the frame to the network layer. */
can327_feed_frame_to_netdev(elm, skb);
return 0;
}
static void can327_parse_line(struct can327 *elm, size_t len)
{
lockdep_assert_held(&elm->lock);
/* Skip empty lines */
if (!len)
return;
/* Skip echo lines */
if (elm->drop_next_line) {
elm->drop_next_line = 0;
return;
} else if (!memcmp(elm->rxbuf, "AT", 2)) {
return;
}
/* Regular parsing */
if (elm->state == CAN327_STATE_RECEIVING &&
can327_parse_frame(elm, len)) {
/* Parse an error line. */
can327_parse_error(elm, len);
/* Start afresh. */
can327_kick_into_cmd_mode(elm);
}
}
static void can327_handle_prompt(struct can327 *elm)
{
struct can_frame *frame = &elm->can_frame_to_send;
/* Size this buffer for the largest ELM327 line we may generate,
* which is currently an 8 byte CAN frame's payload hexdump.
* Items in can327_init_script must fit here, too!
*/
char local_txbuf[sizeof("0102030405060708\r")];
lockdep_assert_held(&elm->lock);
if (!elm->cmds_todo) {
/* Enter CAN monitor mode */
can327_send(elm, "ATMA\r", 5);
elm->state = CAN327_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(CAN327_TX_DO_INIT, &elm->cmds_todo)) {
snprintf(local_txbuf, sizeof(local_txbuf), "%s",
*elm->next_init_cmd);
elm->next_init_cmd++;
if (!(*elm->next_init_cmd)) {
clear_bit(CAN327_TX_DO_INIT, &elm->cmds_todo);
/* Init finished. */
}
} else if (test_and_clear_bit(CAN327_TX_DO_SILENT_MONITOR, &elm->cmds_todo)) {
snprintf(local_txbuf, sizeof(local_txbuf),
"ATCSM%i\r",
!!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
} else if (test_and_clear_bit(CAN327_TX_DO_RESPONSES, &elm->cmds_todo)) {
snprintf(local_txbuf, sizeof(local_txbuf),
"ATR%i\r",
!(elm->can.ctrlmode & CAN_CTRLMODE_LISTENONLY));
} else if (test_and_clear_bit(CAN327_TX_DO_CAN_CONFIG, &elm->cmds_todo)) {
snprintf(local_txbuf, sizeof(local_txbuf),
"ATPC\r");
set_bit(CAN327_TX_DO_CAN_CONFIG_PART2, &elm->cmds_todo);
} else if (test_and_clear_bit(CAN327_TX_DO_CAN_CONFIG_PART2, &elm->cmds_todo)) {
snprintf(local_txbuf, sizeof(local_txbuf),
"ATPB%04X\r",
elm->can_config);
} else if (test_and_clear_bit(CAN327_TX_DO_CANID_29BIT_HIGH, &elm->cmds_todo)) {
snprintf(local_txbuf, sizeof(local_txbuf),
"ATCP%02X\r",
(frame->can_id & CAN_EFF_MASK) >> 24);
} else if (test_and_clear_bit(CAN327_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));
} else if (test_and_clear_bit(CAN327_TX_DO_CANID_11BIT, &elm->cmds_todo)) {
snprintf(local_txbuf, sizeof(local_txbuf),
"ATSH%03X\r",
frame->can_id & CAN_SFF_MASK);
} else if (test_and_clear_bit(CAN327_TX_DO_CAN_DATA, &elm->cmds_todo)) {
if (frame->can_id & CAN_RTR_FLAG) {
/* Send an RTR frame. Their DLC is fixed.
* Some chips don't send them at all.
*/
snprintf(local_txbuf, sizeof(local_txbuf), "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]);
}
snprintf(&local_txbuf[2 * i], sizeof(local_txbuf),
"\r");
}
elm->drop_next_line = 1;
elm->state = CAN327_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);
}
can327_send(elm, local_txbuf, strlen(local_txbuf));
}
static bool can327_is_ready_char(char c)
{
/* Bits 0xc0 are sometimes set (randomly), hence the mask.
* Probably bad hardware.
*/
return (c & 0x3f) == CAN327_READY_CHAR;
}
static void can327_drop_bytes(struct can327 *elm, size_t i)
{
lockdep_assert_held(&elm->lock);
memmove(&elm->rxbuf[0], &elm->rxbuf[i], CAN327_SIZE_RXBUF - i);
elm->rxfill -= i;
}
static void can327_parse_rxbuf(struct can327 *elm, size_t first_new_char_idx)
{
size_t len, pos;
lockdep_assert_held(&elm->lock);
switch (elm->state) {
case CAN327_STATE_NOTINIT:
elm->rxfill = 0;
break;
case CAN327_STATE_GETDUMMYCHAR:
/* Wait for 'y' or '>' */
for (pos = 0; pos < elm->rxfill; pos++) {
if (elm->rxbuf[pos] == CAN327_DUMMY_CHAR) {
can327_send(elm, "\r", 1);
elm->state = CAN327_STATE_GETPROMPT;
pos++;
break;
} else if (can327_is_ready_char(elm->rxbuf[pos])) {
can327_send(elm, CAN327_DUMMY_STRING, 1);
pos++;
break;
}
}
can327_drop_bytes(elm, pos);
break;
case CAN327_STATE_GETPROMPT:
/* Wait for '>' */
if (can327_is_ready_char(elm->rxbuf[elm->rxfill - 1]))
can327_handle_prompt(elm);
elm->rxfill = 0;
break;
case CAN327_STATE_RECEIVING:
/* Find <CR> delimiting feedback lines. */
len = first_new_char_idx;
while (len < elm->rxfill && elm->rxbuf[len] != '\r')
len++;
if (len == CAN327_SIZE_RXBUF) {
/* Assume the buffer ran full with garbage.
* Did we even connect at the right baud rate?
*/
netdev_err(elm->dev,
"RX buffer overflow. Faulty ELM327 or UART?\n");
can327_uart_side_failure(elm);
} else if (len == elm->rxfill) {
if (can327_is_ready_char(elm->rxbuf[elm->rxfill - 1])) {
/* The ELM327's AT ST response timeout ran out,
* so we got a prompt.
* Clear RX buffer and restart listening.
*/
elm->rxfill = 0;
can327_handle_prompt(elm);
}
/* No <CR> found - we haven't received a full line yet.
* Wait for more data.
*/
} else {
/* We have a full line to parse. */
can327_parse_line(elm, len);
/* Remove parsed data from RX buffer. */
can327_drop_bytes(elm, len + 1);
/* More data to parse? */
if (elm->rxfill)
can327_parse_rxbuf(elm, 0);
}
}
}
static int can327_netdev_open(struct net_device *dev)
{
struct can327 *elm = netdev_priv(dev);
int err;
spin_lock_bh(&elm->lock);
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) {
spin_unlock_bh(&elm->lock);
return err;
}
can327_init_device(elm);
spin_unlock_bh(&elm->lock);
err = can_rx_offload_add_manual(dev, &elm->offload, CAN327_NAPI_WEIGHT);
if (err) {
close_candev(dev);
return err;
}
can_rx_offload_enable(&elm->offload);
elm->can.state = CAN_STATE_ERROR_ACTIVE;
netif_start_queue(dev);
return 0;
}
static int can327_netdev_close(struct net_device *dev)
{
struct can327 *elm = netdev_priv(dev);
/* Interrupt whatever the ELM327 is doing right now */
spin_lock_bh(&elm->lock);
can327_send(elm, CAN327_DUMMY_STRING, 1);
spin_unlock_bh(&elm->lock);
netif_stop_queue(dev);
/* We don't flush the UART TX queue here, as we want final stop
* commands (like the above dummy char) to be flushed out.
*/
can_rx_offload_disable(&elm->offload);
elm->can.state = CAN_STATE_STOPPED;
can_rx_offload_del(&elm->offload);
close_candev(dev);
return 0;
}
/* Send a can_frame to a TTY. */
static netdev_tx_t can327_netdev_start_xmit(struct sk_buff *skb,
struct net_device *dev)
{
struct can327 *elm = netdev_priv(dev);
struct can_frame *frame = (struct can_frame *)skb->data;
if (can_dev_dropped_skb(dev, skb))
return NETDEV_TX_OK;
/* We shouldn't get here after a hardware fault:
* can_bus_off() calls netif_carrier_off()
*/
if (elm->uart_side_failure) {
WARN_ON_ONCE(elm->uart_side_failure);
goto out;
}
netif_stop_queue(dev);
/* BHs are already disabled, so no spin_lock_bh().
* See Documentation/networking/netdevices.rst
*/
spin_lock(&elm->lock);
can327_send_frame(elm, frame);
spin_unlock(&elm->lock);
dev->stats.tx_packets++;
dev->stats.tx_bytes += frame->can_id & CAN_RTR_FLAG ? 0 : frame->len;
skb_tx_timestamp(skb);
out:
kfree_skb(skb);
return NETDEV_TX_OK;
}
static const struct net_device_ops can327_netdev_ops = {
.ndo_open = can327_netdev_open,
.ndo_stop = can327_netdev_close,
.ndo_start_xmit = can327_netdev_start_xmit,
.ndo_change_mtu = can_change_mtu,
};
static const struct ethtool_ops can327_ethtool_ops = {
.get_ts_info = ethtool_op_get_ts_info,
};
static bool can327_is_valid_rx_char(u8 c)
{
static const bool lut_char_is_valid['z'] = {
['\r'] = true,
[' '] = true,
['.'] = true,
['0'] = true, true, true, true, true,
['5'] = true, true, true, true, true,
['<'] = true,
[CAN327_READY_CHAR] = true,
['?'] = true,
['A'] = true, true, true, true, true, true, true,
['H'] = true, true, true, true, true, true, true,
['O'] = true, true, true, true, true, true, true,
['V'] = true, true, true, true, true,
['a'] = true,
['b'] = true,
['v'] = true,
[CAN327_DUMMY_CHAR] = true,
};
BUILD_BUG_ON(CAN327_DUMMY_CHAR >= 'z');
return (c < ARRAY_SIZE(lut_char_is_valid) && lut_char_is_valid[c]);
}
/* Handle incoming ELM327 ASCII data.
* This will not be re-entered while running, but other ldisc
* functions may be called in parallel.
*/
static void can327_ldisc_rx(struct tty_struct *tty, const unsigned char *cp,
const char *fp, int count)
{
struct can327 *elm = (struct can327 *)tty->disc_data;
size_t first_new_char_idx;
if (elm->uart_side_failure)
return;
spin_lock_bh(&elm->lock);
/* Store old rxfill, so can327_parse_rxbuf() will have
* the option of skipping already checked characters.
*/
first_new_char_idx = elm->rxfill;
while (count-- && elm->rxfill < CAN327_SIZE_RXBUF) {
if (fp && *fp++) {
netdev_err(elm->dev,
"Error in received character stream. Check your wiring.");
can327_uart_side_failure(elm);
spin_unlock_bh(&elm->lock);
return;
}
/* Ignore NUL characters, which the PIC microcontroller may
* inadvertently insert due to a known hardware bug.
* See ELM327 documentation, which refers to a Microchip PIC
* bug description.
*/
if (*cp) {
/* Check for stray characters on the UART line.
* Likely caused by bad hardware.
*/
if (!can327_is_valid_rx_char(*cp)) {
netdev_err(elm->dev,
"Received illegal character %02x.\n",
*cp);
can327_uart_side_failure(elm);
spin_unlock_bh(&elm->lock);
return;
}
elm->rxbuf[elm->rxfill++] = *cp;
}
cp++;
}
if (count >= 0) {
netdev_err(elm->dev,
"Receive buffer overflowed. Bad chip or wiring? count = %i",
count);
can327_uart_side_failure(elm);
spin_unlock_bh(&elm->lock);
return;
}
can327_parse_rxbuf(elm, first_new_char_idx);
spin_unlock_bh(&elm->lock);
}
/* Write out remaining transmit buffer.
* Scheduled when TTY is writable.
*/
static void can327_ldisc_tx_worker(struct work_struct *work)
{
struct can327 *elm = container_of(work, struct can327, tx_work);
ssize_t written;
if (elm->uart_side_failure)
return;
spin_lock_bh(&elm->lock);
if (elm->txleft) {
written = elm->tty->ops->write(elm->tty, elm->txhead,
elm->txleft);
if (written < 0) {
netdev_err(elm->dev, "Failed to write to tty %s.\n",
elm->tty->name);
can327_uart_side_failure(elm);
spin_unlock_bh(&elm->lock);
return;
}
elm->txleft -= written;
elm->txhead += written;
}
if (!elm->txleft)
clear_bit(TTY_DO_WRITE_WAKEUP, &elm->tty->flags);
spin_unlock_bh(&elm->lock);
}
/* Called by the driver when there's room for more data. */
static void can327_ldisc_tx_wakeup(struct tty_struct *tty)
{
struct can327 *elm = (struct can327 *)tty->disc_data;
schedule_work(&elm->tx_work);
}
/* 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.
*/
static const u32 can327_bitrate_const[] = {
7812, 7936, 8064, 8196, 8333, 8474, 8620, 8771,
8928, 9090, 9259, 9433, 9615, 9803, 10000, 10204,
10416, 10638, 10869, 11111, 11363, 11627, 11904, 12195,
12500, 12820, 13157, 13513, 13888, 14285, 14705, 15151,
15625, 16129, 16666, 17241, 17857, 18518, 19230, 20000,
20833, 21739, 22727, 23809, 25000, 26315, 27777, 29411,
31250, 33333, 35714, 38461, 41666, 45454, 50000, 55555,
62500, 71428, 83333, 100000, 125000, 166666, 250000, 500000
};
static int can327_ldisc_open(struct tty_struct *tty)
{
struct net_device *dev;
struct can327 *elm;
int err;
if (!capable(CAP_NET_ADMIN))
return -EPERM;
if (!tty->ops->write)
return -EOPNOTSUPP;
dev = alloc_candev(sizeof(struct can327), 0);
if (!dev)
return -ENFILE;
elm = netdev_priv(dev);
/* Configure TTY interface */
tty->receive_room = 65536; /* We don't flow control */
spin_lock_init(&elm->lock);
INIT_WORK(&elm->tx_work, can327_ldisc_tx_worker);
/* Configure CAN metadata */
elm->can.bitrate_const = can327_bitrate_const;
elm->can.bitrate_const_cnt = ARRAY_SIZE(can327_bitrate_const);
elm->can.ctrlmode_supported = CAN_CTRLMODE_LISTENONLY;
/* Configure netdev interface */
elm->dev = dev;
dev->netdev_ops = &can327_netdev_ops;
dev->ethtool_ops = &can327_ethtool_ops;
/* Mark ldisc channel as alive */
elm->tty = tty;
tty->disc_data = elm;
/* Let 'er rip */
err = register_candev(elm->dev);
if (err) {
free_candev(elm->dev);
return err;
}
netdev_info(elm->dev, "can327 on %s.\n", tty->name);
return 0;
}
/* Close down a can327 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.
*
* We also use this function for a hangup event.
*/
static void can327_ldisc_close(struct tty_struct *tty)
{
struct can327 *elm = (struct can327 *)tty->disc_data;
/* unregister_netdev() calls .ndo_stop() so we don't have to. */
unregister_candev(elm->dev);
/* Give UART one final chance to flush.
* No need to clear TTY_DO_WRITE_WAKEUP since .write_wakeup() is
* serialised against .close() and will not be called once we return.
*/
flush_work(&elm->tx_work);
/* Mark channel as dead */
spin_lock_bh(&elm->lock);
tty->disc_data = NULL;
elm->tty = NULL;
spin_unlock_bh(&elm->lock);
netdev_info(elm->dev, "can327 off %s.\n", tty->name);
free_candev(elm->dev);
}
static int can327_ldisc_ioctl(struct tty_struct *tty, unsigned int cmd,
unsigned long arg)
{
struct can327 *elm = (struct can327 *)tty->disc_data;
unsigned int tmp;
switch (cmd) {
case SIOCGIFNAME:
tmp = strnlen(elm->dev->name, IFNAMSIZ - 1) + 1;
if (copy_to_user((void __user *)arg, elm->dev->name, tmp))
return -EFAULT;
return 0;
case SIOCSIFHWADDR:
return -EINVAL;
default:
return tty_mode_ioctl(tty, cmd, arg);
}
}
static struct tty_ldisc_ops can327_ldisc = {
.owner = THIS_MODULE,
.name = KBUILD_MODNAME,
.num = N_CAN327,
.receive_buf = can327_ldisc_rx,
.write_wakeup = can327_ldisc_tx_wakeup,
.open = can327_ldisc_open,
.close = can327_ldisc_close,
.ioctl = can327_ldisc_ioctl,
};
static int __init can327_init(void)
{
int status;
status = tty_register_ldisc(&can327_ldisc);
if (status)
pr_err("Can't register line discipline\n");
return status;
}
static void __exit can327_exit(void)
{
/* This will only be called when all channels have been closed by
* userspace - tty_ldisc.c takes care of the module's refcount.
*/
tty_unregister_ldisc(&can327_ldisc);
}
module_init(can327_init);
module_exit(can327_exit);
MODULE_ALIAS_LDISC(N_CAN327);
MODULE_DESCRIPTION("ELM327 based CAN interface");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Max Staudt <max@enpas.org>");
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