Merge tag 'linux-can-next-for-5.20-20220703' of git://git.kernel.org/pub/scm/linux/kernel/git/mkl/linux-can-next

Marc Kleine-Budde says:

====================
pull-request: can-next 2022-07-03

this is a pull request of 15 patches for net-next/master.

The first 2 patches are by Max Staudt and add the can327 serial CAN
driver along with a new line discipline ID.

The next patch is by me an fixes a typo in the ctucanfd driver.

The last 12 patches are by Dario Binacchi and integrate slcan CAN
serial driver better into the existing CAN driver API.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

14 files changed, 2034 insertions, 107 deletions

diff --git a/Documentation/networking/device_drivers/can/can327.rst b/Documentation/networking/device_drivers/can/can327.rst
new file mode 100644
index 000000000000..b87bfbe5d51c
--- /dev/null
+++ b/Documentation/networking/device_drivers/can/can327.rst
@@ -0,0 +1,331 @@
+.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause)
+
+can327: ELM327 driver for Linux SocketCAN
+==========================================
+
+Authors
+--------
+
+Max Staudt <max@enpas.org>
+
+
+
+Motivation
+-----------
+
+This driver aims to lower the initial cost for hackers interested in
+working with CAN buses.
+
+CAN adapters are expensive, few, and far between.
+ELM327 interfaces are cheap and plentiful.
+Let's use ELM327s as CAN adapters.
+
+
+
+Introduction
+-------------
+
+This driver is an effort to turn abundant ELM327 based OBD interfaces
+into full fledged (as far as possible) CAN interfaces.
+
+Since the ELM327 was never meant to be a stand alone CAN controller,
+the driver has to switch between its modes as quickly as possible in
+order to fake full-duplex operation.
+
+As such, can327 is a best effort driver. However, this is more than
+enough to implement simple request-response protocols (such as OBD II),
+and to monitor broadcast messages on a bus (such as in a vehicle).
+
+Most ELM327s come as nondescript serial devices, attached via USB or
+Bluetooth. The driver cannot recognize them by itself, and as such it
+is up to the user to attach it in form of a TTY line discipline
+(similar to PPP, SLIP, slcan, ...).
+
+This driver is meant for ELM327 versions 1.4b and up, see below for
+known limitations in older controllers and clones.
+
+
+
+Data sheet
+-----------
+
+The official data sheets can be found at ELM electronics' home page:
+
+  https://www.elmelectronics.com/
+
+
+
+How to attach the line discipline
+----------------------------------
+
+Every ELM327 chip is factory programmed to operate at a serial setting
+of 38400 baud/s, 8 data bits, no parity, 1 stopbit.
+
+If you have kept this default configuration, the line discipline can
+be attached on a command prompt as follows::
+
+    sudo ldattach \
+           --debug \
+           --speed 38400 \
+           --eightbits \
+           --noparity \
+           --onestopbit \
+           --iflag -ICRNL,INLCR,-IXOFF \
+           30 \
+           /dev/ttyUSB0
+
+To change the ELM327's serial settings, please refer to its data
+sheet. This needs to be done before attaching the line discipline.
+
+Once the ldisc is attached, the CAN interface starts out unconfigured.
+Set the speed before starting it::
+
+    # The interface needs to be down to change parameters
+    sudo ip link set can0 down
+    sudo ip link set can0 type can bitrate 500000
+    sudo ip link set can0 up
+
+500000 bit/s is a common rate for OBD-II diagnostics.
+If you're connecting straight to a car's OBD port, this is the speed
+that most cars (but not all!) expect.
+
+After this, you can set out as usual with candump, cansniffer, etc.
+
+
+
+How to check the controller version
+------------------------------------
+
+Use a terminal program to attach to the controller.
+
+After issuing the "``AT WS``" command, the controller will respond with
+its version::
+
+    >AT WS
+
+
+    ELM327 v1.4b
+
+    >
+
+Note that clones may claim to be any version they like.
+It is not indicative of their actual feature set.
+
+
+
+
+Communication example
+----------------------
+
+This is a short and incomplete introduction on how to talk to an ELM327.
+It is here to guide understanding of the controller's and the driver's
+limitation (listed below) as well as manual testing.
+
+
+The ELM327 has two modes:
+
+- Command mode
+- Reception mode
+
+In command mode, it expects one command per line, terminated by CR.
+By default, the prompt is a "``>``", after which a command can be
+entered::
+
+    >ATE1
+    OK
+    >
+
+The init script in the driver switches off several configuration options
+that are only meaningful in the original OBD scenario the chip is meant
+for, and are actually a hindrance for can327.
+
+
+When a command is not recognized, such as by an older version of the
+ELM327, a question mark is printed as a response instead of OK::
+
+    >ATUNKNOWN
+    ?
+    >
+
+At present, can327 does not evaluate this response. See the section
+below on known limitations for details.
+
+
+When a CAN frame is to be sent, the target address is configured, after
+which the frame is sent as a command that consists of the data's hex
+dump::
+
+    >ATSH123
+    OK
+    >DEADBEEF12345678
+    OK
+    >
+
+The above interaction sends the SFF frame "``DE AD BE EF 12 34 56 78``"
+with (11 bit) CAN ID ``0x123``.
+For this to function, the controller must be configured for SFF sending
+mode (using "``AT PB``", see code or datasheet).
+
+
+Once a frame has been sent and wait-for-reply mode is on (``ATR1``,
+configured on ``listen-only=off``), or when the reply timeout expires
+and the driver sets the controller into monitoring mode (``ATMA``),
+the ELM327 will send one line for each received CAN frame, consisting
+of CAN ID, DLC, and data::
+
+    123 8 DEADBEEF12345678
+
+For EFF (29 bit) CAN frames, the address format is slightly different,
+which can327 uses to tell the two apart::
+
+    12 34 56 78 8 DEADBEEF12345678
+
+The ELM327 will receive both SFF and EFF frames - the current CAN
+config (``ATPB``) does not matter.
+
+
+If the ELM327's internal UART sending buffer runs full, it will abort
+the monitoring mode, print "BUFFER FULL" and drop back into command
+mode. Note that in this case, unlike with other error messages, the
+error message may appear on the same line as the last (usually
+incomplete) data frame::
+
+    12 34 56 78 8 DEADBEEF123 BUFFER FULL
+
+
+
+Known limitations of the controller
+------------------------------------
+
+- Clone devices ("v1.5" and others)
+
+  Sending RTR frames is not supported and will be dropped silently.
+
+  Receiving RTR with DLC 8 will appear to be a regular frame with
+  the last received frame's DLC and payload.
+
+  "``AT CSM``" (CAN Silent Monitoring, i.e. don't send CAN ACKs) is
+  not supported, and is hard coded to ON. Thus, frames are not ACKed
+  while listening: "``AT MA``" (Monitor All) will always be "silent".
+  However, immediately after sending a frame, the ELM327 will be in
+  "receive reply" mode, in which it *does* ACK any received frames.
+  Once the bus goes silent, or an error occurs (such as BUFFER FULL),
+  or the receive reply timeout runs out, the ELM327 will end reply
+  reception mode on its own and can327 will fall back to "``AT MA``"
+  in order to keep monitoring the bus.
+
+  Other limitations may apply, depending on the clone and the quality
+  of its firmware.
+
+
+- All versions
+
+  No full duplex operation is supported. The driver will switch
+  between input/output mode as quickly as possible.
+
+  The length of outgoing RTR frames cannot be set. In fact, some
+  clones (tested with one identifying as "``v1.5``") are unable to
+  send RTR frames at all.
+
+  We don't have a way to get real-time notifications on CAN errors.
+  While there is a command (``AT CS``) to retrieve some basic stats,
+  we don't poll it as it would force us to interrupt reception mode.
+
+
+- Versions prior to 1.4b
+
+  These versions do not send CAN ACKs when in monitoring mode (AT MA).
+  However, they do send ACKs while waiting for a reply immediately
+  after sending a frame. The driver maximizes this time to make the
+  controller as useful as possible.
+
+  Starting with version 1.4b, the ELM327 supports the "``AT CSM``"
+  command, and the "listen-only" CAN option will take effect.
+
+
+- Versions prior to 1.4
+
+  These chips do not support the "``AT PB``" command, and thus cannot
+  change bitrate or SFF/EFF mode on-the-fly. This will have to be
+  programmed by the user before attaching the line discipline. See the
+  data sheet for details.
+
+
+- Versions prior to 1.3
+
+  These chips cannot be used at all with can327. They do not support
+  the "``AT D1``" command, which is necessary to avoid parsing conflicts
+  on incoming data, as well as distinction of RTR frame lengths.
+
+  Specifically, this allows for easy distinction of SFF and EFF
+  frames, and to check whether frames are complete. While it is possible
+  to deduce the type and length from the length of the line the ELM327
+  sends us, this method fails when the ELM327's UART output buffer
+  overruns. It may abort sending in the middle of the line, which will
+  then be mistaken for something else.
+
+
+
+Known limitations of the driver
+--------------------------------
+
+- No 8/7 timing.
+
+  ELM327 can only set CAN bitrates that are of the form 500000/n, where
+  n is an integer divisor.
+  However there is an exception: With a separate flag, it may set the
+  speed to be 8/7 of the speed indicated by the divisor.
+  This mode is not currently implemented.
+
+- No evaluation of command responses.
+
+  The ELM327 will reply with OK when a command is understood, and with ?
+  when it is not. The driver does not currently check this, and simply
+  assumes that the chip understands every command.
+  The driver is built such that functionality degrades gracefully
+  nevertheless. See the section on known limitations of the controller.
+
+- No use of hardware CAN ID filtering
+
+  An ELM327's UART sending buffer will easily overflow on heavy CAN bus
+  load, resulting in the "``BUFFER FULL``" message. Using the hardware
+  filters available through "``AT CF xxx``" and "``AT CM xxx``" would be
+  helpful here, however SocketCAN does not currently provide a facility
+  to make use of such hardware features.
+
+
+
+Rationale behind the chosen configuration
+------------------------------------------
+
+``AT E1``
+  Echo on
+
+  We need this to be able to get a prompt reliably.
+
+``AT S1``
+  Spaces on
+
+  We need this to distinguish 11/29 bit CAN addresses received.
+
+  Note:
+  We can usually do this using the line length (odd/even),
+  but this fails if the line is not transmitted fully to
+  the host (BUFFER FULL).
+
+``AT D1``
+  DLC on
+
+  We need this to tell the "length" of RTR frames.
+
+
+
+A note on CAN bus termination
+------------------------------
+
+Your adapter may have resistors soldered in which are meant to terminate
+the bus. This is correct when it is plugged into a OBD-II socket, but
+not helpful when trying to tap into the middle of an existing CAN bus.
+
+If communications don't work with the adapter connected, check for the
+termination resistors on its PCB and try removing them.
diff --git a/Documentation/networking/device_drivers/can/index.rst b/Documentation/networking/device_drivers/can/index.rst
index 0c3cc6633559..6a8a4f74fa26 100644
--- a/Documentation/networking/device_drivers/can/index.rst
+++ b/Documentation/networking/device_drivers/can/index.rst
@@ -10,6 +10,7 @@ Contents:
 .. toctree::
    :maxdepth: 2
 
+   can327
    ctu/ctucanfd-driver
    freescale/flexcan
 
diff --git a/MAINTAINERS b/MAINTAINERS
index 99f8a65fd79b..28108e4fdb8f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7320,6 +7320,13 @@ L:	netdev@vger.kernel.org
 S:	Maintained
 F:	drivers/net/ethernet/ibm/ehea/
 
+ELM327 CAN NETWORK DRIVER
+M:	Max Staudt <max@enpas.org>
+L:	linux-can@vger.kernel.org
+S:	Maintained
+F:	Documentation/networking/device_drivers/can/can327.rst
+F:	drivers/net/can/can327.c
+
 EM28XX VIDEO4LINUX DRIVER
 M:	Mauro Carvalho Chehab <mchehab@kernel.org>
 L:	linux-media@vger.kernel.org
diff --git a/drivers/net/can/Kconfig b/drivers/net/can/Kconfig
index 806f15146f69..3048ad77edb3 100644
--- a/drivers/net/can/Kconfig
+++ b/drivers/net/can/Kconfig
@@ -49,26 +49,6 @@ config CAN_VXCAN
 	  This driver can also be built as a module.  If so, the module
 	  will be called vxcan.
 
-config CAN_SLCAN
-	tristate "Serial / USB serial CAN Adaptors (slcan)"
-	depends on TTY
-	help
-	  CAN driver for several 'low cost' CAN interfaces that are attached
-	  via serial lines or via USB-to-serial adapters using the LAWICEL
-	  ASCII protocol. The driver implements the tty linediscipline N_SLCAN.
-
-	  As only the sending and receiving of CAN frames is implemented, this
-	  driver should work with the (serial/USB) CAN hardware from:
-	  www.canusb.com / www.can232.com / www.mictronics.de / www.canhack.de
-
-	  Userspace tools to attach the SLCAN line discipline (slcan_attach,
-	  slcand) can be found in the can-utils at the linux-can project, see
-	  https://github.com/linux-can/can-utils for details.
-
-	  The slcan driver supports up to 10 CAN netdevices by default which
-	  can be changed by the 'maxdev=xx' module option. This driver can
-	  also be built as a module. If so, the module will be called slcan.
-
 config CAN_NETLINK
 	bool "CAN device drivers with Netlink support"
 	default y
@@ -113,6 +93,24 @@ config CAN_AT91
 	  This is a driver for the SoC CAN controller in Atmel's AT91SAM9263
 	  and AT91SAM9X5 processors.
 
+config CAN_CAN327
+	tristate "Serial / USB serial ELM327 based OBD-II Interfaces (can327)"
+	depends on TTY
+	select CAN_RX_OFFLOAD
+	help
+	  CAN driver for several 'low cost' OBD-II interfaces based on the
+	  ELM327 OBD-II interpreter chip.
+
+	  This is a best effort driver - the ELM327 interface was never
+	  designed to be used as a standalone CAN interface. However, it can
+	  still be used for simple request-response protocols (such as OBD II),
+	  and to monitor broadcast messages on a bus (such as in a vehicle).
+
+	  Please refer to the documentation for information on how to use it:
+	  Documentation/networking/device_drivers/can/can327.rst
+
+	  If this driver is built as a module, it will be called can327.
+
 config CAN_FLEXCAN
 	tristate "Support for Freescale FLEXCAN based chips"
 	depends on OF || COLDFIRE || COMPILE_TEST
@@ -154,6 +152,26 @@ config CAN_KVASER_PCIEFD
 	    Kvaser Mini PCI Express HS v2
 	    Kvaser Mini PCI Express 2xHS v2
 
+config CAN_SLCAN
+	tristate "Serial / USB serial CAN Adaptors (slcan)"
+	depends on TTY
+	help
+	  CAN driver for several 'low cost' CAN interfaces that are attached
+	  via serial lines or via USB-to-serial adapters using the LAWICEL
+	  ASCII protocol. The driver implements the tty linediscipline N_SLCAN.
+
+	  As only the sending and receiving of CAN frames is implemented, this
+	  driver should work with the (serial/USB) CAN hardware from:
+	  www.canusb.com / www.can232.com / www.mictronics.de / www.canhack.de
+
+	  Userspace tools to attach the SLCAN line discipline (slcan_attach,
+	  slcand) can be found in the can-utils at the linux-can project, see
+	  https://github.com/linux-can/can-utils for details.
+
+	  The slcan driver supports up to 10 CAN netdevices by default which
+	  can be changed by the 'maxdev=xx' module option. This driver can
+	  also be built as a module. If so, the module will be called slcan.
+
 config CAN_SUN4I
 	tristate "Allwinner A10 CAN controller"
 	depends on MACH_SUN4I || MACH_SUN7I || COMPILE_TEST
diff --git a/drivers/net/can/Makefile b/drivers/net/can/Makefile
index 0af85983634c..61c75ce9d500 100644
--- a/drivers/net/can/Makefile
+++ b/drivers/net/can/Makefile
@@ -5,7 +5,7 @@
 
 obj-$(CONFIG_CAN_VCAN)		+= vcan.o
 obj-$(CONFIG_CAN_VXCAN)		+= vxcan.o
-obj-$(CONFIG_CAN_SLCAN)		+= slcan.o
+obj-$(CONFIG_CAN_SLCAN)		+= slcan/
 
 obj-y				+= dev/
 obj-y				+= rcar/
@@ -14,6 +14,7 @@ obj-y				+= usb/
 obj-y				+= softing/
 
 obj-$(CONFIG_CAN_AT91)		+= at91_can.o
+obj-$(CONFIG_CAN_CAN327)	+= can327.o
 obj-$(CONFIG_CAN_CC770)		+= cc770/
 obj-$(CONFIG_CAN_C_CAN)		+= c_can/
 obj-$(CONFIG_CAN_CTUCANFD)	+= ctucanfd/
diff --git a/drivers/net/can/can327.c b/drivers/net/can/can327.c
new file mode 100644
index 000000000000..5da7778d92dc
--- /dev/null
+++ b/drivers/net/can/can327.c
@@ -0,0 +1,1137 @@
+// 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) "can327: " 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))
+		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);
+
+	/* 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;
+	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_dropped_invalid_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.txt
+	 */
+	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;
+
+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 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;
+
+	/* 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.
+	 * Our .ndo_stop() also flushes the TTY write wakeup handler,
+	 * so we can safely set elm->tty = NULL after this.
+	 */
+	unregister_candev(elm->dev);
+
+	/* 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 = "can327",
+	.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>");
diff --git a/drivers/net/can/ctucanfd/ctucanfd_base.c b/drivers/net/can/ctucanfd/ctucanfd_base.c
index 64990bf20fdc..14ac7c0ee04c 100644
--- a/drivers/net/can/ctucanfd/ctucanfd_base.c
+++ b/drivers/net/can/ctucanfd/ctucanfd_base.c
@@ -1087,7 +1087,7 @@ clear:
 /**
  * ctucan_interrupt() - CAN Isr
  * @irq:	irq number
- * @dev_id:	device id poniter
+ * @dev_id:	device id pointer
  *
  * This is the CTU CAN FD ISR. It checks for the type of interrupt
  * and invokes the corresponding ISR.
diff --git a/drivers/net/can/dev/netlink.c b/drivers/net/can/dev/netlink.c
index 037824011266..8efa22d9f214 100644
--- a/drivers/net/can/dev/netlink.c
+++ b/drivers/net/can/dev/netlink.c
@@ -511,7 +511,8 @@ static int can_fill_info(struct sk_buff *skb, const struct net_device *dev)
 	if (priv->do_get_state)
 		priv->do_get_state(dev, &state);
 
-	if ((priv->bittiming.bitrate &&
+	if ((priv->bittiming.bitrate != CAN_BITRATE_UNSET &&
+	     priv->bittiming.bitrate != CAN_BITRATE_UNKNOWN &&
 	     nla_put(skb, IFLA_CAN_BITTIMING,
 		     sizeof(priv->bittiming), &priv->bittiming)) ||
 
diff --git a/drivers/net/can/slcan/Makefile b/drivers/net/can/slcan/Makefile
new file mode 100644
index 000000000000..8a88e484ee21
--- /dev/null
+++ b/drivers/net/can/slcan/Makefile
@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_CAN_SLCAN) += slcan.o
+
+slcan-objs :=
+slcan-objs += slcan-core.o
+slcan-objs += slcan-ethtool.o
diff --git a/drivers/net/can/slcan.c b/drivers/net/can/slcan/slcan-core.c
index 64a3aee8a7da..54d29a410ad5 100644
--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan/slcan-core.c
@@ -54,8 +54,10 @@
 #include <linux/kernel.h>
 #include <linux/workqueue.h>
 #include <linux/can.h>
+#include <linux/can/dev.h>
 #include <linux/can/skb.h>
-#include <linux/can/can-ml.h>
+
+#include "slcan.h"
 
 MODULE_ALIAS_LDISC(N_SLCAN);
 MODULE_DESCRIPTION("serial line CAN interface");
@@ -76,8 +78,13 @@ MODULE_PARM_DESC(maxdev, "Maximum number of slcan interfaces");
 #define SLC_CMD_LEN 1
 #define SLC_SFF_ID_LEN 3
 #define SLC_EFF_ID_LEN 8
-
+#define SLC_STATE_LEN 1
+#define SLC_STATE_BE_RXCNT_LEN 3
+#define SLC_STATE_BE_TXCNT_LEN 3
+#define SLC_STATE_FRAME_LEN       (1 + SLC_CMD_LEN + SLC_STATE_BE_RXCNT_LEN + \
+				   SLC_STATE_BE_TXCNT_LEN)
 struct slcan {
+	struct can_priv         can;
 	int			magic;
 
 	/* Various fields. */
@@ -96,10 +103,42 @@ struct slcan {
 	unsigned long		flags;		/* Flag values/ mode etc     */
 #define SLF_INUSE		0		/* Channel in use            */
 #define SLF_ERROR		1               /* Parity, etc. error        */
+#define SLF_XCMD		2               /* Command transmission      */
+	unsigned long           cmd_flags;      /* Command flags             */
+#define CF_ERR_RST		0               /* Reset errors on open      */
+	wait_queue_head_t       xcmd_wait;      /* Wait queue for commands   */
+						/* transmission              */
 };
 
 static struct net_device **slcan_devs;
 
+static const u32 slcan_bitrate_const[] = {
+	10000, 20000, 50000, 100000, 125000,
+	250000, 500000, 800000, 1000000
+};
+
+bool slcan_err_rst_on_open(struct net_device *ndev)
+{
+	struct slcan *sl = netdev_priv(ndev);
+
+	return !!test_bit(CF_ERR_RST, &sl->cmd_flags);
+}
+
+int slcan_enable_err_rst_on_open(struct net_device *ndev, bool on)
+{
+	struct slcan *sl = netdev_priv(ndev);
+
+	if (netif_running(ndev))
+		return -EBUSY;
+
+	if (on)
+		set_bit(CF_ERR_RST, &sl->cmd_flags);
+	else
+		clear_bit(CF_ERR_RST, &sl->cmd_flags);
+
+	return 0;
+}
+
  /************************************************************************
   *			SLCAN ENCAPSULATION FORMAT			 *
   ************************************************************************/
@@ -140,88 +179,289 @@ static struct net_device **slcan_devs;
   ************************************************************************/
 
 /* Send one completely decapsulated can_frame to the network layer */
-static void slc_bump(struct slcan *sl)
+static void slc_bump_frame(struct slcan *sl)
 {
 	struct sk_buff *skb;
-	struct can_frame cf;
+	struct can_frame *cf;
 	int i, tmp;
 	u32 tmpid;
 	char *cmd = sl->rbuff;
 
-	memset(&cf, 0, sizeof(cf));
+	skb = alloc_can_skb(sl->dev, &cf);
+	if (unlikely(!skb)) {
+		sl->dev->stats.rx_dropped++;
+		return;
+	}
 
 	switch (*cmd) {
 	case 'r':
-		cf.can_id = CAN_RTR_FLAG;
+		cf->can_id = CAN_RTR_FLAG;
 		fallthrough;
 	case 't':
 		/* store dlc ASCII value and terminate SFF CAN ID string */
-		cf.len = sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN];
+		cf->len = sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN];
 		sl->rbuff[SLC_CMD_LEN + SLC_SFF_ID_LEN] = 0;
 		/* point to payload data behind the dlc */
 		cmd += SLC_CMD_LEN + SLC_SFF_ID_LEN + 1;
 		break;
 	case 'R':
-		cf.can_id = CAN_RTR_FLAG;
+		cf->can_id = CAN_RTR_FLAG;
 		fallthrough;
 	case 'T':
-		cf.can_id |= CAN_EFF_FLAG;
+		cf->can_id |= CAN_EFF_FLAG;
 		/* store dlc ASCII value and terminate EFF CAN ID string */
-		cf.len = sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN];
+		cf->len = sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN];
 		sl->rbuff[SLC_CMD_LEN + SLC_EFF_ID_LEN] = 0;
 		/* point to payload data behind the dlc */
 		cmd += SLC_CMD_LEN + SLC_EFF_ID_LEN + 1;
 		break;
 	default:
-		return;
+		goto decode_failed;
 	}
 
 	if (kstrtou32(sl->rbuff + SLC_CMD_LEN, 16, &tmpid))
-		return;
+		goto decode_failed;
 
-	cf.can_id |= tmpid;
+	cf->can_id |= tmpid;
 
 	/* get len from sanitized ASCII value */
-	if (cf.len >= '0' && cf.len < '9')
-		cf.len -= '0';
+	if (cf->len >= '0' && cf->len < '9')
+		cf->len -= '0';
 	else
-		return;
+		goto decode_failed;
 
 	/* RTR frames may have a dlc > 0 but they never have any data bytes */
-	if (!(cf.can_id & CAN_RTR_FLAG)) {
-		for (i = 0; i < cf.len; i++) {
+	if (!(cf->can_id & CAN_RTR_FLAG)) {
+		for (i = 0; i < cf->len; i++) {
 			tmp = hex_to_bin(*cmd++);
 			if (tmp < 0)
-				return;
-			cf.data[i] = (tmp << 4);
+				goto decode_failed;
+
+			cf->data[i] = (tmp << 4);
 			tmp = hex_to_bin(*cmd++);
 			if (tmp < 0)
-				return;
-			cf.data[i] |= tmp;
+				goto decode_failed;
+
+			cf->data[i] |= tmp;
 		}
 	}
 
-	skb = dev_alloc_skb(sizeof(struct can_frame) +
-			    sizeof(struct can_skb_priv));
-	if (!skb)
+	sl->dev->stats.rx_packets++;
+	if (!(cf->can_id & CAN_RTR_FLAG))
+		sl->dev->stats.rx_bytes += cf->len;
+
+	netif_rx(skb);
+	return;
+
+decode_failed:
+	sl->dev->stats.rx_errors++;
+	dev_kfree_skb(skb);
+}
+
+/* A change state frame must contain state info and receive and transmit
+ * error counters.
+ *
+ * Examples:
+ *
+ * sb256256 : state bus-off: rx counter 256, tx counter 256
+ * sa057033 : state active, rx counter 57, tx counter 33
+ */
+static void slc_bump_state(struct slcan *sl)
+{
+	struct net_device *dev = sl->dev;
+	struct sk_buff *skb;
+	struct can_frame *cf;
+	char *cmd = sl->rbuff;
+	u32 rxerr, txerr;
+	enum can_state state, rx_state, tx_state;
+
+	switch (cmd[1]) {
+	case 'a':
+		state = CAN_STATE_ERROR_ACTIVE;
+		break;
+	case 'w':
+		state = CAN_STATE_ERROR_WARNING;
+		break;
+	case 'p':
+		state = CAN_STATE_ERROR_PASSIVE;
+		break;
+	case 'b':
+		state = CAN_STATE_BUS_OFF;
+		break;
+	default:
+		return;
+	}
+
+	if (state == sl->can.state || sl->rcount < SLC_STATE_FRAME_LEN)
 		return;
 
-	skb->dev = sl->dev;
-	skb->protocol = htons(ETH_P_CAN);
-	skb->pkt_type = PACKET_BROADCAST;
-	skb->ip_summed = CHECKSUM_UNNECESSARY;
+	cmd += SLC_STATE_BE_RXCNT_LEN + SLC_CMD_LEN + 1;
+	cmd[SLC_STATE_BE_TXCNT_LEN] = 0;
+	if (kstrtou32(cmd, 10, &txerr))
+		return;
 
-	can_skb_reserve(skb);
-	can_skb_prv(skb)->ifindex = sl->dev->ifindex;
-	can_skb_prv(skb)->skbcnt = 0;
+	*cmd = 0;
+	cmd -= SLC_STATE_BE_RXCNT_LEN;
+	if (kstrtou32(cmd, 10, &rxerr))
+		return;
 
-	skb_put_data(skb, &cf, sizeof(struct can_frame));
+	skb = alloc_can_err_skb(dev, &cf);
+	if (skb) {
+		cf->data[6] = txerr;
+		cf->data[7] = rxerr;
+	} else {
+		cf = NULL;
+	}
 
-	sl->dev->stats.rx_packets++;
-	if (!(cf.can_id & CAN_RTR_FLAG))
-		sl->dev->stats.rx_bytes += cf.len;
+	tx_state = txerr >= rxerr ? state : 0;
+	rx_state = txerr <= rxerr ? state : 0;
+	can_change_state(dev, cf, tx_state, rx_state);
 
-	netif_rx(skb);
+	if (state == CAN_STATE_BUS_OFF)
+		can_bus_off(dev);
+
+	if (skb)
+		netif_rx(skb);
+}
+
+/* An error frame can contain more than one type of error.
+ *
+ * Examples:
+ *
+ * e1a : len 1, errors: ACK error
+ * e3bcO: len 3, errors: Bit0 error, CRC error, Tx overrun error
+ */
+static void slc_bump_err(struct slcan *sl)
+{
+	struct net_device *dev = sl->dev;
+	struct sk_buff *skb;
+	struct can_frame *cf;
+	char *cmd = sl->rbuff;
+	bool rx_errors = false, tx_errors = false, rx_over_errors = false;
+	int i, len;
+
+	/* get len from sanitized ASCII value */
+	len = cmd[1];
+	if (len >= '0' && len < '9')
+		len -= '0';
+	else
+		return;
+
+	if ((len + SLC_CMD_LEN + 1) > sl->rcount)
+		return;
+
+	skb = alloc_can_err_skb(dev, &cf);
+
+	if (skb)
+		cf->can_id |= CAN_ERR_PROT | CAN_ERR_BUSERROR;
+
+	cmd += SLC_CMD_LEN + 1;
+	for (i = 0; i < len; i++, cmd++) {
+		switch (*cmd) {
+		case 'a':
+			netdev_dbg(dev, "ACK error\n");
+			tx_errors = true;
+			if (skb) {
+				cf->can_id |= CAN_ERR_ACK;
+				cf->data[3] = CAN_ERR_PROT_LOC_ACK;
+			}
+
+			break;
+		case 'b':
+			netdev_dbg(dev, "Bit0 error\n");
+			tx_errors = true;
+			if (skb)
+				cf->data[2] |= CAN_ERR_PROT_BIT0;
+
+			break;
+		case 'B':
+			netdev_dbg(dev, "Bit1 error\n");
+			tx_errors = true;
+			if (skb)
+				cf->data[2] |= CAN_ERR_PROT_BIT1;
+
+			break;
+		case 'c':
+			netdev_dbg(dev, "CRC error\n");
+			rx_errors = true;
+			if (skb) {
+				cf->data[2] |= CAN_ERR_PROT_BIT;
+				cf->data[3] = CAN_ERR_PROT_LOC_CRC_SEQ;
+			}
+
+			break;
+		case 'f':
+			netdev_dbg(dev, "Form Error\n");
+			rx_errors = true;
+			if (skb)
+				cf->data[2] |= CAN_ERR_PROT_FORM;
+
+			break;
+		case 'o':
+			netdev_dbg(dev, "Rx overrun error\n");
+			rx_over_errors = true;
+			rx_errors = true;
+			if (skb) {
+				cf->can_id |= CAN_ERR_CRTL;
+				cf->data[1] = CAN_ERR_CRTL_RX_OVERFLOW;
+			}
+
+			break;
+		case 'O':
+			netdev_dbg(dev, "Tx overrun error\n");
+			tx_errors = true;
+			if (skb) {
+				cf->can_id |= CAN_ERR_CRTL;
+				cf->data[1] = CAN_ERR_CRTL_TX_OVERFLOW;
+			}
+
+			break;
+		case 's':
+			netdev_dbg(dev, "Stuff error\n");
+			rx_errors = true;
+			if (skb)
+				cf->data[2] |= CAN_ERR_PROT_STUFF;
+
+			break;
+		default:
+			if (skb)
+				dev_kfree_skb(skb);
+
+			return;
+		}
+	}
+
+	if (rx_errors)
+		dev->stats.rx_errors++;
+
+	if (rx_over_errors)
+		dev->stats.rx_over_errors++;
+
+	if (tx_errors)
+		dev->stats.tx_errors++;
+
+	if (skb)
+		netif_rx(skb);
+}
+
+static void slc_bump(struct slcan *sl)
+{
+	switch (sl->rbuff[0]) {
+	case 'r':
+		fallthrough;
+	case 't':
+		fallthrough;
+	case 'R':
+		fallthrough;
+	case 'T':
+		return slc_bump_frame(sl);
+	case 'e':
+		return slc_bump_err(sl);
+	case 's':
+		return slc_bump_state(sl);
+	default:
+		return;
+	}
 }
 
 /* parse tty input stream */
@@ -318,12 +558,22 @@ static void slcan_transmit(struct work_struct *work)
 
 	spin_lock_bh(&sl->lock);
 	/* First make sure we're connected. */
-	if (!sl->tty || sl->magic != SLCAN_MAGIC || !netif_running(sl->dev)) {
+	if (!sl->tty || sl->magic != SLCAN_MAGIC ||
+	    (unlikely(!netif_running(sl->dev)) &&
+	     likely(!test_bit(SLF_XCMD, &sl->flags)))) {
 		spin_unlock_bh(&sl->lock);
 		return;
 	}
 
 	if (sl->xleft <= 0)  {
+		if (unlikely(test_bit(SLF_XCMD, &sl->flags))) {
+			clear_bit(SLF_XCMD, &sl->flags);
+			clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
+			spin_unlock_bh(&sl->lock);
+			wake_up(&sl->xcmd_wait);
+			return;
+		}
+
 		/* Now serial buffer is almost free & we can start
 		 * transmission of another packet */
 		sl->dev->stats.tx_packets++;
@@ -365,7 +615,7 @@ static netdev_tx_t slc_xmit(struct sk_buff *skb, struct net_device *dev)
 	spin_lock(&sl->lock);
 	if (!netif_running(dev))  {
 		spin_unlock(&sl->lock);
-		printk(KERN_WARNING "%s: xmit: iface is down\n", dev->name);
+		netdev_warn(dev, "xmit: iface is down\n");
 		goto out;
 	}
 	if (sl->tty == NULL) {
@@ -387,17 +637,63 @@ out:
  *   Routines looking at netdevice side.
  ******************************************/
 
+static int slcan_transmit_cmd(struct slcan *sl, const unsigned char *cmd)
+{
+	int ret, actual, n;
+
+	spin_lock(&sl->lock);
+	if (!sl->tty) {
+		spin_unlock(&sl->lock);
+		return -ENODEV;
+	}
+
+	n = snprintf(sl->xbuff, sizeof(sl->xbuff), "%s", cmd);
+	set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
+	actual = sl->tty->ops->write(sl->tty, sl->xbuff, n);
+	sl->xleft = n - actual;
+	sl->xhead = sl->xbuff + actual;
+	set_bit(SLF_XCMD, &sl->flags);
+	spin_unlock(&sl->lock);
+	ret = wait_event_interruptible_timeout(sl->xcmd_wait,
+					       !test_bit(SLF_XCMD, &sl->flags),
+					       HZ);
+	clear_bit(SLF_XCMD, &sl->flags);
+	if (ret == -ERESTARTSYS)
+		return ret;
+
+	if (ret == 0)
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
 /* Netdevice UP -> DOWN routine */
 static int slc_close(struct net_device *dev)
 {
 	struct slcan *sl = netdev_priv(dev);
+	int err;
 
 	spin_lock_bh(&sl->lock);
 	if (sl->tty) {
+		if (sl->can.bittiming.bitrate &&
+		    sl->can.bittiming.bitrate != CAN_BITRATE_UNKNOWN) {
+			spin_unlock_bh(&sl->lock);
+			err = slcan_transmit_cmd(sl, "C\r");
+			spin_lock_bh(&sl->lock);
+			if (err)
+				netdev_warn(dev,
+					    "failed to send close command 'C\\r'\n");
+		}
+
 		/* TTY discipline is running. */
 		clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
 	}
 	netif_stop_queue(dev);
+	close_candev(dev);
+	sl->can.state = CAN_STATE_STOPPED;
+	if (sl->can.bittiming.bitrate == CAN_BITRATE_UNKNOWN)
+		sl->can.bittiming.bitrate = CAN_BITRATE_UNSET;
+
 	sl->rcount   = 0;
 	sl->xleft    = 0;
 	spin_unlock_bh(&sl->lock);
@@ -409,20 +705,77 @@ static int slc_close(struct net_device *dev)
 static int slc_open(struct net_device *dev)
 {
 	struct slcan *sl = netdev_priv(dev);
+	unsigned char cmd[SLC_MTU];
+	int err, s;
 
 	if (sl->tty == NULL)
 		return -ENODEV;
 
-	sl->flags &= (1 << SLF_INUSE);
+	/* The baud rate is not set with the command
+	 * `ip link set <iface> type can bitrate <baud>' and therefore
+	 * can.bittiming.bitrate is CAN_BITRATE_UNSET (0), causing
+	 * open_candev() to fail. So let's set to a fake value.
+	 */
+	if (sl->can.bittiming.bitrate == CAN_BITRATE_UNSET)
+		sl->can.bittiming.bitrate = CAN_BITRATE_UNKNOWN;
+
+	err = open_candev(dev);
+	if (err) {
+		netdev_err(dev, "failed to open can device\n");
+		return err;
+	}
+
+	sl->flags &= BIT(SLF_INUSE);
+
+	if (sl->can.bittiming.bitrate != CAN_BITRATE_UNKNOWN) {
+		for (s = 0; s < ARRAY_SIZE(slcan_bitrate_const); s++) {
+			if (sl->can.bittiming.bitrate == slcan_bitrate_const[s])
+				break;
+		}
+
+		/* The CAN framework has already validate the bitrate value,
+		 * so we can avoid to check if `s' has been properly set.
+		 */
+
+		snprintf(cmd, sizeof(cmd), "C\rS%d\r", s);
+		err = slcan_transmit_cmd(sl, cmd);
+		if (err) {
+			netdev_err(dev,
+				   "failed to send bitrate command 'C\\rS%d\\r'\n",
+				   s);
+			goto cmd_transmit_failed;
+		}
+
+		if (test_bit(CF_ERR_RST, &sl->cmd_flags)) {
+			err = slcan_transmit_cmd(sl, "F\r");
+			if (err) {
+				netdev_err(dev,
+					   "failed to send error command 'F\\r'\n");
+				goto cmd_transmit_failed;
+			}
+		}
+
+		err = slcan_transmit_cmd(sl, "O\r");
+		if (err) {
+			netdev_err(dev, "failed to send open command 'O\\r'\n");
+			goto cmd_transmit_failed;
+		}
+	}
+
+	sl->can.state = CAN_STATE_ERROR_ACTIVE;
 	netif_start_queue(dev);
 	return 0;
+
+cmd_transmit_failed:
+	close_candev(dev);
+	return err;
 }
 
-/* Hook the destructor so we can free slcan devs at the right point in time */
-static void slc_free_netdev(struct net_device *dev)
+static void slc_dealloc(struct slcan *sl)
 {
-	int i = dev->base_addr;
+	int i = sl->dev->base_addr;
 
+	free_candev(sl->dev);
 	slcan_devs[i] = NULL;
 }
 
@@ -438,24 +791,6 @@ static const struct net_device_ops slc_netdev_ops = {
 	.ndo_change_mtu         = slcan_change_mtu,
 };
 
-static void slc_setup(struct net_device *dev)
-{
-	dev->netdev_ops		= &slc_netdev_ops;
-	dev->needs_free_netdev	= true;
-	dev->priv_destructor	= slc_free_netdev;
-
-	dev->hard_header_len	= 0;
-	dev->addr_len		= 0;
-	dev->tx_queue_len	= 10;
-
-	dev->mtu		= CAN_MTU;
-	dev->type		= ARPHRD_CAN;
-
-	/* New-style flags. */
-	dev->flags		= IFF_NOARP;
-	dev->features           = NETIF_F_HW_CSUM;
-}
-
 /******************************************
   Routines looking at TTY side.
  ******************************************/
@@ -518,11 +853,8 @@ static void slc_sync(void)
 static struct slcan *slc_alloc(void)
 {
 	int i;
-	char name[IFNAMSIZ];
 	struct net_device *dev = NULL;
-	struct can_ml_priv *can_ml;
 	struct slcan       *sl;
-	int size;
 
 	for (i = 0; i < maxdev; i++) {
 		dev = slcan_devs[i];
@@ -535,22 +867,24 @@ static struct slcan *slc_alloc(void)
 	if (i >= maxdev)
 		return NULL;
 
-	sprintf(name, "slcan%d", i);
-	size = ALIGN(sizeof(*sl), NETDEV_ALIGN) + sizeof(struct can_ml_priv);
-	dev = alloc_netdev(size, name, NET_NAME_UNKNOWN, slc_setup);
+	dev = alloc_candev(sizeof(*sl), 1);
 	if (!dev)
 		return NULL;
 
+	snprintf(dev->name, sizeof(dev->name), "slcan%d", i);
+	dev->netdev_ops = &slc_netdev_ops;
 	dev->base_addr  = i;
+	slcan_set_ethtool_ops(dev);
 	sl = netdev_priv(dev);
-	can_ml = (void *)sl + ALIGN(sizeof(*sl), NETDEV_ALIGN);
-	can_set_ml_priv(dev, can_ml);
 
 	/* Initialize channel control data */
 	sl->magic = SLCAN_MAGIC;
 	sl->dev	= dev;
+	sl->can.bitrate_const = slcan_bitrate_const;
+	sl->can.bitrate_const_cnt = ARRAY_SIZE(slcan_bitrate_const);
 	spin_lock_init(&sl->lock);
 	INIT_WORK(&sl->tx_work, slcan_transmit);
+	init_waitqueue_head(&sl->xcmd_wait);
 	slcan_devs[i] = dev;
 
 	return sl;
@@ -609,26 +943,28 @@ static int slcan_open(struct tty_struct *tty)
 
 		set_bit(SLF_INUSE, &sl->flags);
 
-		err = register_netdevice(sl->dev);
-		if (err)
+		rtnl_unlock();
+		err = register_candev(sl->dev);
+		if (err) {
+			pr_err("slcan: can't register candev\n");
 			goto err_free_chan;
+		}
+	} else {
+		rtnl_unlock();
 	}
 
-	/* Done.  We have linked the TTY line to a channel. */
-	rtnl_unlock();
 	tty->receive_room = 65536;	/* We don't flow control */
 
 	/* TTY layer expects 0 on success */
 	return 0;
 
 err_free_chan:
+	rtnl_lock();
 	sl->tty = NULL;
 	tty->disc_data = NULL;
 	clear_bit(SLF_INUSE, &sl->flags);
-	slc_free_netdev(sl->dev);
-	/* do not call free_netdev before rtnl_unlock */
+	slc_dealloc(sl);
 	rtnl_unlock();
-	free_netdev(sl->dev);
 	return err;
 
 err_exit:
@@ -662,9 +998,11 @@ static void slcan_close(struct tty_struct *tty)
 	synchronize_rcu();
 	flush_work(&sl->tx_work);
 
-	/* Flush network side */
-	unregister_netdev(sl->dev);
-	/* This will complete via sl_free_netdev */
+	slc_close(sl->dev);
+	unregister_candev(sl->dev);
+	rtnl_lock();
+	slc_dealloc(sl);
+	rtnl_unlock();
 }
 
 static void slcan_hangup(struct tty_struct *tty)
@@ -772,15 +1110,15 @@ static void __exit slcan_exit(void)
 		dev = slcan_devs[i];
 		if (!dev)
 			continue;
-		slcan_devs[i] = NULL;
 
 		sl = netdev_priv(dev);
 		if (sl->tty) {
-			printk(KERN_ERR "%s: tty discipline still running\n",
-			       dev->name);
+			netdev_err(dev, "tty discipline still running\n");
 		}
 
-		unregister_netdev(dev);
+		slc_close(dev);
+		unregister_candev(dev);
+		slc_dealloc(sl);
 	}
 
 	kfree(slcan_devs);
diff --git a/drivers/net/can/slcan/slcan-ethtool.c b/drivers/net/can/slcan/slcan-ethtool.c
new file mode 100644
index 000000000000..bf0afdc4e49d
--- /dev/null
+++ b/drivers/net/can/slcan/slcan-ethtool.c
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: GPL-2.0+
+/* Copyright (c) 2022 Amarula Solutions, Dario Binacchi <dario.binacchi@amarulasolutions.com>
+ *
+ */
+
+#include <linux/can/dev.h>
+#include <linux/ethtool.h>
+#include <linux/kernel.h>
+#include <linux/netdevice.h>
+#include <linux/platform_device.h>
+
+#include "slcan.h"
+
+static const char slcan_priv_flags_strings[][ETH_GSTRING_LEN] = {
+#define SLCAN_PRIV_FLAGS_ERR_RST_ON_OPEN BIT(0)
+	"err-rst-on-open",
+};
+
+static void slcan_get_strings(struct net_device *ndev, u32 stringset, u8 *data)
+{
+	switch (stringset) {
+	case ETH_SS_PRIV_FLAGS:
+		memcpy(data, slcan_priv_flags_strings,
+		       sizeof(slcan_priv_flags_strings));
+	}
+}
+
+static u32 slcan_get_priv_flags(struct net_device *ndev)
+{
+	u32 flags = 0;
+
+	if (slcan_err_rst_on_open(ndev))
+		flags |= SLCAN_PRIV_FLAGS_ERR_RST_ON_OPEN;
+
+	return flags;
+}
+
+static int slcan_set_priv_flags(struct net_device *ndev, u32 flags)
+{
+	bool err_rst_op_open = !!(flags & SLCAN_PRIV_FLAGS_ERR_RST_ON_OPEN);
+
+	return slcan_enable_err_rst_on_open(ndev, err_rst_op_open);
+}
+
+static int slcan_get_sset_count(struct net_device *netdev, int sset)
+{
+	switch (sset) {
+	case ETH_SS_PRIV_FLAGS:
+		return ARRAY_SIZE(slcan_priv_flags_strings);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static const struct ethtool_ops slcan_ethtool_ops = {
+	.get_strings = slcan_get_strings,
+	.get_priv_flags = slcan_get_priv_flags,
+	.set_priv_flags = slcan_set_priv_flags,
+	.get_sset_count = slcan_get_sset_count,
+};
+
+void slcan_set_ethtool_ops(struct net_device *netdev)
+{
+	netdev->ethtool_ops = &slcan_ethtool_ops;
+}
diff --git a/drivers/net/can/slcan/slcan.h b/drivers/net/can/slcan/slcan.h
new file mode 100644
index 000000000000..d463c8d99e22
--- /dev/null
+++ b/drivers/net/can/slcan/slcan.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0
+ * slcan.h - serial line CAN interface driver
+ *
+ * Copyright (C) Laurence Culhane <loz@holmes.demon.co.uk>
+ * Copyright (C) Fred N. van Kempen <waltje@uwalt.nl.mugnet.org>
+ * Copyright (C) Oliver Hartkopp <socketcan@hartkopp.net>
+ * Copyright (C) 2022 Amarula Solutions, Dario Binacchi <dario.binacchi@amarulasolutions.com>
+ *
+ */
+
+#ifndef _SLCAN_H
+#define _SLCAN_H
+
+bool slcan_err_rst_on_open(struct net_device *ndev);
+int slcan_enable_err_rst_on_open(struct net_device *ndev, bool on);
+void slcan_set_ethtool_ops(struct net_device *ndev);
+
+#endif /* _SLCAN_H */
diff --git a/include/linux/can/bittiming.h b/include/linux/can/bittiming.h
index 7ae21c0f7f23..ef0a77173e3c 100644
--- a/include/linux/can/bittiming.h
+++ b/include/linux/can/bittiming.h
@@ -11,6 +11,8 @@
 
 #define CAN_SYNC_SEG 1
 
+#define CAN_BITRATE_UNSET 0
+#define CAN_BITRATE_UNKNOWN (-1U)
 
 #define CAN_CTRLMODE_TDC_MASK					\
 	(CAN_CTRLMODE_TDC_AUTO | CAN_CTRLMODE_TDC_MANUAL)
diff --git a/include/uapi/linux/tty.h b/include/uapi/linux/tty.h
index 9d0f06bfbac3..68aeae2addec 100644
--- a/include/uapi/linux/tty.h
+++ b/include/uapi/linux/tty.h
@@ -38,8 +38,9 @@
 #define N_NULL		27	/* Null ldisc used for error handling */
 #define N_MCTP		28	/* MCTP-over-serial */
 #define N_DEVELOPMENT	29	/* Manual out-of-tree testing */
+#define N_CAN327	30	/* ELM327 based OBD-II interfaces */
 
 /* Always the newest line discipline + 1 */
-#define NR_LDISCS	30
+#define NR_LDISCS	31
 
 #endif /* _UAPI_LINUX_TTY_H */