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Subject[PATCH v2 1/7] [PATCH 1/8] can: Documentation for the CAN device driver interface
This patch documents the CAN netowrk device drivers interface, removes
obsolete documentation and adds some useful links to CAN resources.

Signed-off-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: Oliver Hartkopp <oliver.hartkopp@volkswagen.de>
---
Documentation/networking/can.txt | 239 ++++++++++++++++++++++++++++++++-------
1 file changed, 199 insertions(+), 40 deletions(-)

Index: net-next-2.6/Documentation/networking/can.txt
===================================================================
--- net-next-2.6.orig/Documentation/networking/can.txt 2009-05-12 10:47:10.546720893 +0200
+++ net-next-2.6/Documentation/networking/can.txt 2009-05-12 10:47:23.470719178 +0200
@@ -36,10 +36,15 @@
6.2 local loopback of sent frames
6.3 CAN controller hardware filters
6.4 The virtual CAN driver (vcan)
- 6.5 currently supported CAN hardware
- 6.6 todo
+ 6.5 The CAN network device driver interface
+ 6.5.1 Netlink interface to set/get devices properties
+ 6.5.2 Setting the CAN bit-timing
+ 6.5.3 Starting and stopping the CAN network device
+ 6.6 supported CAN hardware

- 7 Credits
+ 7 Socket CAN resources
+
+ 8 Credits

============================================================================

@@ -234,6 +239,8 @@
the user application using the common CAN filter mechanisms. Inside
this filter definition the (interested) type of errors may be
selected. The reception of error frames is disabled by default.
+ The format of the CAN error frame is briefly decribed in the Linux
+ header file "include/linux/can/error.h".

4. How to use Socket CAN
------------------------
@@ -605,61 +612,213 @@
removal of vcan network devices can be managed with the ip(8) tool:

- Create a virtual CAN network interface:
- ip link add type vcan
+ $ ip link add type vcan

- Create a virtual CAN network interface with a specific name 'vcan42':
- ip link add dev vcan42 type vcan
+ $ ip link add dev vcan42 type vcan

- Remove a (virtual CAN) network interface 'vcan42':
- ip link del vcan42
-
- The tool 'vcan' from the SocketCAN SVN repository on BerliOS is obsolete.
-
- Virtual CAN network device creation in older Kernels:
- In Linux Kernel versions < 2.6.24 the vcan driver creates 4 vcan
- netdevices at module load time by default. This value can be changed
- with the module parameter 'numdev'. E.g. 'modprobe vcan numdev=8'
-
- 6.5 currently supported CAN hardware
-
- On the project website http://developer.berlios.de/projects/socketcan
- there are different drivers available:
-
- vcan: Virtual CAN interface driver (if no real hardware is available)
- sja1000: Philips SJA1000 CAN controller (recommended)
- i82527: Intel i82527 CAN controller
- mscan: Motorola/Freescale CAN controller (e.g. inside SOC MPC5200)
- ccan: CCAN controller core (e.g. inside SOC h7202)
- slcan: For a bunch of CAN adaptors that are attached via a
- serial line ASCII protocol (for serial / USB adaptors)
+ $ ip link del vcan42

- Additionally the different CAN adaptors (ISA/PCI/PCMCIA/USB/Parport)
- from PEAK Systemtechnik support the CAN netdevice driver model
- since Linux driver v6.0: http://www.peak-system.com/linux/index.htm
+ 6.5 The CAN network device driver interface

- Please check the Mailing Lists on the berlios OSS project website.
+ The CAN network device driver interface provides a generic interface
+ to setup, configure and monitor CAN network devices. The user can then
+ configure the CAN device, like setting the bit-timing parameters, via
+ the netlink interface using the program "ip" from the "IPROUTE2"
+ utility suite. The following chapter describes briefly how to use it.
+ Furthermore, the interface uses a common data structure and exports a
+ set of common functions, which all real CAN network device drivers
+ should use. Please have a look to the SJA1000 or MSCAN driver to
+ understand how to use them. The name of the module is can-dev.ko.
+
+ 6.5.1 Netlink interface to set/get devices properties
+
+ The CAN device must be configured via netlink interface. The supported
+ netlink message types are defined and briefly described in
+ "include/linux/can/netlink.h". CAN link support for the program "ip"
+ of the IPROUTE2 utility suite is avaiable and it can be used as shown
+ below:
+
+ - Setting CAN device properties:
+
+ $ ip link set can0 type can help
+ Usage: ip link set DEVICE type can
+ [ bitrate BITRATE [ sample-point SAMPLE-POINT] ] |
+ [ tq TQ prop-seg PROP_SEG phase-seg1 PHASE-SEG1
+ phase-seg2 PHASE-SEG2 [ sjw SJW ] ]
+
+ [ loopback { on | off } ]
+ [ listen-only { on | off } ]
+ [ triple-sampling { on | off } ]
+
+ [ restart-ms TIME-MS ]
+ [ restart ]
+
+ Where: BITRATE := { 1..1000000 }
+ SAMPLE-POINT := { 0.000..0.999 }
+ TQ := { NUMBER }
+ PROP-SEG := { 1..8 }
+ PHASE-SEG1 := { 1..8 }
+ PHASE-SEG2 := { 1..8 }
+ SJW := { 1..4 }
+ RESTART-MS := { 0 | NUMBER }
+
+ - Display CAN device details and statistics:
+
+ $ ip -details -statistics link show can0
+ 2: can0: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UP qlen 10
+ link/can
+ can <TRIPLE-SAMPLING> state ERROR-ACTIVE restart-ms 100
+ bitrate 125000 sample_point 0.875
+ tq 125 prop-seg 6 phase-seg1 7 phase-seg2 2 sjw 1
+ sja1000: tseg1 1..16 tseg2 1..8 sjw 1..4 brp 1..64 brp-inc 1
+ clock 8000000
+ re-started bus-errors arbit-lost error-warn error-pass bus-off
+ 41 17457 0 41 42 41
+ RX: bytes packets errors dropped overrun mcast
+ 140859 17608 17457 0 0 0
+ TX: bytes packets errors dropped carrier collsns
+ 861 112 0 41 0 0
+
+ More info to the above output:
+
+ "<TRIPLE-SAMPLING>"
+ Shows the list of selected CAN controller modes: LOOPBACK,
+ LISTEN-ONLY, or TRIPLE-SAMPLING.
+
+ "state ERROR-ACTIVE"
+ The current state of the CAN controller: "ERROR-ACTIVE",
+ "ERROR-WARNING", "ERROR-PASSIVE", "BUS-OFF" or "STOPPED"
+
+ "restart-ms 100"
+ Automatic restart delay time. If set to a non-zero value, a
+ restart of the CAN controller will be triggered automatically
+ in case of a bus-off condition after the specified delay time
+ in milliseconds. By default it's off.
+
+ "bitrate 125000 sample_point 0.875"
+ Shows the real bit-rate in bits/sec and the sample-point in the
+ range 0.000..0.999. If the calculation of bit-timing parameters
+ is enabled in the kernel (CONFIG_CAN_CALC_BITTIMING=y), the
+ bit-timing can be defined by setting the "bitrate" argument.
+ Optionally the "sample-point" can be specified. By default it's
+ 0.000 assuming CIA-recommended sample-points.
+
+ "tq 125 prop-seg 6 phase-seg1 7 phase-seg2 2 sjw 1"
+ Shows the time quanta in ns, propagation segment, phase buffer
+ segment 1 and 2 and the synchronisation jump width in units of
+ tq. They allow to define the CAN bit-timing in a hardware
+ independent format as proposed by the Bosch CAN 2.0 spec (see
+ chapter 8 of http://www.semiconductors.bosch.de/pdf/can2spec.pdf).
+
+ "sja1000: tseg1 1..16 tseg2 1..8 sjw 1..4 brp 1..64 brp-inc 1
+ clock 8000000"
+ Shows the bit-timing constants of the CAN controller, here the
+ "sja1000". The minimum and maximum values of the time segment 1
+ and 2, the synchronisation jump width in units of tq, the
+ bitrate pre-scaler and the CAN system clock frequency in Hz.
+ These constants could be used for user-defined (non-standard)
+ bit-timing calculation algorithms in user-space.
+
+ "re-started bus-errors arbit-lost error-warn error-pass bus-off"
+ Shows the number of restarts, bus and arbitration lost errors,
+ and the state changes to the error-warning, error-passive and
+ bus-off state. RX overrun errors are listed in the "overrun"
+ field of the standard network statistics.
+
+ 6.5.2 Setting the CAN bit-timing
+
+ The CAN bit-timing parameters can always be defined in a hardware
+ independent format as proposed in the Bosch CAN 2.0 specification
+ specifying the arguments "tq", "prop_seg", "phase_seg1", "phase_seg2"
+ and "sjw":
+
+ $ ip link set canX type can tq 125 prop-seg 6 \
+ phase-seg1 7 phase-seg2 2 sjw 1
+
+ If the kernel option CONFIG_CAN_CALC_BITTIMING is enabled, CIA
+ recommended CAN bit-timing parameters will be calculated if the bit-
+ rate is specified with the argument "bitrate":
+
+ $ ip link set canX type can bitrate 125000
+
+ Note that this works fine for the most common CAN controllers with
+ standard bit-rates but may *fail* for exotic bit-rates or CAN system
+ clock frequencies. Disabling CONFIG_CAN_CALC_BITTIMING saves some
+ space and allows user-space tools to solely determine and set the
+ bit-timing parameters. The CAN controller specific bit-timing
+ constants can be used for that purpose. They are listed by the
+ following command:
+
+ $ ip -details link show can0
+ ...
+ sja1000: clock 8000000 tseg1 1..16 tseg2 1..8 sjw 1..4 brp 1..64 brp-inc 1
+
+ 6.5.3 Starting and stopping the CAN network device
+
+ A CAN network device is started or stopped as usual with the command
+ "ifconfig canX up/down" or "ip link set canX up/down". Be aware that
+ you *must* define proper bit-timing parameters for real CAN devices
+ before you can start it to avoid error-prone default settings:
+
+ $ ip link set canX up type can bitrate 125000
+
+ A device may enter the "bus-off" state if too much errors occurred on
+ the CAN bus. Then no more messages are received or sent. An automatic
+ bus-off recovery can be enabled by setting the "restart-ms" to a
+ non-zero value, e.g.:
+
+ $ ip link set canX type can restart-ms 100
+
+ Alternatively, the application may realize the "bus-off" condition
+ by monitoring CAN error frames and do a restart when appropriate with
+ the command:
+
+ $ ip link set canX type can restart
+
+ Note that a restart will also create a CAN error frame (see also
+ chapter 3.4).
+
+ 6.6 Supported CAN hardware
+
+ Please check the "Kconfig" file in "drivers/net/can" to get an actual
+ list of the support CAN hardware. On the Socket CAN project website
+ (see chapter 7) there might be further drivers available, also for
+ older kernel versions.
+
+7. Socket CAN resources
+-----------------------
+
+ You can find further resources for Socket CAN like user space tools,
+ support for old kernel versions, more drivers, mailing lists, etc.
+ at the BerliOS OSS project website for Socket CAN:

- 6.6 todo
+ http://developer.berlios.de/projects/socketcan

- The configuration interface for CAN network drivers is still an open
- issue that has not been finalized in the socketcan project. Also the
- idea of having a library module (candev.ko) that holds functions
- that are needed by all CAN netdevices is not ready to ship.
- Your contribution is welcome.
+ If you have questions, bug fixes, etc., don't hesitate to post them to
+ the Socketcan-Users mailing list. But please search the archives first.

-7. Credits
+8. Credits
----------

- Oliver Hartkopp (PF_CAN core, filters, drivers, bcm)
+ Oliver Hartkopp (PF_CAN core, filters, drivers, bcm, SJA1000 driver)
Urs Thuermann (PF_CAN core, kernel integration, socket interfaces, raw, vcan)
Jan Kizka (RT-SocketCAN core, Socket-API reconciliation)
- Wolfgang Grandegger (RT-SocketCAN core & drivers, Raw Socket-API reviews)
+ Wolfgang Grandegger (RT-SocketCAN core & drivers, Raw Socket-API reviews,
+ CAN device driver interface, MSCAN driver)
Robert Schwebel (design reviews, PTXdist integration)
Marc Kleine-Budde (design reviews, Kernel 2.6 cleanups, drivers)
Benedikt Spranger (reviews)
Thomas Gleixner (LKML reviews, coding style, posting hints)
- Andrey Volkov (kernel subtree structure, ioctls, mscan driver)
+ Andrey Volkov (kernel subtree structure, ioctls, MSCAN driver)
Matthias Brukner (first SJA1000 CAN netdevice implementation Q2/2003)
Klaus Hitschler (PEAK driver integration)
Uwe Koppe (CAN netdevices with PF_PACKET approach)
Michael Schulze (driver layer loopback requirement, RT CAN drivers review)
+ Pavel Pisa (Bit-timing calculation)
+ Sascha Hauer (SJA1000 platform driver)
+ Sebastian Haas (SJA1000 EMS PCI driver)
+ Markus Plessing (SJA1000 EMS PCI driver)
+ Per Dalen (SJA1000 Kvaser PCI driver)
+ Sam Ravnborg (reviews, coding style, kbuild help)


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