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Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/networking/can.txt | 235 |
1 files changed, 197 insertions, 38 deletions
diff --git a/Documentation/networking/can.txt b/Documentation/networking/can.txt index 2035bc4..6cd6627 100644 --- a/Documentation/networking/can.txt +++ b/Documentation/networking/can.txt @@ -36,10 +36,15 @@ This file contains 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 @@ solution for a couple of reasons: 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 @@ solution for a couple of reasons: 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CAN) network interface 'vcan42': - ip link del vcan42 - - The tool 'vcan' from the SocketCAN SVN repository on BerliOS is obsolete.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 + $ ip link del vcan42 + + 6.5 The CAN network device driver interface + + 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). - On the project website http://developer.berlios.de/projects/socketcan - there are different drivers available: + 6.6 Supported CAN hardware - 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) + 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. - 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 +7. Socket CAN resources +----------------------- - Please check the Mailing Lists on the berlios OSS project website. + 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) |
