Lines Matching +full:default +full:- +full:sample +full:- +full:phase
2 SocketCAN - Controller Area Network
20 .. _socketcan-motivation:
29 functionality. Usually, there is only a hardware-specific device
32 Queueing of frames and higher-level transport protocols like ISO-TP
34 character-device implementations support only one single process to
47 protocol family module and also vice-versa. Also, the protocol family
57 communicate using a specific transport protocol, e.g. ISO-TP, just
60 CAN-IDs, frames, etc.
62 Similar functionality visible from user-space could be provided by a
74 * **Abstraction:** In most existing character-device implementations, the
75 hardware-specific device driver for a CAN controller directly
83 application on the one hand, and a interface for hardware-specific
103 .. _socketcan-concept:
108 As described in :ref:`socketcan-motivation` the main goal of SocketCAN is to
111 TCP/IP and ethernet networking, the CAN bus is a broadcast-only(!)
112 medium that has no MAC-layer addressing like ethernet. The CAN-identifier
113 (can_id) is used for arbitration on the CAN-bus. Therefore the CAN-IDs
114 have to be chosen uniquely on the bus. When designing a CAN-ECU
115 network the CAN-IDs are mapped to be sent by a specific ECU.
116 For this reason a CAN-ID can be treated best as a kind of source address.
119 .. _socketcan-receive-lists:
122 -------------
126 CAN-IDs from the same CAN network interface. The SocketCAN core
127 module - which implements the protocol family CAN - provides several
130 requests the (range of) CAN-IDs from the SocketCAN core that are
132 CAN-IDs can be done for specific CAN interfaces or for all(!) known
134 CAN protocol modules by the SocketCAN core (see :ref:`socketcan-core-module`).
137 filter complexity for a given use-case.
140 .. _socketcan-local-loopback1:
143 -----------------------------
156 -----------------(1)- CAN bus -(2)---------------
163 The Linux network devices (by default) just can handle the
165 arbitration on the CAN bus the transmission of a low prio CAN-ID
171 See :ref:`socketcan-local-loopback2` for details (recommended).
173 The loopback functionality is enabled by default to reflect standard
175 the RT-SocketCAN group the loopback optionally may be disabled for each
176 separate socket. See sockopts from the CAN RAW sockets in :ref:`socketcan-raw-sockets`.
182 .. _socketcan-network-problem-notifications:
185 -----------------------------
202 by default. The format of the CAN error message frame is briefly
225 - see :ref:`socketcan-concept`). After binding (CAN_RAW) or connecting (CAN_BCM)
234 .. code-block:: C
264 default. A read(2) system call on a CAN_RAW socket transfers a
270 .. code-block:: C
303 .. code-block:: C
331 .. code-block:: C
358 .. code-block:: C
376 .. code-block:: C
389 .. code-block:: C
401 bitrates for the arbitration phase and the payload phase of the CAN FD frame
407 and Classical CAN frames simultaneously (see :ref:`socketcan-rawfd`).
411 .. code-block:: C
426 all structure elements can be used as-is - only the data[] becomes extended.
435 the mapping to the bus-relevant data length code (DLC), see :ref:`socketcan-can-fd-driver`.
441 .. code-block:: C
447 .. _socketcan-raw-sockets:
450 ------------------------------------------------
457 - The filters are set to exactly one filter receiving everything
458 - The socket only receives valid data frames (=> no error message frames)
459 - The loopback of sent CAN frames is enabled (see :ref:`socketcan-local-loopback2`)
460 - The socket does not receive its own sent frames (in loopback mode)
462 These default settings may be changed before or after binding the socket.
467 .. _socketcan-rawfilter:
477 .. code-block:: C
486 .. code-block:: C
496 .. code-block:: C
509 .. code-block:: C
515 having this 'send only' use-case we may remove the receive list in the
521 The CAN filters are processed in per-device filter lists at CAN frame
537 .. code-block:: C
547 .. code-block:: C
562 As described in :ref:`socketcan-network-problem-notifications` the CAN interface driver can generat…
570 .. code-block:: C
581 To meet multi user needs the local loopback is enabled by default
582 (see :ref:`socketcan-local-loopback1` for details). But in some embedded use-cases
586 .. code-block:: C
588 int loopback = 0; /* 0 = disabled, 1 = enabled (default) */
598 frames' CAN-ID on this given interface to meet the multi user
601 disabled by default. This default behaviour may be changed on
604 .. code-block:: C
606 int recv_own_msgs = 1; /* 0 = disabled (default), 1 = enabled */
612 filtering as other CAN frames (see :ref:`socketcan-rawfilter`).
614 .. _socketcan-rawfd:
620 CAN_RAW_FD_FRAMES which is off by default. When the new socket option is
622 CAN_RAW_FD_FRAMES option returns the error -ENOPROTOOPT.
628 .. code-block:: C
631 CAN_RAW_FD_FRAMES disabled: only CAN_MTU is allowed (default)
635 .. code-block:: C
685 applied (see :ref:`socketcan-rawfilter`).
699 When using recvmsg() call, the msg->msg_flags may contain following flags:
708 :ref:`socketcan-local-loopback1` and :ref:`socketcan-local-loopback2`.
713 -----------------------------------------------
718 Receive filters can be used to down sample frequent messages; detect events
719 such as message contents changes, packet length changes, and do time-out
734 .. code-block:: C
747 at the beginning of :ref:`socketcan-rawfd` and in the include/linux/can.h include. All
753 .. code-block:: C
878 Send reply for RTR-request (placed in op->frames[0]).
902 .. code-block:: C
923 The timer values ival1 or ival2 may be set to non-zero values at RX_SETUP.
929 is activated directly - even without a former CAN frame reception.
949 .. code-block:: C
951 /* usually used to clear CAN frame data[] - beware of endian problems! */
952 #define U64_DATA(p) (*(unsigned long long*)(p)->data)
981 .. code-block:: C
999 ----------------------------------------------
1005 --------------------------------------------
1010 .. _socketcan-core-module:
1018 modules to subscribe needed CAN IDs (see :ref:`socketcan-receive-lists`).
1022 --------------------
1024 - **stats_timer**:
1027 invoked at can.ko module start time by default. This timer can be
1030 - **debug**:
1035 --------------
1037 As described in :ref:`socketcan-receive-lists` the SocketCAN core uses several filter
1055 rcvlist_all - list for unfiltered entries (no filter operations)
1056 rcvlist_eff - list for single extended frame (EFF) entries
1057 rcvlist_err - list for error message frames masks
1058 rcvlist_fil - list for mask/value filters
1059 rcvlist_inv - list for mask/value filters (inverse semantic)
1060 rcvlist_sff - list for single standard frame (SFF) entries
1064 stats - SocketCAN core statistics (rx/tx frames, match ratios, ...)
1065 reset_stats - manual statistic reset
1066 version - prints SocketCAN core and ABI version (removed in Linux 5.10)
1070 --------------------------------
1080 can_rx_register - subscribe CAN frames from a specific interface
1081 can_rx_unregister - unsubscribe CAN frames from a specific interface
1082 can_send - transmit a CAN frame (optional with local loopback)
1095 - TX: Put the CAN frame from the socket buffer to the CAN controller.
1096 - RX: Put the CAN frame from the CAN controller to the socket buffer.
1103 ----------------
1105 .. code-block:: C
1107 dev->type = ARPHRD_CAN; /* the netdevice hardware type */
1108 dev->flags = IFF_NOARP; /* CAN has no arp */
1110 dev->mtu = CAN_MTU; /* sizeof(struct can_frame) -> Classical CAN interface */
1113 dev->mtu = CANFD_MTU; /* sizeof(struct canfd_frame) -> CAN FD interface */
1119 .. _socketcan-local-loopback2:
1122 -----------------------------
1124 As described in :ref:`socketcan-local-loopback1` the CAN network device driver should
1130 dev->flags = (IFF_NOARP | IFF_ECHO);
1134 -------------------------------
1139 controller and have to be identified as not feasible in a multi-user
1141 hardware filters could make sense in a very dedicated use-case, as a
1142 filter on driver level would affect all users in the multi-user
1152 --------------------------------
1161 $ ip -details link show can0
1173 To enable termination resistor support to a can-controller, either
1174 implement in the controller's struct can-priv::
1181 Documentation/devicetree/bindings/net/can/can-controller.yaml
1185 -----------------------------
1190 - a unique CAN Identifier (CAN ID)
1191 - the CAN bus this CAN ID is transmitted on (e.g. can0)
1204 - Create a virtual CAN network interface:
1207 - Create a virtual CAN network interface with a specific name 'vcan42':
1210 - Remove a (virtual CAN) network interface 'vcan42':
1215 ---------------------------------------
1219 configure the CAN device, like setting the bit-timing parameters, via
1225 understand how to use them. The name of the module is can-dev.ko.
1241 [ bitrate BITRATE [ sample-point SAMPLE-POINT] ] |
1242 [ tq TQ prop-seg PROP_SEG phase-seg1 PHASE-SEG1
1243 phase-seg2 PHASE-SEG2 [ sjw SJW ] ]
1245 [ dbitrate BITRATE [ dsample-point SAMPLE-POINT] ] |
1246 [ dtq TQ dprop-seg PROP_SEG dphase-seg1 PHASE-SEG1
1247 dphase-seg2 PHASE-SEG2 [ dsjw SJW ] ]
1250 [ listen-only { on | off } ]
1251 [ triple-sampling { on | off } ]
1252 [ one-shot { on | off } ]
1253 [ berr-reporting { on | off } ]
1255 [ fd-non-iso { on | off } ]
1256 [ presume-ack { on | off } ]
1257 [ cc-len8-dlc { on | off } ]
1259 [ restart-ms TIME-MS ]
1263 SAMPLE-POINT := { 0.000..0.999 }
1265 PROP-SEG := { 1..8 }
1266 PHASE-SEG1 := { 1..8 }
1267 PHASE-SEG2 := { 1..8 }
1269 RESTART-MS := { 0 | NUMBER }
1273 $ ip -details -statistics link show can0
1276 can <TRIPLE-SAMPLING> state ERROR-ACTIVE restart-ms 100
1278 tq 125 prop-seg 6 phase-seg1 7 phase-seg2 2 sjw 1
1279 sja1000: tseg1 1..16 tseg2 1..8 sjw 1..4 brp 1..64 brp-inc 1
1281 re-started bus-errors arbit-lost error-warn error-pass bus-off
1290 "<TRIPLE-SAMPLING>"
1292 LISTEN-ONLY, or TRIPLE-SAMPLING.
1294 "state ERROR-ACTIVE"
1295 The current state of the CAN controller: "ERROR-ACTIVE",
1296 "ERROR-WARNING", "ERROR-PASSIVE", "BUS-OFF" or "STOPPED"
1298 "restart-ms 100"
1299 Automatic restart delay time. If set to a non-zero value, a
1301 in case of a bus-off condition after the specified delay time
1302 in milliseconds. By default it's off.
1304 "bitrate 125000 sample-point 0.875"
1305 Shows the real bit-rate in bits/sec and the sample-point in the
1306 range 0.000..0.999. If the calculation of bit-timing parameters
1308 bit-timing can be defined by setting the "bitrate" argument.
1309 Optionally the "sample-point" can be specified. By default it's
1310 0.000 assuming CIA-recommended sample-points.
1312 "tq 125 prop-seg 6 phase-seg1 7 phase-seg2 2 sjw 1"
1313 Shows the time quanta in ns, propagation segment, phase buffer
1315 tq. They allow to define the CAN bit-timing in a hardware
1319 "sja1000: tseg1 1..16 tseg2 1..8 sjw 1..4 brp 1..64 brp-inc 1 clock 8000000"
1320 Shows the bit-timing constants of the CAN controller, here the
1323 bitrate pre-scaler and the CAN system clock frequency in Hz.
1324 These constants could be used for user-defined (non-standard)
1325 bit-timing calculation algorithms in user-space.
1327 "re-started bus-errors arbit-lost error-warn error-pass bus-off"
1329 and the state changes to the error-warning, error-passive and
1330 bus-off state. RX overrun errors are listed in the "overrun"
1333 Setting the CAN Bit-Timing
1336 The CAN bit-timing parameters can always be defined in a hardware
1341 $ ip link set canX type can tq 125 prop-seg 6 \
1342 phase-seg1 7 phase-seg2 2 sjw 1
1345 recommended CAN bit-timing parameters will be calculated if the bit-
1351 standard bit-rates but may *fail* for exotic bit-rates or CAN system
1353 space and allows user-space tools to solely determine and set the
1354 bit-timing parameters. The CAN controller specific bit-timing
1358 $ ip -details link show can0
1360 sja1000: clock 8000000 tseg1 1..16 tseg2 1..8 sjw 1..4 brp 1..64 brp-inc 1
1368 you *must* define proper bit-timing parameters for real CAN devices
1369 before you can start it to avoid error-prone default settings::
1373 A device may enter the "bus-off" state if too many errors occurred on
1375 bus-off recovery can be enabled by setting the "restart-ms" to a
1376 non-zero value, e.g.::
1378 $ ip link set canX type can restart-ms 100
1380 Alternatively, the application may realize the "bus-off" condition
1387 also :ref:`socketcan-network-problem-notifications`).
1390 .. _socketcan-can-fd-driver:
1393 ------------------------------------------
1396 arbitration phase and the payload phase of the CAN FD frame. Therefore a
1404 CAN frames anyway. The payload length to the bus-relevant DLC mapping is
1418 has to be set. This bitrate for the data phase of the CAN FD frame has to be
1419 at least the bitrate which was configured for the arbitration phase. This
1422 dsample-point, dsjw or dtq and similar settings. When a data bitrate is set
1431 - ISO compliant: The ISO 11898-1:2015 CAN FD implementation (default)
1432 - non-ISO compliant: The CAN FD implementation following the 2012 whitepaper
1437 2. non-ISO compliant (fixed, like the M_CAN IP core v3.0.1 in m_can.c)
1438 3. ISO/non-ISO CAN FD controllers (switchable, like the PEAK PCAN-USB FD)
1440 The current ISO/non-ISO mode is announced by the CAN controller driver via
1441 netlink and displayed by the 'ip' tool (controller option FD-NON-ISO).
1442 The ISO/non-ISO-mode can be altered by setting 'fd-non-iso {on|off}' for
1447 $ ip link set can0 up type can bitrate 500000 sample-point 0.75 \
1448 dbitrate 4000000 dsample-point 0.8 fd on
1449 $ ip -details link show can0
1451 mode DEFAULT group default qlen 10
1453 can <FD> state ERROR-ACTIVE (berr-counter tx 0 rx 0) restart-ms 0
1454 bitrate 500000 sample-point 0.750
1455 tq 50 prop-seg 14 phase-seg1 15 phase-seg2 10 sjw 1
1457 brp-inc 1
1458 dbitrate 4000000 dsample-point 0.800
1459 dtq 12 dprop-seg 7 dphase-seg1 8 dphase-seg2 4 dsjw 1
1461 dbrp-inc 1
1464 Example when 'fd-non-iso on' is added on this switchable CAN FD adapter::
1466 can <FD,FD-NON-ISO> state ERROR-ACTIVE (berr-counter tx 0 rx 0) restart-ms 0
1470 ----------------------
1474 (see :ref:`socketcan-resources`) there might be further drivers available, also for
1478 .. _socketcan-resources:
1490 - Oliver Hartkopp (PF_CAN core, filters, drivers, bcm, SJA1000 driver)
1491 - Urs Thuermann (PF_CAN core, kernel integration, socket interfaces, raw, vcan)
1492 - Jan Kizka (RT-SocketCAN core, Socket-API reconciliation)
1493 - Wolfgang Grandegger (RT-SocketCAN core & drivers, Raw Socket-API reviews, CAN device driver inter…
1494 - Robert Schwebel (design reviews, PTXdist integration)
1495 - Marc Kleine-Budde (design reviews, Kernel 2.6 cleanups, drivers)
1496 - Benedikt Spranger (reviews)
1497 - Thomas Gleixner (LKML reviews, coding style, posting hints)
1498 - Andrey Volkov (kernel subtree structure, ioctls, MSCAN driver)
1499 - Matthias Brukner (first SJA1000 CAN netdevice implementation Q2/2003)
1500 - Klaus Hitschler (PEAK driver integration)
1501 - Uwe Koppe (CAN netdevices with PF_PACKET approach)
1502 - Michael Schulze (driver layer loopback requirement, RT CAN drivers review)
1503 - Pavel Pisa (Bit-timing calculation)
1504 - Sascha Hauer (SJA1000 platform driver)
1505 - Sebastian Haas (SJA1000 EMS PCI driver)
1506 - Markus Plessing (SJA1000 EMS PCI driver)
1507 - Per Dalen (SJA1000 Kvaser PCI driver)
1508 - Sam Ravnborg (reviews, coding style, kbuild help)