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-loopback1` 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
248 default. A read(2) system call on a CAN_RAW socket transfers a
254 .. code-block:: C
270 .. code-block:: C
298 .. code-block:: C
325 .. code-block:: C
343 .. code-block:: C
356 .. code-block:: C
368 bitrates for the arbitration phase and the payload phase of the CAN FD frame
374 and (legacy) CAN frames simultaneously (see :ref:`socketcan-rawfd`).
378 .. code-block:: C
393 all structure elements can be used as-is - only the data[] becomes extended.
402 the mapping to the bus-relevant data length code (DLC), see :ref:`socketcan-can-fd-driver`.
408 .. code-block:: C
414 .. _socketcan-raw-sockets:
417 ------------------------------------------------
424 - The filters are set to exactly one filter receiving everything
425 - The socket only receives valid data frames (=> no error message frames)
426 - The loopback of sent CAN frames is enabled (see :ref:`socketcan-local-loopback2`)
427 - The socket does not receive its own sent frames (in loopback mode)
429 These default settings may be changed before or after binding the socket.
434 .. _socketcan-rawfilter:
444 .. code-block:: C
453 .. code-block:: C
463 .. code-block:: C
476 .. code-block:: C
482 having this 'send only' use-case we may remove the receive list in the
488 The CAN filters are processed in per-device filter lists at CAN frame
504 .. code-block:: C
514 .. code-block:: C
529 As described in :ref:`socketcan-network-problem-notifications` the CAN interface driver can generat…
537 .. code-block:: C
548 To meet multi user needs the local loopback is enabled by default
549 (see :ref:`socketcan-local-loopback1` for details). But in some embedded use-cases
553 .. code-block:: C
555 int loopback = 0; /* 0 = disabled, 1 = enabled (default) */
565 frames' CAN-ID on this given interface to meet the multi user
568 disabled by default. This default behaviour may be changed on
571 .. code-block:: C
573 int recv_own_msgs = 1; /* 0 = disabled (default), 1 = enabled */
579 .. _socketcan-rawfd:
585 CAN_RAW_FD_FRAMES which is off by default. When the new socket option is
587 CAN_RAW_FD_FRAMES option returns the error -ENOPROTOOPT.
593 .. code-block:: C
596 CAN_RAW_FD_FRAMES disabled: only CAN_MTU is allowed (default)
600 .. code-block:: C
650 applied (see :ref:`socketcan-rawfilter`).
664 When using recvmsg() call, the msg->msg_flags may contain following flags:
673 :ref:`socketcan-local-loopback1` and :ref:`socketcan-local-loopback2`.
678 -----------------------------------------------
683 Receive filters can be used to down sample frequent messages; detect events
684 such as message contents changes, packet length changes, and do time-out
699 .. code-block:: C
712 at the beginning of :ref:`socketcan-rawfd` and in the include/linux/can.h include. All
718 .. code-block:: C
843 Send reply for RTR-request (placed in op->frames[0]).
865 .. code-block:: C
886 The timer values ival1 or ival2 may be set to non-zero values at RX_SETUP.
892 is activated directly - even without a former CAN frame reception.
912 .. code-block:: C
914 /* usually used to clear CAN frame data[] - beware of endian problems! */
915 #define U64_DATA(p) (*(unsigned long long*)(p)->data)
944 .. code-block:: C
962 ----------------------------------------------
968 --------------------------------------------
973 .. _socketcan-core-module:
981 modules to subscribe needed CAN IDs (see :ref:`socketcan-receive-lists`).
985 --------------------
987 - **stats_timer**:
990 invoked at can.ko module start time by default. This timer can be
993 - **debug**:
998 --------------
1000 As described in :ref:`socketcan-receive-lists` the SocketCAN core uses several filter
1018 rcvlist_all - list for unfiltered entries (no filter operations)
1019 rcvlist_eff - list for single extended frame (EFF) entries
1020 rcvlist_err - list for error message frames masks
1021 rcvlist_fil - list for mask/value filters
1022 rcvlist_inv - list for mask/value filters (inverse semantic)
1023 rcvlist_sff - list for single standard frame (SFF) entries
1027 stats - SocketCAN core statistics (rx/tx frames, match ratios, ...)
1028 reset_stats - manual statistic reset
1029 version - prints the SocketCAN core version and the ABI version
1033 --------------------------------
1043 can_rx_register - subscribe CAN frames from a specific interface
1044 can_rx_unregister - unsubscribe CAN frames from a specific interface
1045 can_send - transmit a CAN frame (optional with local loopback)
1058 - TX: Put the CAN frame from the socket buffer to the CAN controller.
1059 - RX: Put the CAN frame from the CAN controller to the socket buffer.
1066 ----------------
1068 .. code-block:: C
1070 dev->type = ARPHRD_CAN; /* the netdevice hardware type */
1071 dev->flags = IFF_NOARP; /* CAN has no arp */
1073 dev->mtu = CAN_MTU; /* sizeof(struct can_frame) -> legacy CAN interface */
1076 dev->mtu = CANFD_MTU; /* sizeof(struct canfd_frame) -> CAN FD interface */
1082 .. _socketcan-local-loopback2:
1085 -----------------------------
1087 As described in :ref:`socketcan-local-loopback1` the CAN network device driver should
1093 dev->flags = (IFF_NOARP | IFF_ECHO);
1097 -------------------------------
1102 controller and have to be identified as not feasible in a multi-user
1104 hardware filters could make sense in a very dedicated use-case, as a
1105 filter on driver level would affect all users in the multi-user
1115 -----------------------------
1120 - a unique CAN Identifier (CAN ID)
1121 - the CAN bus this CAN ID is transmitted on (e.g. can0)
1134 - Create a virtual CAN network interface:
1137 - Create a virtual CAN network interface with a specific name 'vcan42':
1140 - Remove a (virtual CAN) network interface 'vcan42':
1145 ---------------------------------------
1149 configure the CAN device, like setting the bit-timing parameters, via
1155 understand how to use them. The name of the module is can-dev.ko.
1171 [ bitrate BITRATE [ sample-point SAMPLE-POINT] ] |
1172 [ tq TQ prop-seg PROP_SEG phase-seg1 PHASE-SEG1
1173 phase-seg2 PHASE-SEG2 [ sjw SJW ] ]
1175 [ dbitrate BITRATE [ dsample-point SAMPLE-POINT] ] |
1176 [ dtq TQ dprop-seg PROP_SEG dphase-seg1 PHASE-SEG1
1177 dphase-seg2 PHASE-SEG2 [ dsjw SJW ] ]
1180 [ listen-only { on | off } ]
1181 [ triple-sampling { on | off } ]
1182 [ one-shot { on | off } ]
1183 [ berr-reporting { on | off } ]
1185 [ fd-non-iso { on | off } ]
1186 [ presume-ack { on | off } ]
1188 [ restart-ms TIME-MS ]
1192 SAMPLE-POINT := { 0.000..0.999 }
1194 PROP-SEG := { 1..8 }
1195 PHASE-SEG1 := { 1..8 }
1196 PHASE-SEG2 := { 1..8 }
1198 RESTART-MS := { 0 | NUMBER }
1202 $ ip -details -statistics link show can0
1205 can <TRIPLE-SAMPLING> state ERROR-ACTIVE restart-ms 100
1207 tq 125 prop-seg 6 phase-seg1 7 phase-seg2 2 sjw 1
1208 sja1000: tseg1 1..16 tseg2 1..8 sjw 1..4 brp 1..64 brp-inc 1
1210 re-started bus-errors arbit-lost error-warn error-pass bus-off
1219 "<TRIPLE-SAMPLING>"
1221 LISTEN-ONLY, or TRIPLE-SAMPLING.
1223 "state ERROR-ACTIVE"
1224 The current state of the CAN controller: "ERROR-ACTIVE",
1225 "ERROR-WARNING", "ERROR-PASSIVE", "BUS-OFF" or "STOPPED"
1227 "restart-ms 100"
1228 Automatic restart delay time. If set to a non-zero value, a
1230 in case of a bus-off condition after the specified delay time
1231 in milliseconds. By default it's off.
1233 "bitrate 125000 sample-point 0.875"
1234 Shows the real bit-rate in bits/sec and the sample-point in the
1235 range 0.000..0.999. If the calculation of bit-timing parameters
1237 bit-timing can be defined by setting the "bitrate" argument.
1238 Optionally the "sample-point" can be specified. By default it's
1239 0.000 assuming CIA-recommended sample-points.
1241 "tq 125 prop-seg 6 phase-seg1 7 phase-seg2 2 sjw 1"
1242 Shows the time quanta in ns, propagation segment, phase buffer
1244 tq. They allow to define the CAN bit-timing in a hardware
1248 "sja1000: tseg1 1..16 tseg2 1..8 sjw 1..4 brp 1..64 brp-inc 1 clock 8000000"
1249 Shows the bit-timing constants of the CAN controller, here the
1252 bitrate pre-scaler and the CAN system clock frequency in Hz.
1253 These constants could be used for user-defined (non-standard)
1254 bit-timing calculation algorithms in user-space.
1256 "re-started bus-errors arbit-lost error-warn error-pass bus-off"
1258 and the state changes to the error-warning, error-passive and
1259 bus-off state. RX overrun errors are listed in the "overrun"
1262 Setting the CAN Bit-Timing
1265 The CAN bit-timing parameters can always be defined in a hardware
1270 $ ip link set canX type can tq 125 prop-seg 6 \
1271 phase-seg1 7 phase-seg2 2 sjw 1
1274 recommended CAN bit-timing parameters will be calculated if the bit-
1280 standard bit-rates but may *fail* for exotic bit-rates or CAN system
1282 space and allows user-space tools to solely determine and set the
1283 bit-timing parameters. The CAN controller specific bit-timing
1287 $ ip -details link show can0
1289 sja1000: clock 8000000 tseg1 1..16 tseg2 1..8 sjw 1..4 brp 1..64 brp-inc 1
1297 you *must* define proper bit-timing parameters for real CAN devices
1298 before you can start it to avoid error-prone default settings::
1302 A device may enter the "bus-off" state if too many errors occurred on
1304 bus-off recovery can be enabled by setting the "restart-ms" to a
1305 non-zero value, e.g.::
1307 $ ip link set canX type can restart-ms 100
1309 Alternatively, the application may realize the "bus-off" condition
1316 also :ref:`socketcan-network-problem-notifications`).
1319 .. _socketcan-can-fd-driver:
1322 ------------------------------------------
1325 arbitration phase and the payload phase of the CAN FD frame. Therefore a
1333 CAN frames anyway. The payload length to the bus-relevant DLC mapping is
1347 has to be set. This bitrate for the data phase of the CAN FD frame has to be
1348 at least the bitrate which was configured for the arbitration phase. This
1351 dsample-point, dsjw or dtq and similar settings. When a data bitrate is set
1360 - ISO compliant: The ISO 11898-1:2015 CAN FD implementation (default)
1361 - non-ISO compliant: The CAN FD implementation following the 2012 whitepaper
1366 2. non-ISO compliant (fixed, like the M_CAN IP core v3.0.1 in m_can.c)
1367 3. ISO/non-ISO CAN FD controllers (switchable, like the PEAK PCAN-USB FD)
1369 The current ISO/non-ISO mode is announced by the CAN controller driver via
1370 netlink and displayed by the 'ip' tool (controller option FD-NON-ISO).
1371 The ISO/non-ISO-mode can be altered by setting 'fd-non-iso {on|off}' for
1376 $ ip link set can0 up type can bitrate 500000 sample-point 0.75 \
1377 dbitrate 4000000 dsample-point 0.8 fd on
1378 $ ip -details link show can0
1380 mode DEFAULT group default qlen 10
1382 can <FD> state ERROR-ACTIVE (berr-counter tx 0 rx 0) restart-ms 0
1383 bitrate 500000 sample-point 0.750
1384 tq 50 prop-seg 14 phase-seg1 15 phase-seg2 10 sjw 1
1386 brp-inc 1
1387 dbitrate 4000000 dsample-point 0.800
1388 dtq 12 dprop-seg 7 dphase-seg1 8 dphase-seg2 4 dsjw 1
1390 dbrp-inc 1
1393 Example when 'fd-non-iso on' is added on this switchable CAN FD adapter::
1395 can <FD,FD-NON-ISO> state ERROR-ACTIVE (berr-counter tx 0 rx 0) restart-ms 0
1399 ----------------------
1403 (see :ref:`socketcan-resources`) there might be further drivers available, also for
1407 .. _socketcan-resources:
1419 - Oliver Hartkopp (PF_CAN core, filters, drivers, bcm, SJA1000 driver)
1420 - Urs Thuermann (PF_CAN core, kernel integration, socket interfaces, raw, vcan)
1421 - Jan Kizka (RT-SocketCAN core, Socket-API reconciliation)
1422 - Wolfgang Grandegger (RT-SocketCAN core & drivers, Raw Socket-API reviews, CAN device driver inter…
1423 - Robert Schwebel (design reviews, PTXdist integration)
1424 - Marc Kleine-Budde (design reviews, Kernel 2.6 cleanups, drivers)
1425 - Benedikt Spranger (reviews)
1426 - Thomas Gleixner (LKML reviews, coding style, posting hints)
1427 - Andrey Volkov (kernel subtree structure, ioctls, MSCAN driver)
1428 - Matthias Brukner (first SJA1000 CAN netdevice implementation Q2/2003)
1429 - Klaus Hitschler (PEAK driver integration)
1430 - Uwe Koppe (CAN netdevices with PF_PACKET approach)
1431 - Michael Schulze (driver layer loopback requirement, RT CAN drivers review)
1432 - Pavel Pisa (Bit-timing calculation)
1433 - Sascha Hauer (SJA1000 platform driver)
1434 - Sebastian Haas (SJA1000 EMS PCI driver)
1435 - Markus Plessing (SJA1000 EMS PCI driver)
1436 - Per Dalen (SJA1000 Kvaser PCI driver)
1437 - Sam Ravnborg (reviews, coding style, kbuild help)