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Diffstat (limited to 'Documentation/networking/can.txt')
| -rw-r--r-- | Documentation/networking/can.txt | 217 |
1 files changed, 0 insertions, 217 deletions
diff --git a/Documentation/networking/can.txt b/Documentation/networking/can.txt index 4c07241..820f553 100644 --- a/Documentation/networking/can.txt +++ b/Documentation/networking/can.txt @@ -25,12 +25,6 @@ This file contains 4.1.5 RAW socket option CAN_RAW_FD_FRAMES 4.1.6 RAW socket returned message flags 4.2 Broadcast Manager protocol sockets (SOCK_DGRAM) - 4.2.1 Broadcast Manager operations - 4.2.2 Broadcast Manager message flags - 4.2.3 Broadcast Manager transmission timers - 4.2.4 Broadcast Manager message sequence transmission - 4.2.5 Broadcast Manager receive filter timers - 4.2.6 Broadcast Manager multiplex message receive filter 4.3 connected transport protocols (SOCK_SEQPACKET) 4.4 unconnected transport protocols (SOCK_DGRAM) @@ -599,217 +593,6 @@ solution for a couple of reasons: In order to receive such messages, CAN_RAW_RECV_OWN_MSGS must be set. 4.2 Broadcast Manager protocol sockets (SOCK_DGRAM) - - The Broadcast Manager protocol provides a command based configuration - interface to filter and send (e.g. cyclic) CAN messages in kernel space. - - Receive filters can be used to down sample frequent messages; detect events - such as message contents changes, packet length changes, and do time-out - monitoring of received messages. - - Periodic transmission tasks of CAN frames or a sequence of CAN frames can be - created and modified at runtime; both the message content and the two - possible transmit intervals can be altered. - - A BCM socket is not intended for sending individual CAN frames using the - struct can_frame as known from the CAN_RAW socket. Instead a special BCM - configuration message is defined. The basic BCM configuration message used - to communicate with the broadcast manager and the available operations are - defined in the linux/can/bcm.h include. The BCM message consists of a - message header with a command ('opcode') followed by zero or more CAN frames. - The broadcast manager sends responses to user space in the same form: - - struct bcm_msg_head { - __u32 opcode; /* command */ - __u32 flags; /* special flags */ - __u32 count; /* run 'count' times with ival1 */ - struct timeval ival1, ival2; /* count and subsequent interval */ - canid_t can_id; /* unique can_id for task */ - __u32 nframes; /* number of can_frames following */ - struct can_frame frames[0]; - }; - - The aligned payload 'frames' uses the same basic CAN frame structure defined - at the beginning of section 4 and in the include/linux/can.h include. All - messages to the broadcast manager from user space have this structure. - - Note a CAN_BCM socket must be connected instead of bound after socket - creation (example without error checking): - - int s; - struct sockaddr_can addr; - struct ifreq ifr; - - s = socket(PF_CAN, SOCK_DGRAM, CAN_BCM); - - strcpy(ifr.ifr_name, "can0"); - ioctl(s, SIOCGIFINDEX, &ifr); - - addr.can_family = AF_CAN; - addr.can_ifindex = ifr.ifr_ifindex; - - connect(s, (struct sockaddr *)&addr, sizeof(addr)) - - (..) - - The broadcast manager socket is able to handle any number of in flight - transmissions or receive filters concurrently. The different RX/TX jobs are - distinguished by the unique can_id in each BCM message. However additional - CAN_BCM sockets are recommended to communicate on multiple CAN interfaces. - When the broadcast manager socket is bound to 'any' CAN interface (=> the - interface index is set to zero) the configured receive filters apply to any - CAN interface unless the sendto() syscall is used to overrule the 'any' CAN - interface index. When using recvfrom() instead of read() to retrieve BCM - socket messages the originating CAN interface is provided in can_ifindex. - - 4.2.1 Broadcast Manager operations - - The opcode defines the operation for the broadcast manager to carry out, - or details the broadcast managers response to several events, including - user requests. - - Transmit Operations (user space to broadcast manager): - - TX_SETUP: Create (cyclic) transmission task. - - TX_DELETE: Remove (cyclic) transmission task, requires only can_id. - - TX_READ: Read properties of (cyclic) transmission task for can_id. - - TX_SEND: Send one CAN frame. - - Transmit Responses (broadcast manager to user space): - - TX_STATUS: Reply to TX_READ request (transmission task configuration). - - TX_EXPIRED: Notification when counter finishes sending at initial interval - 'ival1'. Requires the TX_COUNTEVT flag to be set at TX_SETUP. - - Receive Operations (user space to broadcast manager): - - RX_SETUP: Create RX content filter subscription. - - RX_DELETE: Remove RX content filter subscription, requires only can_id. - - RX_READ: Read properties of RX content filter subscription for can_id. - - Receive Responses (broadcast manager to user space): - - RX_STATUS: Reply to RX_READ request (filter task configuration). - - RX_TIMEOUT: Cyclic message is detected to be absent (timer ival1 expired). - - RX_CHANGED: BCM message with updated CAN frame (detected content change). - Sent on first message received or on receipt of revised CAN messages. - - 4.2.2 Broadcast Manager message flags - - When sending a message to the broadcast manager the 'flags' element may - contain the following flag definitions which influence the behaviour: - - SETTIMER: Set the values of ival1, ival2 and count - - STARTTIMER: Start the timer with the actual values of ival1, ival2 - and count. Starting the timer leads simultaneously to emit a CAN frame. - - TX_COUNTEVT: Create the message TX_EXPIRED when count expires - - TX_ANNOUNCE: A change of data by the process is emitted immediately. - - TX_CP_CAN_ID: Copies the can_id from the message header to each - subsequent frame in frames. This is intended as usage simplification. For - TX tasks the unique can_id from the message header may differ from the - can_id(s) stored for transmission in the subsequent struct can_frame(s). - - RX_FILTER_ID: Filter by can_id alone, no frames required (nframes=0). - - RX_CHECK_DLC: A change of the DLC leads to an RX_CHANGED. - - RX_NO_AUTOTIMER: Prevent automatically starting the timeout monitor. - - RX_ANNOUNCE_RESUME: If passed at RX_SETUP and a receive timeout occured, a - RX_CHANGED message will be generated when the (cyclic) receive restarts. - - TX_RESET_MULTI_IDX: Reset the index for the multiple frame transmission. - - RX_RTR_FRAME: Send reply for RTR-request (placed in op->frames[0]). - - 4.2.3 Broadcast Manager transmission timers - - Periodic transmission configurations may use up to two interval timers. - In this case the BCM sends a number of messages ('count') at an interval - 'ival1', then continuing to send at another given interval 'ival2'. When - only one timer is needed 'count' is set to zero and only 'ival2' is used. - When SET_TIMER and START_TIMER flag were set the timers are activated. - The timer values can be altered at runtime when only SET_TIMER is set. - - 4.2.4 Broadcast Manager message sequence transmission - - Up to 256 CAN frames can be transmitted in a sequence in the case of a cyclic - TX task configuration. The number of CAN frames is provided in the 'nframes' - element of the BCM message head. The defined number of CAN frames are added - as array to the TX_SETUP BCM configuration message. - - /* create a struct to set up a sequence of four CAN frames */ - struct { - struct bcm_msg_head msg_head; - struct can_frame frame[4]; - } mytxmsg; - - (..) - mytxmsg.nframes = 4; - (..) - - write(s, &mytxmsg, sizeof(mytxmsg)); - - With every transmission the index in the array of CAN frames is increased - and set to zero at index overflow. - - 4.2.5 Broadcast Manager receive filter timers - - The timer values ival1 or ival2 may be set to non-zero values at RX_SETUP. - When the SET_TIMER flag is set the timers are enabled: - - ival1: Send RX_TIMEOUT when a received message is not received again within - the given time. When START_TIMER is set at RX_SETUP the timeout detection - is activated directly - even without a former CAN frame reception. - - ival2: Throttle the received message rate down to the value of ival2. This - is useful to reduce messages for the application when the signal inside the - CAN frame is stateless as state changes within the ival2 periode may get - lost. - - 4.2.6 Broadcast Manager multiplex message receive filter - - To filter for content changes in multiplex message sequences an array of more - than one CAN frames can be passed in a RX_SETUP configuration message. The - data bytes of the first CAN frame contain the mask of relevant bits that - have to match in the subsequent CAN frames with the received CAN frame. - If one of the subsequent CAN frames is matching the bits in that frame data - mark the relevant content to be compared with the previous received content. - Up to 257 CAN frames (multiplex filter bit mask CAN frame plus 256 CAN - filters) can be added as array to the TX_SETUP BCM configuration message. - - /* usually used to clear CAN frame data[] - beware of endian problems! */ - #define U64_DATA(p) (*(unsigned long long*)(p)->data) - - struct { - struct bcm_msg_head msg_head; - struct can_frame frame[5]; - } msg; - - msg.msg_head.opcode = RX_SETUP; - msg.msg_head.can_id = 0x42; - msg.msg_head.flags = 0; - msg.msg_head.nframes = 5; - U64_DATA(&msg.frame[0]) = 0xFF00000000000000ULL; /* MUX mask */ - U64_DATA(&msg.frame[1]) = 0x01000000000000FFULL; /* data mask (MUX 0x01) */ - U64_DATA(&msg.frame[2]) = 0x0200FFFF000000FFULL; /* data mask (MUX 0x02) */ - U64_DATA(&msg.frame[3]) = 0x330000FFFFFF0003ULL; /* data mask (MUX 0x33) */ - U64_DATA(&msg.frame[4]) = 0x4F07FC0FF0000000ULL; /* data mask (MUX 0x4F) */ - - write(s, &msg, sizeof(msg)); - 4.3 connected transport protocols (SOCK_SEQPACKET) 4.4 unconnected transport protocols (SOCK_DGRAM) |