can: update MAINTAINERS and Documentation

  3 SocketCAN concept

    3.1 receive lists

    3.2 local loopback of sent frames

    3.3 network security issues (capabilities)

    3.4 network problem notifications

    3.3 network problem notifications

  4 How to use SocketCAN

    4.1 RAW protocol sockets with can_filters (SOCK_RAW)

SocketCAN was designed to overcome all of these limitations.  A new

protocol family has been implemented which provides a socket interface

to user space applications and which builds upon the Linux network

layer, so to use all of the provided queueing functionality.  A device

layer, enabling use all of the provided queueing functionality.  A device

driver for CAN controller hardware registers itself with the Linux

network layer as a network device, so that CAN frames from the

controller can be passed up to the network layer and on to the CAN

  * = you really like to have this when you're running analyser tools

      like 'candump' or 'cansniffer' on the (same) node.

  3.3 network security issues (capabilities)

  The Controller Area Network is a local field bus transmitting only

  broadcast messages without any routing and security concepts.

  In the majority of cases the user application has to deal with

  raw CAN frames. Therefore it might be reasonable NOT to restrict

  the CAN access only to the user root, as known from other networks.

  Since the currently implemented CAN_RAW and CAN_BCM sockets can only

  send and receive frames to/from CAN interfaces it does not affect

  security of others networks to allow all users to access the CAN.

  To enable non-root users to access CAN_RAW and CAN_BCM protocol

  sockets the Kconfig options CAN_RAW_USER and/or CAN_BCM_USER may be

  selected at kernel compile time.

  3.4 network problem notifications

  3.3 network problem notifications

  The use of the CAN bus may lead to several problems on the physical

  and media access control layer. Detecting and logging of these lower

    };

  The alignment of the (linear) payload data[] to a 64bit boundary

  allows the user to define own structs and unions to easily access the

  CAN payload. There is no given byteorder on the CAN bus by

  allows the user to define their own structs and unions to easily access

  the CAN payload. There is no given byteorder on the CAN bus by

  default. A read(2) system call on a CAN_RAW socket transfers a

  struct can_frame to the user space.

    setsockopt(s, SOL_CAN_RAW, CAN_RAW_FILTER, NULL, 0);

  To set the filters to zero filters is quite obsolete as not read

  To set the filters to zero filters is quite obsolete as to not read

  data causes the raw socket to discard the received CAN frames. But

  having this 'send only' use-case we may remove the receive list in the

  Kernel to save a little (really a very little!) CPU usage.

    $ ip link set canX up type can bitrate 125000

  A device may enter the "bus-off" state if too much errors occurred on

  A device may enter the "bus-off" state if too many 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.:

7. SocketCAN 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:

    http://developer.berlios.de/projects/socketcan

  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.

  The Linux CAN / SocketCAN project ressources (project site / mailing list)

  are referenced in the MAINTAINERS file in the Linux source tree.

  Search for CAN NETWORK [LAYERS|DRIVERS].

8. Credits

----------

W:	http://gitorious.org/linux-can

T:	git git://gitorious.org/linux-can/linux-can-next.git

S:	Maintained

F:	Documentation/networking/can.txt

F:	net/can/

F:	include/linux/can/core.h

F:	include/uapi/linux/can.h