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diff --git a/docs/can.txt b/docs/can.txt new file mode 100644 index 0000000000..a357105762 --- /dev/null +++ b/docs/can.txt @@ -0,0 +1,107 @@ +QEMU CAN bus emulation support +============================== + +The CAN bus emulation provides mechanism to connect multiple +emulated CAN controller chips together by one or multiple CAN busses +(the controller device "canbus" parameter). The individual busses +can be connected to host system CAN API (at this time only Linux +SocketCAN is supported). + +The concept of busses is generic and different CAN controllers +can be implemented for it but at this time only SJA1000 chip +controller is implemented. + +The PCI addon card hardware has been selected as the first CAN +interface to implement because such device can be easily connected +to systems with different CPU architectures (x86, PowerPC, ARM, etc.). + +The project has been initially started in frame of RTEMS GSoC 2013 +slot by Jin Yang under our mentoring The initial idea was to provide generic +CAN subsystem for RTEMS. But lack of common environment for code and RTEMS +testing lead to goal change to provide environment which provides complete +emulated environment for testing and RTEMS GSoC slot has been donated +to work on CAN hardware emulation on QEMU. + +Examples how to use CAN emulation +================================= + +When QEMU with CAN PCI support is compiled then one of the next +CAN boards can be selected + + (1) CAN bus Kvaser PCI CAN-S (single SJA1000 channel) boad. QEMU startup options + -object can-bus,id=canbus0 + -device kvaser_pci,canbus=canbus0 + Add "can-host-socketcan" object to connect device to host system CAN bus + -object can-host-socketcan,id=canhost0,if=can0,canbus=canbus0 + + (2) CAN bus PCM-3680I PCI (dual SJA1000 channel) emulation + -object can-bus,id=canbus0 + -device pcm3680_pci,canbus0=canbus0,canbus1=canbus0 + + another example: + -object can-bus,id=canbus0 + -object can-bus,id=canbus1 + -device pcm3680_pci,canbus0=canbus0,canbus1=canbus1 + + (3) CAN bus MIOe-3680 PCI (dual SJA1000 channel) emulation + -device mioe3680_pci,canbus0=canbus0 + + +The ''kvaser_pci'' board/device model is compatible with and has been tested with +''kvaser_pci'' driver included in mainline Linux kernel. +The tested setup was Linux 4.9 kernel on the host and guest side. +Example for qemu-system-x86_64: + + qemu-system-x86_64 -enable-kvm -kernel /boot/vmlinuz-4.9.0-4-amd64 \ + -initrd ramdisk.cpio \ + -virtfs local,path=shareddir,security_model=none,mount_tag=shareddir \ + -object can-bus,id=canbus0 \ + -object can-host-socketcan,id=canhost0,if=can0,canbus=canbus0 \ + -device kvaser_pci,canbus=canbus0 \ + -nographic -append "console=ttyS0" + +Example for qemu-system-arm: + + qemu-system-arm -cpu arm1176 -m 256 -M versatilepb \ + -kernel kernel-qemu-arm1176-versatilepb \ + -hda rpi-wheezy-overlay \ + -append "console=ttyAMA0 root=/dev/sda2 ro init=/sbin/init-overlay" \ + -nographic \ + -virtfs local,path=shareddir,security_model=none,mount_tag=shareddir \ + -object can-bus,id=canbus0 \ + -object can-host-socketcan,id=canhost0,if=can0,canbus=canbus0 \ + -device kvaser_pci,canbus=canbus0,host=can0 \ + +The CAN interface of the host system has to be configured for proper +bitrate and set up. Configuration is not propagated from emulated +devices through bus to the physical host device. Example configuration +for 1 Mbit/s + + ip link set can0 type can bitrate 1000000 + ip link set can0 up + +Virtual (host local only) can interface can be used on the host +side instead of physical interface + + ip link add dev can0 type vcan + +The CAN interface on the host side can be used to analyze CAN +traffic with "candump" command which is included in "can-utils". + + candump can0 + +Links to other resources +======================== + + (1) Repository with development branch can-pci at Czech Technical University + https://gitlab.fel.cvut.cz/canbus/qemu-canbus + (2) GitHub repository with can-pci and our other changes included + https://gitlab.fel.cvut.cz/canbus/qemu-canbus + (3) RTEMS page describing project + https://devel.rtems.org/wiki/Developer/Simulators/QEMU/CANEmulation + (4) RTLWS 2015 article about the projevt and its use with CANopen emulation + http://rtime.felk.cvut.cz/publications/public/rtlws2015-qemu-can.pdf + Slides + http://rtime.felk.cvut.cz/publications/public/rtlws2015-qemu-can-slides.pdf + (5) Linux SocketCAN utilities + https://github.com/linux-can/can-utils/
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