Hi there! I have been working on getting my device compatible with both, CAN and CAN FD. For receiving this is working straight forward. My physical interface is CAN FD capable and no matter whether I set it up as ip link set can0 type can bitrate 500000 fd off or ip link set can0 type can bitrate 500000 fd dbitrate 2000000 off in code I can always just use the canfd_frame struct and set the CAN_RAW_FD_FRAMES option. Doing this I can receive CAN and CAN FD frames in both modes without having to fall back to the can_frame struct (as explained in the docs). For sending I expected a similar behavior. I set the CAN_RAW_FD_FRAMES option and always sent using the canfd_frame struct. Sadly, this fails while writing on the interface when it is not in FD-mode with an Invalid Argument error. To make this work without falling back to the can_frame struct I just do write(sock, &canfdf, sizeof(struct can_frame)); where canfdf is a canfd_frame. Not setting CAN_RAW_FD_FRAMES when the interface is in CAN mode but sending using the full canfd_frame won't work too. Is this expected behavior? Shouldn't the error only be returned if the canfd_frame I pass has more than 8 bytes when the interface is not in FD-mode? Regards, Thomas
