From: Oliver Hartkopp <socketcan@xxxxxxxxxxxx> The struct can_frame and struct canfd_frame intentionally share the same layout to be able to write CAN frame content into a CAN FD frame structure. When this is done the former differentiation via CAN_MTU / CANFD_MTU is lost. CANFD_FDF allows programmers to mark CAN FD frames in the case of using struct canfd_frame for mixed CAN/CAN FD content (dual use). N.B. the Kernel APIs do NOT provide mixed CAN / CAN FD content inside of struct canfd_frame therefore the CANFD_FDF flag is disregarded by Linux. Link: https://lore.kernel.org/r/20170411134343.3089-1-socketcan@xxxxxxxxxxxx Signed-off-by: Oliver Hartkopp <socketcan@xxxxxxxxxxxx> Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> --- include/uapi/linux/can.h | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/include/uapi/linux/can.h b/include/uapi/linux/can.h index ac5d7a31671f..90801ada2bbe 100644 --- a/include/uapi/linux/can.h +++ b/include/uapi/linux/can.h @@ -135,9 +135,18 @@ struct can_frame { * controller only the CANFD_BRS bit is relevant for real CAN controllers when * building a CAN FD frame for transmission. Setting the CANFD_ESI bit can make * sense for virtual CAN interfaces to test applications with echoed frames. + * + * The struct can_frame and struct canfd_frame intentionally share the same + * layout to be able to write CAN frame content into a CAN FD frame structure. + * When this is done the former differentiation via CAN_MTU / CANFD_MTU gets + * lost. CANFD_FDF allows programmers to mark CAN FD frames in the case of + * using struct canfd_frame for mixed CAN / CAN FD content (dual use). + * N.B. the Kernel APIs do NOT provide mixed CAN / CAN FD content inside of + * struct canfd_frame therefore the CANFD_FDF flag is disregarded by Linux. */ #define CANFD_BRS 0x01 /* bit rate switch (second bitrate for payload data) */ #define CANFD_ESI 0x02 /* error state indicator of the transmitting node */ +#define CANFD_FDF 0x04 /* mark CAN FD for dual use of struct canfd_frame */ /** * struct canfd_frame - CAN flexible data rate frame structure -- 2.30.2
