From: Oliver Hartkopp Subject: [PATCH] can: introduce CANFD_FDF flag for mixed content in struct canfd_frame Date: Tue, 11 Apr 2017 15:43:43 +0200 Message-ID: <20170411134343.3089-1-socketcan@hartkopp.net> Return-path: Received: from mo4-p00-ob.smtp.rzone.de ([81.169.146.221]:25023 "EHLO mo4-p00-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752224AbdDKNnv (ORCPT ); Tue, 11 Apr 2017 09:43:51 -0400 Sender: linux-can-owner@vger.kernel.org List-ID: To: linux-can@vger.kernel.org Cc: Oliver Hartkopp The struct can_frame and struct canfd_frame intentionaly 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. Signed-off-by: Oliver Hartkopp --- 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 c48d93a28d1a..02f64221fb52 100644 --- a/include/uapi/linux/can.h +++ b/include/uapi/linux/can.h @@ -124,9 +124,18 @@ 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 intentionaly 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 -- 2.11.0