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List: linux-can
Subject: [PATCH v2 1/6] canfd: add new data structures and constants
From: Oliver Hartkopp <socketcan () hartkopp ! net>
Date: 2012-06-19 19:19:10
Message-ID: 4FE0D0AE.3010500 () hartkopp ! net
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From d8976f0565e1d1c354c4ac0025b4ced7c4810e77 Mon Sep 17 00:00:00 2001
From: Oliver Hartkopp <socketcan@hartkopp.net>
Date: Wed, 13 Jun 2012 20:04:33 +0200
Subject: [PATCH 1/6] canfd: add new data structures and constants
- add new struct canfd_frame
- check identical element offsets in struct can_frame and struct canfd_frame
- new ETH_P_CANFD definition to tag CAN FD skbs correctly
- add CAN_MTU and CANFD_MTU definitions for easy frame and mode detection
- add CAN[FD]_MAX_[DLC|DLEN] helper constants to remove hard coded values
- update existing struct can_frame with helper constants and comments
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
include/linux/can.h | 59 ++++++++++++++++++++++++++++++++++++++++++----
include/linux/if_ether.h | 3 ++-
net/can/af_can.c | 7 ++++++
3 files changed, 63 insertions(+), 6 deletions(-)
diff --git a/include/linux/can.h b/include/linux/can.h
index 17334c0..1a66cf61 100644
--- a/include/linux/can.h
+++ b/include/linux/can.h
@@ -46,18 +46,67 @@ typedef __u32 canid_t;
*/
typedef __u32 can_err_mask_t;
+/* CAN payload length and DLC definitions according to ISO 11898-1 */
+#define CAN_MAX_DLC 8
+#define CAN_MAX_DLEN 8
+
+/* CAN FD payload length and DLC definitions according to ISO 11898-7 */
+#define CANFD_MAX_DLC 15
+#define CANFD_MAX_DLEN 64
+
/**
* struct can_frame - basic CAN frame structure
- * @can_id: the CAN ID of the frame and CAN_*_FLAG flags, see above.
- * @can_dlc: the data length field of the CAN frame
- * @data: the CAN frame payload.
+ * @can_id: CAN ID of the frame and CAN_*_FLAG flags, see canid_t definition
+ * @can_dlc: frame payload length in byte (0 .. 8) aka data length code
+ * N.B. the DLC field from ISO 11898-1 Chapter 8.4.2.3 has a 1:1
+ * mapping of the 'data length code' to the real payload length
+ * @data: CAN frame payload (up to 8 byte)
*/
struct can_frame {
canid_t can_id; /* 32 bit CAN_ID + EFF/RTR/ERR flags */
- __u8 can_dlc; /* data length code: 0 .. 8 */
- __u8 data[8] __attribute__((aligned(8)));
+ __u8 can_dlc; /* frame payload length in byte (0 .. CAN_MAX_DLEN) */
+ __u8 data[CAN_MAX_DLEN] __attribute__((aligned(8)));
};
+/*
+ * defined bits for canfd_frame.flags
+ *
+ * As the default for CAN FD should be to support the high data rate in the
+ * payload section of the frame (HDR) and to support up to 64 byte in the
+ * data section (EDL) the bits are only set in the non-default case.
+ * Btw. as long as there's no real implementation for CAN FD network driver
+ * these bits are only preliminary.
+ *
+ * RX: NOHDR/NOEDL - info about received CAN FD frame
+ * ESI - bit from originating CAN controller
+ * TX: NOHDR/NOEDL - control per-frame settings if supported by CAN controller
+ * ESI - bit is set by local CAN controller
+ */
+#define CANFD_NOHDR 0x01 /* frame without high data rate */
+#define CANFD_NOEDL 0x02 /* frame without extended data length */
+#define CANFD_ESI 0x04 /* error state indicator */
+
+/**
+ * struct canfd_frame - CAN flexible data rate frame structure
+ * @can_id: CAN ID of the frame and CAN_*_FLAG flags, see canid_t definition
+ * @len: frame payload length in byte (0 .. CANFD_MAX_DLEN)
+ * @flags: additional flags for CAN FD
+ * @__res0: reserved / padding
+ * @__res1: reserved / padding
+ * @data: CAN FD frame payload (up to CANFD_MAX_DLEN byte)
+ */
+struct canfd_frame {
+ canid_t can_id; /* 32 bit CAN_ID + EFF/RTR/ERR flags */
+ __u8 len; /* frame payload length in byte */
+ __u8 flags; /* additional flags for CAN FD */
+ __u8 __res0; /* reserved / padding */
+ __u8 __res1; /* reserved / padding */
+ __u8 data[CANFD_MAX_DLEN] __attribute__((aligned(8)));
+};
+
+#define CAN_MTU (sizeof(struct can_frame))
+#define CANFD_MTU (sizeof(struct canfd_frame))
+
/* particular protocols of the protocol family PF_CAN */
#define CAN_RAW 1 /* RAW sockets */
#define CAN_BCM 2 /* Broadcast Manager */
diff --git a/include/linux/if_ether.h b/include/linux/if_ether.h
index 56d907a..167ce5b 100644
--- a/include/linux/if_ether.h
+++ b/include/linux/if_ether.h
@@ -105,7 +105,8 @@
#define ETH_P_WAN_PPP 0x0007 /* Dummy type for WAN PPP frames*/
#define ETH_P_PPP_MP 0x0008 /* Dummy type for PPP MP frames */
#define ETH_P_LOCALTALK 0x0009 /* Localtalk pseudo type */
-#define ETH_P_CAN 0x000C /* Controller Area Network */
+#define ETH_P_CAN 0x000C /* CAN: Controller Area Network */
+#define ETH_P_CANFD 0x000D /* CANFD: CAN flexible data rate*/
#define ETH_P_PPPTALK 0x0010 /* Dummy type for Atalk over PPP*/
#define ETH_P_TR_802_2 0x0011 /* 802.2 frames */
#define ETH_P_MOBITEX 0x0015 /* Mobitex (kaz@cafe.net) */
diff --git a/net/can/af_can.c b/net/can/af_can.c
index 6efcd37..c96140a 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -41,6 +41,7 @@
*/
#include <linux/module.h>
+#include <linux/stddef.h>
#include <linux/init.h>
#include <linux/kmod.h>
#include <linux/slab.h>
@@ -824,6 +825,12 @@ static struct notifier_block can_netdev_notifier __read_mostly = {
static __init int can_init(void)
{
+ /* check for correct padding to be able to use the structs similarly */
+ BUILD_BUG_ON(offsetof(struct can_frame, can_dlc) !=
+ offsetof(struct canfd_frame, len) ||
+ offsetof(struct can_frame, data) !=
+ offsetof(struct canfd_frame, data));
+
printk(banner);
memset(&can_rx_alldev_list, 0, sizeof(can_rx_alldev_list));
--
1.7.10.4
--
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