[RFC PATCH 1/5] can: canxl: introduce CAN XL data structure

[Oliver Hartkopp <socketcan@hartkopp.net>]

This patch adds defines for data structures and length information for
CAN XL (CAN with eXtended data Length) which can transfer up to 2048
byte insinde a single frame.

Notable changes from CAN FD:

- the 11 bit arbitration field is now named 'priority' instead of 'can_id'
  (there are no 29 bit identifiers nor RTR frames anymore)
- the data length needs a uint16 value to cover up to 2048 byte
  (the length element position is different to struct can[fd]_frame)
- new fields (SDT, AF) and a SEC bit have been introduced
- the virtual CAN interface identifier is not part if the CAN XL frame
  struct as this VCID value is stored in struct skbuff (analog to vlan id)

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
 include/uapi/linux/can.h | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/include/uapi/linux/can.h b/include/uapi/linux/can.h
index 90801ada2bbe..9f97a5d06f3b 100644
--- a/include/uapi/linux/can.h
+++ b/include/uapi/linux/can.h
@@ -58,10 +58,11 @@
 
 /* valid bits in CAN ID for frame formats */
 #define CAN_SFF_MASK 0x000007FFU /* standard frame format (SFF) */
 #define CAN_EFF_MASK 0x1FFFFFFFU /* extended frame format (EFF) */
 #define CAN_ERR_MASK 0x1FFFFFFFU /* omit EFF, RTR, ERR flags */
+#define CANXL_PRIO_MASK CAN_SFF_MASK /* 11 bit priority mask */
 
 /*
  * Controller Area Network Identifier structure
  *
  * bit 0-28	: CAN identifier (11/29 bit)
@@ -71,10 +72,11 @@
  */
 typedef __u32 canid_t;
 
 #define CAN_SFF_ID_BITS		11
 #define CAN_EFF_ID_BITS		29
+#define CANXL_PRIO_BITS		CAN_SFF_ID_BITS
 
 /*
  * Controller Area Network Error Message Frame Mask structure
  *
  * bit 0-28	: error class mask (see include/uapi/linux/can/error.h)
@@ -89,10 +91,18 @@ typedef __u32 can_err_mask_t;
 
 /* CAN FD payload length and DLC definitions according to ISO 11898-7 */
 #define CANFD_MAX_DLC 15
 #define CANFD_MAX_DLEN 64
 
+/*
+ * CAN XL payload length and DLC definitions according to ISO 11898-1
+ * CAN XL DLC ranges from 0 .. 2047 => data length from 1 .. 2048 byte
+ */
+#define CANXL_MAX_DLC 2047
+#define CANXL_MAX_DLC_MASK 0x07FF
+#define CANXL_MAX_DLEN 2048
+
 /**
  * struct can_frame - Classical CAN frame structure (aka CAN 2.0B)
  * @can_id:   CAN ID of the frame and CAN_*_FLAG flags, see canid_t definition
  * @len:      CAN frame payload length in byte (0 .. 8)
  * @can_dlc:  deprecated name for CAN frame payload length in byte (0 .. 8)
@@ -141,14 +151,20 @@ struct can_frame {
  * 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.
+ * Same applies to the CANXL_XLF bit.
+ *
+ * For CAN XL the SEC bit has been added to the flags field which shares the
+ * same position in struct can[fd|xl]_frame.
  */
 #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 */
+#define CANXL_XLF 0x08 /* mark CAN XL for dual use of struct canfd_frame */
+#define CANXL_SEC 0x10 /* Simple Extended Content (security/segmentation) */
 
 /**
  * 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)
@@ -164,12 +180,34 @@ struct canfd_frame {
 	__u8    __res0;  /* reserved / padding */
 	__u8    __res1;  /* reserved / padding */
 	__u8    data[CANFD_MAX_DLEN] __attribute__((aligned(8)));
 };
 
+/**
+ * struct canxl_frame - CAN with e'X'tended frame 'L'ength frame structure
+ * @prio:  11 bit arbitration priority with zero'ed CAN_*_FLAG flags
+ * @sdt:   SDU (service data unit) type
+ * @flags: additional flags for CAN XL
+ * @len:   frame payload length in byte (1 .. CANXL_MAX_DLEN)
+ * @af:    acceptance field
+ * @data:  CAN XL frame payload (up to CANXL_MAX_DLEN byte)
+ *
+ * @prio shares the same position as @can_id from struct canfd_frame.
+ * Same applies to the relative position and length of @flags.
+ */
+struct canxl_frame {
+	canid_t prio;  /* 11 bit priority for arbitration (canid_t) */
+	__u8    sdt;   /* SDU (service data unit) type */
+	__u8    flags; /* additional flags for CAN XL */
+	__u16   len;   /* frame payload length in byte */
+	__u32   af;    /* acceptance field */
+	__u8    data[CANXL_MAX_DLEN];
+};
+
 #define CAN_MTU		(sizeof(struct can_frame))
 #define CANFD_MTU	(sizeof(struct canfd_frame))
+#define CANXL_MTU	(sizeof(struct canxl_frame))
 
 /* particular protocols of the protocol family PF_CAN */
 #define CAN_RAW		1 /* RAW sockets */
 #define CAN_BCM		2 /* Broadcast Manager */
 #define CAN_TP16	3 /* VAG Transport Protocol v1.6 */
-- 
2.30.2