ISO 11898-1 Chapter 8.4.2.3 defines a 4 bit data length code (DLC) table which maps the DLC to the payload length of the CAN frame in bytes: DLC -> payload length 0 .. 8 -> 0 .. 8 9 .. 15 -> 8 Although the DLC values 8 .. 15 in Classical CAN always result in a payload length of 8 bytes these DLC values are transparently transmitted on the CAN bus. As the struct can_frame only provides a 'len' element (formerly 'can_dlc') which contains the plain payload length ( 0 .. 8 ) of the CAN frame, the raw DLC is not visible to the application programmer, e.g. for testing use-cases. To access the raw DLC values 9 .. 15 the len8_dlc element is introduced, which is only valid when the payload length 'len' is 8 and the DLC is greater than 8. The len8_dlc element is filled by the CAN interface driver and used for CAN frame creation by the CAN driver when the CAN_CTRLMODE_CC_LEN8_DLC flag is supported by the driver and enabled via netlink configuration interface.
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| @@ -84,6 +84,7 @@ typedef __u32 can_err_mask_t; · 83 unmodified lines | ||
| 84 | 84 | |
| 85 | 85 | /* CAN payload length and DLC definitions according to ISO 11898-1 */ |
| 86 | 86 | #define CAN_MAX_DLC 8 |
| 87 | +#define CAN_MAX_RAW_DLC 15 | |
| 87 | 88 | #define CAN_MAX_DLEN 8 |
| 88 | 89 | |
| 89 | 90 | /* CAN FD payload length and DLC definitions according to ISO 11898-7 */ |
| @@ -91,23 +92,32 @@ typedef __u32 can_err_mask_t; · 1 unmodified line | ||
| 91 | 92 | #define CANFD_MAX_DLEN 64 |
| 92 | 93 | |
| 93 | 94 | /** |
| 94 | − * struct can_frame - basic CAN frame structure | |
| 95 | − * @can_id: CAN ID of the frame and CAN_*_FLAG flags, see canid_t definition | |
| 96 | − * @can_dlc: frame payload length in byte (0 .. 8) aka data length code | |
| 97 | − * N.B. the DLC field from ISO 11898-1 Chapter 8.4.2.3 has a 1:1 | |
| 98 | − * mapping of the 'data length code' to the real payload length | |
| 99 | − * @__pad: padding | |
| 100 | − * @__res0: reserved / padding | |
| 101 | − * @__res1: reserved / padding | |
| 102 | − * @data: CAN frame payload (up to 8 byte) | |
| 95 | + * struct can_frame - Classical CAN frame structure (aka CAN 2.0B) | |
| 96 | + * @can_id: CAN ID of the frame and CAN_*_FLAG flags, see canid_t definition | |
| 97 | + * @len: CAN frame payload length in byte (0 .. 8) | |
| 98 | + * @can_dlc: deprecated name for CAN frame payload length in byte (0 .. 8) | |
| 99 | + * @__pad: padding | |
| 100 | + * @__res0: reserved / padding | |
| 101 | + * @len8_dlc: optional DLC value (9 .. 15) at 8 byte payload length | |
| 102 | + * len8_dlc contains values from 9 .. 15 when the payload length is | |
| 103 | + * 8 bytes but the DLC value (see ISO 11898-1) is greater then 8. | |
| 104 | + * CAN_CTRLMODE_CC_LEN8_DLC flag has to be enabled in CAN driver. | |
| 105 | + * @data: CAN frame payload (up to 8 byte) | |
| 103 | 106 | */ |
| 104 | 107 | struct can_frame { |
| 105 | 108 | canid_t can_id; /* 32 bit CAN_ID + EFF/RTR/ERR flags */ |
| 106 | − __u8 can_dlc; /* frame payload length in byte (0 .. CAN_MAX_DLEN) */ | |
| 107 | − __u8 __pad; /* padding */ | |
| 108 | − __u8 __res0; /* reserved / padding */ | |
| 109 | − __u8 __res1; /* reserved / padding */ | |
| 110 | − __u8 data[CAN_MAX_DLEN] __attribute__((aligned(8))); | |
| 109 | + union { | |
| 110 | + /* CAN frame payload length in byte (0 .. CAN_MAX_DLEN) | |
| 111 | + * was previously named can_dlc so we need to carry that | |
| 112 | + * name for legacy support | |
| 113 | + */ | |
| 114 | + __u8 len; | |
| 115 | + __u8 can_dlc; /* deprecated */ | |
| 116 | + }; | |
| 117 | + __u8 __pad; /* padding */ | |
| 118 | + __u8 __res0; /* reserved / padding */ | |
| 119 | + __u8 len8_dlc; /* optional DLC for 8 byte payload length (9 .. 15) */ | |
| 120 | + __u8 data[CAN_MAX_DLEN] __attribute__((aligned(8))); | |
| 111 | 121 | }; |
| 112 | 122 | |
| 113 | 123 | /* |
| @@ -100,6 +100,7 @@ struct can_ctrlmode { · 99 unmodified lines | ||
| 100 | 100 | #define CAN_CTRLMODE_FD 0x20 /* CAN FD mode */ |
| 101 | 101 | #define CAN_CTRLMODE_PRESUME_ACK 0x40 /* Ignore missing CAN ACKs */ |
| 102 | 102 | #define CAN_CTRLMODE_FD_NON_ISO 0x80 /* CAN FD in non-ISO mode */ |
| 103 | +#define CAN_CTRLMODE_CC_LEN8_DLC 0x100 /* Classic CAN DLC option */ | |
| 103 | 104 | |
| 104 | 105 | /* |
| 105 | 106 | * CAN device statistics |