1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* Copyright (C) 2020 Oliver Hartkopp <[email protected]> 3 * Copyright (C) 2020 Marc Kleine-Budde <[email protected]> 4 */ 5 6 #ifndef _CAN_LENGTH_H 7 #define _CAN_LENGTH_H 8 9 #include <linux/can.h> 10 #include <linux/can/netlink.h> 11 12 /* 13 * Size of a Classical CAN Standard Frame 14 * 15 * Name of Field Bits 16 * --------------------------------------------------------- 17 * Start-of-frame 1 18 * Identifier 11 19 * Remote transmission request (RTR) 1 20 * Identifier extension bit (IDE) 1 21 * Reserved bit (r0) 1 22 * Data length code (DLC) 4 23 * Data field 0...64 24 * CRC 15 25 * CRC delimiter 1 26 * ACK slot 1 27 * ACK delimiter 1 28 * End-of-frame (EOF) 7 29 * Inter frame spacing 3 30 * 31 * rounded up and ignoring bitstuffing 32 */ 33 #define CAN_FRAME_OVERHEAD_SFF DIV_ROUND_UP(47, 8) 34 35 /* 36 * Size of a Classical CAN Extended Frame 37 * 38 * Name of Field Bits 39 * --------------------------------------------------------- 40 * Start-of-frame 1 41 * Identifier A 11 42 * Substitute remote request (SRR) 1 43 * Identifier extension bit (IDE) 1 44 * Identifier B 18 45 * Remote transmission request (RTR) 1 46 * Reserved bits (r1, r0) 2 47 * Data length code (DLC) 4 48 * Data field 0...64 49 * CRC 15 50 * CRC delimiter 1 51 * ACK slot 1 52 * ACK delimiter 1 53 * End-of-frame (EOF) 7 54 * Inter frame spacing 3 55 * 56 * rounded up and ignoring bitstuffing 57 */ 58 #define CAN_FRAME_OVERHEAD_EFF DIV_ROUND_UP(67, 8) 59 60 /* 61 * Size of a CAN-FD Standard Frame 62 * 63 * Name of Field Bits 64 * --------------------------------------------------------- 65 * Start-of-frame 1 66 * Identifier 11 67 * Reserved bit (r1) 1 68 * Identifier extension bit (IDE) 1 69 * Flexible data rate format (FDF) 1 70 * Reserved bit (r0) 1 71 * Bit Rate Switch (BRS) 1 72 * Error Status Indicator (ESI) 1 73 * Data length code (DLC) 4 74 * Data field 0...512 75 * Stuff Bit Count (SBC) 0...16: 4 20...64:5 76 * CRC 0...16: 17 20...64:21 77 * CRC delimiter (CD) 1 78 * ACK slot (AS) 1 79 * ACK delimiter (AD) 1 80 * End-of-frame (EOF) 7 81 * Inter frame spacing 3 82 * 83 * assuming CRC21, rounded up and ignoring bitstuffing 84 */ 85 #define CANFD_FRAME_OVERHEAD_SFF DIV_ROUND_UP(61, 8) 86 87 /* 88 * Size of a CAN-FD Extended Frame 89 * 90 * Name of Field Bits 91 * --------------------------------------------------------- 92 * Start-of-frame 1 93 * Identifier A 11 94 * Substitute remote request (SRR) 1 95 * Identifier extension bit (IDE) 1 96 * Identifier B 18 97 * Reserved bit (r1) 1 98 * Flexible data rate format (FDF) 1 99 * Reserved bit (r0) 1 100 * Bit Rate Switch (BRS) 1 101 * Error Status Indicator (ESI) 1 102 * Data length code (DLC) 4 103 * Data field 0...512 104 * Stuff Bit Count (SBC) 0...16: 4 20...64:5 105 * CRC 0...16: 17 20...64:21 106 * CRC delimiter (CD) 1 107 * ACK slot (AS) 1 108 * ACK delimiter (AD) 1 109 * End-of-frame (EOF) 7 110 * Inter frame spacing 3 111 * 112 * assuming CRC21, rounded up and ignoring bitstuffing 113 */ 114 #define CANFD_FRAME_OVERHEAD_EFF DIV_ROUND_UP(80, 8) 115 116 /* 117 * Maximum size of a Classical CAN frame 118 * (rounded up and ignoring bitstuffing) 119 */ 120 #define CAN_FRAME_LEN_MAX (CAN_FRAME_OVERHEAD_EFF + CAN_MAX_DLEN) 121 122 /* 123 * Maximum size of a CAN-FD frame 124 * (rounded up and ignoring bitstuffing) 125 */ 126 #define CANFD_FRAME_LEN_MAX (CANFD_FRAME_OVERHEAD_EFF + CANFD_MAX_DLEN) 127 128 /* 129 * can_cc_dlc2len(value) - convert a given data length code (dlc) of a 130 * Classical CAN frame into a valid data length of max. 8 bytes. 131 * 132 * To be used in the CAN netdriver receive path to ensure conformance with 133 * ISO 11898-1 Chapter 8.4.2.3 (DLC field) 134 */ 135 #define can_cc_dlc2len(dlc) (min_t(u8, (dlc), CAN_MAX_DLEN)) 136 137 /* helper to get the data length code (DLC) for Classical CAN raw DLC access */ 138 static inline u8 can_get_cc_dlc(const struct can_frame *cf, const u32 ctrlmode) 139 { 140 /* return len8_dlc as dlc value only if all conditions apply */ 141 if ((ctrlmode & CAN_CTRLMODE_CC_LEN8_DLC) && 142 (cf->len == CAN_MAX_DLEN) && 143 (cf->len8_dlc > CAN_MAX_DLEN && cf->len8_dlc <= CAN_MAX_RAW_DLC)) 144 return cf->len8_dlc; 145 146 /* return the payload length as dlc value */ 147 return cf->len; 148 } 149 150 /* helper to set len and len8_dlc value for Classical CAN raw DLC access */ 151 static inline void can_frame_set_cc_len(struct can_frame *cf, const u8 dlc, 152 const u32 ctrlmode) 153 { 154 /* the caller already ensured that dlc is a value from 0 .. 15 */ 155 if (ctrlmode & CAN_CTRLMODE_CC_LEN8_DLC && dlc > CAN_MAX_DLEN) 156 cf->len8_dlc = dlc; 157 158 /* limit the payload length 'len' to CAN_MAX_DLEN */ 159 cf->len = can_cc_dlc2len(dlc); 160 } 161 162 /* get data length from raw data length code (DLC) */ 163 u8 can_fd_dlc2len(u8 dlc); 164 165 /* map the sanitized data length to an appropriate data length code */ 166 u8 can_fd_len2dlc(u8 len); 167 168 /* calculate the CAN Frame length in bytes of a given skb */ 169 unsigned int can_skb_get_frame_len(const struct sk_buff *skb); 170 171 /* map the data length to an appropriate data link layer length */ 172 static inline u8 canfd_sanitize_len(u8 len) 173 { 174 return can_fd_dlc2len(can_fd_len2dlc(len)); 175 } 176 177 #endif /* !_CAN_LENGTH_H */ 178