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1/* SPDX-License-Identifier: GPL-2.0 */2/* Copyright (C) 2020 Oliver Hartkopp <socketcan@hartkopp.net>3 * Copyright (C) 2020 Marc Kleine-Budde <kernel@pengutronix.de>4 * Copyright (C) 2020, 2023 Vincent Mailhol <mailhol.vincent@wanadoo.fr>5 */6 7#ifndef _CAN_LENGTH_H8#define _CAN_LENGTH_H9 10#include <linux/bits.h>11#include <linux/can.h>12#include <linux/can/netlink.h>13#include <linux/math.h>14 15/*16 * Size of a Classical CAN Standard Frame header in bits17 *18 * Name of Field Bits19 * ---------------------------------------------------------20 * Start Of Frame (SOF) 121 * Arbitration field:22 * base ID 1123 * Remote Transmission Request (RTR) 124 * Control field:25 * IDentifier Extension bit (IDE) 126 * FD Format indicator (FDF) 127 * Data Length Code (DLC) 428 *29 * including all fields preceding the data field, ignoring bitstuffing30 */31#define CAN_FRAME_HEADER_SFF_BITS 1932 33/*34 * Size of a Classical CAN Extended Frame header in bits35 *36 * Name of Field Bits37 * ---------------------------------------------------------38 * Start Of Frame (SOF) 139 * Arbitration field:40 * base ID 1141 * Substitute Remote Request (SRR) 142 * IDentifier Extension bit (IDE) 143 * ID extension 1844 * Remote Transmission Request (RTR) 145 * Control field:46 * FD Format indicator (FDF) 147 * Reserved bit (r0) 148 * Data length code (DLC) 449 *50 * including all fields preceding the data field, ignoring bitstuffing51 */52#define CAN_FRAME_HEADER_EFF_BITS 3953 54/*55 * Size of a CAN-FD Standard Frame in bits56 *57 * Name of Field Bits58 * ---------------------------------------------------------59 * Start Of Frame (SOF) 160 * Arbitration field:61 * base ID 1162 * Remote Request Substitution (RRS) 163 * Control field:64 * IDentifier Extension bit (IDE) 165 * FD Format indicator (FDF) 166 * Reserved bit (res) 167 * Bit Rate Switch (BRS) 168 * Error Status Indicator (ESI) 169 * Data length code (DLC) 470 *71 * including all fields preceding the data field, ignoring bitstuffing72 */73#define CANFD_FRAME_HEADER_SFF_BITS 2274 75/*76 * Size of a CAN-FD Extended Frame in bits77 *78 * Name of Field Bits79 * ---------------------------------------------------------80 * Start Of Frame (SOF) 181 * Arbitration field:82 * base ID 1183 * Substitute Remote Request (SRR) 184 * IDentifier Extension bit (IDE) 185 * ID extension 1886 * Remote Request Substitution (RRS) 187 * Control field:88 * FD Format indicator (FDF) 189 * Reserved bit (res) 190 * Bit Rate Switch (BRS) 191 * Error Status Indicator (ESI) 192 * Data length code (DLC) 493 *94 * including all fields preceding the data field, ignoring bitstuffing95 */96#define CANFD_FRAME_HEADER_EFF_BITS 4197 98/*99 * Size of a CAN CRC Field in bits100 *101 * Name of Field Bits102 * ---------------------------------------------------------103 * CRC sequence (CRC15) 15104 * CRC Delimiter 1105 *106 * ignoring bitstuffing107 */108#define CAN_FRAME_CRC_FIELD_BITS 16109 110/*111 * Size of a CAN-FD CRC17 Field in bits (length: 0..16)112 *113 * Name of Field Bits114 * ---------------------------------------------------------115 * Stuff Count 4116 * CRC Sequence (CRC17) 17117 * CRC Delimiter 1118 * Fixed stuff bits 6119 */120#define CANFD_FRAME_CRC17_FIELD_BITS 28121 122/*123 * Size of a CAN-FD CRC21 Field in bits (length: 20..64)124 *125 * Name of Field Bits126 * ---------------------------------------------------------127 * Stuff Count 4128 * CRC sequence (CRC21) 21129 * CRC Delimiter 1130 * Fixed stuff bits 7131 */132#define CANFD_FRAME_CRC21_FIELD_BITS 33133 134/*135 * Size of a CAN(-FD) Frame footer in bits136 *137 * Name of Field Bits138 * ---------------------------------------------------------139 * ACK slot 1140 * ACK delimiter 1141 * End Of Frame (EOF) 7142 *143 * including all fields following the CRC field144 */145#define CAN_FRAME_FOOTER_BITS 9146 147/*148 * First part of the Inter Frame Space149 * (a.k.a. IMF - intermission field)150 */151#define CAN_INTERMISSION_BITS 3152 153/**154 * can_bitstuffing_len() - Calculate the maximum length with bitstuffing155 * @destuffed_len: length of a destuffed bit stream156 *157 * The worst bit stuffing case is a sequence in which dominant and158 * recessive bits alternate every four bits:159 *160 * Destuffed: 1 1111 0000 1111 0000 1111161 * Stuffed: 1 1111o 0000i 1111o 0000i 1111o162 *163 * Nomenclature164 *165 * - "0": dominant bit166 * - "o": dominant stuff bit167 * - "1": recessive bit168 * - "i": recessive stuff bit169 *170 * Aside from the first bit, one stuff bit is added every four bits.171 *172 * Return: length of the stuffed bit stream in the worst case scenario.173 */174#define can_bitstuffing_len(destuffed_len) \175 (destuffed_len + (destuffed_len - 1) / 4)176 177#define __can_bitstuffing_len(bitstuffing, destuffed_len) \178 (bitstuffing ? can_bitstuffing_len(destuffed_len) : \179 destuffed_len)180 181#define __can_cc_frame_bits(is_eff, bitstuffing, \182 intermission, data_len) \183( \184 __can_bitstuffing_len(bitstuffing, \185 (is_eff ? CAN_FRAME_HEADER_EFF_BITS : \186 CAN_FRAME_HEADER_SFF_BITS) + \187 (data_len) * BITS_PER_BYTE + \188 CAN_FRAME_CRC_FIELD_BITS) + \189 CAN_FRAME_FOOTER_BITS + \190 (intermission ? CAN_INTERMISSION_BITS : 0) \191)192 193#define __can_fd_frame_bits(is_eff, bitstuffing, \194 intermission, data_len) \195( \196 __can_bitstuffing_len(bitstuffing, \197 (is_eff ? CANFD_FRAME_HEADER_EFF_BITS : \198 CANFD_FRAME_HEADER_SFF_BITS) + \199 (data_len) * BITS_PER_BYTE) + \200 ((data_len) <= 16 ? \201 CANFD_FRAME_CRC17_FIELD_BITS : \202 CANFD_FRAME_CRC21_FIELD_BITS) + \203 CAN_FRAME_FOOTER_BITS + \204 (intermission ? CAN_INTERMISSION_BITS : 0) \205)206 207/**208 * can_frame_bits() - Calculate the number of bits on the wire in a209 * CAN frame210 * @is_fd: true: CAN-FD frame; false: Classical CAN frame.211 * @is_eff: true: Extended frame; false: Standard frame.212 * @bitstuffing: true: calculate the bitstuffing worst case; false:213 * calculate the bitstuffing best case (no dynamic214 * bitstuffing). CAN-FD's fixed stuff bits are always included.215 * @intermission: if and only if true, include the inter frame space216 * assuming no bus idle (i.e. only the intermission). Strictly217 * speaking, the inter frame space is not part of the218 * frame. However, it is needed when calculating the delay219 * between the Start Of Frame of two consecutive frames.220 * @data_len: length of the data field in bytes. Correspond to221 * can(fd)_frame->len. Should be zero for remote frames. No222 * sanitization is done on @data_len and it shall have no side223 * effects.224 *225 * Return: the numbers of bits on the wire of a CAN frame.226 */227#define can_frame_bits(is_fd, is_eff, bitstuffing, \228 intermission, data_len) \229( \230 is_fd ? __can_fd_frame_bits(is_eff, bitstuffing, \231 intermission, data_len) : \232 __can_cc_frame_bits(is_eff, bitstuffing, \233 intermission, data_len) \234)235 236/*237 * Number of bytes in a CAN frame238 * (rounded up, including intermission)239 */240#define can_frame_bytes(is_fd, is_eff, bitstuffing, data_len) \241 DIV_ROUND_UP(can_frame_bits(is_fd, is_eff, bitstuffing, \242 true, data_len), \243 BITS_PER_BYTE)244 245/*246 * Maximum size of a Classical CAN frame247 * (rounded up, ignoring bitstuffing but including intermission)248 */249#define CAN_FRAME_LEN_MAX can_frame_bytes(false, true, false, CAN_MAX_DLEN)250 251/*252 * Maximum size of a CAN-FD frame253 * (rounded up, ignoring dynamic bitstuffing but including intermission)254 */255#define CANFD_FRAME_LEN_MAX can_frame_bytes(true, true, false, CANFD_MAX_DLEN)256 257/*258 * can_cc_dlc2len(value) - convert a given data length code (dlc) of a259 * Classical CAN frame into a valid data length of max. 8 bytes.260 *261 * To be used in the CAN netdriver receive path to ensure conformance with262 * ISO 11898-1 Chapter 8.4.2.3 (DLC field)263 */264#define can_cc_dlc2len(dlc) (min_t(u8, (dlc), CAN_MAX_DLEN))265 266/* helper to get the data length code (DLC) for Classical CAN raw DLC access */267static inline u8 can_get_cc_dlc(const struct can_frame *cf, const u32 ctrlmode)268{269 /* return len8_dlc as dlc value only if all conditions apply */270 if ((ctrlmode & CAN_CTRLMODE_CC_LEN8_DLC) &&271 (cf->len == CAN_MAX_DLEN) &&272 (cf->len8_dlc > CAN_MAX_DLEN && cf->len8_dlc <= CAN_MAX_RAW_DLC))273 return cf->len8_dlc;274 275 /* return the payload length as dlc value */276 return cf->len;277}278 279/* helper to set len and len8_dlc value for Classical CAN raw DLC access */280static inline void can_frame_set_cc_len(struct can_frame *cf, const u8 dlc,281 const u32 ctrlmode)282{283 /* the caller already ensured that dlc is a value from 0 .. 15 */284 if (ctrlmode & CAN_CTRLMODE_CC_LEN8_DLC && dlc > CAN_MAX_DLEN)285 cf->len8_dlc = dlc;286 287 /* limit the payload length 'len' to CAN_MAX_DLEN */288 cf->len = can_cc_dlc2len(dlc);289}290 291/* get data length from raw data length code (DLC) */292u8 can_fd_dlc2len(u8 dlc);293 294/* map the sanitized data length to an appropriate data length code */295u8 can_fd_len2dlc(u8 len);296 297/* calculate the CAN Frame length in bytes of a given skb */298unsigned int can_skb_get_frame_len(const struct sk_buff *skb);299 300/* map the data length to an appropriate data link layer length */301static inline u8 canfd_sanitize_len(u8 len)302{303 return can_fd_dlc2len(can_fd_len2dlc(len));304}305 306#endif /* !_CAN_LENGTH_H */307