/* SPDX-License-Identifier: GPL-2.0 */ /* Copyright (C) 2020 Oliver Hartkopp <socketcan@hartkopp.net> * Copyright (C) 2020 Marc Kleine-Budde <kernel@pengutronix.de> * Copyright (C) 2020, 2023 Vincent Mailhol <mailhol.vincent@wanadoo.fr> */ #ifndef _CAN_LENGTH_H #define _CAN_LENGTH_H #include <linux/bits.h> #include <linux/can.h> #include <linux/can/netlink.h> #include <linux/math.h> /* * Size of a Classical CAN Standard Frame header in bits * * Name of Field Bits * --------------------------------------------------------- * Start Of Frame (SOF) 1 * Arbitration field: * base ID 11 * Remote Transmission Request (RTR) 1 * Control field: * IDentifier Extension bit (IDE) 1 * FD Format indicator (FDF) 1 * Data Length Code (DLC) 4 * * including all fields preceding the data field, ignoring bitstuffing */ #define CAN_FRAME_HEADER_SFF_BITS 19 /* * Size of a Classical CAN Extended Frame header in bits * * Name of Field Bits * --------------------------------------------------------- * Start Of Frame (SOF) 1 * Arbitration field: * base ID 11 * Substitute Remote Request (SRR) 1 * IDentifier Extension bit (IDE) 1 * ID extension 18 * Remote Transmission Request (RTR) 1 * Control field: * FD Format indicator (FDF) 1 * Reserved bit (r0) 1 * Data length code (DLC) 4 * * including all fields preceding the data field, ignoring bitstuffing */ #define CAN_FRAME_HEADER_EFF_BITS 39 /* * Size of a CAN-FD Standard Frame in bits * * Name of Field Bits * --------------------------------------------------------- * Start Of Frame (SOF) 1 * Arbitration field: * base ID 11 * Remote Request Substitution (RRS) 1 * Control field: * IDentifier Extension bit (IDE) 1 * FD Format indicator (FDF) 1 * Reserved bit (res) 1 * Bit Rate Switch (BRS) 1 * Error Status Indicator (ESI) 1 * Data length code (DLC) 4 * * including all fields preceding the data field, ignoring bitstuffing */ #define CANFD_FRAME_HEADER_SFF_BITS 22 /* * Size of a CAN-FD Extended Frame in bits * * Name of Field Bits * --------------------------------------------------------- * Start Of Frame (SOF) 1 * Arbitration field: * base ID 11 * Substitute Remote Request (SRR) 1 * IDentifier Extension bit (IDE) 1 * ID extension 18 * Remote Request Substitution (RRS) 1 * Control field: * FD Format indicator (FDF) 1 * Reserved bit (res) 1 * Bit Rate Switch (BRS) 1 * Error Status Indicator (ESI) 1 * Data length code (DLC) 4 * * including all fields preceding the data field, ignoring bitstuffing */ #define CANFD_FRAME_HEADER_EFF_BITS 41 /* * Size of a CAN CRC Field in bits * * Name of Field Bits * --------------------------------------------------------- * CRC sequence (CRC15) 15 * CRC Delimiter 1 * * ignoring bitstuffing */ #define CAN_FRAME_CRC_FIELD_BITS 16 /* * Size of a CAN-FD CRC17 Field in bits (length: 0..16) * * Name of Field Bits * --------------------------------------------------------- * Stuff Count 4 * CRC Sequence (CRC17) 17 * CRC Delimiter 1 * Fixed stuff bits 6 */ #define CANFD_FRAME_CRC17_FIELD_BITS 28 /* * Size of a CAN-FD CRC21 Field in bits (length: 20..64) * * Name of Field Bits * --------------------------------------------------------- * Stuff Count 4 * CRC sequence (CRC21) 21 * CRC Delimiter 1 * Fixed stuff bits 7 */ #define CANFD_FRAME_CRC21_FIELD_BITS 33 /* * Size of a CAN(-FD) Frame footer in bits * * Name of Field Bits * --------------------------------------------------------- * ACK slot 1 * ACK delimiter 1 * End Of Frame (EOF) 7 * * including all fields following the CRC field */ #define CAN_FRAME_FOOTER_BITS 9 /* * First part of the Inter Frame Space * (a.k.a. IMF - intermission field) */ #define CAN_INTERMISSION_BITS 3 /** * can_bitstuffing_len() - Calculate the maximum length with bitstuffing * @destuffed_len: length of a destuffed bit stream * * The worst bit stuffing case is a sequence in which dominant and * recessive bits alternate every four bits: * * Destuffed: 1 1111 0000 1111 0000 1111 * Stuffed: 1 1111o 0000i 1111o 0000i 1111o * * Nomenclature * * - "0": dominant bit * - "o": dominant stuff bit * - "1": recessive bit * - "i": recessive stuff bit * * Aside from the first bit, one stuff bit is added every four bits. * * Return: length of the stuffed bit stream in the worst case scenario. */ #define can_bitstuffing_len(destuffed_len) \ (destuffed_len + (destuffed_len - 1) / 4) #define __can_bitstuffing_len(bitstuffing, destuffed_len) \ (bitstuffing ? can_bitstuffing_len(destuffed_len) : \ destuffed_len) #define __can_cc_frame_bits(is_eff, bitstuffing, \ intermission, data_len) \ ( \ __can_bitstuffing_len(bitstuffing, \ (is_eff ? CAN_FRAME_HEADER_EFF_BITS : \ CAN_FRAME_HEADER_SFF_BITS) + \ (data_len) * BITS_PER_BYTE + \ CAN_FRAME_CRC_FIELD_BITS) + \ CAN_FRAME_FOOTER_BITS + \ (intermission ? CAN_INTERMISSION_BITS : 0) \ ) #define __can_fd_frame_bits(is_eff, bitstuffing, \ intermission, data_len) \ ( \ __can_bitstuffing_len(bitstuffing, \ (is_eff ? CANFD_FRAME_HEADER_EFF_BITS : \ CANFD_FRAME_HEADER_SFF_BITS) + \ (data_len) * BITS_PER_BYTE) + \ ((data_len) <= 16 ? \ CANFD_FRAME_CRC17_FIELD_BITS : \ CANFD_FRAME_CRC21_FIELD_BITS) + \ CAN_FRAME_FOOTER_BITS + \ (intermission ? CAN_INTERMISSION_BITS : 0) \ ) /** * can_frame_bits() - Calculate the number of bits on the wire in a * CAN frame * @is_fd: true: CAN-FD frame; false: Classical CAN frame. * @is_eff: true: Extended frame; false: Standard frame. * @bitstuffing: true: calculate the bitstuffing worst case; false: * calculate the bitstuffing best case (no dynamic * bitstuffing). CAN-FD's fixed stuff bits are always included. * @intermission: if and only if true, include the inter frame space * assuming no bus idle (i.e. only the intermission). Strictly * speaking, the inter frame space is not part of the * frame. However, it is needed when calculating the delay * between the Start Of Frame of two consecutive frames. * @data_len: length of the data field in bytes. Correspond to * can(fd)_frame->len. Should be zero for remote frames. No * sanitization is done on @data_len and it shall have no side * effects. * * Return: the numbers of bits on the wire of a CAN frame. */ #define can_frame_bits(is_fd, is_eff, bitstuffing, \ intermission, data_len) \ ( \ is_fd ? __can_fd_frame_bits(is_eff, bitstuffing, \ intermission, data_len) : \ __can_cc_frame_bits(is_eff, bitstuffing, \ intermission, data_len) \ ) /* * Number of bytes in a CAN frame * (rounded up, including intermission) */ #define can_frame_bytes(is_fd, is_eff, bitstuffing, data_len) \ DIV_ROUND_UP(can_frame_bits(is_fd, is_eff, bitstuffing, \ true, data_len), \ BITS_PER_BYTE) /* * Maximum size of a Classical CAN frame * (rounded up, ignoring bitstuffing but including intermission) */ #define CAN_FRAME_LEN_MAX can_frame_bytes(false, true, false, CAN_MAX_DLEN) /* * Maximum size of a CAN-FD frame * (rounded up, ignoring dynamic bitstuffing but including intermission) */ #define CANFD_FRAME_LEN_MAX can_frame_bytes(true, true, false, CANFD_MAX_DLEN) /* * can_cc_dlc2len(value) - convert a given data length code (dlc) of a * Classical CAN frame into a valid data length of max. 8 bytes. * * To be used in the CAN netdriver receive path to ensure conformance with * ISO 11898-1 Chapter 8.4.2.3 (DLC field) */ #define can_cc_dlc2len(dlc) (min_t(u8, (dlc), CAN_MAX_DLEN)) /* helper to get the data length code (DLC) for Classical CAN raw DLC access */ static inline u8 can_get_cc_dlc(const struct can_frame *cf, const u32 ctrlmode) { /* return len8_dlc as dlc value only if all conditions apply */ if ((ctrlmode & CAN_CTRLMODE_CC_LEN8_DLC) && (cf->len == CAN_MAX_DLEN) && (cf->len8_dlc > CAN_MAX_DLEN && cf->len8_dlc <= CAN_MAX_RAW_DLC)) return cf->len8_dlc; /* return the payload length as dlc value */ return cf->len; } /* helper to set len and len8_dlc value for Classical CAN raw DLC access */ static inline void can_frame_set_cc_len(struct can_frame *cf, const u8 dlc, const u32 ctrlmode) { /* the caller already ensured that dlc is a value from 0 .. 15 */ if (ctrlmode & CAN_CTRLMODE_CC_LEN8_DLC && dlc > CAN_MAX_DLEN) cf->len8_dlc = dlc; /* limit the payload length 'len' to CAN_MAX_DLEN */ cf->len = can_cc_dlc2len(dlc); } /* get data length from raw data length code (DLC) */ u8 can_fd_dlc2len(u8 dlc); /* map the sanitized data length to an appropriate data length code */ u8 can_fd_len2dlc(u8 len); /* calculate the CAN Frame length in bytes of a given skb */ unsigned int can_skb_get_frame_len(const struct sk_buff *skb); /* map the data length to an appropriate data link layer length */ static inline u8 canfd_sanitize_len(u8 len) { return can_fd_dlc2len(can_fd_len2dlc(len)); } #endif /* !_CAN_LENGTH_H */