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Diffstat (limited to 'include/linux/can/length.h')
| -rw-r--r-- | include/linux/can/length.h | 306 |
1 files changed, 306 insertions, 0 deletions
diff --git a/include/linux/can/length.h b/include/linux/can/length.h new file mode 100644 index 000000000..abc978b38 --- /dev/null +++ b/include/linux/can/length.h @@ -0,0 +1,306 @@ +/* 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 */ |