From: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx> Introduce a method to calculate the exact size in bits of a CAN(-FD) frame with or without dynamic bitstuffing. These are all the possible combinations taken into account: - Classical CAN or CAN-FD - Standard or Extended frame format - CAN-FD CRC17 or CRC21 - Include or not intermission Instead of doing several individual macro definitions, declare the can_frame_bits() function-like macro. To this extent, do a full refactoring of the length definitions. In addition add the can_frame_bytes(). This function-like macro replaces the existing macro: - CAN_FRAME_OVERHEAD_SFF: can_frame_bytes(false, false, 0) - CAN_FRAME_OVERHEAD_EFF: can_frame_bytes(false, true, 0) - CANFD_FRAME_OVERHEAD_SFF: can_frame_bytes(true, false, 0) - CANFD_FRAME_OVERHEAD_EFF: can_frame_bytes(true, true, 0) Function-like macros were chosen over inline functions because they can be used to initialize const struct fields. The different maximum frame lengths (maximum data length, including intermission) are as follow: Frame type bits bytes ------------------------------------------------------- Classic CAN SFF no bitstuffing 111 14 Classic CAN EFF no bitstuffing 131 17 Classic CAN SFF bitstuffing 135 17 Classic CAN EFF bitstuffing 160 20 CAN-FD SFF no bitstuffing 579 73 CAN-FD EFF no bitstuffing 598 75 CAN-FD SFF bitstuffing 712 89 CAN-FD EFF bitstuffing 736 92 The macro CAN_FRAME_LEN_MAX and CANFD_FRAME_LEN_MAX are kept as an alias to, respectively, can_frame_bytes(false, true, CAN_MAX_DLEN) and can_frame_bytes(true, true, CANFD_MAX_DLEN). In addition to the above: - Use ISO 11898-1:2015 definitions for the names of the CAN frame fields. - Include linux/bits.h for use of BITS_PER_BYTE. - Include linux/math.h for use of mult_frac() and DIV_ROUND_UP(). N.B: the use of DIV_ROUND_UP() is not new to this patch, but the include was previously omitted. - Add copyright 2023 for myself. Suggested-by: Thomas Kopp <Thomas.Kopp@xxxxxxxxxxxxx> Signed-off-by: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx> Reviewed-by: Thomas Kopp <Thomas.Kopp@xxxxxxxxxxxxx> Link: https://lore.kernel.org/all/20230611025728.450837-4-mailhol.vincent@xxxxxxxxxx Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> --- drivers/net/can/dev/length.c | 15 +- include/linux/can/length.h | 318 ++++++++++++++++++++++++----------- 2 files changed, 224 insertions(+), 109 deletions(-) diff --git a/drivers/net/can/dev/length.c b/drivers/net/can/dev/length.c index b48140b1102e..b7f4d76dd444 100644 --- a/drivers/net/can/dev/length.c +++ b/drivers/net/can/dev/length.c @@ -78,18 +78,7 @@ unsigned int can_skb_get_frame_len(const struct sk_buff *skb) else len = cf->len; - if (can_is_canfd_skb(skb)) { - if (cf->can_id & CAN_EFF_FLAG) - len += CANFD_FRAME_OVERHEAD_EFF; - else - len += CANFD_FRAME_OVERHEAD_SFF; - } else { - if (cf->can_id & CAN_EFF_FLAG) - len += CAN_FRAME_OVERHEAD_EFF; - else - len += CAN_FRAME_OVERHEAD_SFF; - } - - return len; + return can_frame_bytes(can_is_canfd_skb(skb), cf->can_id & CAN_EFF_FLAG, + false, len); } EXPORT_SYMBOL_GPL(can_skb_get_frame_len); diff --git a/include/linux/can/length.h b/include/linux/can/length.h index 521fdbce2d69..abc978b38f79 100644 --- a/include/linux/can/length.h +++ b/include/linux/can/length.h @@ -1,132 +1,258 @@ /* SPDX-License-Identifier: GPL-2.0 */ /* Copyright (C) 2020 Oliver Hartkopp <socketcan@xxxxxxxxxxxx> * Copyright (C) 2020 Marc Kleine-Budde <kernel@xxxxxxxxxxxxxx> - * Copyright (C) 2020 Vincent Mailhol <mailhol.vincent@xxxxxxxxxx> + * Copyright (C) 2020, 2023 Vincent Mailhol <mailhol.vincent@xxxxxxxxxx> */ #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 + * 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 * --------------------------------------------------------- - * Start-of-frame 1 - * Identifier 11 - * Remote transmission request (RTR) 1 - * Identifier extension bit (IDE) 1 - * Reserved bit (r0) 1 - * Data length code (DLC) 4 - * Data field 0...64 - * CRC 15 - * CRC delimiter 1 * ACK slot 1 * ACK delimiter 1 - * End-of-frame (EOF) 7 - * Inter frame spacing 3 + * End Of Frame (EOF) 7 * - * rounded up and ignoring bitstuffing + * including all fields following the CRC field */ -#define CAN_FRAME_OVERHEAD_SFF DIV_ROUND_UP(47, 8) +#define CAN_FRAME_FOOTER_BITS 9 /* - * Size of a Classical CAN Extended Frame - * - * Name of Field Bits - * --------------------------------------------------------- - * Start-of-frame 1 - * Identifier A 11 - * Substitute remote request (SRR) 1 - * Identifier extension bit (IDE) 1 - * Identifier B 18 - * Remote transmission request (RTR) 1 - * Reserved bits (r1, r0) 2 - * Data length code (DLC) 4 - * Data field 0...64 - * CRC 15 - * CRC delimiter 1 - * ACK slot 1 - * ACK delimiter 1 - * End-of-frame (EOF) 7 - * Inter frame spacing 3 - * - * rounded up and ignoring bitstuffing + * First part of the Inter Frame Space + * (a.k.a. IMF - intermission field) */ -#define CAN_FRAME_OVERHEAD_EFF DIV_ROUND_UP(67, 8) +#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) \ +) /* - * Size of a CAN-FD Standard Frame - * - * Name of Field Bits - * --------------------------------------------------------- - * Start-of-frame 1 - * Identifier 11 - * Remote Request Substitution (RRS) 1 - * Identifier extension bit (IDE) 1 - * Flexible data rate format (FDF) 1 - * Reserved bit (r0) 1 - * Bit Rate Switch (BRS) 1 - * Error Status Indicator (ESI) 1 - * Data length code (DLC) 4 - * Data field 0...512 - * Stuff Bit Count (SBC) 4 - * CRC 0...16: 17 20...64:21 - * CRC delimiter (CD) 1 - * Fixed Stuff bits (FSB) 0...16: 6 20...64:7 - * ACK slot (AS) 1 - * ACK delimiter (AD) 1 - * End-of-frame (EOF) 7 - * Inter frame spacing 3 - * - * assuming CRC21, rounded up and ignoring dynamic bitstuffing + * Number of bytes in a CAN frame + * (rounded up, including intermission) */ -#define CANFD_FRAME_OVERHEAD_SFF DIV_ROUND_UP(67, 8) - -/* - * Size of a CAN-FD Extended Frame - * - * Name of Field Bits - * --------------------------------------------------------- - * Start-of-frame 1 - * Identifier A 11 - * Substitute remote request (SRR) 1 - * Identifier extension bit (IDE) 1 - * Identifier B 18 - * Remote Request Substitution (RRS) 1 - * Flexible data rate format (FDF) 1 - * Reserved bit (r0) 1 - * Bit Rate Switch (BRS) 1 - * Error Status Indicator (ESI) 1 - * Data length code (DLC) 4 - * Data field 0...512 - * Stuff Bit Count (SBC) 4 - * CRC 0...16: 17 20...64:21 - * CRC delimiter (CD) 1 - * Fixed Stuff bits (FSB) 0...16: 6 20...64:7 - * ACK slot (AS) 1 - * ACK delimiter (AD) 1 - * End-of-frame (EOF) 7 - * Inter frame spacing 3 - * - * assuming CRC21, rounded up and ignoring dynamic bitstuffing - */ -#define CANFD_FRAME_OVERHEAD_EFF DIV_ROUND_UP(86, 8) +#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 and ignoring bitstuffing) + * (rounded up, ignoring bitstuffing but including intermission) */ -#define CAN_FRAME_LEN_MAX (CAN_FRAME_OVERHEAD_EFF + CAN_MAX_DLEN) +#define CAN_FRAME_LEN_MAX can_frame_bytes(false, true, false, CAN_MAX_DLEN) /* * Maximum size of a CAN-FD frame - * (rounded up and ignoring bitstuffing) + * (rounded up, ignoring dynamic bitstuffing but including intermission) */ -#define CANFD_FRAME_LEN_MAX (CANFD_FRAME_OVERHEAD_EFF + CANFD_MAX_DLEN) +#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 -- 2.40.1
