include/linux/can/length.h - kernel/common - Git at Google

 /* SPDX-License-Identifier: GPL-2.0 */
 /* Copyright (C) 2020 Oliver Hartkopp <[email protected]>
  * Copyright (C) 2020 Marc Kleine-Budde <[email protected]>
  * Copyright (C) 2020, 2023 Vincent Mailhol <[email protected]>
  */

 #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 */
	/* SPDX-License-Identifier: GPL-2.0 */
	/* Copyright (C) 2020 Oliver Hartkopp <[email protected]>
	* Copyright (C) 2020 Marc Kleine-Budde <[email protected]>
	* Copyright (C) 2020, 2023 Vincent Mailhol <[email protected]>
	*/

	#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 */