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  */
5 
6 #ifndef _CAN_LENGTH_H
7 #define _CAN_LENGTH_H
8 
9 /*
10  * Size of a Classical CAN Standard Frame
11  *
12  * Name of Field			Bits
13  * ---------------------------------------------------------
14  * Start-of-frame			1
15  * Identifier				11
16  * Remote transmission request (RTR)	1
17  * Identifier extension bit (IDE)	1
18  * Reserved bit (r0)			1
19  * Data length code (DLC)		4
20  * Data field				0...64
21  * CRC					15
22  * CRC delimiter			1
23  * ACK slot				1
24  * ACK delimiter			1
25  * End-of-frame (EOF)			7
26  * Inter frame spacing			3
27  *
28  * rounded up and ignoring bitstuffing
29  */
30 #define CAN_FRAME_OVERHEAD_SFF DIV_ROUND_UP(47, 8)
31 
32 /*
33  * Size of a Classical CAN Extended Frame
34  *
35  * Name of Field			Bits
36  * ---------------------------------------------------------
37  * Start-of-frame			1
38  * Identifier A				11
39  * Substitute remote request (SRR)	1
40  * Identifier extension bit (IDE)	1
41  * Identifier B				18
42  * Remote transmission request (RTR)	1
43  * Reserved bits (r1, r0)		2
44  * Data length code (DLC)		4
45  * Data field				0...64
46  * CRC					15
47  * CRC delimiter			1
48  * ACK slot				1
49  * ACK delimiter			1
50  * End-of-frame (EOF)			7
51  * Inter frame spacing			3
52  *
53  * rounded up and ignoring bitstuffing
54  */
55 #define CAN_FRAME_OVERHEAD_EFF DIV_ROUND_UP(67, 8)
56 
57 /*
58  * Size of a CAN-FD Standard Frame
59  *
60  * Name of Field			Bits
61  * ---------------------------------------------------------
62  * Start-of-frame			1
63  * Identifier				11
64  * Reserved bit (r1)			1
65  * Identifier extension bit (IDE)	1
66  * Flexible data rate format (FDF)	1
67  * Reserved bit (r0)			1
68  * Bit Rate Switch (BRS)		1
69  * Error Status Indicator (ESI)		1
70  * Data length code (DLC)		4
71  * Data field				0...512
72  * Stuff Bit Count (SBC)		0...16: 4 20...64:5
73  * CRC					0...16: 17 20...64:21
74  * CRC delimiter (CD)			1
75  * ACK slot (AS)			1
76  * ACK delimiter (AD)			1
77  * End-of-frame (EOF)			7
78  * Inter frame spacing			3
79  *
80  * assuming CRC21, rounded up and ignoring bitstuffing
81  */
82 #define CANFD_FRAME_OVERHEAD_SFF DIV_ROUND_UP(61, 8)
83 
84 /*
85  * Size of a CAN-FD Extended Frame
86  *
87  * Name of Field			Bits
88  * ---------------------------------------------------------
89  * Start-of-frame			1
90  * Identifier A				11
91  * Substitute remote request (SRR)	1
92  * Identifier extension bit (IDE)	1
93  * Identifier B				18
94  * Reserved bit (r1)			1
95  * Flexible data rate format (FDF)	1
96  * Reserved bit (r0)			1
97  * Bit Rate Switch (BRS)		1
98  * Error Status Indicator (ESI)		1
99  * Data length code (DLC)		4
100  * Data field				0...512
101  * Stuff Bit Count (SBC)		0...16: 4 20...64:5
102  * CRC					0...16: 17 20...64:21
103  * CRC delimiter (CD)			1
104  * ACK slot (AS)			1
105  * ACK delimiter (AD)			1
106  * End-of-frame (EOF)			7
107  * Inter frame spacing			3
108  *
109  * assuming CRC21, rounded up and ignoring bitstuffing
110  */
111 #define CANFD_FRAME_OVERHEAD_EFF DIV_ROUND_UP(80, 8)
112 
113 /*
114  * Maximum size of a Classical CAN frame
115  * (rounded up and ignoring bitstuffing)
116  */
117 #define CAN_FRAME_LEN_MAX (CAN_FRAME_OVERHEAD_EFF + CAN_MAX_DLEN)
118 
119 /*
120  * Maximum size of a CAN-FD frame
121  * (rounded up and ignoring bitstuffing)
122  */
123 #define CANFD_FRAME_LEN_MAX (CANFD_FRAME_OVERHEAD_EFF + CANFD_MAX_DLEN)
124 
125 /*
126  * can_cc_dlc2len(value) - convert a given data length code (dlc) of a
127  * Classical CAN frame into a valid data length of max. 8 bytes.
128  *
129  * To be used in the CAN netdriver receive path to ensure conformance with
130  * ISO 11898-1 Chapter 8.4.2.3 (DLC field)
131  */
132 #define can_cc_dlc2len(dlc)	(min_t(u8, (dlc), CAN_MAX_DLEN))
133 
134 /* helper to get the data length code (DLC) for Classical CAN raw DLC access */
can_get_cc_dlc(const struct can_frame * cf,const u32 ctrlmode)135 static inline u8 can_get_cc_dlc(const struct can_frame *cf, const u32 ctrlmode)
136 {
137 	/* return len8_dlc as dlc value only if all conditions apply */
138 	if ((ctrlmode & CAN_CTRLMODE_CC_LEN8_DLC) &&
139 	    (cf->len == CAN_MAX_DLEN) &&
140 	    (cf->len8_dlc > CAN_MAX_DLEN && cf->len8_dlc <= CAN_MAX_RAW_DLC))
141 		return cf->len8_dlc;
142 
143 	/* return the payload length as dlc value */
144 	return cf->len;
145 }
146 
147 /* helper to set len and len8_dlc value for Classical CAN raw DLC access */
can_frame_set_cc_len(struct can_frame * cf,const u8 dlc,const u32 ctrlmode)148 static inline void can_frame_set_cc_len(struct can_frame *cf, const u8 dlc,
149 					const u32 ctrlmode)
150 {
151 	/* the caller already ensured that dlc is a value from 0 .. 15 */
152 	if (ctrlmode & CAN_CTRLMODE_CC_LEN8_DLC && dlc > CAN_MAX_DLEN)
153 		cf->len8_dlc = dlc;
154 
155 	/* limit the payload length 'len' to CAN_MAX_DLEN */
156 	cf->len = can_cc_dlc2len(dlc);
157 }
158 
159 /* get data length from raw data length code (DLC) */
160 u8 can_fd_dlc2len(u8 dlc);
161 
162 /* map the sanitized data length to an appropriate data length code */
163 u8 can_fd_len2dlc(u8 len);
164 
165 /* calculate the CAN Frame length in bytes of a given skb */
166 unsigned int can_skb_get_frame_len(const struct sk_buff *skb);
167 
168 /* map the data length to an appropriate data link layer length */
canfd_sanitize_len(u8 len)169 static inline u8 canfd_sanitize_len(u8 len)
170 {
171 	return can_fd_dlc2len(can_fd_len2dlc(len));
172 }
173 
174 #endif /* !_CAN_LENGTH_H */
175