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 * Copyright (C) 2020, 2023 Vincent Mailhol <mailhol.vincent@wanadoo.fr>
5 */
6
7 #ifndef _CAN_LENGTH_H
8 #define _CAN_LENGTH_H
9
10 #include <linux/bits.h>
11 #include <linux/can.h>
12 #include <linux/can/netlink.h>
13 #include <linux/math.h>
14
15 /*
16 * Size of a Classical CAN Standard Frame header in bits
17 *
18 * Name of Field Bits
19 * ---------------------------------------------------------
20 * Start Of Frame (SOF) 1
21 * Arbitration field:
22 * base ID 11
23 * Remote Transmission Request (RTR) 1
24 * Control field:
25 * IDentifier Extension bit (IDE) 1
26 * FD Format indicator (FDF) 1
27 * Data Length Code (DLC) 4
28 *
29 * including all fields preceding the data field, ignoring bitstuffing
30 */
31 #define CAN_FRAME_HEADER_SFF_BITS 19
32
33 /*
34 * Size of a Classical CAN Extended Frame header in bits
35 *
36 * Name of Field Bits
37 * ---------------------------------------------------------
38 * Start Of Frame (SOF) 1
39 * Arbitration field:
40 * base ID 11
41 * Substitute Remote Request (SRR) 1
42 * IDentifier Extension bit (IDE) 1
43 * ID extension 18
44 * Remote Transmission Request (RTR) 1
45 * Control field:
46 * FD Format indicator (FDF) 1
47 * Reserved bit (r0) 1
48 * Data length code (DLC) 4
49 *
50 * including all fields preceding the data field, ignoring bitstuffing
51 */
52 #define CAN_FRAME_HEADER_EFF_BITS 39
53
54 /*
55 * Size of a CAN-FD Standard Frame in bits
56 *
57 * Name of Field Bits
58 * ---------------------------------------------------------
59 * Start Of Frame (SOF) 1
60 * Arbitration field:
61 * base ID 11
62 * Remote Request Substitution (RRS) 1
63 * Control field:
64 * IDentifier Extension bit (IDE) 1
65 * FD Format indicator (FDF) 1
66 * Reserved bit (res) 1
67 * Bit Rate Switch (BRS) 1
68 * Error Status Indicator (ESI) 1
69 * Data length code (DLC) 4
70 *
71 * including all fields preceding the data field, ignoring bitstuffing
72 */
73 #define CANFD_FRAME_HEADER_SFF_BITS 22
74
75 /*
76 * Size of a CAN-FD Extended Frame in bits
77 *
78 * Name of Field Bits
79 * ---------------------------------------------------------
80 * Start Of Frame (SOF) 1
81 * Arbitration field:
82 * base ID 11
83 * Substitute Remote Request (SRR) 1
84 * IDentifier Extension bit (IDE) 1
85 * ID extension 18
86 * Remote Request Substitution (RRS) 1
87 * Control field:
88 * FD Format indicator (FDF) 1
89 * Reserved bit (res) 1
90 * Bit Rate Switch (BRS) 1
91 * Error Status Indicator (ESI) 1
92 * Data length code (DLC) 4
93 *
94 * including all fields preceding the data field, ignoring bitstuffing
95 */
96 #define CANFD_FRAME_HEADER_EFF_BITS 41
97
98 /*
99 * Size of a CAN CRC Field in bits
100 *
101 * Name of Field Bits
102 * ---------------------------------------------------------
103 * CRC sequence (CRC15) 15
104 * CRC Delimiter 1
105 *
106 * ignoring bitstuffing
107 */
108 #define CAN_FRAME_CRC_FIELD_BITS 16
109
110 /*
111 * Size of a CAN-FD CRC17 Field in bits (length: 0..16)
112 *
113 * Name of Field Bits
114 * ---------------------------------------------------------
115 * Stuff Count 4
116 * CRC Sequence (CRC17) 17
117 * CRC Delimiter 1
118 * Fixed stuff bits 6
119 */
120 #define CANFD_FRAME_CRC17_FIELD_BITS 28
121
122 /*
123 * Size of a CAN-FD CRC21 Field in bits (length: 20..64)
124 *
125 * Name of Field Bits
126 * ---------------------------------------------------------
127 * Stuff Count 4
128 * CRC sequence (CRC21) 21
129 * CRC Delimiter 1
130 * Fixed stuff bits 7
131 */
132 #define CANFD_FRAME_CRC21_FIELD_BITS 33
133
134 /*
135 * Size of a CAN(-FD) Frame footer in bits
136 *
137 * Name of Field Bits
138 * ---------------------------------------------------------
139 * ACK slot 1
140 * ACK delimiter 1
141 * End Of Frame (EOF) 7
142 *
143 * including all fields following the CRC field
144 */
145 #define CAN_FRAME_FOOTER_BITS 9
146
147 /*
148 * First part of the Inter Frame Space
149 * (a.k.a. IMF - intermission field)
150 */
151 #define CAN_INTERMISSION_BITS 3
152
153 /**
154 * can_bitstuffing_len() - Calculate the maximum length with bitstuffing
155 * @destuffed_len: length of a destuffed bit stream
156 *
157 * The worst bit stuffing case is a sequence in which dominant and
158 * recessive bits alternate every four bits:
159 *
160 * Destuffed: 1 1111 0000 1111 0000 1111
161 * Stuffed: 1 1111o 0000i 1111o 0000i 1111o
162 *
163 * Nomenclature
164 *
165 * - "": dominant bit
166 * - "o": dominant stuff bit
167 * - "1": recessive bit
168 * - "i": recessive stuff bit
169 *
170 * Aside from the first bit, one stuff bit is added every four bits.
171 *
172 * Return: length of the stuffed bit stream in the worst case scenario.
173 */
174 #define can_bitstuffing_len(destuffed_len) \
175 (destuffed_len + (destuffed_len - 1) / 4)
176
177 #define __can_bitstuffing_len(bitstuffing, destuffed_len) \
178 (bitstuffing ? can_bitstuffing_len(destuffed_len) : \
179 destuffed_len)
180
181 #define __can_cc_frame_bits(is_eff, bitstuffing, \
182 intermission, data_len) \
183 ( \
184 __can_bitstuffing_len(bitstuffing, \
185 (is_eff ? CAN_FRAME_HEADER_EFF_BITS : \
186 CAN_FRAME_HEADER_SFF_BITS) + \
187 (data_len) * BITS_PER_BYTE + \
188 CAN_FRAME_CRC_FIELD_BITS) + \
189 CAN_FRAME_FOOTER_BITS + \
190 (intermission ? CAN_INTERMISSION_BITS : 0) \
191 )
192
193 #define __can_fd_frame_bits(is_eff, bitstuffing, \
194 intermission, data_len) \
195 ( \
196 __can_bitstuffing_len(bitstuffing, \
197 (is_eff ? CANFD_FRAME_HEADER_EFF_BITS : \
198 CANFD_FRAME_HEADER_SFF_BITS) + \
199 (data_len) * BITS_PER_BYTE) + \
200 ((data_len) <= 16 ? \
201 CANFD_FRAME_CRC17_FIELD_BITS : \
202 CANFD_FRAME_CRC21_FIELD_BITS) + \
203 CAN_FRAME_FOOTER_BITS + \
204 (intermission ? CAN_INTERMISSION_BITS : 0) \
205 )
206
207 /**
208 * can_frame_bits() - Calculate the number of bits on the wire in a
209 * CAN frame
210 * @is_fd: true: CAN-FD frame; false: Classical CAN frame.
211 * @is_eff: true: Extended frame; false: Standard frame.
212 * @bitstuffing: true: calculate the bitstuffing worst case; false:
213 * calculate the bitstuffing best case (no dynamic
214 * bitstuffing). CAN-FD's fixed stuff bits are always included.
215 * @intermission: if and only if true, include the inter frame space
216 * assuming no bus idle (i.e. only the intermission). Strictly
217 * speaking, the inter frame space is not part of the
218 * frame. However, it is needed when calculating the delay
219 * between the Start Of Frame of two consecutive frames.
220 * @data_len: length of the data field in bytes. Correspond to
221 * can(fd)_frame->len. Should be zero for remote frames. No
222 * sanitization is done on @data_len and it shall have no side
223 * effects.
224 *
225 * Return: the numbers of bits on the wire of a CAN frame.
226 */
227 #define can_frame_bits(is_fd, is_eff, bitstuffing, \
228 intermission, data_len) \
229 ( \
230 is_fd ? __can_fd_frame_bits(is_eff, bitstuffing, \
231 intermission, data_len) : \
232 __can_cc_frame_bits(is_eff, bitstuffing, \
233 intermission, data_len) \
234 )
235
236 /*
237 * Number of bytes in a CAN frame
238 * (rounded up, including intermission)
239 */
240 #define can_frame_bytes(is_fd, is_eff, bitstuffing, data_len) \
241 DIV_ROUND_UP(can_frame_bits(is_fd, is_eff, bitstuffing, \
242 true, data_len), \
243 BITS_PER_BYTE)
244
245 /*
246 * Maximum size of a Classical CAN frame
247 * (rounded up, ignoring bitstuffing but including intermission)
248 */
249 #define CAN_FRAME_LEN_MAX can_frame_bytes(false, true, false, CAN_MAX_DLEN)
250
251 /*
252 * Maximum size of a CAN-FD frame
253 * (rounded up, ignoring dynamic bitstuffing but including intermission)
254 */
255 #define CANFD_FRAME_LEN_MAX can_frame_bytes(true, true, false, CANFD_MAX_DLEN)
256
257 /*
258 * can_cc_dlc2len(value) - convert a given data length code (dlc) of a
259 * Classical CAN frame into a valid data length of max. 8 bytes.
260 *
261 * To be used in the CAN netdriver receive path to ensure conformance with
262 * ISO 11898-1 Chapter 8.4.2.3 (DLC field)
263 */
264 #define can_cc_dlc2len(dlc) (min_t(u8, (dlc), CAN_MAX_DLEN))
265
266 /* helper to get the data length code (DLC) for Classical CAN raw DLC access */
267 static inline u8 can_get_cc_dlc(const struct can_frame *cf, const u32 ctrlmode)
268 {
269 /* return len8_dlc as dlc value only if all conditions apply */
270 if ((ctrlmode & CAN_CTRLMODE_CC_LEN8_DLC) &&
271 (cf->len == CAN_MAX_DLEN) &&
272 (cf->len8_dlc > CAN_MAX_DLEN && cf->len8_dlc <= CAN_MAX_RAW_DLC))
273 return cf->len8_dlc;
274
275 /* return the payload length as dlc value */
276 return cf->len;
277 }
278
279 /* helper to set len and len8_dlc value for Classical CAN raw DLC access */
280 static inline void can_frame_set_cc_len(struct can_frame *cf, const u8 dlc,
281 const u32 ctrlmode)
282 {
283 /* the caller already ensured that dlc is a value from 0 .. 15 */
284 if (ctrlmode & CAN_CTRLMODE_CC_LEN8_DLC && dlc > CAN_MAX_DLEN)
285 cf->len8_dlc = dlc;
286
287 /* limit the payload length 'len' to CAN_MAX_DLEN */
288 cf->len = can_cc_dlc2len(dlc);
289 }
290
291 /* get data length from raw data length code (DLC) */
292 u8 can_fd_dlc2len(u8 dlc);
293
294 /* map the sanitized data length to an appropriate data length code */
295 u8 can_fd_len2dlc(u8 len);
296
297 /* calculate the CAN Frame length in bytes of a given skb */
298 unsigned int can_skb_get_frame_len(const struct sk_buff *skb);
299
300 /* map the data length to an appropriate data link layer length */
301 static inline u8 canfd_sanitize_len(u8 len)
302 {
303 return can_fd_dlc2len(can_fd_len2dlc(len));
304 }
305
306 #endif /* !_CAN_LENGTH_H */
307
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.