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 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 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 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 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 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 | * - "0": 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(dlc: can_fd_len2dlc(len)); |
304 | } |
305 | |
306 | #endif /* !_CAN_LENGTH_H */ |
307 | |