1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* Copyright (C) 2012, 2020 Oliver Hartkopp <socketcan@hartkopp.net> |
3 | */ |
4 | |
5 | #include <linux/can/dev.h> |
6 | |
7 | /* CAN DLC to real data length conversion helpers */ |
8 | |
9 | static const u8 dlc2len[] = { |
10 | 0, 1, 2, 3, 4, 5, 6, 7, |
11 | 8, 12, 16, 20, 24, 32, 48, 64 |
12 | }; |
13 | |
14 | /* get data length from raw data length code (DLC) */ |
15 | u8 can_fd_dlc2len(u8 dlc) |
16 | { |
17 | return dlc2len[dlc & 0x0F]; |
18 | } |
19 | EXPORT_SYMBOL_GPL(can_fd_dlc2len); |
20 | |
21 | static const u8 len2dlc[] = { |
22 | 0, 1, 2, 3, 4, 5, 6, 7, 8, /* 0 - 8 */ |
23 | 9, 9, 9, 9, /* 9 - 12 */ |
24 | 10, 10, 10, 10, /* 13 - 16 */ |
25 | 11, 11, 11, 11, /* 17 - 20 */ |
26 | 12, 12, 12, 12, /* 21 - 24 */ |
27 | 13, 13, 13, 13, 13, 13, 13, 13, /* 25 - 32 */ |
28 | 14, 14, 14, 14, 14, 14, 14, 14, /* 33 - 40 */ |
29 | 14, 14, 14, 14, 14, 14, 14, 14, /* 41 - 48 */ |
30 | 15, 15, 15, 15, 15, 15, 15, 15, /* 49 - 56 */ |
31 | 15, 15, 15, 15, 15, 15, 15, 15 /* 57 - 64 */ |
32 | }; |
33 | |
34 | /* map the sanitized data length to an appropriate data length code */ |
35 | u8 can_fd_len2dlc(u8 len) |
36 | { |
37 | /* check for length mapping table size at build time */ |
38 | BUILD_BUG_ON(ARRAY_SIZE(len2dlc) != CANFD_MAX_DLEN + 1); |
39 | |
40 | if (unlikely(len > CANFD_MAX_DLEN)) |
41 | return CANFD_MAX_DLC; |
42 | |
43 | return len2dlc[len]; |
44 | } |
45 | EXPORT_SYMBOL_GPL(can_fd_len2dlc); |
46 | |
47 | /** |
48 | * can_skb_get_frame_len() - Calculate the CAN Frame length in bytes |
49 | * of a given skb. |
50 | * @skb: socket buffer of a CAN message. |
51 | * |
52 | * Do a rough calculation: bit stuffing is ignored and length in bits |
53 | * is rounded up to a length in bytes. |
54 | * |
55 | * Rationale: this function is to be used for the BQL functions |
56 | * (netdev_sent_queue() and netdev_completed_queue()) which expect a |
57 | * value in bytes. Just using skb->len is insufficient because it will |
58 | * return the constant value of CAN(FD)_MTU. Doing the bit stuffing |
59 | * calculation would be too expensive in term of computing resources |
60 | * for no noticeable gain. |
61 | * |
62 | * Remarks: The payload of CAN FD frames with BRS flag are sent at a |
63 | * different bitrate. Currently, the can-utils canbusload tool does |
64 | * not support CAN-FD yet and so we could not run any benchmark to |
65 | * measure the impact. There might be possible improvement here. |
66 | * |
67 | * Return: length in bytes. |
68 | */ |
69 | unsigned int can_skb_get_frame_len(const struct sk_buff *skb) |
70 | { |
71 | const struct canfd_frame *cf = (const struct canfd_frame *)skb->data; |
72 | u8 len; |
73 | |
74 | if (can_is_canfd_skb(skb)) |
75 | len = canfd_sanitize_len(len: cf->len); |
76 | else if (cf->can_id & CAN_RTR_FLAG) |
77 | len = 0; |
78 | else |
79 | len = cf->len; |
80 | |
81 | return can_frame_bytes(can_is_canfd_skb(skb), cf->can_id & CAN_EFF_FLAG, |
82 | false, len); |
83 | } |
84 | EXPORT_SYMBOL_GPL(can_skb_get_frame_len); |
85 | |