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
9static 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) */
15u8 can_fd_dlc2len(u8 dlc)
16{
17	return dlc2len[dlc & 0x0F];
18}
19EXPORT_SYMBOL_GPL(can_fd_dlc2len);
20
21static 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 */
35u8 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}
45EXPORT_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 */
69unsigned 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(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}
84EXPORT_SYMBOL_GPL(can_skb_get_frame_len);
85