85 lines · c
1// SPDX-License-Identifier: GPL-2.0-only2/* 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, 6412};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 bytes49 * 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 bits53 * is rounded up to a length in bytes.54 *55 * Rationale: this function is to be used for the BQL functions56 * (netdev_sent_queue() and netdev_completed_queue()) which expect a57 * value in bytes. Just using skb->len is insufficient because it will58 * return the constant value of CAN(FD)_MTU. Doing the bit stuffing59 * calculation would be too expensive in term of computing resources60 * for no noticeable gain.61 *62 * Remarks: The payload of CAN FD frames with BRS flag are sent at a63 * different bitrate. Currently, the can-utils canbusload tool does64 * not support CAN-FD yet and so we could not run any benchmark to65 * 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 else79 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