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54eca60b1c
In commit652562e5ff("can: length: can_fd_len2dlc(): simplify length calculcation") the readability of the code degraded and became more error prone. To counteract this, partially convert that patch and replace open coded values (of the original code) with proper defines. Fixes:652562e5ff("can: length: can_fd_len2dlc(): simplify length calculcation") Cc: Vincent MAILHOL <mailhol.vincent@wanadoo.fr> Link: https://lore.kernel.org/r/20210118201346.79422-1-socketcan@hartkopp.net Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
95 lines
2.7 KiB
C
95 lines
2.7 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/* Copyright (C) 2012, 2020 Oliver Hartkopp <socketcan@hartkopp.net>
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*/
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#include <linux/can/dev.h>
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/* CAN DLC to real data length conversion helpers */
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static const u8 dlc2len[] = {
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0, 1, 2, 3, 4, 5, 6, 7,
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8, 12, 16, 20, 24, 32, 48, 64
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};
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/* get data length from raw data length code (DLC) */
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u8 can_fd_dlc2len(u8 dlc)
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{
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return dlc2len[dlc & 0x0F];
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}
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EXPORT_SYMBOL_GPL(can_fd_dlc2len);
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static const u8 len2dlc[] = {
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0, 1, 2, 3, 4, 5, 6, 7, 8, /* 0 - 8 */
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9, 9, 9, 9, /* 9 - 12 */
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10, 10, 10, 10, /* 13 - 16 */
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11, 11, 11, 11, /* 17 - 20 */
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12, 12, 12, 12, /* 21 - 24 */
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13, 13, 13, 13, 13, 13, 13, 13, /* 25 - 32 */
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14, 14, 14, 14, 14, 14, 14, 14, /* 33 - 40 */
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14, 14, 14, 14, 14, 14, 14, 14, /* 41 - 48 */
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15, 15, 15, 15, 15, 15, 15, 15, /* 49 - 56 */
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15, 15, 15, 15, 15, 15, 15, 15 /* 57 - 64 */
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};
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/* map the sanitized data length to an appropriate data length code */
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u8 can_fd_len2dlc(u8 len)
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{
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/* check for length mapping table size at build time */
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BUILD_BUG_ON(ARRAY_SIZE(len2dlc) != CANFD_MAX_DLEN + 1);
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if (unlikely(len > CANFD_MAX_DLEN))
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return CANFD_MAX_DLC;
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return len2dlc[len];
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}
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EXPORT_SYMBOL_GPL(can_fd_len2dlc);
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/**
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* can_skb_get_frame_len() - Calculate the CAN Frame length in bytes
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* of a given skb.
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* @skb: socket buffer of a CAN message.
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*
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* Do a rough calculation: bit stuffing is ignored and length in bits
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* is rounded up to a length in bytes.
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*
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* Rationale: this function is to be used for the BQL functions
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* (netdev_sent_queue() and netdev_completed_queue()) which expect a
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* value in bytes. Just using skb->len is insufficient because it will
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* return the constant value of CAN(FD)_MTU. Doing the bit stuffing
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* calculation would be too expensive in term of computing resources
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* for no noticeable gain.
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*
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* Remarks: The payload of CAN FD frames with BRS flag are sent at a
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* different bitrate. Currently, the can-utils canbusload tool does
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* not support CAN-FD yet and so we could not run any benchmark to
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* measure the impact. There might be possible improvement here.
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*
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* Return: length in bytes.
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*/
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unsigned int can_skb_get_frame_len(const struct sk_buff *skb)
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{
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const struct canfd_frame *cf = (const struct canfd_frame *)skb->data;
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u8 len;
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if (can_is_canfd_skb(skb))
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len = canfd_sanitize_len(cf->len);
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else if (cf->can_id & CAN_RTR_FLAG)
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len = 0;
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else
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len = cf->len;
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if (can_is_canfd_skb(skb)) {
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if (cf->can_id & CAN_EFF_FLAG)
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len += CANFD_FRAME_OVERHEAD_EFF;
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else
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len += CANFD_FRAME_OVERHEAD_SFF;
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} else {
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if (cf->can_id & CAN_EFF_FLAG)
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len += CAN_FRAME_OVERHEAD_EFF;
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else
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len += CAN_FRAME_OVERHEAD_SFF;
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}
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return len;
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}
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EXPORT_SYMBOL_GPL(can_skb_get_frame_len);
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