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can: length: fix description of the RRS field

The CAN-FD frames only have one reserved bit. The bit corresponding to
Classical CAN frame's RTR bit is called the "Remote Request
Substitution (RRS)" [1].

N.B. The RRS is not to be confused with the Substitute Remote Request
(SRR).

Fix the description in the CANFD_FRAME_OVERHEAD_SFF/EFF macros.

The total remains unchanged, so this is just a documentation fix.

In addition to the above add myself as copyright owner for 2020 (as
coauthor of the initial version, c.f. Fixes tag).

[1] ISO 11898-1:2015 paragraph 10.4.2.3 "Arbitration field":

RSS bit [only in FD Frames]

The RRS bit shall be transmitted in FD Frames at the position of
the RTR bit in Classical Frames. The RRS bit shall be transmitted
dominant, but receivers shall accept recessive and dominant RRS
bits.

Fixes: 85d99c3e2a13 ("can: length: can_skb_get_frame_len(): introduce function to get data length of frame in data link layer")
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Reviewed-by: Thomas Kopp <Thomas.Kopp@microchip.com>
Link: https://lore.kernel.org/all/20230611025728.450837-3-mailhol.vincent@wanadoo.fr
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

authored by

Vincent Mailhol and committed by
Marc Kleine-Budde 10711b11 9fde4c55

+3 -2
+3 -2
include/linux/can/length.h
··· 1 1 /* SPDX-License-Identifier: GPL-2.0 */ 2 2 /* Copyright (C) 2020 Oliver Hartkopp <socketcan@hartkopp.net> 3 3 * Copyright (C) 2020 Marc Kleine-Budde <kernel@pengutronix.de> 4 + * Copyright (C) 2020 Vincent Mailhol <mailhol.vincent@wanadoo.fr> 4 5 */ 5 6 6 7 #ifndef _CAN_LENGTH_H ··· 65 64 * --------------------------------------------------------- 66 65 * Start-of-frame 1 67 66 * Identifier 11 68 - * Reserved bit (r1) 1 67 + * Remote Request Substitution (RRS) 1 69 68 * Identifier extension bit (IDE) 1 70 69 * Flexible data rate format (FDF) 1 71 70 * Reserved bit (r0) 1 ··· 96 95 * Substitute remote request (SRR) 1 97 96 * Identifier extension bit (IDE) 1 98 97 * Identifier B 18 99 - * Reserved bit (r1) 1 98 + * Remote Request Substitution (RRS) 1 100 99 * Flexible data rate format (FDF) 1 101 100 * Reserved bit (r0) 1 102 101 * Bit Rate Switch (BRS) 1