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[124.33.176.97]) by smtp.gmail.com with ESMTPSA id z6-20020a170903018600b001a3d041ca71sm5338360plg.275.2023.05.07.08.55.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 07 May 2023 08:55:16 -0700 (PDT) Sender: Vincent Mailhol From: Vincent Mailhol To: Marc Kleine-Budde , linux-can@vger.kernel.org, Marek Vasut Cc: linux-kernel@vger.kernel.org, Vincent Mailhol Subject: [PATCH] can: length: add definitions for frame lengths in bits Date: Mon, 8 May 2023 00:55:06 +0900 Message-Id: <20230507155506.3179711-1-mailhol.vincent@wanadoo.fr> X-Mailer: git-send-email 2.39.3 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When created in [1], frames length definitions were added to implement byte queue limits (bql). Because bql expects lengths in bytes, bit length definitions were not considered back then. Recently, a need to refer to the exact frame length in bits, with CAN bit stuffing, appeared in [2]. Add 9 frames length definitions: - CAN_FRAME_OVERHEAD_SFF_BITS: - CAN_FRAME_OVERHEAD_EFF_BITS - CANFD_FRAME_OVERHEAD_SFF_BITS - CANFD_FRAME_OVERHEAD_EFF_BITS - CAN_BIT_STUFFING_OVERHEAD - CAN_FRAME_LEN_MAX_BITS_NO_STUFFING - CAN_FRAME_LEN_MAX_BITS_STUFFING - CANFD_FRAME_LEN_MAX_BITS_NO_STUFFING - CANFD_FRAME_LEN_MAX_BITS_STUFFING CAN_FRAME_LEN_MAX_BITS_STUFFING and CANFD_FRAME_LEN_MAX_BITS_STUFFING define respectively the maximum number of bits in a classical CAN and CAN-FD frame including bit stuffing. The other definitions are intermediate values. In addition to the above: - Include linux/bits.h and then replace the value 8 by BITS_PER_BYTE whenever relevant. - Include linux/math.h because of DIV_ROUND_UP(). N.B: the use of DIV_ROUND_UP() is not new to this patch, but the include was previously omitted. - Update the existing length definitions to use the newly defined values. - Add myself as copyright owner for 2020 (as coauthor of the initial version, c.f. [1]) and for 2023 (this patch). [1] commit 85d99c3e2a13 ("can: length: can_skb_get_frame_len(): introduce function to get data length of frame in data link layer") Link: https://git.kernel.org/torvalds/c/85d99c3e2a13 [2] RE: [PATCH] can: mcp251xfd: Increase poll timeout Link: https://lore.kernel.org/linux-can/BL3PR11MB64846C83ACD04E9330B0FE66FB= 729@BL3PR11MB6484.namprd11.prod.outlook.com/ Signed-off-by: Vincent Mailhol --- As always, let me know if you have better inspiration than me for the naming. --- include/linux/can/length.h | 84 ++++++++++++++++++++++++++++++++------ 1 file changed, 72 insertions(+), 12 deletions(-) diff --git a/include/linux/can/length.h b/include/linux/can/length.h index 6995092b774e..60492fcbe34d 100644 --- a/include/linux/can/length.h +++ b/include/linux/can/length.h @@ -1,13 +1,17 @@ /* SPDX-License-Identifier: GPL-2.0 */ /* Copyright (C) 2020 Oliver Hartkopp * Copyright (C) 2020 Marc Kleine-Budde + * Copyright (C) 2020, 2023 Vincent Mailhol */ =20 #ifndef _CAN_LENGTH_H #define _CAN_LENGTH_H =20 +#include +#include + /* - * Size of a Classical CAN Standard Frame + * Size of a Classical CAN Standard Frame in bits * * Name of Field Bits * --------------------------------------------------------- @@ -25,12 +29,19 @@ * End-of-frame (EOF) 7 * Inter frame spacing 3 * - * rounded up and ignoring bitstuffing + * ignoring bitstuffing */ -#define CAN_FRAME_OVERHEAD_SFF DIV_ROUND_UP(47, 8) +#define CAN_FRAME_OVERHEAD_SFF_BITS 47 =20 /* - * Size of a Classical CAN Extended Frame + * Size of a Classical CAN Standard Frame + * (rounded up and ignoring bitstuffing) + */ +#define CAN_FRAME_OVERHEAD_SFF \ + DIV_ROUND_UP(CAN_FRAME_OVERHEAD_SFF_BITS, BITS_PER_BYTE) + +/* + * Size of a Classical CAN Extended Frame in bits * * Name of Field Bits * --------------------------------------------------------- @@ -50,12 +61,19 @@ * End-of-frame (EOF) 7 * Inter frame spacing 3 * - * rounded up and ignoring bitstuffing + * ignoring bitstuffing */ -#define CAN_FRAME_OVERHEAD_EFF DIV_ROUND_UP(67, 8) +#define CAN_FRAME_OVERHEAD_EFF_BITS 67 =20 /* - * Size of a CAN-FD Standard Frame + * Size of a Classical CAN Extended Frame + * (rounded up and ignoring bitstuffing) + */ +#define CAN_FRAME_OVERHEAD_EFF \ + DIV_ROUND_UP(CAN_FRAME_OVERHEAD_EFF_BITS, BITS_PER_BYTE) + +/* + * Size of a CAN-FD Standard Frame in bits * * Name of Field Bits * --------------------------------------------------------- @@ -77,12 +95,19 @@ * End-of-frame (EOF) 7 * Inter frame spacing 3 * - * assuming CRC21, rounded up and ignoring bitstuffing + * assuming CRC21 and ignoring bitstuffing */ -#define CANFD_FRAME_OVERHEAD_SFF DIV_ROUND_UP(61, 8) +#define CANFD_FRAME_OVERHEAD_SFF_BITS 61 =20 /* - * Size of a CAN-FD Extended Frame + * Size of a CAN-FD Standard Frame + * (assuming CRC21, rounded up and ignoring bitstuffing) + */ +#define CANFD_FRAME_OVERHEAD_SFF \ + DIV_ROUND_UP(CANFD_FRAME_OVERHEAD_SFF_BITS, BITS_PER_BYTE) + +/* + * Size of a CAN-FD Extended Frame in bits * * Name of Field Bits * --------------------------------------------------------- @@ -106,9 +131,32 @@ * End-of-frame (EOF) 7 * Inter frame spacing 3 * - * assuming CRC21, rounded up and ignoring bitstuffing + * assuming CRC21 and ignoring bitstuffing + */ +#define CANFD_FRAME_OVERHEAD_EFF_BITS 80 + +/* + * Size of a CAN-FD Extended Frame + * (assuming CRC21, rounded up and ignoring bitstuffing) + */ +#define CANFD_FRAME_OVERHEAD_EFF \ + DIV_ROUND_UP(CANFD_FRAME_OVERHEAD_EFF_BITS, BITS_PER_BYTE) + +/* CAN bit stuffing overhead multiplication factor */ +#define CAN_BIT_STUFFING_OVERHEAD 1.2 + +/* + * Maximum size of a Classical CAN frame in bits, ignoring bitstuffing */ -#define CANFD_FRAME_OVERHEAD_EFF DIV_ROUND_UP(80, 8) +#define CAN_FRAME_LEN_MAX_BITS_NO_STUFFING \ + (CAN_FRAME_OVERHEAD_EFF_BITS + CAN_MAX_DLEN * BITS_PER_BYTE) + +/* + * Maximum size of a Classical CAN frame in bits, including bitstuffing + */ +#define CAN_FRAME_LEN_MAX_BITS_STUFFING \ + ((unsigned int)(CAN_FRAME_LEN_MAX_BITS_NO_STUFFING * \ + CAN_BIT_STUFFING_OVERHEAD)) =20 /* * Maximum size of a Classical CAN frame @@ -116,6 +164,18 @@ */ #define CAN_FRAME_LEN_MAX (CAN_FRAME_OVERHEAD_EFF + CAN_MAX_DLEN) =20 +/* + * Maximum size of a CAN-FD frame in bits, ignoring bitstuffing + */ +#define CANFD_FRAME_LEN_MAX_BITS_NO_STUFFING \ + (CANFD_FRAME_OVERHEAD_EFF_BITS + CANFD_MAX_DLEN * BITS_PER_BYTE) + +/* + * Maximum size of a CAN-FD frame in bits, ignoring bitstuffing + */ +#define CANFD_FRAME_LEN_MAX_BITS_STUFFING \ + ((unsigned int)(CANFD_FRAME_LEN_MAX_BITS_NO_STUFFING * \ + CAN_BIT_STUFFING_OVERHEAD)) /* * Maximum size of a CAN-FD frame * (rounded up and ignoring bitstuffing) --=20 2.39.3