Re: [net-next 04/13] can: dev: move length related code into seperate file

[Oliver Hartkopp <socketcan@hartkopp.net>]

Hi Marc,

nice cleanup!

On 09.01.21 18:40, Marc Kleine-Budde wrote:
> This patch moves all CAN frame length related code of the CAN device
> infrastructure into a separate file.
> 


> diff --git a/drivers/net/can/dev/length.c b/drivers/net/can/dev/length.c
> new file mode 100644
> index 000000000000..540d40dc0bc2
> --- /dev/null
> +++ b/drivers/net/can/dev/length.c
> @@ -0,0 +1,40 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Copyright (C) 2005 Marc Kleine-Budde, Pengutronix
> + * Copyright (C) 2006 Andrey Volkov, Varma Electronics
> + * Copyright (C) 2008-2009 Wolfgang Grandegger <wg@grandegger.com>
> + */

See comment below ...

> +
> +#include <linux/can/dev.h>
> +
> +/* CAN DLC to real data length conversion helpers */
> +
> +static const u8 dlc2len[] = {0, 1, 2, 3, 4, 5, 6, 7,
> +			     8, 12, 16, 20, 24, 32, 48, 64};
> +
> +/* get data length from raw data length code (DLC) */
> +u8 can_fd_dlc2len(u8 dlc)
> +{
> +	return dlc2len[dlc & 0x0F];
> +}
> +EXPORT_SYMBOL_GPL(can_fd_dlc2len);
> +
> +static const u8 len2dlc[] = {0, 1, 2, 3, 4, 5, 6, 7, 8,		/* 0 - 8 */
> +			     9, 9, 9, 9,			/* 9 - 12 */
> +			     10, 10, 10, 10,			/* 13 - 16 */
> +			     11, 11, 11, 11,			/* 17 - 20 */
> +			     12, 12, 12, 12,			/* 21 - 24 */
> +			     13, 13, 13, 13, 13, 13, 13, 13,	/* 25 - 32 */
> +			     14, 14, 14, 14, 14, 14, 14, 14,	/* 33 - 40 */
> +			     14, 14, 14, 14, 14, 14, 14, 14,	/* 41 - 48 */
> +			     15, 15, 15, 15, 15, 15, 15, 15,	/* 49 - 56 */
> +			     15, 15, 15, 15, 15, 15, 15, 15};	/* 57 - 64 */
> +
> +/* map the sanitized data length to an appropriate data length code */
> +u8 can_fd_len2dlc(u8 len)
> +{
> +	if (unlikely(len > 64))
> +		return 0xF;
> +
> +	return len2dlc[len];
> +}
> +EXPORT_SYMBOL_GPL(can_fd_len2dlc);
> diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
> index 054c3bed190b..d75fba1d030a 100644
> --- a/include/linux/can/dev.h
> +++ b/include/linux/can/dev.h
> @@ -18,6 +18,7 @@
>   #include <linux/can/bittiming.h>
>   #include <linux/can/error.h>
>   #include <linux/can/led.h>
> +#include <linux/can/length.h>
>   #include <linux/can/netlink.h>
>   #include <linux/can/skb.h>
>   #include <linux/netdevice.h>
> @@ -83,15 +84,6 @@ struct can_priv {


(..)

> diff --git a/include/linux/can/length.h b/include/linux/can/length.h
> new file mode 100644
> index 000000000000..fabd93bcde3e
> --- /dev/null
> +++ b/include/linux/can/length.h
> @@ -0,0 +1,51 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2006 Andrey Volkov <avolkov@varma-el.com>
> + *               Varma Electronics Oy
> + * Copyright (C) 2008 Wolfgang Grandegger <wg@grandegger.com>

The CAN FD and len8_dlc length stuff was completely contributed by myself.

So if this code is now moved to a separate file the former Copyrights 
should be replaced with

Copyright (C) 2020 Oliver Hartkopp <socketcan@hartkopp.net>

;-)

Best,
Oliver


> + */
> +
> +#ifndef _CAN_LENGTH_H
> +#define _CAN_LENGTH_H
> +
> +/*
> + * can_cc_dlc2len(value) - convert a given data length code (dlc) of a
> + * Classical CAN frame into a valid data length of max. 8 bytes.
> + *
> + * To be used in the CAN netdriver receive path to ensure conformance with
> + * ISO 11898-1 Chapter 8.4.2.3 (DLC field)
> + */
> +#define can_cc_dlc2len(dlc)	(min_t(u8, (dlc), CAN_MAX_DLEN))
> +
> +/* helper to get the data length code (DLC) for Classical CAN raw DLC access */
> +static inline u8 can_get_cc_dlc(const struct can_frame *cf, const u32 ctrlmode)
> +{
> +	/* return len8_dlc as dlc value only if all conditions apply */
> +	if ((ctrlmode & CAN_CTRLMODE_CC_LEN8_DLC) &&
> +	    (cf->len == CAN_MAX_DLEN) &&
> +	    (cf->len8_dlc > CAN_MAX_DLEN && cf->len8_dlc <= CAN_MAX_RAW_DLC))
> +		return cf->len8_dlc;
> +
> +	/* return the payload length as dlc value */
> +	return cf->len;
> +}
> +
> +/* helper to set len and len8_dlc value for Classical CAN raw DLC access */
> +static inline void can_frame_set_cc_len(struct can_frame *cf, const u8 dlc,
> +					const u32 ctrlmode)
> +{
> +	/* the caller already ensured that dlc is a value from 0 .. 15 */
> +	if (ctrlmode & CAN_CTRLMODE_CC_LEN8_DLC && dlc > CAN_MAX_DLEN)
> +		cf->len8_dlc = dlc;
> +
> +	/* limit the payload length 'len' to CAN_MAX_DLEN */
> +	cf->len = can_cc_dlc2len(dlc);
> +}
> +
> +/* get data length from raw data length code (DLC) */
> +u8 can_fd_dlc2len(u8 dlc);
> +
> +/* map the sanitized data length to an appropriate data length code */
> +u8 can_fd_len2dlc(u8 len);
> +
> +#endif /* !_CAN_LENGTH_H */
>