linux-kernel - Re: [PATCH] can: bittiming: replace CAN units with the SI metric

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Message-ID: <38544770-9e5f-1b1b-1f0a-a7ff1719327d@hartkopp.net>
Date:   Sun, 21 Nov 2021 19:27:47 +0100
From:   Oliver Hartkopp <socketcan@...tkopp.net>
To:     Vincent Mailhol <mailhol.vincent@...adoo.fr>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        linux-can@...r.kernel.org
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jimmy Assarsson <extja@...ser.com>
Subject: Re: [PATCH] can: bittiming: replace CAN units with the SI metric



On 19.11.21 17:18, Vincent Mailhol wrote:
> In [1], we introduced a set of units in linux/can/bittiming.h. Since
> then, generic SI prefix were added to linux/units.h in [2]. Those new
> prefix can perfectly replace the CAN specific units.
> 
> This patch replaces all occurrences of the CAN units with their
> corresponding prefix according to below table.
> 
>   CAN units	SI metric prefix
>   -------------------------------
>   CAN_KBPS	KILO
>   CAN_MBPS	MEGA
>   CAM_MHZ	MEGA
> 
> The macro declarations are then removed from linux/can/bittiming.h
> 
> [1] commit 1d7750760b70 ("can: bittiming: add CAN_KBPS, CAN_MBPS and
> CAN_MHZ macros")
> 
> [2] commit 26471d4a6cf8 ("units: Add SI metric prefix definitions")
> 
> Suggested-by: Jimmy Assarsson <extja@...ser.com>
> Signed-off-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>
> ---
>   drivers/net/can/dev/bittiming.c           | 5 +++--
>   drivers/net/can/usb/etas_es58x/es581_4.c  | 5 +++--
>   drivers/net/can/usb/etas_es58x/es58x_fd.c | 5 +++--
>   include/linux/can/bittiming.h             | 7 -------
>   4 files changed, 9 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/can/dev/bittiming.c b/drivers/net/can/dev/bittiming.c
> index 0509625c3082..a5c9f973802a 100644
> --- a/drivers/net/can/dev/bittiming.c
> +++ b/drivers/net/can/dev/bittiming.c
> @@ -4,6 +4,7 @@
>    * Copyright (C) 2008-2009 Wolfgang Grandegger <wg@...ndegger.com>
>    */
>   
> +#include <linux/units.h>
>   #include <linux/can/dev.h>
>   
>   #ifdef CONFIG_CAN_CALC_BITTIMING
> @@ -81,9 +82,9 @@ int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
>   	if (bt->sample_point) {
>   		sample_point_nominal = bt->sample_point;
>   	} else {
> -		if (bt->bitrate > 800 * CAN_KBPS)
> +		if (bt->bitrate > 800 * KILO)
>   			sample_point_nominal = 750;
> -		else if (bt->bitrate > 500 * CAN_KBPS)
> +		else if (bt->bitrate > 500 * KILO)
>   			sample_point_nominal = 800;
>   		else
>   			sample_point_nominal = 875;
> diff --git a/drivers/net/can/usb/etas_es58x/es581_4.c b/drivers/net/can/usb/etas_es58x/es581_4.c
> index 14e360c9f2c9..ed340141c712 100644
> --- a/drivers/net/can/usb/etas_es58x/es581_4.c
> +++ b/drivers/net/can/usb/etas_es58x/es581_4.c
> @@ -10,6 +10,7 @@
>    */
>   
>   #include <linux/kernel.h>
> +#include <linux/units.h>
>   #include <asm/unaligned.h>
>   
>   #include "es58x_core.h"
> @@ -469,8 +470,8 @@ const struct es58x_parameters es581_4_param = {
>   	.bittiming_const = &es581_4_bittiming_const,
>   	.data_bittiming_const = NULL,
>   	.tdc_const = NULL,
> -	.bitrate_max = 1 * CAN_MBPS,
> -	.clock = {.freq = 50 * CAN_MHZ},
> +	.bitrate_max = 1 * MEGA,
> +	.clock = {.freq = 50 * MEGA},

IMO we are losing information here.

It feels you suggest to replace MHz with M.

So where is the Hz information then?

>   	.ctrlmode_supported = CAN_CTRLMODE_CC_LEN8_DLC,
>   	.tx_start_of_frame = 0xAFAF,
>   	.rx_start_of_frame = 0xFAFA,
> diff --git a/drivers/net/can/usb/etas_es58x/es58x_fd.c b/drivers/net/can/usb/etas_es58x/es58x_fd.c
> index 4f0cae29f4d8..aec299bed6dc 100644
> --- a/drivers/net/can/usb/etas_es58x/es58x_fd.c
> +++ b/drivers/net/can/usb/etas_es58x/es58x_fd.c
> @@ -12,6 +12,7 @@
>    */
>   
>   #include <linux/kernel.h>
> +#include <linux/units.h>
>   #include <asm/unaligned.h>
>   
>   #include "es58x_core.h"
> @@ -522,8 +523,8 @@ const struct es58x_parameters es58x_fd_param = {
>   	 * Mbps work in an optimal environment but are not recommended
>   	 * for production environment.
>   	 */
> -	.bitrate_max = 8 * CAN_MBPS,
> -	.clock = {.freq = 80 * CAN_MHZ},
> +	.bitrate_max = 8 * MEGA,
> +	.clock = {.freq = 80 * MEGA},
>   	.ctrlmode_supported = CAN_CTRLMODE_LOOPBACK | CAN_CTRLMODE_LISTENONLY |
>   	    CAN_CTRLMODE_3_SAMPLES | CAN_CTRLMODE_FD | CAN_CTRLMODE_FD_NON_ISO |
>   	    CAN_CTRLMODE_CC_LEN8_DLC | CAN_CTRLMODE_TDC_AUTO,
> diff --git a/include/linux/can/bittiming.h b/include/linux/can/bittiming.h
> index 20b50baf3a02..a81652d1c6f3 100644
> --- a/include/linux/can/bittiming.h
> +++ b/include/linux/can/bittiming.h
> @@ -12,13 +12,6 @@
>   #define CAN_SYNC_SEG 1
>   
>   
> -/* Kilobits and Megabits per second */
> -#define CAN_KBPS 1000UL
> -#define CAN_MBPS 1000000UL
> -
> -/* Megahertz */
> -#define CAN_MHZ 1000000UL

So what about

#define CAN_KBPS KILO /* kilo bits per second */
#define CAN_MBPS MEGA /* mega bits per second */

#define CAN_MHZ MEGA /* mega hertz */


??

Regards,
Oliver


> -
>   #define CAN_CTRLMODE_TDC_MASK					\
>   	(CAN_CTRLMODE_TDC_AUTO | CAN_CTRLMODE_TDC_MANUAL)
>   
>