netdev - Re: [PATCH v6 7/8] can-dev: introduce helpers to access Classical CAN DLC values

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Date:   Tue, 10 Nov 2020 16:50:04 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Oliver Hartkopp <socketcan@...tkopp.net>,
        linux-can@...r.kernel.org, mailhol.vincent@...adoo.fr
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH v6 7/8] can-dev: introduce helpers to access Classical CAN
 DLC values

On 11/10/20 11:18 AM, Oliver Hartkopp wrote:
> can_get_cc_dlc: get the data length code for Classical CAN raw DLC access
> can_get_cc_len: get len and len8_dlc value for Classical CAN raw DLC access

The final patch needs a bit more prose, like:

This patch adds the following helper to functions to access Classical CAN DLC
values.

> Signed-off-by: Oliver Hartkopp <socketcan@...tkopp.net>
> ---
>  include/linux/can/dev.h | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
> index e767a96ae075..9a787f73399e 100644
> --- a/include/linux/can/dev.h
> +++ b/include/linux/can/dev.h
> @@ -168,10 +168,38 @@ static inline bool can_is_canfd_skb(const struct sk_buff *skb)
>  {
>  	/* the CAN specific type of skb is identified by its data length */
>  	return skb->len == CANFD_MTU;
>  }
>  
> +/* helper to get the data length code (DLC) for Classical CAN raw DLC access */
> +static inline u8 can_get_cc_dlc(const u32 ctrlmode, const struct can_frame *cf)

Please make the cf the first argument.

> +{
> +	/* 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 get len and len8_dlc value for Classical CAN raw DLC access */
> +static inline u8 can_get_cc_len(const u32 ctrlmode, struct can_frame *cf,
> +				u8 dlc)

Please make the cf the first argument.

> +{
> +	/* 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 */
> +	if (dlc > CAN_MAX_DLEN)
> +		return CAN_MAX_DLEN;

can_cc_dlc2len()

I still think, that can_frame_set_cc_len() makes more sense. See my just posted
patches for illustration.

> +
> +	return dlc;
> +}
> +
>  /* helper to define static CAN controller features at device creation time */
>  static inline void can_set_static_ctrlmode(struct net_device *dev,
>  					   u32 static_mode)
>  {
>  	struct can_priv *priv = netdev_priv(dev);
> 

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |



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