Subject: Re: [PATCH v4 10/11] can: lin: Support setting LIN mode

From: Ilpo Järvinen <[email-masked]>
Date: Fri, 10 May 2024 17:39:14 +0300 (EEST)

On Thu, 9 May 2024, Christoph Fritz wrote:

> A LIN node can work as commander or responder, so introduce a new
> control mode (CAN_CTRLMODE_LIN_COMMANDER) for configuration.
> 
> This enables e.g. the userland tool ip from iproute2 to turn on
> commander mode when the device is being brought up.
> 
> Signed-off-by: Christoph Fritz <[email-masked]>
> ---
>  drivers/net/can/lin.c            | 40 +++++++++++++++++++++++++++++++-
>  include/net/lin.h                |  7 ++++++
>  include/uapi/linux/can/netlink.h |  1 +
>  3 files changed, 47 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/can/lin.c b/drivers/net/can/lin.c
> index f77abd7d7d21c..03ddf5d5a31b8 100644
> --- a/drivers/net/can/lin.c
> +++ b/drivers/net/can/lin.c
> @@ -262,11 +262,40 @@ static netdev_tx_t lin_start_xmit(struct sk_buff *skb,
>  	return NETDEV_TX_OK;
>  }
>  
> +static int lin_update_mode(struct net_device *ndev)
> +{
> +	struct lin_device *ldev = netdev_priv(ndev);
> +	u32 ctrlmode = ldev->can.ctrlmode;
> +	enum lin_mode lm;
> +	int ret = 0;
> +
> +	lm = (ctrlmode & CAN_CTRLMODE_LIN_COMMANDER) ? LINBUS_COMMANDER :
> +						       LINBUS_RESPONDER;
> +	if (ldev->lmode != lm) {
> +		if (!ldev->ldev_ops->update_lin_mode) {
> +			netdev_err(ndev, "setting lin mode unsupported\n");

In user visible messages, it would be best to use the expected 
capitalization, which I suppose is LIN given you use capitals in the 
commit message yourself?

> +			return -EINVAL;
> +		}
> +		ret = ldev->ldev_ops->update_lin_mode(ldev, lm);
> +		if (ret) {
> +			netdev_err(ndev, "Failed to set lin mode: %d\n", ret);

Ditto.

There might be other cases in any of the patches, please check.

> +			return ret;
> +		}
> +		ldev->lmode = lm;
> +	}
> +
> +	return ret;
> +}
> +
>  static int lin_open(struct net_device *ndev)
>  {
>  	struct lin_device *ldev = netdev_priv(ndev);
>  	int ret;
>  
> +	ret = lin_update_mode(ndev);
> +	if (ret)
> +		return ret;
> +
>  	ldev->tx_busy = false;
>  
>  	ret = open_candev(ndev);
> @@ -443,7 +472,7 @@ struct lin_device *register_lin(struct device *dev,
>  	ndev->sysfs_groups[0] = &lin_sysfs_group;
>  	ldev->can.bittiming.bitrate = LIN_DEFAULT_BAUDRATE;
>  	ldev->can.ctrlmode = CAN_CTRLMODE_LIN;
> -	ldev->can.ctrlmode_supported = 0;
> +	ldev->can.ctrlmode_supported = CAN_CTRLMODE_LIN_COMMANDER;
>  	ldev->can.bitrate_const = lin_bitrate;
>  	ldev->can.bitrate_const_cnt = ARRAY_SIZE(lin_bitrate);
>  	ldev->can.do_set_bittiming = lin_set_bittiming;
> @@ -458,6 +487,15 @@ struct lin_device *register_lin(struct device *dev,
>  		goto exit_candev;
>  	}
>  
> +	ldev->lmode = LINBUS_RESPONDER;
> +	if (ldev->ldev_ops->update_lin_mode) {
> +		ret = ldev->ldev_ops->update_lin_mode(ldev, ldev->lmode);
> +		if (ret) {
> +			netdev_err(ndev, "updating lin mode failed\n");

Ditto.

> +			goto exit_candev;
> +		}
> +	}
> +
>  	ret = register_candev(ndev);
>  	if (ret)
>  		goto exit_candev;
> diff --git a/include/net/lin.h b/include/net/lin.h
> index 31bb0feefd188..63ac870a0ab6f 100644
> --- a/include/net/lin.h
> +++ b/include/net/lin.h
> @@ -36,6 +36,11 @@ struct lin_attr {
>  	struct lin_device *ldev;
>  };
>  
> +enum lin_mode {
> +	LINBUS_RESPONDER = 0,
> +	LINBUS_COMMANDER,
> +};
> +
>  struct lin_device {
>  	struct can_priv can;  /* must be the first member */
>  	struct net_device *ndev;
> @@ -45,6 +50,7 @@ struct lin_device {
>  	struct work_struct tx_work;
>  	bool tx_busy;
>  	struct sk_buff *tx_skb;
> +	enum lin_mode lmode;
>  };
>  
>  enum lin_checksum_mode {
> @@ -71,6 +77,7 @@ struct lin_device_ops {
>  	int (*ldo_open)(struct lin_device *ldev);
>  	int (*ldo_stop)(struct lin_device *ldev);
>  	int (*ldo_tx)(struct lin_device *ldev, const struct lin_frame *frame);
> +	int (*update_lin_mode)(struct lin_device *ldev, enum lin_mode lm);
>  	int (*update_bitrate)(struct lin_device *ldev, u16 bitrate);
>  	int (*update_responder_answer)(struct lin_device *ldev,
>  				       const struct lin_responder_answer *answ);
> diff --git a/include/uapi/linux/can/netlink.h b/include/uapi/linux/can/netlink.h
> index a37f56d86c5f2..cc390f6444d59 100644
> --- a/include/uapi/linux/can/netlink.h
> +++ b/include/uapi/linux/can/netlink.h
> @@ -104,6 +104,7 @@ struct can_ctrlmode {
>  #define CAN_CTRLMODE_TDC_AUTO		0x200	/* CAN transiver automatically calculates TDCV */
>  #define CAN_CTRLMODE_TDC_MANUAL		0x400	/* TDCV is manually set up by user */
>  #define CAN_CTRLMODE_LIN		BIT(11)	/* LIN bus mode */
> +#define CAN_CTRLMODE_LIN_COMMANDER	BIT(12)	/* LIN bus specific commander mode */
>  
>  /*
>   * CAN device statistics
> 

-- 
 i.