Re: [PATCH v4 09/11] can: lin: Handle rx offload config frames

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

On Thu, 9 May 2024, Christoph Fritz wrote:

> The CAN Broadcast Manager now has the capability to dispatch CANFD
> frames marked with the id LINBUS_RXOFFLOAD_ID.
> 
> Introduce functionality to interpret these specific frames, enabling the
> configuration of RX offloading within the LIN driver.
> 
> Signed-off-by: Christoph Fritz <christoph.fritz@hexdev.de>
> ---
>  drivers/net/can/lin.c | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/drivers/net/can/lin.c b/drivers/net/can/lin.c
> index a22768c17e3f8..f77abd7d7d21c 100644
> --- a/drivers/net/can/lin.c
> +++ b/drivers/net/can/lin.c
> @@ -185,6 +185,27 @@ static const struct attribute_group lin_sysfs_group = {
>  	.attrs = lin_sysfs_attrs,
>  };
>  
> +static int lin_setup_rxoffload(struct lin_device *ldev,
> +			       struct canfd_frame *cfd)
> +{
> +	struct lin_responder_answer answ;
> +
> +	if (!(cfd->flags & CANFD_FDF))
> +		return -EINVAL;
> +
> +	BUILD_BUG_ON(sizeof(answ) > sizeof(cfd->data));
> +	memcpy(&answ, cfd->data, sizeof(answ));
> +
> +	answ.lf.checksum_mode = (cfd->can_id & LIN_ENHANCED_CKSUM_FLAG) ?
> +			LINBUS_ENHANCED : LINBUS_CLASSIC;
> +
> +	if (answ.lf.lin_id > LIN_ID_MASK ||
> +	    answ.event_associated_id > LIN_ID_MASK)
> +		return -EINVAL;

These can be reverse so that error check occur before the checksum_mode 
assignment? It would feel more natural that way.

...Even better, if the error check could be done before the memcpy().

-- 
 i.


> +	return ldev->ldev_ops->update_responder_answer(ldev, &answ);
> +}
> +
>  static void lin_tx_work_handler(struct work_struct *ws)
>  {
>  	struct lin_device *ldev = container_of(ws, struct lin_device,
> @@ -197,6 +218,14 @@ static void lin_tx_work_handler(struct work_struct *ws)
>  	ldev->tx_busy = true;
>  
>  	cfd = (struct canfd_frame *)ldev->tx_skb->data;
> +
> +	if (cfd->can_id & LIN_RXOFFLOAD_DATA_FLAG) {
> +		ret = lin_setup_rxoffload(ldev, cfd);
> +		if (ret < 0)
> +			netdev_err(ndev, "setting up rx failed %d\n", ret);
> +		goto lin_tx_out;
> +	}
> +
>  	lf.checksum_mode = (cfd->can_id & LIN_ENHANCED_CKSUM_FLAG) ?
>  			   LINBUS_ENHANCED : LINBUS_CLASSIC;
>  	lf.lin_id = cfd->can_id & LIN_ID_MASK;
>