Re: [PATCH v3 08/11] can: bcm: Add LIN answer offloading for responder mode

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

On Thu, 2 May 2024, Christoph Fritz wrote:

> Enhance CAN broadcast manager with RX_LIN_SETUP and RX_LIN_DELETE
> operations to setup automatic LIN frame responses in responder mode.
> 
> Additionally, the patch introduces the LIN_EVENT_FRAME flag to
> setup event-triggered LIN frames.
> 
> Signed-off-by: Christoph Fritz <christoph.fritz@hexdev.de>
> ---
>  include/uapi/linux/can/bcm.h |  5 ++-
>  net/can/bcm.c                | 74 +++++++++++++++++++++++++++++++++++-
>  2 files changed, 77 insertions(+), 2 deletions(-)
> 
> diff --git a/include/uapi/linux/can/bcm.h b/include/uapi/linux/can/bcm.h
> index f1e45f533a72c..c46268a114078 100644
> --- a/include/uapi/linux/can/bcm.h
> +++ b/include/uapi/linux/can/bcm.h
> @@ -86,7 +86,9 @@ enum {
>  	TX_EXPIRED,	/* notification on performed transmissions (count=0) */
>  	RX_STATUS,	/* reply to RX_READ request */
>  	RX_TIMEOUT,	/* cyclic message is absent */
> -	RX_CHANGED	/* updated CAN frame (detected content change) */
> +	RX_CHANGED,	/* updated CAN frame (detected content change) */
> +	RX_LIN_SETUP,	/* create auto-response for LIN frame */
> +	RX_LIN_DELETE,  /* remove auto-response for LIN frame */
>  };
>  
>  #define SETTIMER            0x0001
> @@ -101,5 +103,6 @@ enum {
>  #define TX_RESET_MULTI_IDX  0x0200
>  #define RX_RTR_FRAME        0x0400
>  #define CAN_FD_FRAME        0x0800
> +#define LIN_EVENT_FRAME     0x1000
>  
>  #endif /* !_UAPI_CAN_BCM_H */
> diff --git a/net/can/bcm.c b/net/can/bcm.c
> index 27d5fcf0eac9d..a717e594234d1 100644
> --- a/net/can/bcm.c
> +++ b/net/can/bcm.c
> @@ -59,6 +59,7 @@
>  #include <linux/can/bcm.h>
>  #include <linux/slab.h>
>  #include <net/sock.h>
> +#include <net/lin.h>
>  #include <net/net_namespace.h>
>  
>  /*
> @@ -1330,6 +1331,59 @@ static int bcm_tx_send(struct msghdr *msg, int ifindex, struct sock *sk,
>  	return cfsiz + MHSIZ;
>  }
>  
> +static int bcm_lin_setup(struct bcm_msg_head *msg_head, struct msghdr *msg,
> +			 int ifindex, struct sock *sk, int cfsiz, int is_active)
> +{
> +	struct lin_responder_answer answ;
> +	struct net_device *dev;
> +	struct sk_buff *skb;
> +	struct canfd_frame cf;
> +	netdevice_tracker tracker;
> +	size_t sz;
> +	int ret;
> +
> +	if (msg_head->nframes > 1)
> +		return -EINVAL;
> +
> +	if (!(msg_head->flags & CAN_FD_FRAME))
> +		return -EINVAL;
> +
> +	ret = memcpy_from_msg(&cf, msg, cfsiz);
> +	if (ret < 0)
> +		return ret;
> +
> +	answ.lf.lin_id = cf.can_id & LIN_ID_MASK;
> +	answ.is_active = is_active;
> +	answ.is_event_frame = !!(msg_head->flags & LIN_EVENT_FRAME);
> +	answ.event_associated_id = msg_head->can_id;
> +	answ.lf.len = min(cf.len, LIN_MAX_DLEN);
> +	memcpy(answ.lf.data, cf.data, answ.lf.len);
> +	sz = min(sizeof(struct lin_responder_answer), sizeof(cf.data));
> +	cf.can_id |= LIN_RXOFFLOAD_DATA_FLAG;
> +	memcpy(cf.data, &answ, sz);
> +
> +	dev = netdev_get_by_index(sock_net(sk), ifindex, &tracker, GFP_KERNEL);
> +	if (!dev)
> +		return -ENODEV;
> +
> +	skb = alloc_skb(cfsiz + sizeof(struct can_skb_priv), gfp_any());

You just called the other function with GFP_KERNEL and you now need 
gfp_any(). Which is correct??

> +	if (!skb)
> +		goto lin_out;
> +
> +	can_skb_reserve(skb);
> +	can_skb_prv(skb)->ifindex = dev->ifindex;
> +	can_skb_prv(skb)->skbcnt = 0;
> +	skb_put_data(skb, &cf, cfsiz);
> +
> +	skb->dev = dev;
> +	can_skb_set_owner(skb, sk);
> +	ret = can_send(skb, 1); /* send with loopback */
> +
> +lin_out:
> +	netdev_put(dev, &tracker);
> +	return ret;
> +}
> +
>  /*
>   * bcm_sendmsg - process BCM commands (opcodes) from the userspace
>   */
> @@ -1429,12 +1483,30 @@ static int bcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
>  
>  	case TX_SEND:
>  		/* we need exactly one CAN frame behind the msg head */
> -		if ((msg_head.nframes != 1) || (size != cfsiz + MHSIZ))
> +		if (msg_head.nframes != 1 || size != cfsiz + MHSIZ)

Unrelated style fix, doesn't belong to this patch.

>  			ret = -EINVAL;
>  		else
>  			ret = bcm_tx_send(msg, ifindex, sk, cfsiz);
>  		break;
>  
> +	case RX_LIN_SETUP:
> +		/* we need exactly one CAN frame behind the msg head */
> +		if (msg_head.nframes != 1 || size != cfsiz + MHSIZ)
> +			ret = -EINVAL;
> +		else
> +			ret = bcm_lin_setup(&msg_head, msg, ifindex, sk, cfsiz,
> +					    1);
> +		break;
> +
> +	case RX_LIN_DELETE:
> +		/* we need exactly one CAN frame behind the msg head */
> +		if (msg_head.nframes != 1 || size != cfsiz + MHSIZ)
> +			ret = -EINVAL;
> +		else
> +			ret = bcm_lin_setup(&msg_head, msg, ifindex, sk, cfsiz,
> +					    0);
> +		break;
> +
>  	default:
>  		ret = -EINVAL;
>  		break;
> 

-- 
 i.