Re: [PATCH v5 1/3] net: mhi : Add support to enable ethernet interface

[Dmitry Baryshkov]

On Thu, Nov 06, 2025 at 06:58:08PM +0530, Vivek Pernamitta wrote:
> From: Vivek Pernamitta <vivek.pernamitta@xxxxxxxxxxxxxxxx>
> 
> Currently, we only have support for the NET driver. This update allows a
> new client to be configured as an Ethernet type over MHI by setting
> "mhi_device_info.ethernet_if = true". A new interface for Ethernet will
> be created with eth%d.

Please describe the reasons for the patch. Also please don't use words
like "This patch" or "This update". Use imperative language instead.

> 
> Signed-off-by: Vivek Pernamitta <vivek.pernamitta@xxxxxxxxxxxxxxxx>
> ---
>  drivers/net/mhi_net.c | 84 +++++++++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 71 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/mhi_net.c b/drivers/net/mhi_net.c
> index ae169929a9d8e449b5a427993abf68e8d032fae2..aeb2d67aeb238e520dbd2a83b35602a7e5144fa2 100644
> --- a/drivers/net/mhi_net.c
> +++ b/drivers/net/mhi_net.c
> @@ -11,6 +11,7 @@
>  #include <linux/netdevice.h>
>  #include <linux/skbuff.h>
>  #include <linux/u64_stats_sync.h>
> +#include <linux/etherdevice.h>

Keep it sorted.

>  
>  #define MHI_NET_MIN_MTU		ETH_MIN_MTU
>  #define MHI_NET_MAX_MTU		0xffff
> @@ -38,10 +39,12 @@ struct mhi_net_dev {
>  	u32 rx_queue_sz;
>  	int msg_enable;
>  	unsigned int mru;
> +	bool ethernet_if;
>  };
>  
>  struct mhi_device_info {
>  	const char *netname;
> +	bool ethernet_if;
>  };
>  
>  static int mhi_ndo_open(struct net_device *ndev)
> @@ -119,11 +122,37 @@ static void mhi_ndo_get_stats64(struct net_device *ndev,
>  	} while (u64_stats_fetch_retry(&mhi_netdev->stats.tx_syncp, start));
>  }
>  
> +static int mhi_mac_address(struct net_device *dev, void *p)
> +{
> +	int ret;
> +
> +	if (dev->type == ARPHRD_ETHER) {
> +		ret = eth_mac_addr(dev, p);
> +	return ret;

Why do you need an interim variable?

> +	}
> +
> +	return 0;
> +}
> +
> +static int mhi_validate_address(struct net_device *dev)
> +{
> +	int ret;
> +
> +	if (dev->type == ARPHRD_ETHER) {
> +		ret = eth_validate_addr(dev);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
>  static const struct net_device_ops mhi_netdev_ops = {
>  	.ndo_open               = mhi_ndo_open,
>  	.ndo_stop               = mhi_ndo_stop,
>  	.ndo_start_xmit         = mhi_ndo_xmit,
>  	.ndo_get_stats64	= mhi_ndo_get_stats64,
> +	.ndo_set_mac_address    = mhi_mac_address,
> +	.ndo_validate_addr      = mhi_validate_address,
>  };
>  
>  static void mhi_net_setup(struct net_device *ndev)
> @@ -140,6 +169,14 @@ static void mhi_net_setup(struct net_device *ndev)
>  	ndev->tx_queue_len = 1000;
>  }
>  
> +static void mhi_ethernet_setup(struct net_device *ndev)
> +{
> +	ndev->netdev_ops = &mhi_netdev_ops;
> +	ether_setup(ndev);
> +	ndev->min_mtu = ETH_MIN_MTU;
> +	ndev->max_mtu = ETH_MAX_MTU;
> +}
> +
>  static struct sk_buff *mhi_net_skb_agg(struct mhi_net_dev *mhi_netdev,
>  				       struct sk_buff *skb)
>  {
> @@ -209,16 +246,22 @@ static void mhi_net_dl_callback(struct mhi_device *mhi_dev,
>  			mhi_netdev->skbagg_head = NULL;
>  		}
>  
> -		switch (skb->data[0] & 0xf0) {
> -		case 0x40:
> -			skb->protocol = htons(ETH_P_IP);
> -			break;
> -		case 0x60:
> -			skb->protocol = htons(ETH_P_IPV6);
> -			break;
> -		default:
> -			skb->protocol = htons(ETH_P_MAP);
> -			break;
> +		if (mhi_netdev->ethernet_if) {
> +			skb_copy_to_linear_data(skb, skb->data,
> +						mhi_res->bytes_xferd);
> +			skb->protocol = eth_type_trans(skb, mhi_netdev->ndev);
> +		} else {
> +			switch (skb->data[0] & 0xf0) {
> +			case 0x40:
> +				skb->protocol = htons(ETH_P_IP);
> +				break;
> +			case 0x60:
> +				skb->protocol = htons(ETH_P_IPV6);
> +				break;
> +			default:
> +				skb->protocol = htons(ETH_P_MAP);
> +				break;
> +			}
>  		}
>  
>  		u64_stats_update_begin(&mhi_netdev->stats.rx_syncp);
> @@ -301,11 +344,17 @@ static void mhi_net_rx_refill_work(struct work_struct *work)
>  		schedule_delayed_work(&mhi_netdev->rx_refill, HZ / 2);
>  }
>  
> -static int mhi_net_newlink(struct mhi_device *mhi_dev, struct net_device *ndev)
> +static int mhi_net_newlink(struct mhi_device *mhi_dev, struct net_device *ndev, bool eth_dev)
>  {
>  	struct mhi_net_dev *mhi_netdev;
>  	int err;
>  
> +	if (eth_dev) {
> +		eth_hw_addr_random(ndev);
> +		if (!is_valid_ether_addr(ndev->dev_addr))

Can this actually happen? Can eth_hw_addr_random() generate invalid
address?

> +			return -EADDRNOTAVAIL;
> +	}
> +
>  	mhi_netdev = netdev_priv(ndev);
>  
>  	dev_set_drvdata(&mhi_dev->dev, mhi_netdev);
> @@ -313,6 +362,7 @@ static int mhi_net_newlink(struct mhi_device *mhi_dev, struct net_device *ndev)
>  	mhi_netdev->mdev = mhi_dev;
>  	mhi_netdev->skbagg_head = NULL;
>  	mhi_netdev->mru = mhi_dev->mhi_cntrl->mru;
> +	mhi_netdev->ethernet_if = eth_dev;
>  
>  	INIT_DELAYED_WORK(&mhi_netdev->rx_refill, mhi_net_rx_refill_work);
>  	u64_stats_init(&mhi_netdev->stats.rx_syncp);
> @@ -356,13 +406,14 @@ static int mhi_net_probe(struct mhi_device *mhi_dev,
>  	int err;
>  
>  	ndev = alloc_netdev(sizeof(struct mhi_net_dev), info->netname,
> -			    NET_NAME_PREDICTABLE, mhi_net_setup);
> +			    NET_NAME_PREDICTABLE, info->ethernet_if ?
> +			    mhi_ethernet_setup : mhi_net_setup);
>  	if (!ndev)
>  		return -ENOMEM;
>  
>  	SET_NETDEV_DEV(ndev, &mhi_dev->dev);
>  
> -	err = mhi_net_newlink(mhi_dev, ndev);
> +	err = mhi_net_newlink(mhi_dev, ndev, info->ethernet_if);
>  	if (err) {
>  		free_netdev(ndev);
>  		return err;
> @@ -380,10 +431,17 @@ static void mhi_net_remove(struct mhi_device *mhi_dev)
>  
>  static const struct mhi_device_info mhi_hwip0 = {
>  	.netname = "mhi_hwip%d",
> +	.ethernet_if = false,
>  };
>  
>  static const struct mhi_device_info mhi_swip0 = {
>  	.netname = "mhi_swip%d",
> +	.ethernet_if = false,
> +};
> +
> +static const struct mhi_device_info mhi_eth0 = {

Unused

> +	.netname = "eth%d",
> +	.ethernet_if = true,
>  };
>  
>  static const struct mhi_device_id mhi_net_id_table[] = {
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry