Re: [PATCH 1/2] net: dsa: tag_yt921x: add support for Motorcomm YT921x tags

[Andrew Lunn <andrew@lunn.ch>]

On Sat, Aug 09, 2025 at 01:38:02AM +0800, David Yang wrote:
> Add support for Motorcomm YT921x tags, which includes a configurable
> ethertype field (default to 0x9988).

Hi David

Please take a read of:

https://www.kernel.org/doc/html/latest/process/maintainer-netdev.html

We are in the merge window at the moment, so you need to post patches
as RFC. And you need to indicate the tree in the Subject: line.

> +#define YT921X_TAG_PORT_ENf	BIT(15)
> +#define YT921X_TAG_RX_PORTf	GENMASK(14, 11)
> +#define YT921X_TAG_TX_PORTf	GENMASK(10, 0)
> +#define  YT921X_TAG_TX_PORTnv(port)	BIT(port)

These lower case letters at the end are unusual. What do they
represent?

> +static struct sk_buff *
> +yt921x_tag_xmit(struct sk_buff *skb, struct net_device *netdev)
> +{
> +	struct dsa_port *dp = dsa_user_to_port(netdev);
> +	__be16 *tag;
> +
> +	skb_push(skb, YT921X_TAG_LEN);
> +	dsa_alloc_etype_header(skb, YT921X_TAG_LEN);
> +
> +	tag = (__be16 *)(skb->data + 2 * ETH_ALEN);

dsa_etype_header_pos_tx() ?

> +static struct sk_buff *
> +yt921x_tag_rcv(struct sk_buff *skb, struct net_device *netdev)
> +{
> +	__be16 *tag;
> +	u16 rx;
> +	int rx_port;

Reverse Christmas tree. Longest to shortest.

    Andrew

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