Re: [RFC net-next 1/2] net: dsa: add Realtek RTL8366S switch tag

[Heiner Kallweit <hkallweit1@gmail.com>]

On 17.02.2021 07:21, DENG Qingfang wrote:
> Add support for Realtek RTL8366S switch tag
> 
> Signed-off-by: DENG Qingfang <dqfext@gmail.com>
> ---
>  include/net/dsa.h      |  2 +
>  net/dsa/Kconfig        |  6 +++
>  net/dsa/Makefile       |  1 +
>  net/dsa/tag_rtl8366s.c | 98 ++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 107 insertions(+)
>  create mode 100644 net/dsa/tag_rtl8366s.c
> 
> diff --git a/include/net/dsa.h b/include/net/dsa.h
> index 83a933e563fe..14fedf832f27 100644
> --- a/include/net/dsa.h
> +++ b/include/net/dsa.h
> @@ -49,6 +49,7 @@ struct phylink_link_state;
>  #define DSA_TAG_PROTO_XRS700X_VALUE		19
>  #define DSA_TAG_PROTO_OCELOT_8021Q_VALUE	20
>  #define DSA_TAG_PROTO_SEVILLE_VALUE		21
> +#define DSA_TAG_PROTO_RTL8366S_VALUE		22
>  
>  enum dsa_tag_protocol {
>  	DSA_TAG_PROTO_NONE		= DSA_TAG_PROTO_NONE_VALUE,
> @@ -73,6 +74,7 @@ enum dsa_tag_protocol {
>  	DSA_TAG_PROTO_XRS700X		= DSA_TAG_PROTO_XRS700X_VALUE,
>  	DSA_TAG_PROTO_OCELOT_8021Q	= DSA_TAG_PROTO_OCELOT_8021Q_VALUE,
>  	DSA_TAG_PROTO_SEVILLE		= DSA_TAG_PROTO_SEVILLE_VALUE,
> +	DSA_TAG_PROTO_RTL8366S		= DSA_TAG_PROTO_RTL8366S_VALUE,
>  };
>  
>  struct packet_type;
> diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
> index a45572cfb71a..303228e0ad8b 100644
> --- a/net/dsa/Kconfig
> +++ b/net/dsa/Kconfig
> @@ -104,6 +104,12 @@ config NET_DSA_TAG_RTL4_A
>  	  Realtek switches with 4 byte protocol A tags, sich as found in
>  	  the Realtek RTL8366RB.
>  
> +config NET_DSA_TAG_RTL8366S
> +	tristate "Tag driver for Realtek RTL8366S switch tags"
> +	help
> +	  Say Y or M if you want to enable support for tagging frames for the
> +	  Realtek RTL8366S switch.
> +
>  config NET_DSA_TAG_OCELOT
>  	tristate "Tag driver for Ocelot family of switches, using NPI port"
>  	select PACKING
> diff --git a/net/dsa/Makefile b/net/dsa/Makefile
> index 44bc79952b8b..df158e73a30b 100644
> --- a/net/dsa/Makefile
> +++ b/net/dsa/Makefile
> @@ -12,6 +12,7 @@ obj-$(CONFIG_NET_DSA_TAG_GSWIP) += tag_gswip.o
>  obj-$(CONFIG_NET_DSA_TAG_HELLCREEK) += tag_hellcreek.o
>  obj-$(CONFIG_NET_DSA_TAG_KSZ) += tag_ksz.o
>  obj-$(CONFIG_NET_DSA_TAG_RTL4_A) += tag_rtl4_a.o
> +obj-$(CONFIG_NET_DSA_TAG_RTL8366S) += tag_rtl8366s.o
>  obj-$(CONFIG_NET_DSA_TAG_LAN9303) += tag_lan9303.o
>  obj-$(CONFIG_NET_DSA_TAG_MTK) += tag_mtk.o
>  obj-$(CONFIG_NET_DSA_TAG_OCELOT) += tag_ocelot.o
> diff --git a/net/dsa/tag_rtl8366s.c b/net/dsa/tag_rtl8366s.c
> new file mode 100644
> index 000000000000..6c6c66853e4c
> --- /dev/null
> +++ b/net/dsa/tag_rtl8366s.c
> @@ -0,0 +1,98 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Handler for Realtek RTL8366S switch tags
> + * Copyright (c) 2021 DENG, Qingfang <dqfext@gmail.com>
> + *
> + * This tag header looks like:
> + *
> + * -------------------------------------------------
> + * | MAC DA | MAC SA | 0x8899 | 2-byte tag  | Type |
> + * -------------------------------------------------
> + *
> + * The 2-byte tag format in tag_rcv:
> + *       +------+------+------+------+------+------+------+------+
> + * 15: 8 |   Protocol number (0x9)   |  Priority   |  Reserved   |
> + *       +------+------+------+------+------+------+------+------+
> + *  7: 0 |             Reserved             | Source port number |
> + *       +------+------+------+------+------+------+------+------+
> + *
> + * The 2-byte tag format in tag_xmit:
> + *       +------+------+------+------+------+------+------+------+
> + * 15: 8 |   Protocol number (0x9)   |  Priority   |  Reserved   |
> + *       +------+------+------+------+------+------+------+------+
> + *  7: 0 |  Reserved   |          Destination port mask          |
> + *       +------+------+------+------+------+------+------+------+
> + */
> +
> +#include <linux/etherdevice.h>
> +
> +#include "dsa_priv.h"
> +
> +#define RTL8366S_HDR_LEN	4
> +#define RTL8366S_ETHERTYPE	0x8899

I found this protocol referenced as Realtek Remote Control Protocol (RRCP)
and it seems to be used by few Realtek chips. Not sure whether this
protocol is officially registered. If yes, then it should be added to
the list of ethernet protocol id's in include/uapi/linux/if_ether.h.
If not, then it may be better to define it using the usual naming
scheme as ETH_P_RRCP in realtek-smi-core.h.


> +#define RTL8366S_PROTOCOL_SHIFT	12
> +#define RTL8366S_PROTOCOL	0x9
> +#define RTL8366S_TAG	\
> +	(RTL8366S_PROTOCOL << RTL8366S_PROTOCOL_SHIFT)
> +
> +static struct sk_buff *rtl8366s_tag_xmit(struct sk_buff *skb,
> +					 struct net_device *dev)
> +{
> +	struct dsa_port *dp = dsa_slave_to_port(dev);
> +	__be16 *tag;
> +
> +	/* Make sure the frame is at least 60 bytes long _before_
> +	 * inserting the CPU tag, or it will be dropped by the switch.
> +	 */
> +	if (unlikely(eth_skb_pad(skb)))
> +		return NULL;
> +
> +	skb_push(skb, RTL8366S_HDR_LEN);
> +	memmove(skb->data, skb->data + RTL8366S_HDR_LEN,
> +		2 * ETH_ALEN);
> +
> +	tag = (__be16 *)(skb->data + 2 * ETH_ALEN);
> +	tag[0] = htons(RTL8366S_ETHERTYPE);
> +	tag[1] = htons(RTL8366S_TAG | BIT(dp->index));
> +
> +	return skb;
> +}
> +
> +static struct sk_buff *rtl8366s_tag_rcv(struct sk_buff *skb,
> +					struct net_device *dev,
> +					struct packet_type *pt)
> +{
> +	u8 *tag;
> +	u8 port;
> +
> +	if (unlikely(!pskb_may_pull(skb, RTL8366S_HDR_LEN)))
> +		return NULL;
> +
> +	tag = skb->data - 2;
> +	port = tag[3] & 0x7;
> +
> +	skb->dev = dsa_master_find_slave(dev, 0, port);
> +	if (unlikely(!skb->dev))
> +		return NULL;
> +
> +	skb_pull_rcsum(skb, RTL8366S_HDR_LEN);
> +	memmove(skb->data - ETH_HLEN,
> +		skb->data - ETH_HLEN - RTL8366S_HDR_LEN,
> +		2 * ETH_ALEN);
> +
> +	skb->offload_fwd_mark = 1;
> +
> +	return skb;
> +}
> +
> +static const struct dsa_device_ops rtl8366s_netdev_ops = {
> +	.name		= "rtl8366s",
> +	.proto		= DSA_TAG_PROTO_RTL8366S,
> +	.xmit		= rtl8366s_tag_xmit,
> +	.rcv		= rtl8366s_tag_rcv,
> +	.overhead	= RTL8366S_HDR_LEN,
> +};
> +module_dsa_tag_driver(rtl8366s_netdev_ops);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_RTL8366S);
>