netdev - Re: [PATCH net-next 1/3] dsa: add support for Arrow XRS700x tag trailer

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Date:   Fri, 20 Nov 2020 19:58:53 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     George McCollister <george.mccollister@...il.com>
Cc:     Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S . Miller " <davem@...emloft.net>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH net-next 1/3] dsa: add support for Arrow XRS700x tag
 trailer

On Fri, Nov 20, 2020 at 12:16:25PM -0600, George McCollister wrote:
> Add support for Arrow SpeedChips XRS700x single byte tag trailer. This
> is modeled on tag_trailer.c which works in a similar way.
> 
> Signed-off-by: George McCollister <george.mccollister@...il.com>
> ---
>  include/net/dsa.h     |  2 ++
>  net/dsa/Kconfig       |  6 ++++
>  net/dsa/Makefile      |  1 +
>  net/dsa/tag_xrs700x.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 100 insertions(+)
>  create mode 100644 net/dsa/tag_xrs700x.c
> 
> diff --git a/include/net/dsa.h b/include/net/dsa.h
> index 2e64e8de4631..eb46ecdcf165 100644
> --- a/include/net/dsa.h
> +++ b/include/net/dsa.h
> @@ -46,6 +46,7 @@ struct phylink_link_state;
>  #define DSA_TAG_PROTO_AR9331_VALUE		16
>  #define DSA_TAG_PROTO_RTL4_A_VALUE		17
>  #define DSA_TAG_PROTO_HELLCREEK_VALUE		18
> +#define DSA_TAG_PROTO_XRS700X_VALUE		19
>  
>  enum dsa_tag_protocol {
>  	DSA_TAG_PROTO_NONE		= DSA_TAG_PROTO_NONE_VALUE,
> @@ -67,6 +68,7 @@ enum dsa_tag_protocol {
>  	DSA_TAG_PROTO_AR9331		= DSA_TAG_PROTO_AR9331_VALUE,
>  	DSA_TAG_PROTO_RTL4_A		= DSA_TAG_PROTO_RTL4_A_VALUE,
>  	DSA_TAG_PROTO_HELLCREEK		= DSA_TAG_PROTO_HELLCREEK_VALUE,
> +	DSA_TAG_PROTO_XRS700X		= DSA_TAG_PROTO_XRS700X_VALUE,
>  };
>  
>  struct packet_type;
> diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
> index dfecd7b22fd7..2d226a5c085f 100644
> --- a/net/dsa/Kconfig
> +++ b/net/dsa/Kconfig
> @@ -139,4 +139,10 @@ config NET_DSA_TAG_TRAILER
>  	  Say Y or M if you want to enable support for tagging frames at
>  	  with a trailed. e.g. Marvell 88E6060.
>  
> +config NET_DSA_TAG_XRS700X
> +	tristate "Tag driver for XRS700x switches"
> +	help
> +	  Say Y or M if you want to enable support for tagging frames for
> +	  Arrow SpeedChips XRS700x switches that use a single byte tag trailer.
> +
>  endif
> diff --git a/net/dsa/Makefile b/net/dsa/Makefile
> index 0fb2b75a7ae3..92cea2132241 100644
> --- a/net/dsa/Makefile
> +++ b/net/dsa/Makefile
> @@ -18,3 +18,4 @@ obj-$(CONFIG_NET_DSA_TAG_OCELOT) += tag_ocelot.o
>  obj-$(CONFIG_NET_DSA_TAG_QCA) += tag_qca.o
>  obj-$(CONFIG_NET_DSA_TAG_SJA1105) += tag_sja1105.o
>  obj-$(CONFIG_NET_DSA_TAG_TRAILER) += tag_trailer.o
> +obj-$(CONFIG_NET_DSA_TAG_XRS700X) += tag_xrs700x.o
> diff --git a/net/dsa/tag_xrs700x.c b/net/dsa/tag_xrs700x.c
> new file mode 100644
> index 000000000000..2eda57a4a474
> --- /dev/null
> +++ b/net/dsa/tag_xrs700x.c
> @@ -0,0 +1,91 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * XRS700x tag format handling
> + * Copyright (c) 2008-2009 Marvell Semiconductor
> + * Copyright (c) 2020 NovaTech LLC
> + */
> +
> +#include <linux/etherdevice.h>
> +#include <linux/list.h>
> +#include <linux/slab.h>
> +#include <linux/bitops.h>
> +
> +#include "dsa_priv.h"
> +
> +static struct sk_buff *xrs700x_xmit(struct sk_buff *skb, struct net_device *dev)
> +{
> +	struct dsa_port *dp = dsa_slave_to_port(dev);
> +	struct sk_buff *nskb;
> +	int padlen;
> +	u8 *trailer;
> +
> +	/* We have to make sure that the trailer ends up as the very
> +	 * last byte of the packet.  This means that we have to pad
> +	 * the packet to the minimum ethernet frame size, if necessary,
> +	 * before adding the trailer.
> +	 */
> +	padlen = 0;
> +	if (skb->len < 63)
> +		padlen = 63 - skb->len;
> +
> +	nskb = alloc_skb(NET_IP_ALIGN + skb->len + padlen + 1, GFP_ATOMIC);
> +	if (!nskb)
> +		return NULL;
> +	skb_reserve(nskb, NET_IP_ALIGN);

Hi George

This needs updating to take into account:

commit a3b0b6479700a5b0af2c631cb2ec0fb7a0d978f2
Author: Vladimir Oltean <vladimir.oltean@....com>
Date:   Sun Nov 1 21:16:09 2020 +0200

    net: dsa: implement a central TX reallocation procedure

which i think will handle the padding for you.

      Andrew