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

On Fri, Nov 20, 2020 at 12:58 PM Andrew Lunn [off-list ref] wrote:

On Fri, Nov 20, 2020 at 12:16:25PM -0600, George McCollister wrote:

quoted

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@gmail.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 [off-list ref]
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.

Done and tested. Thanks

      Andrew