// SPDX-License-Identifier: (GPL-2.0 OR MIT)
/*
 * net/dsa/tag_hellcreek.c - Hirschmann Hellcreek switch tag format handling
 *
 * Copyright (C) 2019,2020 Linutronix GmbH
 * Author Kurt Kanzenbach <kurt@linutronix.de>
 *
 * Based on tag_ksz.c.
 */

#include <linux/skbuff.h>
#include <net/dsa.h>

#include "tag.h"

#define HELLCREEK_NAME          "hellcreek"

#define HELLCREEK_TAG_LEN       1

static struct sk_buff *hellcreek_xmit(struct sk_buff *skb,
                                      struct net_device *dev)
{
        u8 *tag;

        /* Calculate checksums (if required) before adding the trailer tag to
         * avoid including it in calculations. That would lead to wrong
         * checksums after the switch strips the tag.
         */
        if (skb->ip_summed == CHECKSUM_PARTIAL &&
            skb_checksum_help(skb))
                return NULL;

        /* Tag encoding */
        tag  = skb_put(skb, HELLCREEK_TAG_LEN);
        *tag = dsa_xmit_port_mask(skb, dev);

        return skb;
}

static struct sk_buff *hellcreek_rcv(struct sk_buff *skb,
                                     struct net_device *dev)
{
        /* Tag decoding */
        u8 *tag = skb_tail_pointer(skb) - HELLCREEK_TAG_LEN;
        unsigned int port = tag[0] & 0x03;

        skb->dev = dsa_conduit_find_user(dev, 0, port);
        if (!skb->dev) {
                netdev_warn_once(dev, "Failed to get source port: %d\n", port);
                return NULL;
        }

        if (pskb_trim_rcsum(skb, skb->len - HELLCREEK_TAG_LEN))
                return NULL;

        dsa_default_offload_fwd_mark(skb);

        return skb;
}

static const struct dsa_device_ops hellcreek_netdev_ops = {
        .name     = HELLCREEK_NAME,
        .proto    = DSA_TAG_PROTO_HELLCREEK,
        .xmit     = hellcreek_xmit,
        .rcv      = hellcreek_rcv,
        .needed_tailroom = HELLCREEK_TAG_LEN,
};

MODULE_DESCRIPTION("DSA tag driver for Hirschmann Hellcreek TSN switches");
MODULE_LICENSE("Dual MIT/GPL");
MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_HELLCREEK, HELLCREEK_NAME);

module_dsa_tag_driver(hellcreek_netdev_ops);