// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2024 Pengutronix, Oleksij Rempel <kernel@pengutronix.de>

#include <linux/array_size.h>
#include <linux/printk.h>
#include <linux/types.h>
#include <net/dscp.h>
#include <net/ieee8021q.h>

/* verify that table covers all 8 traffic types */
#define TT_MAP_SIZE_OK(tbl)                                 \
        compiletime_assert(ARRAY_SIZE(tbl) == IEEE8021Q_TT_MAX, \
                           #tbl " size mismatch")

/* The following arrays map Traffic Types (TT) to traffic classes (TC) for
 * different number of queues as shown in the example provided by
 * IEEE 802.1Q-2022 in Annex I "I.3 Traffic type to traffic class mapping" and
 * Table I-1 "Traffic type to traffic class mapping".
 */
static const u8 ieee8021q_8queue_tt_tc_map[] = {
        [IEEE8021Q_TT_BK] = 0,
        [IEEE8021Q_TT_BE] = 1,
        [IEEE8021Q_TT_EE] = 2,
        [IEEE8021Q_TT_CA] = 3,
        [IEEE8021Q_TT_VI] = 4,
        [IEEE8021Q_TT_VO] = 5,
        [IEEE8021Q_TT_IC] = 6,
        [IEEE8021Q_TT_NC] = 7,
};

static const u8 ieee8021q_7queue_tt_tc_map[] = {
        [IEEE8021Q_TT_BK] = 0,
        [IEEE8021Q_TT_BE] = 1,
        [IEEE8021Q_TT_EE] = 2,
        [IEEE8021Q_TT_CA] = 3,
        [IEEE8021Q_TT_VI] = 4,  [IEEE8021Q_TT_VO] = 4,
        [IEEE8021Q_TT_IC] = 5,
        [IEEE8021Q_TT_NC] = 6,
};

static const u8 ieee8021q_6queue_tt_tc_map[] = {
        [IEEE8021Q_TT_BK] = 0,
        [IEEE8021Q_TT_BE] = 1,
        [IEEE8021Q_TT_EE] = 2,  [IEEE8021Q_TT_CA] = 2,
        [IEEE8021Q_TT_VI] = 3,  [IEEE8021Q_TT_VO] = 3,
        [IEEE8021Q_TT_IC] = 4,
        [IEEE8021Q_TT_NC] = 5,
};

static const u8 ieee8021q_5queue_tt_tc_map[] = {
        [IEEE8021Q_TT_BK] = 0, [IEEE8021Q_TT_BE] = 0,
        [IEEE8021Q_TT_EE] = 1, [IEEE8021Q_TT_CA] = 1,
        [IEEE8021Q_TT_VI] = 2, [IEEE8021Q_TT_VO] = 2,
        [IEEE8021Q_TT_IC] = 3,
        [IEEE8021Q_TT_NC] = 4,
};

static const u8 ieee8021q_4queue_tt_tc_map[] = {
        [IEEE8021Q_TT_BK] = 0, [IEEE8021Q_TT_BE] = 0,
        [IEEE8021Q_TT_EE] = 1, [IEEE8021Q_TT_CA] = 1,
        [IEEE8021Q_TT_VI] = 2, [IEEE8021Q_TT_VO] = 2,
        [IEEE8021Q_TT_IC] = 3, [IEEE8021Q_TT_NC] = 3,
};

static const u8 ieee8021q_3queue_tt_tc_map[] = {
        [IEEE8021Q_TT_BK] = 0, [IEEE8021Q_TT_BE] = 0,
        [IEEE8021Q_TT_EE] = 0, [IEEE8021Q_TT_CA] = 0,
        [IEEE8021Q_TT_VI] = 1, [IEEE8021Q_TT_VO] = 1,
        [IEEE8021Q_TT_IC] = 2, [IEEE8021Q_TT_NC] = 2,
};

static const u8 ieee8021q_2queue_tt_tc_map[] = {
        [IEEE8021Q_TT_BK] = 0, [IEEE8021Q_TT_BE] = 0,
        [IEEE8021Q_TT_EE] = 0, [IEEE8021Q_TT_CA] = 0,
        [IEEE8021Q_TT_VI] = 1, [IEEE8021Q_TT_VO] = 1,
        [IEEE8021Q_TT_IC] = 1, [IEEE8021Q_TT_NC] = 1,
};

static const u8 ieee8021q_1queue_tt_tc_map[] = {
        [IEEE8021Q_TT_BK] = 0, [IEEE8021Q_TT_BE] = 0,
        [IEEE8021Q_TT_EE] = 0, [IEEE8021Q_TT_CA] = 0,
        [IEEE8021Q_TT_VI] = 0, [IEEE8021Q_TT_VO] = 0,
        [IEEE8021Q_TT_IC] = 0, [IEEE8021Q_TT_NC] = 0,
};

/**
 * ieee8021q_tt_to_tc - Map IEEE 802.1Q Traffic Type to Traffic Class
 * @tt: IEEE 802.1Q Traffic Type
 * @num_queues: Number of queues
 *
 * This function maps an IEEE 802.1Q Traffic Type to a Traffic Class (TC) based
 * on the number of queues configured on the NIC. The mapping is based on the
 * example provided by IEEE 802.1Q-2022 in Annex I "I.3 Traffic type to traffic
 * class mapping" and Table I-1 "Traffic type to traffic class mapping".
 *
 * Return: Traffic Class corresponding to the given Traffic Type or negative
 * value in case of error.
 */
int ieee8021q_tt_to_tc(enum ieee8021q_traffic_type tt, unsigned int num_queues)
{
        if (tt < 0 || tt >= IEEE8021Q_TT_MAX) {
                pr_err("Requested Traffic Type (%d) is out of range (%d)\n", tt,
                       IEEE8021Q_TT_MAX);
                return -EINVAL;
        }

        switch (num_queues) {
        case 8:
                TT_MAP_SIZE_OK(ieee8021q_8queue_tt_tc_map);
                return ieee8021q_8queue_tt_tc_map[tt];
        case 7:
                TT_MAP_SIZE_OK(ieee8021q_7queue_tt_tc_map);
                return ieee8021q_7queue_tt_tc_map[tt];
        case 6:
                TT_MAP_SIZE_OK(ieee8021q_6queue_tt_tc_map);
                return ieee8021q_6queue_tt_tc_map[tt];
        case 5:
                TT_MAP_SIZE_OK(ieee8021q_5queue_tt_tc_map);
                return ieee8021q_5queue_tt_tc_map[tt];
        case 4:
                TT_MAP_SIZE_OK(ieee8021q_4queue_tt_tc_map);
                return ieee8021q_4queue_tt_tc_map[tt];
        case 3:
                TT_MAP_SIZE_OK(ieee8021q_3queue_tt_tc_map);
                return ieee8021q_3queue_tt_tc_map[tt];
        case 2:
                TT_MAP_SIZE_OK(ieee8021q_2queue_tt_tc_map);
                return ieee8021q_2queue_tt_tc_map[tt];
        case 1:
                TT_MAP_SIZE_OK(ieee8021q_1queue_tt_tc_map);
                return ieee8021q_1queue_tt_tc_map[tt];
        }

        pr_err("Invalid number of queues %d\n", num_queues);

        return -EINVAL;
}
EXPORT_SYMBOL_GPL(ieee8021q_tt_to_tc);

/**
 * ietf_dscp_to_ieee8021q_tt - Map IETF DSCP to IEEE 802.1Q Traffic Type
 * @dscp: IETF DSCP value
 *
 * This function maps an IETF DSCP value to an IEEE 802.1Q Traffic Type (TT).
 * Since there is no corresponding mapping between DSCP and IEEE 802.1Q Traffic
 * Type, this function is inspired by the RFC8325 documentation which describe
 * the mapping between DSCP and 802.11 User Priority (UP) values.
 *
 * Return: IEEE 802.1Q Traffic Type corresponding to the given DSCP value
 */
int ietf_dscp_to_ieee8021q_tt(u8 dscp)
{
        switch (dscp) {
        case DSCP_CS0:
        /* Comment from RFC8325:
         * [RFC4594], Section 4.8, recommends High-Throughput Data be marked
         * AF1x (that is, AF11, AF12, and AF13, according to the rules defined
         * in [RFC2475]).
         *
         * By default (as described in Section 2.3), High-Throughput Data will
         * map to UP 1 and, thus, to the Background Access Category (AC_BK),
         * which is contrary to the intent expressed in [RFC4594].

         * Unfortunately, there really is no corresponding fit for the High-
         * Throughput Data service class within the constrained 4 Access
         * Category [IEEE.802.11-2016] model.  If the High-Throughput Data
         * service class is assigned to the Best Effort Access Category (AC_BE),
         * then it would contend with Low-Latency Data (while [RFC4594]
         * recommends a distinction in servicing between these service classes)
         * as well as with the default service class; alternatively, if it is
         * assigned to the Background Access Category (AC_BK), then it would
         * receive a less-then-best-effort service and contend with Low-Priority
         * Data (as discussed in Section 4.2.10).
         *
         * As such, since there is no directly corresponding fit for the High-
         * Throughout Data service class within the [IEEE.802.11-2016] model, it
         * is generally RECOMMENDED to map High-Throughput Data to UP 0, thereby
         * admitting it to the Best Effort Access Category (AC_BE).
         *
         * Note: The above text is from RFC8325 which is describing the mapping
         * between DSCP and 802.11 User Priority (UP) values. The mapping
         * between UP and IEEE 802.1Q Traffic Type is not defined in the RFC but
         * the 802.11 AC_BK and AC_BE are closely related to the IEEE 802.1Q
         * Traffic Types BE and BK.
         */
        case DSCP_AF11:
        case DSCP_AF12:
        case DSCP_AF13:
                return IEEE8021Q_TT_BE;
        /* Comment from RFC8325:
         * RFC3662 and RFC4594 both recommend Low-Priority Data be marked
         * with DSCP CS1. The Low-Priority Data service class loosely
         * corresponds to the [IEEE.802.11-2016] Background Access Category
         */
        case DSCP_CS1:
                return IEEE8021Q_TT_BK;
        case DSCP_CS2:
        case DSCP_AF21:
        case DSCP_AF22:
        case DSCP_AF23:
                return IEEE8021Q_TT_EE;
        case DSCP_CS3:
        case DSCP_AF31:
        case DSCP_AF32:
        case DSCP_AF33:
                return IEEE8021Q_TT_CA;
        case DSCP_CS4:
        case DSCP_AF41:
        case DSCP_AF42:
        case DSCP_AF43:
                return IEEE8021Q_TT_VI;
        case DSCP_CS5:
        case DSCP_EF:
        case DSCP_VOICE_ADMIT:
                return IEEE8021Q_TT_VO;
        case DSCP_CS6:
                return IEEE8021Q_TT_IC;
        case DSCP_CS7:
                return IEEE8021Q_TT_NC;
        }

        return SIMPLE_IETF_DSCP_TO_IEEE8021Q_TT(dscp);
}
EXPORT_SYMBOL_GPL(ietf_dscp_to_ieee8021q_tt);