// SPDX-License-Identifier: GPL-2.0

/* net/sched/sch_taprio.c        Time Aware Priority Scheduler
 *
 * Authors:     Vinicius Costa Gomes <vinicius.gomes@intel.com>
 *
 */

#include <linux/ethtool.h>
#include <linux/ethtool_netlink.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/list.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <linux/math64.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/rcupdate.h>
#include <linux/time.h>
#include <net/gso.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>
#include <net/sch_generic.h>
#include <net/sock.h>
#include <net/tcp.h>

#define TAPRIO_STAT_NOT_SET     (~0ULL)

#include "sch_mqprio_lib.h"

static LIST_HEAD(taprio_list);
static struct static_key_false taprio_have_broken_mqprio;
static struct static_key_false taprio_have_working_mqprio;

#define TAPRIO_ALL_GATES_OPEN -1

#define TXTIME_ASSIST_IS_ENABLED(flags) ((flags) & TCA_TAPRIO_ATTR_FLAG_TXTIME_ASSIST)
#define FULL_OFFLOAD_IS_ENABLED(flags) ((flags) & TCA_TAPRIO_ATTR_FLAG_FULL_OFFLOAD)
#define TAPRIO_SUPPORTED_FLAGS \
        (TCA_TAPRIO_ATTR_FLAG_TXTIME_ASSIST | TCA_TAPRIO_ATTR_FLAG_FULL_OFFLOAD)
#define TAPRIO_FLAGS_INVALID U32_MAX
/* Minimum value for picos_per_byte to ensure non-zero duration
 * for minimum-sized Ethernet frames (ETH_ZLEN = 60).
 * 60 * 17 > PSEC_PER_NSEC (1000)
 */
#define TAPRIO_PICOS_PER_BYTE_MIN 17

struct sched_entry {
        /* Durations between this GCL entry and the GCL entry where the
         * respective traffic class gate closes
         */
        u64 gate_duration[TC_MAX_QUEUE];
        atomic_t budget[TC_MAX_QUEUE];
        /* The qdisc makes some effort so that no packet leaves
         * after this time
         */
        ktime_t gate_close_time[TC_MAX_QUEUE];
        struct list_head list;
        /* Used to calculate when to advance the schedule */
        ktime_t end_time;
        ktime_t next_txtime;
        int index;
        u32 gate_mask;
        u32 interval;
        u8 command;
};

struct sched_gate_list {
        /* Longest non-zero contiguous gate durations per traffic class,
         * or 0 if a traffic class gate never opens during the schedule.
         */
        u64 max_open_gate_duration[TC_MAX_QUEUE];
        u32 max_frm_len[TC_MAX_QUEUE]; /* for the fast path */
        u32 max_sdu[TC_MAX_QUEUE]; /* for dump */
        struct rcu_head rcu;
        struct list_head entries;
        size_t num_entries;
        ktime_t cycle_end_time;
        s64 cycle_time;
        s64 cycle_time_extension;
        s64 base_time;
};

struct taprio_sched {
        struct Qdisc **qdiscs;
        struct Qdisc *root;
        u32 flags;
        enum tk_offsets tk_offset;
        int clockid;
        bool offloaded;
        bool detected_mqprio;
        bool broken_mqprio;
        atomic64_t picos_per_byte; /* Using picoseconds because for 10Gbps+
                                    * speeds it's sub-nanoseconds per byte
                                    */

        /* Protects the update side of the RCU protected current_entry */
        spinlock_t current_entry_lock;
        struct sched_entry __rcu *current_entry;
        struct sched_gate_list __rcu *oper_sched;
        struct sched_gate_list __rcu *admin_sched;
        struct hrtimer advance_timer;
        struct list_head taprio_list;
        int cur_txq[TC_MAX_QUEUE];
        u32 max_sdu[TC_MAX_QUEUE]; /* save info from the user */
        u32 fp[TC_QOPT_MAX_QUEUE]; /* only for dump and offloading */
        u32 txtime_delay;
};

struct __tc_taprio_qopt_offload {
        refcount_t users;
        struct tc_taprio_qopt_offload offload;
};

static void taprio_calculate_gate_durations(struct taprio_sched *q,
                                            struct sched_gate_list *sched)
{
        struct net_device *dev = qdisc_dev(q->root);
        int num_tc = netdev_get_num_tc(dev);
        struct sched_entry *entry, *cur;
        int tc;

        list_for_each_entry(entry, &sched->entries, list) {
                u32 gates_still_open = entry->gate_mask;

                /* For each traffic class, calculate each open gate duration,
                 * starting at this schedule entry and ending at the schedule
                 * entry containing a gate close event for that TC.
                 */
                cur = entry;

                do {
                        if (!gates_still_open)
                                break;

                        for (tc = 0; tc < num_tc; tc++) {
                                if (!(gates_still_open & BIT(tc)))
                                        continue;

                                if (cur->gate_mask & BIT(tc))
                                        entry->gate_duration[tc] += cur->interval;
                                else
                                        gates_still_open &= ~BIT(tc);
                        }

                        cur = list_next_entry_circular(cur, &sched->entries, list);
                } while (cur != entry);

                /* Keep track of the maximum gate duration for each traffic
                 * class, taking care to not confuse a traffic class which is
                 * temporarily closed with one that is always closed.
                 */
                for (tc = 0; tc < num_tc; tc++)
                        if (entry->gate_duration[tc] &&
                            sched->max_open_gate_duration[tc] < entry->gate_duration[tc])
                                sched->max_open_gate_duration[tc] = entry->gate_duration[tc];
        }
}

static bool taprio_entry_allows_tx(ktime_t skb_end_time,
                                   struct sched_entry *entry, int tc)
{
        return ktime_before(skb_end_time, entry->gate_close_time[tc]);
}

static ktime_t sched_base_time(const struct sched_gate_list *sched)
{
        if (!sched)
                return KTIME_MAX;

        return ns_to_ktime(sched->base_time);
}

static ktime_t taprio_mono_to_any(const struct taprio_sched *q, ktime_t mono)
{
        /* This pairs with WRITE_ONCE() in taprio_parse_clockid() */
        enum tk_offsets tk_offset = READ_ONCE(q->tk_offset);

        switch (tk_offset) {
        case TK_OFFS_MAX:
                return mono;
        default:
                return ktime_mono_to_any(mono, tk_offset);
        }
}

static ktime_t taprio_get_time(const struct taprio_sched *q)
{
        return taprio_mono_to_any(q, ktime_get());
}

static void taprio_free_sched_cb(struct rcu_head *head)
{
        struct sched_gate_list *sched = container_of(head, struct sched_gate_list, rcu);
        struct sched_entry *entry, *n;

        list_for_each_entry_safe(entry, n, &sched->entries, list) {
                list_del(&entry->list);
                kfree(entry);
        }

        kfree(sched);
}

static void switch_schedules(struct taprio_sched *q,
                             struct sched_gate_list **admin,
                             struct sched_gate_list **oper)
{
        rcu_assign_pointer(q->oper_sched, *admin);
        rcu_assign_pointer(q->admin_sched, NULL);

        if (*oper)
                call_rcu(&(*oper)->rcu, taprio_free_sched_cb);

        *oper = *admin;
        *admin = NULL;
}

/* Get how much time has been already elapsed in the current cycle. */
static s32 get_cycle_time_elapsed(struct sched_gate_list *sched, ktime_t time)
{
        ktime_t time_since_sched_start;
        s32 time_elapsed;

        time_since_sched_start = ktime_sub(time, sched->base_time);
        div_s64_rem(time_since_sched_start, sched->cycle_time, &time_elapsed);

        return time_elapsed;
}

static ktime_t get_interval_end_time(struct sched_gate_list *sched,
                                     struct sched_gate_list *admin,
                                     struct sched_entry *entry,
                                     ktime_t intv_start)
{
        s32 cycle_elapsed = get_cycle_time_elapsed(sched, intv_start);
        ktime_t intv_end, cycle_ext_end, cycle_end;

        cycle_end = ktime_add_ns(intv_start, sched->cycle_time - cycle_elapsed);
        intv_end = ktime_add_ns(intv_start, entry->interval);
        cycle_ext_end = ktime_add(cycle_end, sched->cycle_time_extension);

        if (ktime_before(intv_end, cycle_end))
                return intv_end;
        else if (admin && admin != sched &&
                 ktime_after(admin->base_time, cycle_end) &&
                 ktime_before(admin->base_time, cycle_ext_end))
                return admin->base_time;
        else
                return cycle_end;
}

static int length_to_duration(struct taprio_sched *q, int len)
{
        return div_u64(len * atomic64_read(&q->picos_per_byte), PSEC_PER_NSEC);
}

static int duration_to_length(struct taprio_sched *q, u64 duration)
{
        return div_u64(duration * PSEC_PER_NSEC, atomic64_read(&q->picos_per_byte));
}

/* Sets sched->max_sdu[] and sched->max_frm_len[] to the minimum between the
 * q->max_sdu[] requested by the user and the max_sdu dynamically determined by
 * the maximum open gate durations at the given link speed.
 */
static void taprio_update_queue_max_sdu(struct taprio_sched *q,
                                        struct sched_gate_list *sched,
                                        struct qdisc_size_table *stab)
{
        struct net_device *dev = qdisc_dev(q->root);
        int num_tc = netdev_get_num_tc(dev);
        u32 max_sdu_from_user;
        u32 max_sdu_dynamic;
        u32 max_sdu;
        int tc;

        for (tc = 0; tc < num_tc; tc++) {
                max_sdu_from_user = q->max_sdu[tc] ?: U32_MAX;

                /* TC gate never closes => keep the queueMaxSDU
                 * selected by the user
                 */
                if (sched->max_open_gate_duration[tc] == sched->cycle_time) {
                        max_sdu_dynamic = U32_MAX;
                } else {
                        u32 max_frm_len;

                        max_frm_len = duration_to_length(q, sched->max_open_gate_duration[tc]);
                        /* Compensate for L1 overhead from size table,
                         * but don't let the frame size go negative
                         */
                        if (stab) {
                                max_frm_len -= stab->szopts.overhead;
                                max_frm_len = max_t(int, max_frm_len,
                                                    dev->hard_header_len + 1);
                        }
                        max_sdu_dynamic = max_frm_len - dev->hard_header_len;
                        if (max_sdu_dynamic > dev->max_mtu)
                                max_sdu_dynamic = U32_MAX;
                }

                max_sdu = min(max_sdu_dynamic, max_sdu_from_user);

                if (max_sdu != U32_MAX) {
                        sched->max_frm_len[tc] = max_sdu + dev->hard_header_len;
                        sched->max_sdu[tc] = max_sdu;
                } else {
                        sched->max_frm_len[tc] = U32_MAX; /* never oversized */
                        sched->max_sdu[tc] = 0;
                }
        }
}

/* Returns the entry corresponding to next available interval. If
 * validate_interval is set, it only validates whether the timestamp occurs
 * when the gate corresponding to the skb's traffic class is open.
 */
static struct sched_entry *find_entry_to_transmit(struct sk_buff *skb,
                                                  struct Qdisc *sch,
                                                  struct sched_gate_list *sched,
                                                  struct sched_gate_list *admin,
                                                  ktime_t time,
                                                  ktime_t *interval_start,
                                                  ktime_t *interval_end,
                                                  bool validate_interval)
{
        ktime_t curr_intv_start, curr_intv_end, cycle_end, packet_transmit_time;
        ktime_t earliest_txtime = KTIME_MAX, txtime, cycle, transmit_end_time;
        struct sched_entry *entry = NULL, *entry_found = NULL;
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        bool entry_available = false;
        s32 cycle_elapsed;
        int tc, n;

        tc = netdev_get_prio_tc_map(dev, skb->priority);
        packet_transmit_time = length_to_duration(q, qdisc_pkt_len(skb));

        *interval_start = 0;
        *interval_end = 0;

        if (!sched)
                return NULL;

        cycle = sched->cycle_time;
        cycle_elapsed = get_cycle_time_elapsed(sched, time);
        curr_intv_end = ktime_sub_ns(time, cycle_elapsed);
        cycle_end = ktime_add_ns(curr_intv_end, cycle);

        list_for_each_entry(entry, &sched->entries, list) {
                curr_intv_start = curr_intv_end;
                curr_intv_end = get_interval_end_time(sched, admin, entry,
                                                      curr_intv_start);

                if (ktime_after(curr_intv_start, cycle_end))
                        break;

                if (!(entry->gate_mask & BIT(tc)) ||
                    packet_transmit_time > entry->interval)
                        continue;

                txtime = entry->next_txtime;

                if (ktime_before(txtime, time) || validate_interval) {
                        transmit_end_time = ktime_add_ns(time, packet_transmit_time);
                        if ((ktime_before(curr_intv_start, time) &&
                             ktime_before(transmit_end_time, curr_intv_end)) ||
                            (ktime_after(curr_intv_start, time) && !validate_interval)) {
                                entry_found = entry;
                                *interval_start = curr_intv_start;
                                *interval_end = curr_intv_end;
                                break;
                        } else if (!entry_available && !validate_interval) {
                                /* Here, we are just trying to find out the
                                 * first available interval in the next cycle.
                                 */
                                entry_available = true;
                                entry_found = entry;
                                *interval_start = ktime_add_ns(curr_intv_start, cycle);
                                *interval_end = ktime_add_ns(curr_intv_end, cycle);
                        }
                } else if (ktime_before(txtime, earliest_txtime) &&
                           !entry_available) {
                        earliest_txtime = txtime;
                        entry_found = entry;
                        n = div_s64(ktime_sub(txtime, curr_intv_start), cycle);
                        *interval_start = ktime_add(curr_intv_start, n * cycle);
                        *interval_end = ktime_add(curr_intv_end, n * cycle);
                }
        }

        return entry_found;
}

static bool is_valid_interval(struct sk_buff *skb, struct Qdisc *sch)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct sched_gate_list *sched, *admin;
        ktime_t interval_start, interval_end;
        struct sched_entry *entry;

        rcu_read_lock();
        sched = rcu_dereference(q->oper_sched);
        admin = rcu_dereference(q->admin_sched);

        entry = find_entry_to_transmit(skb, sch, sched, admin, skb->tstamp,
                                       &interval_start, &interval_end, true);
        rcu_read_unlock();

        return entry;
}

/* This returns the tstamp value set by TCP in terms of the set clock. */
static ktime_t get_tcp_tstamp(struct taprio_sched *q, struct sk_buff *skb)
{
        unsigned int offset = skb_network_offset(skb);
        const struct ipv6hdr *ipv6h;
        const struct iphdr *iph;
        struct ipv6hdr _ipv6h;

        ipv6h = skb_header_pointer(skb, offset, sizeof(_ipv6h), &_ipv6h);
        if (!ipv6h)
                return 0;

        if (ipv6h->version == 4) {
                iph = (struct iphdr *)ipv6h;
                offset += iph->ihl * 4;

                /* special-case 6in4 tunnelling, as that is a common way to get
                 * v6 connectivity in the home
                 */
                if (iph->protocol == IPPROTO_IPV6) {
                        ipv6h = skb_header_pointer(skb, offset,
                                                   sizeof(_ipv6h), &_ipv6h);

                        if (!ipv6h || ipv6h->nexthdr != IPPROTO_TCP)
                                return 0;
                } else if (iph->protocol != IPPROTO_TCP) {
                        return 0;
                }
        } else if (ipv6h->version == 6 && ipv6h->nexthdr != IPPROTO_TCP) {
                return 0;
        }

        return taprio_mono_to_any(q, skb->skb_mstamp_ns);
}

/* There are a few scenarios where we will have to modify the txtime from
 * what is read from next_txtime in sched_entry. They are:
 * 1. If txtime is in the past,
 *    a. The gate for the traffic class is currently open and packet can be
 *       transmitted before it closes, schedule the packet right away.
 *    b. If the gate corresponding to the traffic class is going to open later
 *       in the cycle, set the txtime of packet to the interval start.
 * 2. If txtime is in the future, there are packets corresponding to the
 *    current traffic class waiting to be transmitted. So, the following
 *    possibilities exist:
 *    a. We can transmit the packet before the window containing the txtime
 *       closes.
 *    b. The window might close before the transmission can be completed
 *       successfully. So, schedule the packet in the next open window.
 */
static long get_packet_txtime(struct sk_buff *skb, struct Qdisc *sch)
{
        ktime_t transmit_end_time, interval_end, interval_start, tcp_tstamp;
        struct taprio_sched *q = qdisc_priv(sch);
        struct sched_gate_list *sched, *admin;
        ktime_t minimum_time, now, txtime;
        int len, packet_transmit_time;
        struct sched_entry *entry;
        bool sched_changed;

        now = taprio_get_time(q);
        minimum_time = ktime_add_ns(now, q->txtime_delay);

        tcp_tstamp = get_tcp_tstamp(q, skb);
        minimum_time = max_t(ktime_t, minimum_time, tcp_tstamp);

        rcu_read_lock();
        admin = rcu_dereference(q->admin_sched);
        sched = rcu_dereference(q->oper_sched);
        if (admin && ktime_after(minimum_time, admin->base_time))
                switch_schedules(q, &admin, &sched);

        /* Until the schedule starts, all the queues are open */
        if (!sched || ktime_before(minimum_time, sched->base_time)) {
                txtime = minimum_time;
                goto done;
        }

        len = qdisc_pkt_len(skb);
        packet_transmit_time = length_to_duration(q, len);

        do {
                sched_changed = false;

                entry = find_entry_to_transmit(skb, sch, sched, admin,
                                               minimum_time,
                                               &interval_start, &interval_end,
                                               false);
                if (!entry) {
                        txtime = 0;
                        goto done;
                }

                txtime = entry->next_txtime;
                txtime = max_t(ktime_t, txtime, minimum_time);
                txtime = max_t(ktime_t, txtime, interval_start);

                if (admin && admin != sched &&
                    ktime_after(txtime, admin->base_time)) {
                        sched = admin;
                        sched_changed = true;
                        continue;
                }

                transmit_end_time = ktime_add(txtime, packet_transmit_time);
                minimum_time = transmit_end_time;

                /* Update the txtime of current entry to the next time it's
                 * interval starts.
                 */
                if (ktime_after(transmit_end_time, interval_end))
                        entry->next_txtime = ktime_add(interval_start, sched->cycle_time);
        } while (sched_changed || ktime_after(transmit_end_time, interval_end));

        entry->next_txtime = transmit_end_time;

done:
        rcu_read_unlock();
        return txtime;
}

/* Devices with full offload are expected to honor this in hardware */
static bool taprio_skb_exceeds_queue_max_sdu(struct Qdisc *sch,
                                             struct sk_buff *skb)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        struct sched_gate_list *sched;
        int prio = skb->priority;
        bool exceeds = false;
        u8 tc;

        tc = netdev_get_prio_tc_map(dev, prio);

        rcu_read_lock();
        sched = rcu_dereference(q->oper_sched);
        if (sched && skb->len > sched->max_frm_len[tc])
                exceeds = true;
        rcu_read_unlock();

        return exceeds;
}

static int taprio_enqueue_one(struct sk_buff *skb, struct Qdisc *sch,
                              struct Qdisc *child, struct sk_buff **to_free)
{
        struct taprio_sched *q = qdisc_priv(sch);

        /* sk_flags are only safe to use on full sockets. */
        if (skb->sk && sk_fullsock(skb->sk) && sock_flag(skb->sk, SOCK_TXTIME)) {
                if (!is_valid_interval(skb, sch))
                        return qdisc_drop(skb, sch, to_free);
        } else if (TXTIME_ASSIST_IS_ENABLED(q->flags)) {
                skb->tstamp = get_packet_txtime(skb, sch);
                if (!skb->tstamp)
                        return qdisc_drop(skb, sch, to_free);
        }

        qdisc_qstats_backlog_inc(sch, skb);
        sch->q.qlen++;

        return qdisc_enqueue(skb, child, to_free);
}

static int taprio_enqueue_segmented(struct sk_buff *skb, struct Qdisc *sch,
                                    struct Qdisc *child,
                                    struct sk_buff **to_free)
{
        unsigned int slen = 0, numsegs = 0, len = qdisc_pkt_len(skb);
        netdev_features_t features = netif_skb_features(skb);
        struct sk_buff *segs, *nskb;
        int ret;

        segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
        if (IS_ERR_OR_NULL(segs))
                return qdisc_drop(skb, sch, to_free);

        skb_list_walk_safe(segs, segs, nskb) {
                skb_mark_not_on_list(segs);
                qdisc_skb_cb(segs)->pkt_len = segs->len;
                qdisc_skb_cb(segs)->pkt_segs = 1;
                slen += segs->len;

                /* FIXME: we should be segmenting to a smaller size
                 * rather than dropping these
                 */
                if (taprio_skb_exceeds_queue_max_sdu(sch, segs))
                        ret = qdisc_drop(segs, sch, to_free);
                else
                        ret = taprio_enqueue_one(segs, sch, child, to_free);

                if (ret != NET_XMIT_SUCCESS) {
                        if (net_xmit_drop_count(ret))
                                qdisc_qstats_drop(sch);
                } else {
                        numsegs++;
                }
        }

        if (numsegs > 1)
                qdisc_tree_reduce_backlog(sch, 1 - numsegs, len - slen);
        consume_skb(skb);

        return numsegs > 0 ? NET_XMIT_SUCCESS : NET_XMIT_DROP;
}

/* Will not be called in the full offload case, since the TX queues are
 * attached to the Qdisc created using qdisc_create_dflt()
 */
static int taprio_enqueue(struct sk_buff *skb, struct Qdisc *sch,
                          struct sk_buff **to_free)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct Qdisc *child;
        int queue;

        queue = skb_get_queue_mapping(skb);

        child = q->qdiscs[queue];
        if (unlikely(!child))
                return qdisc_drop(skb, sch, to_free);

        if (taprio_skb_exceeds_queue_max_sdu(sch, skb)) {
                /* Large packets might not be transmitted when the transmission
                 * duration exceeds any configured interval. Therefore, segment
                 * the skb into smaller chunks. Drivers with full offload are
                 * expected to handle this in hardware.
                 */
                if (skb_is_gso(skb))
                        return taprio_enqueue_segmented(skb, sch, child,
                                                        to_free);

                return qdisc_drop(skb, sch, to_free);
        }

        return taprio_enqueue_one(skb, sch, child, to_free);
}

static struct sk_buff *taprio_peek(struct Qdisc *sch)
{
        WARN_ONCE(1, "taprio only supports operating as root qdisc, peek() not implemented");
        return NULL;
}

static void taprio_set_budgets(struct taprio_sched *q,
                               struct sched_gate_list *sched,
                               struct sched_entry *entry)
{
        struct net_device *dev = qdisc_dev(q->root);
        int num_tc = netdev_get_num_tc(dev);
        int tc, budget;

        for (tc = 0; tc < num_tc; tc++) {
                /* Traffic classes which never close have infinite budget */
                if (entry->gate_duration[tc] == sched->cycle_time)
                        budget = INT_MAX;
                else
                        budget = div64_u64((u64)entry->gate_duration[tc] * PSEC_PER_NSEC,
                                           atomic64_read(&q->picos_per_byte));

                atomic_set(&entry->budget[tc], budget);
        }
}

/* When an skb is sent, it consumes from the budget of all traffic classes */
static int taprio_update_budgets(struct sched_entry *entry, size_t len,
                                 int tc_consumed, int num_tc)
{
        int tc, budget, new_budget = 0;

        for (tc = 0; tc < num_tc; tc++) {
                budget = atomic_read(&entry->budget[tc]);
                /* Don't consume from infinite budget */
                if (budget == INT_MAX) {
                        if (tc == tc_consumed)
                                new_budget = budget;
                        continue;
                }

                if (tc == tc_consumed)
                        new_budget = atomic_sub_return(len, &entry->budget[tc]);
                else
                        atomic_sub(len, &entry->budget[tc]);
        }

        return new_budget;
}

static struct sk_buff *taprio_dequeue_from_txq(struct Qdisc *sch, int txq,
                                               struct sched_entry *entry,
                                               u32 gate_mask)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        struct Qdisc *child = q->qdiscs[txq];
        int num_tc = netdev_get_num_tc(dev);
        struct sk_buff *skb;
        ktime_t guard;
        int prio;
        int len;
        u8 tc;

        if (unlikely(!child))
                return NULL;

        if (TXTIME_ASSIST_IS_ENABLED(q->flags))
                goto skip_peek_checks;

        skb = child->ops->peek(child);
        if (!skb)
                return NULL;

        prio = skb->priority;
        tc = netdev_get_prio_tc_map(dev, prio);

        if (!(gate_mask & BIT(tc)))
                return NULL;

        len = qdisc_pkt_len(skb);
        guard = ktime_add_ns(taprio_get_time(q), length_to_duration(q, len));

        /* In the case that there's no gate entry, there's no
         * guard band ...
         */
        if (gate_mask != TAPRIO_ALL_GATES_OPEN &&
            !taprio_entry_allows_tx(guard, entry, tc))
                return NULL;

        /* ... and no budget. */
        if (gate_mask != TAPRIO_ALL_GATES_OPEN &&
            taprio_update_budgets(entry, len, tc, num_tc) < 0)
                return NULL;

skip_peek_checks:
        skb = child->ops->dequeue(child);
        if (unlikely(!skb))
                return NULL;

        qdisc_bstats_update(sch, skb);
        qdisc_qstats_backlog_dec(sch, skb);
        sch->q.qlen--;

        return skb;
}

static void taprio_next_tc_txq(struct net_device *dev, int tc, int *txq)
{
        int offset = dev->tc_to_txq[tc].offset;
        int count = dev->tc_to_txq[tc].count;

        (*txq)++;
        if (*txq == offset + count)
                *txq = offset;
}

/* Prioritize higher traffic classes, and select among TXQs belonging to the
 * same TC using round robin
 */
static struct sk_buff *taprio_dequeue_tc_priority(struct Qdisc *sch,
                                                  struct sched_entry *entry,
                                                  u32 gate_mask)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        int num_tc = netdev_get_num_tc(dev);
        struct sk_buff *skb;
        int tc;

        for (tc = num_tc - 1; tc >= 0; tc--) {
                int first_txq = q->cur_txq[tc];

                if (!(gate_mask & BIT(tc)))
                        continue;

                do {
                        skb = taprio_dequeue_from_txq(sch, q->cur_txq[tc],
                                                      entry, gate_mask);

                        taprio_next_tc_txq(dev, tc, &q->cur_txq[tc]);

                        if (q->cur_txq[tc] >= dev->num_tx_queues)
                                q->cur_txq[tc] = first_txq;

                        if (skb)
                                return skb;
                } while (q->cur_txq[tc] != first_txq);
        }

        return NULL;
}

/* Broken way of prioritizing smaller TXQ indices and ignoring the traffic
 * class other than to determine whether the gate is open or not
 */
static struct sk_buff *taprio_dequeue_txq_priority(struct Qdisc *sch,
                                                   struct sched_entry *entry,
                                                   u32 gate_mask)
{
        struct net_device *dev = qdisc_dev(sch);
        struct sk_buff *skb;
        int i;

        for (i = 0; i < dev->num_tx_queues; i++) {
                skb = taprio_dequeue_from_txq(sch, i, entry, gate_mask);
                if (skb)
                        return skb;
        }

        return NULL;
}

/* Will not be called in the full offload case, since the TX queues are
 * attached to the Qdisc created using qdisc_create_dflt()
 */
static struct sk_buff *taprio_dequeue(struct Qdisc *sch)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct sk_buff *skb = NULL;
        struct sched_entry *entry;
        u32 gate_mask;

        rcu_read_lock();
        entry = rcu_dereference(q->current_entry);
        /* if there's no entry, it means that the schedule didn't
         * start yet, so force all gates to be open, this is in
         * accordance to IEEE 802.1Qbv-2015 Section 8.6.9.4.5
         * "AdminGateStates"
         */
        gate_mask = entry ? entry->gate_mask : TAPRIO_ALL_GATES_OPEN;
        if (!gate_mask)
                goto done;

        if (static_branch_unlikely(&taprio_have_broken_mqprio) &&
            !static_branch_likely(&taprio_have_working_mqprio)) {
                /* Single NIC kind which is broken */
                skb = taprio_dequeue_txq_priority(sch, entry, gate_mask);
        } else if (static_branch_likely(&taprio_have_working_mqprio) &&
                   !static_branch_unlikely(&taprio_have_broken_mqprio)) {
                /* Single NIC kind which prioritizes properly */
                skb = taprio_dequeue_tc_priority(sch, entry, gate_mask);
        } else {
                /* Mixed NIC kinds present in system, need dynamic testing */
                if (q->broken_mqprio)
                        skb = taprio_dequeue_txq_priority(sch, entry, gate_mask);
                else
                        skb = taprio_dequeue_tc_priority(sch, entry, gate_mask);
        }

done:
        rcu_read_unlock();

        return skb;
}

static bool should_restart_cycle(const struct sched_gate_list *oper,
                                 const struct sched_entry *entry)
{
        if (list_is_last(&entry->list, &oper->entries))
                return true;

        if (ktime_compare(entry->end_time, oper->cycle_end_time) == 0)
                return true;

        return false;
}

static bool should_change_schedules(const struct sched_gate_list *admin,
                                    const struct sched_gate_list *oper,
                                    ktime_t end_time)
{
        ktime_t next_base_time, extension_time;

        if (!admin)
                return false;

        next_base_time = sched_base_time(admin);

        /* This is the simple case, the end_time would fall after
         * the next schedule base_time.
         */
        if (ktime_compare(next_base_time, end_time) <= 0)
                return true;

        /* This is the cycle_time_extension case, if the end_time
         * plus the amount that can be extended would fall after the
         * next schedule base_time, we can extend the current schedule
         * for that amount.
         */
        extension_time = ktime_add_ns(end_time, oper->cycle_time_extension);

        /* FIXME: the IEEE 802.1Q-2018 Specification isn't clear about
         * how precisely the extension should be made. So after
         * conformance testing, this logic may change.
         */
        if (ktime_compare(next_base_time, extension_time) <= 0)
                return true;

        return false;
}

static enum hrtimer_restart advance_sched(struct hrtimer *timer)
{
        struct taprio_sched *q = container_of(timer, struct taprio_sched,
                                              advance_timer);
        struct net_device *dev = qdisc_dev(q->root);
        struct sched_gate_list *oper, *admin;
        int num_tc = netdev_get_num_tc(dev);
        struct sched_entry *entry, *next;
        struct Qdisc *sch = q->root;
        ktime_t end_time;
        int tc;

        spin_lock(&q->current_entry_lock);
        entry = rcu_dereference_protected(q->current_entry,
                                          lockdep_is_held(&q->current_entry_lock));
        oper = rcu_dereference_protected(q->oper_sched,
                                         lockdep_is_held(&q->current_entry_lock));
        admin = rcu_dereference_protected(q->admin_sched,
                                          lockdep_is_held(&q->current_entry_lock));

        if (!oper)
                switch_schedules(q, &admin, &oper);

        /* This can happen in two cases: 1. this is the very first run
         * of this function (i.e. we weren't running any schedule
         * previously); 2. The previous schedule just ended. The first
         * entry of all schedules are pre-calculated during the
         * schedule initialization.
         */
        if (unlikely(!entry || entry->end_time == oper->base_time)) {
                next = list_first_entry(&oper->entries, struct sched_entry,
                                        list);
                end_time = next->end_time;
                goto first_run;
        }

        if (should_restart_cycle(oper, entry)) {
                next = list_first_entry(&oper->entries, struct sched_entry,
                                        list);
                oper->cycle_end_time = ktime_add_ns(oper->cycle_end_time,
                                                    oper->cycle_time);
        } else {
                next = list_next_entry(entry, list);
        }

        end_time = ktime_add_ns(entry->end_time, next->interval);
        end_time = min_t(ktime_t, end_time, oper->cycle_end_time);

        for (tc = 0; tc < num_tc; tc++) {
                if (next->gate_duration[tc] == oper->cycle_time)
                        next->gate_close_time[tc] = KTIME_MAX;
                else
                        next->gate_close_time[tc] = ktime_add_ns(entry->end_time,
                                                                 next->gate_duration[tc]);
        }

        if (should_change_schedules(admin, oper, end_time)) {
                /* Set things so the next time this runs, the new
                 * schedule runs.
                 */
                end_time = sched_base_time(admin);
                switch_schedules(q, &admin, &oper);
        }

        next->end_time = end_time;
        taprio_set_budgets(q, oper, next);

first_run:
        rcu_assign_pointer(q->current_entry, next);
        spin_unlock(&q->current_entry_lock);

        hrtimer_set_expires(&q->advance_timer, end_time);

        rcu_read_lock();
        __netif_schedule(sch);
        rcu_read_unlock();

        return HRTIMER_RESTART;
}

static const struct nla_policy entry_policy[TCA_TAPRIO_SCHED_ENTRY_MAX + 1] = {
        [TCA_TAPRIO_SCHED_ENTRY_INDEX]     = { .type = NLA_U32 },
        [TCA_TAPRIO_SCHED_ENTRY_CMD]       = { .type = NLA_U8 },
        [TCA_TAPRIO_SCHED_ENTRY_GATE_MASK] = { .type = NLA_U32 },
        [TCA_TAPRIO_SCHED_ENTRY_INTERVAL]  = { .type = NLA_U32 },
};

static const struct nla_policy taprio_tc_policy[TCA_TAPRIO_TC_ENTRY_MAX + 1] = {
        [TCA_TAPRIO_TC_ENTRY_INDEX]        = NLA_POLICY_MAX(NLA_U32,
                                                            TC_QOPT_MAX_QUEUE - 1),
        [TCA_TAPRIO_TC_ENTRY_MAX_SDU]      = { .type = NLA_U32 },
        [TCA_TAPRIO_TC_ENTRY_FP]           = NLA_POLICY_RANGE(NLA_U32,
                                                              TC_FP_EXPRESS,
                                                              TC_FP_PREEMPTIBLE),
};

static const struct netlink_range_validation_signed taprio_cycle_time_range = {
        .min = 0,
        .max = INT_MAX,
};

static const struct nla_policy taprio_policy[TCA_TAPRIO_ATTR_MAX + 1] = {
        [TCA_TAPRIO_ATTR_PRIOMAP]              = {
                .len = sizeof(struct tc_mqprio_qopt)
        },
        [TCA_TAPRIO_ATTR_SCHED_ENTRY_LIST]           = { .type = NLA_NESTED },
        [TCA_TAPRIO_ATTR_SCHED_BASE_TIME]            = { .type = NLA_S64 },
        [TCA_TAPRIO_ATTR_SCHED_SINGLE_ENTRY]         = { .type = NLA_NESTED },
        [TCA_TAPRIO_ATTR_SCHED_CLOCKID]              = { .type = NLA_S32 },
        [TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME]           =
                NLA_POLICY_FULL_RANGE_SIGNED(NLA_S64, &taprio_cycle_time_range),
        [TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME_EXTENSION] = { .type = NLA_S64 },
        [TCA_TAPRIO_ATTR_FLAGS]                      =
                NLA_POLICY_MASK(NLA_U32, TAPRIO_SUPPORTED_FLAGS),
        [TCA_TAPRIO_ATTR_TXTIME_DELAY]               = { .type = NLA_U32 },
        [TCA_TAPRIO_ATTR_TC_ENTRY]                   = { .type = NLA_NESTED },
};

static int fill_sched_entry(struct taprio_sched *q, struct nlattr **tb,
                            struct sched_entry *entry,
                            struct netlink_ext_ack *extack)
{
        int min_duration = length_to_duration(q, ETH_ZLEN);
        u32 interval = 0;

        if (tb[TCA_TAPRIO_SCHED_ENTRY_CMD])
                entry->command = nla_get_u8(
                        tb[TCA_TAPRIO_SCHED_ENTRY_CMD]);

        if (tb[TCA_TAPRIO_SCHED_ENTRY_GATE_MASK])
                entry->gate_mask = nla_get_u32(
                        tb[TCA_TAPRIO_SCHED_ENTRY_GATE_MASK]);

        if (tb[TCA_TAPRIO_SCHED_ENTRY_INTERVAL])
                interval = nla_get_u32(
                        tb[TCA_TAPRIO_SCHED_ENTRY_INTERVAL]);

        /* The interval should allow at least the minimum ethernet
         * frame to go out.
         */
        if (interval < min_duration) {
                NL_SET_ERR_MSG(extack, "Invalid interval for schedule entry");
                return -EINVAL;
        }

        entry->interval = interval;

        return 0;
}

static int parse_sched_entry(struct taprio_sched *q, struct nlattr *n,
                             struct sched_entry *entry, int index,
                             struct netlink_ext_ack *extack)
{
        struct nlattr *tb[TCA_TAPRIO_SCHED_ENTRY_MAX + 1] = { };
        int err;

        err = nla_parse_nested_deprecated(tb, TCA_TAPRIO_SCHED_ENTRY_MAX, n,
                                          entry_policy, NULL);
        if (err < 0) {
                NL_SET_ERR_MSG(extack, "Could not parse nested entry");
                return -EINVAL;
        }

        entry->index = index;

        return fill_sched_entry(q, tb, entry, extack);
}

static int parse_sched_list(struct taprio_sched *q, struct nlattr *list,
                            struct sched_gate_list *sched,
                            struct netlink_ext_ack *extack)
{
        struct nlattr *n;
        int err, rem;
        int i = 0;

        if (!list)
                return -EINVAL;

        nla_for_each_nested(n, list, rem) {
                struct sched_entry *entry;

                if (nla_type(n) != TCA_TAPRIO_SCHED_ENTRY) {
                        NL_SET_ERR_MSG(extack, "Attribute is not of type 'entry'");
                        continue;
                }

                entry = kzalloc_obj(*entry);
                if (!entry) {
                        NL_SET_ERR_MSG(extack, "Not enough memory for entry");
                        return -ENOMEM;
                }

                err = parse_sched_entry(q, n, entry, i, extack);
                if (err < 0) {
                        kfree(entry);
                        return err;
                }

                list_add_tail(&entry->list, &sched->entries);
                i++;
        }

        sched->num_entries = i;

        return i;
}

static int parse_taprio_schedule(struct taprio_sched *q, struct nlattr **tb,
                                 struct sched_gate_list *new,
                                 struct netlink_ext_ack *extack)
{
        int err = 0;

        if (tb[TCA_TAPRIO_ATTR_SCHED_SINGLE_ENTRY]) {
                NL_SET_ERR_MSG(extack, "Adding a single entry is not supported");
                return -ENOTSUPP;
        }

        if (tb[TCA_TAPRIO_ATTR_SCHED_BASE_TIME])
                new->base_time = nla_get_s64(tb[TCA_TAPRIO_ATTR_SCHED_BASE_TIME]);

        if (tb[TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME_EXTENSION])
                new->cycle_time_extension = nla_get_s64(tb[TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME_EXTENSION]);

        if (tb[TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME])
                new->cycle_time = nla_get_s64(tb[TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME]);

        if (tb[TCA_TAPRIO_ATTR_SCHED_ENTRY_LIST])
                err = parse_sched_list(q, tb[TCA_TAPRIO_ATTR_SCHED_ENTRY_LIST],
                                       new, extack);
        if (err < 0)
                return err;

        if (!new->cycle_time) {
                struct sched_entry *entry;
                ktime_t cycle = 0;

                list_for_each_entry(entry, &new->entries, list)
                        cycle = ktime_add_ns(cycle, entry->interval);

                if (cycle < 0 || cycle > INT_MAX) {
                        NL_SET_ERR_MSG(extack, "'cycle_time' is too big");
                        return -EINVAL;
                }

                new->cycle_time = cycle;
        }

        if (new->cycle_time < new->num_entries * length_to_duration(q, ETH_ZLEN)) {
                NL_SET_ERR_MSG(extack, "'cycle_time' is too small");
                return -EINVAL;
        }

        taprio_calculate_gate_durations(q, new);

        return 0;
}

static int taprio_parse_mqprio_opt(struct net_device *dev,
                                   struct tc_mqprio_qopt *qopt,
                                   struct netlink_ext_ack *extack,
                                   u32 taprio_flags)
{
        bool allow_overlapping_txqs = TXTIME_ASSIST_IS_ENABLED(taprio_flags);

        if (!qopt) {
                if (!dev->num_tc) {
                        NL_SET_ERR_MSG(extack, "'mqprio' configuration is necessary");
                        return -EINVAL;
                }
                return 0;
        }

        /* taprio imposes that traffic classes map 1:n to tx queues */
        if (qopt->num_tc > dev->num_tx_queues) {
                NL_SET_ERR_MSG(extack, "Number of traffic classes is greater than number of HW queues");
                return -EINVAL;
        }

        /* For some reason, in txtime-assist mode, we allow TXQ ranges for
         * different TCs to overlap, and just validate the TXQ ranges.
         */
        return mqprio_validate_qopt(dev, qopt, true, allow_overlapping_txqs,
                                    extack);
}

static int taprio_get_start_time(struct Qdisc *sch,
                                 struct sched_gate_list *sched,
                                 ktime_t *start)
{
        struct taprio_sched *q = qdisc_priv(sch);
        ktime_t now, base, cycle;
        s64 n;

        base = sched_base_time(sched);
        now = taprio_get_time(q);

        if (ktime_after(base, now)) {
                *start = base;
                return 0;
        }

        cycle = sched->cycle_time;

        /* The qdisc is expected to have at least one sched_entry.  Moreover,
         * any entry must have 'interval' > 0. Thus if the cycle time is zero,
         * something went really wrong. In that case, we should warn about this
         * inconsistent state and return error.
         */
        if (WARN_ON(!cycle))
                return -EFAULT;

        /* Schedule the start time for the beginning of the next
         * cycle.
         */
        n = div64_s64(ktime_sub_ns(now, base), cycle);
        *start = ktime_add_ns(base, (n + 1) * cycle);
        return 0;
}

static void setup_first_end_time(struct taprio_sched *q,
                                 struct sched_gate_list *sched, ktime_t base)
{
        struct net_device *dev = qdisc_dev(q->root);
        int num_tc = netdev_get_num_tc(dev);
        struct sched_entry *first;
        ktime_t cycle;
        int tc;

        first = list_first_entry(&sched->entries,
                                 struct sched_entry, list);

        cycle = sched->cycle_time;

        /* FIXME: find a better place to do this */
        sched->cycle_end_time = ktime_add_ns(base, cycle);

        first->end_time = ktime_add_ns(base, first->interval);
        taprio_set_budgets(q, sched, first);

        for (tc = 0; tc < num_tc; tc++) {
                if (first->gate_duration[tc] == sched->cycle_time)
                        first->gate_close_time[tc] = KTIME_MAX;
                else
                        first->gate_close_time[tc] = ktime_add_ns(base, first->gate_duration[tc]);
        }

        rcu_assign_pointer(q->current_entry, NULL);
}

static void taprio_start_sched(struct Qdisc *sch,
                               ktime_t start, struct sched_gate_list *new)
{
        struct taprio_sched *q = qdisc_priv(sch);
        ktime_t expires;

        if (FULL_OFFLOAD_IS_ENABLED(q->flags))
                return;

        expires = hrtimer_get_expires(&q->advance_timer);
        if (expires == 0)
                expires = KTIME_MAX;

        /* If the new schedule starts before the next expiration, we
         * reprogram it to the earliest one, so we change the admin
         * schedule to the operational one at the right time.
         */
        start = min_t(ktime_t, start, expires);

        hrtimer_start(&q->advance_timer, start, HRTIMER_MODE_ABS);
}

static void taprio_set_picos_per_byte(struct net_device *dev,
                                      struct taprio_sched *q,
                                      struct netlink_ext_ack *extack)
{
        struct ethtool_link_ksettings ecmd;
        int speed = SPEED_10;
        int picos_per_byte;
        int err;

        err = __ethtool_get_link_ksettings(dev, &ecmd);
        if (err < 0)
                goto skip;

        if (ecmd.base.speed && ecmd.base.speed != SPEED_UNKNOWN)
                speed = ecmd.base.speed;

skip:
        picos_per_byte = (USEC_PER_SEC * 8) / speed;
        if (picos_per_byte < TAPRIO_PICOS_PER_BYTE_MIN) {
                if (!extack)
                        pr_warn("Link speed %d is too high. Schedule may be inaccurate.\n",
                                speed);
                NL_SET_ERR_MSG_FMT_MOD(extack,
                                       "Link speed %d is too high. Schedule may be inaccurate.",
                                       speed);
                picos_per_byte = TAPRIO_PICOS_PER_BYTE_MIN;
        }

        atomic64_set(&q->picos_per_byte, picos_per_byte);
        netdev_dbg(dev, "taprio: set %s's picos_per_byte to: %lld, linkspeed: %d\n",
                   dev->name, (long long)atomic64_read(&q->picos_per_byte),
                   ecmd.base.speed);
}

static int taprio_dev_notifier(struct notifier_block *nb, unsigned long event,
                               void *ptr)
{
        struct net_device *dev = netdev_notifier_info_to_dev(ptr);
        struct sched_gate_list *oper, *admin;
        struct qdisc_size_table *stab;
        struct taprio_sched *q;

        ASSERT_RTNL();

        if (event != NETDEV_UP && event != NETDEV_CHANGE)
                return NOTIFY_DONE;

        list_for_each_entry(q, &taprio_list, taprio_list) {
                if (dev != qdisc_dev(q->root))
                        continue;

                taprio_set_picos_per_byte(dev, q, NULL);

                stab = rtnl_dereference(q->root->stab);

                rcu_read_lock();
                oper = rcu_dereference(q->oper_sched);
                if (oper)
                        taprio_update_queue_max_sdu(q, oper, stab);

                admin = rcu_dereference(q->admin_sched);
                if (admin)
                        taprio_update_queue_max_sdu(q, admin, stab);
                rcu_read_unlock();

                break;
        }

        return NOTIFY_DONE;
}

static void setup_txtime(struct taprio_sched *q,
                         struct sched_gate_list *sched, ktime_t base)
{
        struct sched_entry *entry;
        u64 interval = 0;

        list_for_each_entry(entry, &sched->entries, list) {
                entry->next_txtime = ktime_add_ns(base, interval);
                interval += entry->interval;
        }
}

static struct tc_taprio_qopt_offload *taprio_offload_alloc(int num_entries)
{
        struct __tc_taprio_qopt_offload *__offload;

        __offload = kzalloc_flex(*__offload, offload.entries, num_entries);
        if (!__offload)
                return NULL;

        refcount_set(&__offload->users, 1);

        return &__offload->offload;
}

struct tc_taprio_qopt_offload *taprio_offload_get(struct tc_taprio_qopt_offload
                                                  *offload)
{
        struct __tc_taprio_qopt_offload *__offload;

        __offload = container_of(offload, struct __tc_taprio_qopt_offload,
                                 offload);

        refcount_inc(&__offload->users);

        return offload;
}
EXPORT_SYMBOL_GPL(taprio_offload_get);

void taprio_offload_free(struct tc_taprio_qopt_offload *offload)
{
        struct __tc_taprio_qopt_offload *__offload;

        __offload = container_of(offload, struct __tc_taprio_qopt_offload,
                                 offload);

        if (!refcount_dec_and_test(&__offload->users))
                return;

        kfree(__offload);
}
EXPORT_SYMBOL_GPL(taprio_offload_free);

/* The function will only serve to keep the pointers to the "oper" and "admin"
 * schedules valid in relation to their base times, so when calling dump() the
 * users looks at the right schedules.
 * When using full offload, the admin configuration is promoted to oper at the
 * base_time in the PHC time domain.  But because the system time is not
 * necessarily in sync with that, we can't just trigger a hrtimer to call
 * switch_schedules at the right hardware time.
 * At the moment we call this by hand right away from taprio, but in the future
 * it will be useful to create a mechanism for drivers to notify taprio of the
 * offload state (PENDING, ACTIVE, INACTIVE) so it can be visible in dump().
 * This is left as TODO.
 */
static void taprio_offload_config_changed(struct taprio_sched *q)
{
        struct sched_gate_list *oper, *admin;

        oper = rtnl_dereference(q->oper_sched);
        admin = rtnl_dereference(q->admin_sched);

        switch_schedules(q, &admin, &oper);
}

static u32 tc_map_to_queue_mask(struct net_device *dev, u32 tc_mask)
{
        u32 i, queue_mask = 0;

        for (i = 0; i < dev->num_tc; i++) {
                u32 offset, count;

                if (!(tc_mask & BIT(i)))
                        continue;

                offset = dev->tc_to_txq[i].offset;
                count = dev->tc_to_txq[i].count;

                queue_mask |= GENMASK(offset + count - 1, offset);
        }

        return queue_mask;
}

static void taprio_sched_to_offload(struct net_device *dev,
                                    struct sched_gate_list *sched,
                                    struct tc_taprio_qopt_offload *offload,
                                    const struct tc_taprio_caps *caps)
{
        struct sched_entry *entry;
        int i = 0;

        offload->base_time = sched->base_time;
        offload->cycle_time = sched->cycle_time;
        offload->cycle_time_extension = sched->cycle_time_extension;

        list_for_each_entry(entry, &sched->entries, list) {
                struct tc_taprio_sched_entry *e = &offload->entries[i];

                e->command = entry->command;
                e->interval = entry->interval;
                if (caps->gate_mask_per_txq)
                        e->gate_mask = tc_map_to_queue_mask(dev,
                                                            entry->gate_mask);
                else
                        e->gate_mask = entry->gate_mask;

                i++;
        }

        offload->num_entries = i;
}

static void taprio_detect_broken_mqprio(struct taprio_sched *q)
{
        struct net_device *dev = qdisc_dev(q->root);
        struct tc_taprio_caps caps;

        qdisc_offload_query_caps(dev, TC_SETUP_QDISC_TAPRIO,
                                 &caps, sizeof(caps));

        q->broken_mqprio = caps.broken_mqprio;
        if (q->broken_mqprio)
                static_branch_inc(&taprio_have_broken_mqprio);
        else
                static_branch_inc(&taprio_have_working_mqprio);

        q->detected_mqprio = true;
}

static void taprio_cleanup_broken_mqprio(struct taprio_sched *q)
{
        if (!q->detected_mqprio)
                return;

        if (q->broken_mqprio)
                static_branch_dec(&taprio_have_broken_mqprio);
        else
                static_branch_dec(&taprio_have_working_mqprio);
}

static int taprio_enable_offload(struct net_device *dev,
                                 struct taprio_sched *q,
                                 struct sched_gate_list *sched,
                                 struct netlink_ext_ack *extack)
{
        const struct net_device_ops *ops = dev->netdev_ops;
        struct tc_taprio_qopt_offload *offload;
        struct tc_taprio_caps caps;
        int tc, err = 0;

        if (!ops->ndo_setup_tc) {
                NL_SET_ERR_MSG(extack,
                               "Device does not support taprio offload");
                return -EOPNOTSUPP;
        }

        qdisc_offload_query_caps(dev, TC_SETUP_QDISC_TAPRIO,
                                 &caps, sizeof(caps));

        if (!caps.supports_queue_max_sdu) {
                for (tc = 0; tc < TC_MAX_QUEUE; tc++) {
                        if (q->max_sdu[tc]) {
                                NL_SET_ERR_MSG_MOD(extack,
                                                   "Device does not handle queueMaxSDU");
                                return -EOPNOTSUPP;
                        }
                }
        }

        offload = taprio_offload_alloc(sched->num_entries);
        if (!offload) {
                NL_SET_ERR_MSG(extack,
                               "Not enough memory for enabling offload mode");
                return -ENOMEM;
        }
        offload->cmd = TAPRIO_CMD_REPLACE;
        offload->extack = extack;
        mqprio_qopt_reconstruct(dev, &offload->mqprio.qopt);
        offload->mqprio.extack = extack;
        taprio_sched_to_offload(dev, sched, offload, &caps);
        mqprio_fp_to_offload(q->fp, &offload->mqprio);

        for (tc = 0; tc < TC_MAX_QUEUE; tc++)
                offload->max_sdu[tc] = q->max_sdu[tc];

        err = ops->ndo_setup_tc(dev, TC_SETUP_QDISC_TAPRIO, offload);
        if (err < 0) {
                NL_SET_ERR_MSG_WEAK(extack,
                                    "Device failed to setup taprio offload");
                goto done;
        }

        q->offloaded = true;

done:
        /* The offload structure may linger around via a reference taken by the
         * device driver, so clear up the netlink extack pointer so that the
         * driver isn't tempted to dereference data which stopped being valid
         */
        offload->extack = NULL;
        offload->mqprio.extack = NULL;
        taprio_offload_free(offload);

        return err;
}

static int taprio_disable_offload(struct net_device *dev,
                                  struct taprio_sched *q,
                                  struct netlink_ext_ack *extack)
{
        const struct net_device_ops *ops = dev->netdev_ops;
        struct tc_taprio_qopt_offload *offload;
        int err;

        if (!q->offloaded)
                return 0;

        offload = taprio_offload_alloc(0);
        if (!offload) {
                NL_SET_ERR_MSG(extack,
                               "Not enough memory to disable offload mode");
                return -ENOMEM;
        }
        offload->cmd = TAPRIO_CMD_DESTROY;

        err = ops->ndo_setup_tc(dev, TC_SETUP_QDISC_TAPRIO, offload);
        if (err < 0) {
                NL_SET_ERR_MSG(extack,
                               "Device failed to disable offload");
                goto out;
        }

        q->offloaded = false;

out:
        taprio_offload_free(offload);

        return err;
}

/* If full offload is enabled, the only possible clockid is the net device's
 * PHC. For that reason, specifying a clockid through netlink is incorrect.
 * For txtime-assist, it is implicitly assumed that the device's PHC is kept
 * in sync with the specified clockid via a user space daemon such as phc2sys.
 * For both software taprio and txtime-assist, the clockid is used for the
 * hrtimer that advances the schedule and hence mandatory.
 */
static int taprio_parse_clockid(struct Qdisc *sch, struct nlattr **tb,
                                struct netlink_ext_ack *extack)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        int err = -EINVAL;

        if (FULL_OFFLOAD_IS_ENABLED(q->flags)) {
                const struct ethtool_ops *ops = dev->ethtool_ops;
                struct kernel_ethtool_ts_info info = {
                        .cmd = ETHTOOL_GET_TS_INFO,
                        .phc_index = -1,
                };

                if (tb[TCA_TAPRIO_ATTR_SCHED_CLOCKID]) {
                        NL_SET_ERR_MSG(extack,
                                       "The 'clockid' cannot be specified for full offload");
                        goto out;
                }

                if (ops && ops->get_ts_info)
                        err = ops->get_ts_info(dev, &info);

                if (err || info.phc_index < 0) {
                        NL_SET_ERR_MSG(extack,
                                       "Device does not have a PTP clock");
                        err = -ENOTSUPP;
                        goto out;
                }
        } else if (tb[TCA_TAPRIO_ATTR_SCHED_CLOCKID]) {
                int clockid = nla_get_s32(tb[TCA_TAPRIO_ATTR_SCHED_CLOCKID]);
                enum tk_offsets tk_offset;

                /* We only support static clockids and we don't allow
                 * for it to be modified after the first init.
                 */
                if (clockid < 0 ||
                    (q->clockid != -1 && q->clockid != clockid)) {
                        NL_SET_ERR_MSG(extack,
                                       "Changing the 'clockid' of a running schedule is not supported");
                        err = -ENOTSUPP;
                        goto out;
                }

                switch (clockid) {
                case CLOCK_REALTIME:
                        tk_offset = TK_OFFS_REAL;
                        break;
                case CLOCK_MONOTONIC:
                        tk_offset = TK_OFFS_MAX;
                        break;
                case CLOCK_BOOTTIME:
                        tk_offset = TK_OFFS_BOOT;
                        break;
                case CLOCK_TAI:
                        tk_offset = TK_OFFS_TAI;
                        break;
                default:
                        NL_SET_ERR_MSG(extack, "Invalid 'clockid'");
                        err = -EINVAL;
                        goto out;
                }
                /* This pairs with READ_ONCE() in taprio_mono_to_any */
                WRITE_ONCE(q->tk_offset, tk_offset);

                q->clockid = clockid;
        } else {
                NL_SET_ERR_MSG(extack, "Specifying a 'clockid' is mandatory");
                goto out;
        }

        /* Everything went ok, return success. */
        err = 0;

out:
        return err;
}

static int taprio_parse_tc_entry(struct Qdisc *sch,
                                 struct nlattr *opt,
                                 u32 max_sdu[TC_QOPT_MAX_QUEUE],
                                 u32 fp[TC_QOPT_MAX_QUEUE],
                                 unsigned long *seen_tcs,
                                 struct netlink_ext_ack *extack)
{
        struct nlattr *tb[TCA_TAPRIO_TC_ENTRY_MAX + 1] = { };
        struct net_device *dev = qdisc_dev(sch);
        int err, tc;
        u32 val;

        err = nla_parse_nested(tb, TCA_TAPRIO_TC_ENTRY_MAX, opt,
                               taprio_tc_policy, extack);
        if (err < 0)
                return err;

        if (NL_REQ_ATTR_CHECK(extack, opt, tb, TCA_TAPRIO_TC_ENTRY_INDEX)) {
                NL_SET_ERR_MSG_MOD(extack, "TC entry index missing");
                return -EINVAL;
        }

        tc = nla_get_u32(tb[TCA_TAPRIO_TC_ENTRY_INDEX]);
        if (*seen_tcs & BIT(tc)) {
                NL_SET_ERR_MSG_ATTR(extack, tb[TCA_TAPRIO_TC_ENTRY_INDEX],
                                    "Duplicate tc entry");
                return -EINVAL;
        }

        *seen_tcs |= BIT(tc);

        if (tb[TCA_TAPRIO_TC_ENTRY_MAX_SDU]) {
                val = nla_get_u32(tb[TCA_TAPRIO_TC_ENTRY_MAX_SDU]);
                if (val > dev->max_mtu) {
                        NL_SET_ERR_MSG_MOD(extack, "TC max SDU exceeds device max MTU");
                        return -ERANGE;
                }

                max_sdu[tc] = val;
        }

        if (tb[TCA_TAPRIO_TC_ENTRY_FP])
                fp[tc] = nla_get_u32(tb[TCA_TAPRIO_TC_ENTRY_FP]);

        return 0;
}

static int taprio_parse_tc_entries(struct Qdisc *sch,
                                   struct nlattr *opt,
                                   struct netlink_ext_ack *extack)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        u32 max_sdu[TC_QOPT_MAX_QUEUE];
        bool have_preemption = false;
        unsigned long seen_tcs = 0;
        u32 fp[TC_QOPT_MAX_QUEUE];
        struct nlattr *n;
        int tc, rem;
        int err = 0;

        for (tc = 0; tc < TC_QOPT_MAX_QUEUE; tc++) {
                max_sdu[tc] = q->max_sdu[tc];
                fp[tc] = q->fp[tc];
        }

        nla_for_each_nested_type(n, TCA_TAPRIO_ATTR_TC_ENTRY, opt, rem) {
                err = taprio_parse_tc_entry(sch, n, max_sdu, fp, &seen_tcs,
                                            extack);
                if (err)
                        return err;
        }

        for (tc = 0; tc < TC_QOPT_MAX_QUEUE; tc++) {
                q->max_sdu[tc] = max_sdu[tc];
                q->fp[tc] = fp[tc];
                if (fp[tc] != TC_FP_EXPRESS)
                        have_preemption = true;
        }

        if (have_preemption) {
                if (!FULL_OFFLOAD_IS_ENABLED(q->flags)) {
                        NL_SET_ERR_MSG(extack,
                                       "Preemption only supported with full offload");
                        return -EOPNOTSUPP;
                }

                if (!ethtool_dev_mm_supported(dev)) {
                        NL_SET_ERR_MSG(extack,
                                       "Device does not support preemption");
                        return -EOPNOTSUPP;
                }
        }

        return err;
}

static int taprio_mqprio_cmp(const struct net_device *dev,
                             const struct tc_mqprio_qopt *mqprio)
{
        int i;

        if (!mqprio || mqprio->num_tc != dev->num_tc)
                return -1;

        for (i = 0; i < mqprio->num_tc; i++)
                if (dev->tc_to_txq[i].count != mqprio->count[i] ||
                    dev->tc_to_txq[i].offset != mqprio->offset[i])
                        return -1;

        for (i = 0; i <= TC_BITMASK; i++)
                if (dev->prio_tc_map[i] != mqprio->prio_tc_map[i])
                        return -1;

        return 0;
}

static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
                         struct netlink_ext_ack *extack)
{
        struct qdisc_size_table *stab = rtnl_dereference(sch->stab);
        struct nlattr *tb[TCA_TAPRIO_ATTR_MAX + 1] = { };
        struct sched_gate_list *oper, *admin, *new_admin;
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        struct tc_mqprio_qopt *mqprio = NULL;
        unsigned long flags;
        u32 taprio_flags;
        ktime_t start;
        int i, err;

        err = nla_parse_nested_deprecated(tb, TCA_TAPRIO_ATTR_MAX, opt,
                                          taprio_policy, extack);
        if (err < 0)
                return err;

        if (tb[TCA_TAPRIO_ATTR_PRIOMAP])
                mqprio = nla_data(tb[TCA_TAPRIO_ATTR_PRIOMAP]);

        /* The semantics of the 'flags' argument in relation to 'change()'
         * requests, are interpreted following two rules (which are applied in
         * this order): (1) an omitted 'flags' argument is interpreted as
         * zero; (2) the 'flags' of a "running" taprio instance cannot be
         * changed.
         */
        taprio_flags = nla_get_u32_default(tb[TCA_TAPRIO_ATTR_FLAGS], 0);

        /* txtime-assist and full offload are mutually exclusive */
        if ((taprio_flags & TCA_TAPRIO_ATTR_FLAG_TXTIME_ASSIST) &&
            (taprio_flags & TCA_TAPRIO_ATTR_FLAG_FULL_OFFLOAD)) {
                NL_SET_ERR_MSG_ATTR(extack, tb[TCA_TAPRIO_ATTR_FLAGS],
                                    "TXTIME_ASSIST and FULL_OFFLOAD are mutually exclusive");
                return -EINVAL;
        }

        if (q->flags != TAPRIO_FLAGS_INVALID && q->flags != taprio_flags) {
                NL_SET_ERR_MSG_MOD(extack,
                                   "Changing 'flags' of a running schedule is not supported");
                return -EOPNOTSUPP;
        }
        q->flags = taprio_flags;

        /* Needed for length_to_duration() during netlink attribute parsing */
        taprio_set_picos_per_byte(dev, q, extack);

        err = taprio_parse_mqprio_opt(dev, mqprio, extack, q->flags);
        if (err < 0)
                return err;

        err = taprio_parse_tc_entries(sch, opt, extack);
        if (err)
                return err;

        new_admin = kzalloc_obj(*new_admin);
        if (!new_admin) {
                NL_SET_ERR_MSG(extack, "Not enough memory for a new schedule");
                return -ENOMEM;
        }
        INIT_LIST_HEAD(&new_admin->entries);

        oper = rtnl_dereference(q->oper_sched);
        admin = rtnl_dereference(q->admin_sched);

        /* no changes - no new mqprio settings */
        if (!taprio_mqprio_cmp(dev, mqprio))
                mqprio = NULL;

        if (mqprio && (oper || admin)) {
                NL_SET_ERR_MSG(extack, "Changing the traffic mapping of a running schedule is not supported");
                err = -ENOTSUPP;
                goto free_sched;
        }

        if (mqprio) {
                err = netdev_set_num_tc(dev, mqprio->num_tc);
                if (err)
                        goto free_sched;
                for (i = 0; i < mqprio->num_tc; i++) {
                        netdev_set_tc_queue(dev, i,
                                            mqprio->count[i],
                                            mqprio->offset[i]);
                        q->cur_txq[i] = mqprio->offset[i];
                }

                /* Always use supplied priority mappings */
                for (i = 0; i <= TC_BITMASK; i++)
                        netdev_set_prio_tc_map(dev, i,
                                               mqprio->prio_tc_map[i]);
        }

        err = parse_taprio_schedule(q, tb, new_admin, extack);
        if (err < 0)
                goto free_sched;

        if (new_admin->num_entries == 0) {
                NL_SET_ERR_MSG(extack, "There should be at least one entry in the schedule");
                err = -EINVAL;
                goto free_sched;
        }

        err = taprio_parse_clockid(sch, tb, extack);
        if (err < 0)
                goto free_sched;

        taprio_update_queue_max_sdu(q, new_admin, stab);

        if (FULL_OFFLOAD_IS_ENABLED(q->flags))
                err = taprio_enable_offload(dev, q, new_admin, extack);
        else
                err = taprio_disable_offload(dev, q, extack);
        if (err)
                goto free_sched;

        /* Protects against enqueue()/dequeue() */
        spin_lock_bh(qdisc_lock(sch));

        if (tb[TCA_TAPRIO_ATTR_TXTIME_DELAY]) {
                if (!TXTIME_ASSIST_IS_ENABLED(q->flags)) {
                        NL_SET_ERR_MSG_MOD(extack, "txtime-delay can only be set when txtime-assist mode is enabled");
                        err = -EINVAL;
                        goto unlock;
                }

                q->txtime_delay = nla_get_u32(tb[TCA_TAPRIO_ATTR_TXTIME_DELAY]);
        }

        if (!TXTIME_ASSIST_IS_ENABLED(q->flags) &&
            !FULL_OFFLOAD_IS_ENABLED(q->flags) &&
            !hrtimer_active(&q->advance_timer)) {
                hrtimer_setup(&q->advance_timer, advance_sched, q->clockid, HRTIMER_MODE_ABS);
        }

        err = taprio_get_start_time(sch, new_admin, &start);
        if (err < 0) {
                NL_SET_ERR_MSG(extack, "Internal error: failed get start time");
                goto unlock;
        }

        setup_txtime(q, new_admin, start);

        if (TXTIME_ASSIST_IS_ENABLED(q->flags)) {
                if (!oper) {
                        rcu_assign_pointer(q->oper_sched, new_admin);
                        err = 0;
                        new_admin = NULL;
                        goto unlock;
                }

                /* Not going to race against advance_sched(), but still */
                admin = rcu_replace_pointer(q->admin_sched, new_admin,
                                            lockdep_rtnl_is_held());
                if (admin)
                        call_rcu(&admin->rcu, taprio_free_sched_cb);
        } else {
                setup_first_end_time(q, new_admin, start);

                /* Protects against advance_sched() */
                spin_lock_irqsave(&q->current_entry_lock, flags);

                taprio_start_sched(sch, start, new_admin);

                admin = rcu_replace_pointer(q->admin_sched, new_admin,
                                            lockdep_rtnl_is_held());
                if (admin)
                        call_rcu(&admin->rcu, taprio_free_sched_cb);

                spin_unlock_irqrestore(&q->current_entry_lock, flags);

                if (FULL_OFFLOAD_IS_ENABLED(q->flags))
                        taprio_offload_config_changed(q);
        }

        new_admin = NULL;
        err = 0;

        if (!stab)
                NL_SET_ERR_MSG_MOD(extack,
                                   "Size table not specified, frame length estimations may be inaccurate");

unlock:
        spin_unlock_bh(qdisc_lock(sch));

free_sched:
        if (new_admin)
                call_rcu(&new_admin->rcu, taprio_free_sched_cb);

        return err;
}

static void taprio_reset(struct Qdisc *sch)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        int i;

        hrtimer_cancel(&q->advance_timer);

        if (q->qdiscs) {
                for (i = 0; i < dev->num_tx_queues; i++)
                        if (q->qdiscs[i])
                                qdisc_reset(q->qdiscs[i]);
        }
}

static void taprio_destroy(struct Qdisc *sch)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        struct sched_gate_list *oper, *admin;
        unsigned int i;

        list_del(&q->taprio_list);

        /* Note that taprio_reset() might not be called if an error
         * happens in qdisc_create(), after taprio_init() has been called.
         */
        hrtimer_cancel(&q->advance_timer);
        qdisc_synchronize(sch);

        taprio_disable_offload(dev, q, NULL);

        if (q->qdiscs) {
                for (i = 0; i < dev->num_tx_queues; i++)
                        qdisc_put(q->qdiscs[i]);

                kfree(q->qdiscs);
        }
        q->qdiscs = NULL;

        netdev_reset_tc(dev);

        oper = rtnl_dereference(q->oper_sched);
        admin = rtnl_dereference(q->admin_sched);

        if (oper)
                call_rcu(&oper->rcu, taprio_free_sched_cb);

        if (admin)
                call_rcu(&admin->rcu, taprio_free_sched_cb);

        taprio_cleanup_broken_mqprio(q);
}

static int taprio_init(struct Qdisc *sch, struct nlattr *opt,
                       struct netlink_ext_ack *extack)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        int i, tc;

        spin_lock_init(&q->current_entry_lock);

        hrtimer_setup(&q->advance_timer, advance_sched, CLOCK_TAI, HRTIMER_MODE_ABS);

        q->root = sch;

        /* We only support static clockids. Use an invalid value as default
         * and get the valid one on taprio_change().
         */
        q->clockid = -1;
        q->flags = TAPRIO_FLAGS_INVALID;

        list_add(&q->taprio_list, &taprio_list);

        if (sch->parent != TC_H_ROOT) {
                NL_SET_ERR_MSG_MOD(extack, "Can only be attached as root qdisc");
                return -EOPNOTSUPP;
        }

        if (!netif_is_multiqueue(dev)) {
                NL_SET_ERR_MSG_MOD(extack, "Multi-queue device is required");
                return -EOPNOTSUPP;
        }

        q->qdiscs = kzalloc_objs(q->qdiscs[0], dev->num_tx_queues);
        if (!q->qdiscs)
                return -ENOMEM;

        if (!opt)
                return -EINVAL;

        for (i = 0; i < dev->num_tx_queues; i++) {
                struct netdev_queue *dev_queue;
                struct Qdisc *qdisc;

                dev_queue = netdev_get_tx_queue(dev, i);
                qdisc = qdisc_create_dflt(dev_queue,
                                          &pfifo_qdisc_ops,
                                          TC_H_MAKE(TC_H_MAJ(sch->handle),
                                                    TC_H_MIN(i + 1)),
                                          extack);
                if (!qdisc)
                        return -ENOMEM;

                if (i < dev->real_num_tx_queues)
                        qdisc_hash_add(qdisc, false);

                q->qdiscs[i] = qdisc;
        }

        for (tc = 0; tc < TC_QOPT_MAX_QUEUE; tc++)
                q->fp[tc] = TC_FP_EXPRESS;

        taprio_detect_broken_mqprio(q);

        return taprio_change(sch, opt, extack);
}

static void taprio_attach(struct Qdisc *sch)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        unsigned int ntx;

        /* Attach underlying qdisc */
        for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
                struct netdev_queue *dev_queue = netdev_get_tx_queue(dev, ntx);
                struct Qdisc *old, *dev_queue_qdisc;

                if (FULL_OFFLOAD_IS_ENABLED(q->flags)) {
                        struct Qdisc *qdisc = q->qdiscs[ntx];

                        /* In offload mode, the root taprio qdisc is bypassed
                         * and the netdev TX queues see the children directly
                         */
                        qdisc->flags |= TCQ_F_ONETXQUEUE | TCQ_F_NOPARENT;
                        dev_queue_qdisc = qdisc;
                } else {
                        /* In software mode, attach the root taprio qdisc
                         * to all netdev TX queues, so that dev_qdisc_enqueue()
                         * goes through taprio_enqueue().
                         */
                        dev_queue_qdisc = sch;
                }
                old = dev_graft_qdisc(dev_queue, dev_queue_qdisc);
                /* The qdisc's refcount requires to be elevated once
                 * for each netdev TX queue it is grafted onto
                 */
                qdisc_refcount_inc(dev_queue_qdisc);
                if (old)
                        qdisc_put(old);
        }
}

static struct netdev_queue *taprio_queue_get(struct Qdisc *sch,
                                             unsigned long cl)
{
        struct net_device *dev = qdisc_dev(sch);
        unsigned long ntx = cl - 1;

        if (ntx >= dev->num_tx_queues)
                return NULL;

        return netdev_get_tx_queue(dev, ntx);
}

static int taprio_graft(struct Qdisc *sch, unsigned long cl,
                        struct Qdisc *new, struct Qdisc **old,
                        struct netlink_ext_ack *extack)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        struct netdev_queue *dev_queue = taprio_queue_get(sch, cl);

        if (!dev_queue)
                return -EINVAL;

        if (dev->flags & IFF_UP)
                dev_deactivate(dev);

        /* In offload mode, the child Qdisc is directly attached to the netdev
         * TX queue, and thus, we need to keep its refcount elevated in order
         * to counteract qdisc_graft()'s call to qdisc_put() once per TX queue.
         * However, save the reference to the new qdisc in the private array in
         * both software and offload cases, to have an up-to-date reference to
         * our children.
         */
        *old = q->qdiscs[cl - 1];
        if (FULL_OFFLOAD_IS_ENABLED(q->flags)) {
                WARN_ON_ONCE(dev_graft_qdisc(dev_queue, new) != *old);
                if (new)
                        qdisc_refcount_inc(new);
                if (*old)
                        qdisc_put(*old);
        }

        q->qdiscs[cl - 1] = new;
        if (new)
                new->flags |= TCQ_F_ONETXQUEUE | TCQ_F_NOPARENT;

        if (dev->flags & IFF_UP)
                dev_activate(dev);

        return 0;
}

static int dump_entry(struct sk_buff *msg,
                      const struct sched_entry *entry)
{
        struct nlattr *item;

        item = nla_nest_start_noflag(msg, TCA_TAPRIO_SCHED_ENTRY);
        if (!item)
                return -ENOSPC;

        if (nla_put_u32(msg, TCA_TAPRIO_SCHED_ENTRY_INDEX, entry->index))
                goto nla_put_failure;

        if (nla_put_u8(msg, TCA_TAPRIO_SCHED_ENTRY_CMD, entry->command))
                goto nla_put_failure;

        if (nla_put_u32(msg, TCA_TAPRIO_SCHED_ENTRY_GATE_MASK,
                        entry->gate_mask))
                goto nla_put_failure;

        if (nla_put_u32(msg, TCA_TAPRIO_SCHED_ENTRY_INTERVAL,
                        entry->interval))
                goto nla_put_failure;

        return nla_nest_end(msg, item);

nla_put_failure:
        nla_nest_cancel(msg, item);
        return -1;
}

static int dump_schedule(struct sk_buff *msg,
                         const struct sched_gate_list *root)
{
        struct nlattr *entry_list;
        struct sched_entry *entry;

        if (nla_put_s64(msg, TCA_TAPRIO_ATTR_SCHED_BASE_TIME,
                        root->base_time, TCA_TAPRIO_PAD))
                return -1;

        if (nla_put_s64(msg, TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME,
                        root->cycle_time, TCA_TAPRIO_PAD))
                return -1;

        if (nla_put_s64(msg, TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME_EXTENSION,
                        root->cycle_time_extension, TCA_TAPRIO_PAD))
                return -1;

        entry_list = nla_nest_start_noflag(msg,
                                           TCA_TAPRIO_ATTR_SCHED_ENTRY_LIST);
        if (!entry_list)
                goto error_nest;

        list_for_each_entry(entry, &root->entries, list) {
                if (dump_entry(msg, entry) < 0)
                        goto error_nest;
        }

        nla_nest_end(msg, entry_list);
        return 0;

error_nest:
        nla_nest_cancel(msg, entry_list);
        return -1;
}

static int taprio_dump_tc_entries(struct sk_buff *skb,
                                  struct taprio_sched *q,
                                  struct sched_gate_list *sched)
{
        struct nlattr *n;
        int tc;

        for (tc = 0; tc < TC_MAX_QUEUE; tc++) {
                n = nla_nest_start(skb, TCA_TAPRIO_ATTR_TC_ENTRY);
                if (!n)
                        return -EMSGSIZE;

                if (nla_put_u32(skb, TCA_TAPRIO_TC_ENTRY_INDEX, tc))
                        goto nla_put_failure;

                if (nla_put_u32(skb, TCA_TAPRIO_TC_ENTRY_MAX_SDU,
                                sched->max_sdu[tc]))
                        goto nla_put_failure;

                if (nla_put_u32(skb, TCA_TAPRIO_TC_ENTRY_FP, q->fp[tc]))
                        goto nla_put_failure;

                nla_nest_end(skb, n);
        }

        return 0;

nla_put_failure:
        nla_nest_cancel(skb, n);
        return -EMSGSIZE;
}

static int taprio_put_stat(struct sk_buff *skb, u64 val, u16 attrtype)
{
        if (val == TAPRIO_STAT_NOT_SET)
                return 0;
        if (nla_put_u64_64bit(skb, attrtype, val, TCA_TAPRIO_OFFLOAD_STATS_PAD))
                return -EMSGSIZE;
        return 0;
}

static int taprio_dump_xstats(struct Qdisc *sch, struct gnet_dump *d,
                              struct tc_taprio_qopt_offload *offload,
                              struct tc_taprio_qopt_stats *stats)
{
        struct net_device *dev = qdisc_dev(sch);
        const struct net_device_ops *ops;
        struct sk_buff *skb = d->skb;
        struct nlattr *xstats;
        int err;

        ops = qdisc_dev(sch)->netdev_ops;

        /* FIXME I could use qdisc_offload_dump_helper(), but that messes
         * with sch->flags depending on whether the device reports taprio
         * stats, and I'm not sure whether that's a good idea, considering
         * that stats are optional to the offload itself
         */
        if (!ops->ndo_setup_tc)
                return 0;

        memset(stats, 0xff, sizeof(*stats));

        err = ops->ndo_setup_tc(dev, TC_SETUP_QDISC_TAPRIO, offload);
        if (err == -EOPNOTSUPP)
                return 0;
        if (err)
                return err;

        xstats = nla_nest_start(skb, TCA_STATS_APP);
        if (!xstats)
                goto err;

        if (taprio_put_stat(skb, stats->window_drops,
                            TCA_TAPRIO_OFFLOAD_STATS_WINDOW_DROPS) ||
            taprio_put_stat(skb, stats->tx_overruns,
                            TCA_TAPRIO_OFFLOAD_STATS_TX_OVERRUNS))
                goto err_cancel;

        nla_nest_end(skb, xstats);

        return 0;

err_cancel:
        nla_nest_cancel(skb, xstats);
err:
        return -EMSGSIZE;
}

static int taprio_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
{
        struct tc_taprio_qopt_offload offload = {
                .cmd = TAPRIO_CMD_STATS,
        };

        return taprio_dump_xstats(sch, d, &offload, &offload.stats);
}

static int taprio_dump(struct Qdisc *sch, struct sk_buff *skb)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        struct sched_gate_list *oper, *admin;
        struct tc_mqprio_qopt opt = { 0 };
        struct nlattr *nest, *sched_nest;

        mqprio_qopt_reconstruct(dev, &opt);

        nest = nla_nest_start_noflag(skb, TCA_OPTIONS);
        if (!nest)
                goto start_error;

        if (nla_put(skb, TCA_TAPRIO_ATTR_PRIOMAP, sizeof(opt), &opt))
                goto options_error;

        if (!FULL_OFFLOAD_IS_ENABLED(q->flags) &&
            nla_put_s32(skb, TCA_TAPRIO_ATTR_SCHED_CLOCKID, q->clockid))
                goto options_error;

        if (q->flags && nla_put_u32(skb, TCA_TAPRIO_ATTR_FLAGS, q->flags))
                goto options_error;

        if (q->txtime_delay &&
            nla_put_u32(skb, TCA_TAPRIO_ATTR_TXTIME_DELAY, q->txtime_delay))
                goto options_error;

        rcu_read_lock();

        oper = rtnl_dereference(q->oper_sched);
        admin = rtnl_dereference(q->admin_sched);

        if (oper && taprio_dump_tc_entries(skb, q, oper))
                goto options_error_rcu;

        if (oper && dump_schedule(skb, oper))
                goto options_error_rcu;

        if (!admin)
                goto done;

        sched_nest = nla_nest_start_noflag(skb, TCA_TAPRIO_ATTR_ADMIN_SCHED);
        if (!sched_nest)
                goto options_error_rcu;

        if (dump_schedule(skb, admin))
                goto admin_error;

        nla_nest_end(skb, sched_nest);

done:
        rcu_read_unlock();
        return nla_nest_end(skb, nest);

admin_error:
        nla_nest_cancel(skb, sched_nest);

options_error_rcu:
        rcu_read_unlock();

options_error:
        nla_nest_cancel(skb, nest);

start_error:
        return -ENOSPC;
}

static struct Qdisc *taprio_leaf(struct Qdisc *sch, unsigned long cl)
{
        struct taprio_sched *q = qdisc_priv(sch);
        struct net_device *dev = qdisc_dev(sch);
        unsigned int ntx = cl - 1;

        if (ntx >= dev->num_tx_queues)
                return NULL;

        return q->qdiscs[ntx];
}

static unsigned long taprio_find(struct Qdisc *sch, u32 classid)
{
        unsigned int ntx = TC_H_MIN(classid);

        if (!taprio_queue_get(sch, ntx))
                return 0;
        return ntx;
}

static int taprio_dump_class(struct Qdisc *sch, unsigned long cl,
                             struct sk_buff *skb, struct tcmsg *tcm)
{
        struct Qdisc *child = taprio_leaf(sch, cl);

        tcm->tcm_parent = TC_H_ROOT;
        tcm->tcm_handle |= TC_H_MIN(cl);
        tcm->tcm_info = child->handle;

        return 0;
}

static int taprio_dump_class_stats(struct Qdisc *sch, unsigned long cl,
                                   struct gnet_dump *d)
        __releases(d->lock)
        __acquires(d->lock)
{
        struct Qdisc *child = taprio_leaf(sch, cl);
        struct tc_taprio_qopt_offload offload = {
                .cmd = TAPRIO_CMD_QUEUE_STATS,
                .queue_stats = {
                        .queue = cl - 1,
                },
        };

        if (gnet_stats_copy_basic(d, NULL, &child->bstats, true) < 0 ||
            qdisc_qstats_copy(d, child) < 0)
                return -1;

        return taprio_dump_xstats(sch, d, &offload, &offload.queue_stats.stats);
}

static void taprio_walk(struct Qdisc *sch, struct qdisc_walker *arg)
{
        struct net_device *dev = qdisc_dev(sch);
        unsigned long ntx;

        if (arg->stop)
                return;

        arg->count = arg->skip;
        for (ntx = arg->skip; ntx < dev->num_tx_queues; ntx++) {
                if (!tc_qdisc_stats_dump(sch, ntx + 1, arg))
                        break;
        }
}

static struct netdev_queue *taprio_select_queue(struct Qdisc *sch,
                                                struct tcmsg *tcm)
{
        return taprio_queue_get(sch, TC_H_MIN(tcm->tcm_parent));
}

static const struct Qdisc_class_ops taprio_class_ops = {
        .graft          = taprio_graft,
        .leaf           = taprio_leaf,
        .find           = taprio_find,
        .walk           = taprio_walk,
        .dump           = taprio_dump_class,
        .dump_stats     = taprio_dump_class_stats,
        .select_queue   = taprio_select_queue,
};

static struct Qdisc_ops taprio_qdisc_ops __read_mostly = {
        .cl_ops         = &taprio_class_ops,
        .id             = "taprio",
        .priv_size      = sizeof(struct taprio_sched),
        .init           = taprio_init,
        .change         = taprio_change,
        .destroy        = taprio_destroy,
        .reset          = taprio_reset,
        .attach         = taprio_attach,
        .peek           = taprio_peek,
        .dequeue        = taprio_dequeue,
        .enqueue        = taprio_enqueue,
        .dump           = taprio_dump,
        .dump_stats     = taprio_dump_stats,
        .owner          = THIS_MODULE,
};
MODULE_ALIAS_NET_SCH("taprio");

static struct notifier_block taprio_device_notifier = {
        .notifier_call = taprio_dev_notifier,
};

static int __init taprio_module_init(void)
{
        int err = register_netdevice_notifier(&taprio_device_notifier);

        if (err)
                return err;

        return register_qdisc(&taprio_qdisc_ops);
}

static void __exit taprio_module_exit(void)
{
        unregister_qdisc(&taprio_qdisc_ops);
        unregister_netdevice_notifier(&taprio_device_notifier);
}

module_init(taprio_module_init);
module_exit(taprio_module_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Time Aware Priority qdisc");