/*
 * Copyright 2002-2005, Instant802 Networks, Inc.
 * Copyright 2005-2006, Devicescape Software, Inc.
 * Copyright (c) 2006 Jiri Benc <jbenc@suse.cz>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/kernel.h>
#include <linux/rtnetlink.h>
#include <linux/slab.h>
#include <linux/module.h>
#include "rate.h"
#include "ieee80211_i.h"
#include "debugfs.h"

struct rate_control_alg {
        struct list_head list;
        struct rate_control_ops *ops;
};

static LIST_HEAD(rate_ctrl_algs);
static DEFINE_MUTEX(rate_ctrl_mutex);

static char *ieee80211_default_rc_algo = CONFIG_MAC80211_RC_DEFAULT;
module_param(ieee80211_default_rc_algo, charp, 0644);
MODULE_PARM_DESC(ieee80211_default_rc_algo,
                 "Default rate control algorithm for mac80211 to use");

int ieee80211_rate_control_register(struct rate_control_ops *ops)
{
        struct rate_control_alg *alg;

        if (!ops->name)
                return -EINVAL;

        mutex_lock(&rate_ctrl_mutex);
        list_for_each_entry(alg, &rate_ctrl_algs, list) {
                if (!strcmp(alg->ops->name, ops->name)) {
                        /* don't register an algorithm twice */
                        WARN_ON(1);
                        mutex_unlock(&rate_ctrl_mutex);
                        return -EALREADY;
                }
        }

        alg = kzalloc(sizeof(*alg), GFP_KERNEL);
        if (alg == NULL) {
                mutex_unlock(&rate_ctrl_mutex);
                return -ENOMEM;
        }
        alg->ops = ops;

        list_add_tail(&alg->list, &rate_ctrl_algs);
        mutex_unlock(&rate_ctrl_mutex);

        return 0;
}
EXPORT_SYMBOL(ieee80211_rate_control_register);

void ieee80211_rate_control_unregister(struct rate_control_ops *ops)
{
        struct rate_control_alg *alg;

        mutex_lock(&rate_ctrl_mutex);
        list_for_each_entry(alg, &rate_ctrl_algs, list) {
                if (alg->ops == ops) {
                        list_del(&alg->list);
                        kfree(alg);
                        break;
                }
        }
        mutex_unlock(&rate_ctrl_mutex);
}
EXPORT_SYMBOL(ieee80211_rate_control_unregister);

static struct rate_control_ops *
ieee80211_try_rate_control_ops_get(const char *name)
{
        struct rate_control_alg *alg;
        struct rate_control_ops *ops = NULL;

        if (!name)
                return NULL;

        mutex_lock(&rate_ctrl_mutex);
        list_for_each_entry(alg, &rate_ctrl_algs, list) {
                if (!strcmp(alg->ops->name, name))
                        if (try_module_get(alg->ops->module)) {
                                ops = alg->ops;
                                break;
                        }
        }
        mutex_unlock(&rate_ctrl_mutex);
        return ops;
}

/* Get the rate control algorithm. */
static struct rate_control_ops *
ieee80211_rate_control_ops_get(const char *name)
{
        struct rate_control_ops *ops;
        const char *alg_name;

        kparam_block_sysfs_write(ieee80211_default_rc_algo);
        if (!name)
                alg_name = ieee80211_default_rc_algo;
        else
                alg_name = name;

        ops = ieee80211_try_rate_control_ops_get(alg_name);
        if (!ops) {
                request_module("rc80211_%s", alg_name);
                ops = ieee80211_try_rate_control_ops_get(alg_name);
        }
        if (!ops && name)
                /* try default if specific alg requested but not found */
                ops = ieee80211_try_rate_control_ops_get(ieee80211_default_rc_algo);

        /* try built-in one if specific alg requested but not found */
        if (!ops && strlen(CONFIG_MAC80211_RC_DEFAULT))
                ops = ieee80211_try_rate_control_ops_get(CONFIG_MAC80211_RC_DEFAULT);
        kparam_unblock_sysfs_write(ieee80211_default_rc_algo);

        return ops;
}

static void ieee80211_rate_control_ops_put(struct rate_control_ops *ops)
{
        module_put(ops->module);
}

#ifdef CONFIG_MAC80211_DEBUGFS
static ssize_t rcname_read(struct file *file, char __user *userbuf,
                           size_t count, loff_t *ppos)
{
        struct rate_control_ref *ref = file->private_data;
        int len = strlen(ref->ops->name);

        return simple_read_from_buffer(userbuf, count, ppos,
                                       ref->ops->name, len);
}

static const struct file_operations rcname_ops = {
        .read = rcname_read,
        .open = mac80211_open_file_generic,
        .llseek = default_llseek,
};
#endif

static struct rate_control_ref *rate_control_alloc(const char *name,
                                            struct ieee80211_local *local)
{
        struct dentry *debugfsdir = NULL;
        struct rate_control_ref *ref;

        ref = kmalloc(sizeof(struct rate_control_ref), GFP_KERNEL);
        if (!ref)
                goto fail_ref;
        kref_init(&ref->kref);
        ref->local = local;
        ref->ops = ieee80211_rate_control_ops_get(name);
        if (!ref->ops)
                goto fail_ops;

#ifdef CONFIG_MAC80211_DEBUGFS
        debugfsdir = debugfs_create_dir("rc", local->hw.wiphy->debugfsdir);
        local->debugfs.rcdir = debugfsdir;
        debugfs_create_file("name", 0400, debugfsdir, ref, &rcname_ops);
#endif

        ref->priv = ref->ops->alloc(&local->hw, debugfsdir);
        if (!ref->priv)
                goto fail_priv;
        return ref;

fail_priv:
        ieee80211_rate_control_ops_put(ref->ops);
fail_ops:
        kfree(ref);
fail_ref:
        return NULL;
}

static void rate_control_release(struct kref *kref)
{
        struct rate_control_ref *ctrl_ref;

        ctrl_ref = container_of(kref, struct rate_control_ref, kref);
        ctrl_ref->ops->free(ctrl_ref->priv);

#ifdef CONFIG_MAC80211_DEBUGFS
        debugfs_remove_recursive(ctrl_ref->local->debugfs.rcdir);
        ctrl_ref->local->debugfs.rcdir = NULL;
#endif

        ieee80211_rate_control_ops_put(ctrl_ref->ops);
        kfree(ctrl_ref);
}

static bool rc_no_data_or_no_ack_use_min(struct ieee80211_tx_rate_control *txrc)
{
        struct sk_buff *skb = txrc->skb;
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
        __le16 fc;

        fc = hdr->frame_control;

        return (info->flags & (IEEE80211_TX_CTL_NO_ACK |
                               IEEE80211_TX_CTL_USE_MINRATE)) ||
                !ieee80211_is_data(fc);
}

static void rc_send_low_broadcast(s8 *idx, u32 basic_rates,
                                  struct ieee80211_supported_band *sband)
{
        u8 i;

        if (basic_rates == 0)
                return; /* assume basic rates unknown and accept rate */
        if (*idx < 0)
                return;
        if (basic_rates & (1 << *idx))
                return; /* selected rate is a basic rate */

        for (i = *idx + 1; i <= sband->n_bitrates; i++) {
                if (basic_rates & (1 << i)) {
                        *idx = i;
                        return;
                }
        }

        /* could not find a basic rate; use original selection */
}

static inline s8
rate_lowest_non_cck_index(struct ieee80211_supported_band *sband,
                          struct ieee80211_sta *sta)
{
        int i;

        for (i = 0; i < sband->n_bitrates; i++) {
                struct ieee80211_rate *srate = &sband->bitrates[i];
                if ((srate->bitrate == 10) || (srate->bitrate == 20) ||
                    (srate->bitrate == 55) || (srate->bitrate == 110))
                        continue;

                if (rate_supported(sta, sband->band, i))
                        return i;
        }

        /* No matching rate found */
        return 0;
}


bool rate_control_send_low(struct ieee80211_sta *sta,
                           void *priv_sta,
                           struct ieee80211_tx_rate_control *txrc)
{
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(txrc->skb);
        struct ieee80211_supported_band *sband = txrc->sband;
        int mcast_rate;

        if (!sta || !priv_sta || rc_no_data_or_no_ack_use_min(txrc)) {
                if ((sband->band != IEEE80211_BAND_2GHZ) ||
                    !(info->flags & IEEE80211_TX_CTL_NO_CCK_RATE))
                        info->control.rates[0].idx =
                                rate_lowest_index(txrc->sband, sta);
                else
                        info->control.rates[0].idx =
                                rate_lowest_non_cck_index(txrc->sband, sta);
                info->control.rates[0].count =
                        (info->flags & IEEE80211_TX_CTL_NO_ACK) ?
                        1 : txrc->hw->max_rate_tries;
                if (!sta && txrc->bss) {
                        mcast_rate = txrc->bss_conf->mcast_rate[sband->band];
                        if (mcast_rate > 0) {
                                info->control.rates[0].idx = mcast_rate - 1;
                                return true;
                        }

                        rc_send_low_broadcast(&info->control.rates[0].idx,
                                              txrc->bss_conf->basic_rates,
                                              sband);
                }
                return true;
        }
        return false;
}
EXPORT_SYMBOL(rate_control_send_low);

static void rate_idx_match_mask(struct ieee80211_tx_rate *rate,
                                int n_bitrates, u32 mask)
{
        int j;

        /* See whether the selected rate or anything below it is allowed. */
        for (j = rate->idx; j >= 0; j--) {
                if (mask & (1 << j)) {
                        /* Okay, found a suitable rate. Use it. */
                        rate->idx = j;
                        return;
                }
        }

        /* Try to find a higher rate that would be allowed */
        for (j = rate->idx + 1; j < n_bitrates; j++) {
                if (mask & (1 << j)) {
                        /* Okay, found a suitable rate. Use it. */
                        rate->idx = j;
                        return;
                }
        }

        /*
         * Uh.. No suitable rate exists. This should not really happen with
         * sane TX rate mask configurations. However, should someone manage to
         * configure supported rates and TX rate mask in incompatible way,
         * allow the frame to be transmitted with whatever the rate control
         * selected.
         */
}

void rate_control_get_rate(struct ieee80211_sub_if_data *sdata,
                           struct sta_info *sta,
                           struct ieee80211_tx_rate_control *txrc)
{
        struct rate_control_ref *ref = sdata->local->rate_ctrl;
        void *priv_sta = NULL;
        struct ieee80211_sta *ista = NULL;
        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(txrc->skb);
        int i;
        u32 mask;

        if (sta && test_sta_flag(sta, WLAN_STA_RATE_CONTROL)) {
                ista = &sta->sta;
                priv_sta = sta->rate_ctrl_priv;
        }

        for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
                info->control.rates[i].idx = -1;
                info->control.rates[i].flags = 0;
                info->control.rates[i].count = 0;
        }

        if (sdata->local->hw.flags & IEEE80211_HW_HAS_RATE_CONTROL)
                return;

        ref->ops->get_rate(ref->priv, ista, priv_sta, txrc);

        /*
         * Try to enforce the rateidx mask the user wanted. skip this if the
         * default mask (allow all rates) is used to save some processing for
         * the common case.
         */
        mask = sdata->rc_rateidx_mask[info->band];
        if (mask != (1 << txrc->sband->n_bitrates) - 1) {
                if (sta) {
                        /* Filter out rates that the STA does not support */
                        mask &= sta->sta.supp_rates[info->band];
                }
                /*
                 * Make sure the rate index selected for each TX rate is
                 * included in the configured mask and change the rate indexes
                 * if needed.
                 */
                for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
                        /* Skip invalid rates */
                        if (info->control.rates[i].idx < 0)
                                break;
                        /* Rate masking supports only legacy rates for now */
                        if (info->control.rates[i].flags & IEEE80211_TX_RC_MCS)
                                continue;
                        rate_idx_match_mask(&info->control.rates[i],
                                            txrc->sband->n_bitrates, mask);
                }
        }

        BUG_ON(info->control.rates[0].idx < 0);
}

struct rate_control_ref *rate_control_get(struct rate_control_ref *ref)
{
        kref_get(&ref->kref);
        return ref;
}

void rate_control_put(struct rate_control_ref *ref)
{
        kref_put(&ref->kref, rate_control_release);
}

int ieee80211_init_rate_ctrl_alg(struct ieee80211_local *local,
                                 const char *name)
{
        struct rate_control_ref *ref, *old;

        ASSERT_RTNL();

        if (local->open_count)
                return -EBUSY;

        if (local->hw.flags & IEEE80211_HW_HAS_RATE_CONTROL) {
                if (WARN_ON(!local->ops->set_rts_threshold))
                        return -EINVAL;
                return 0;
        }

        ref = rate_control_alloc(name, local);
        if (!ref) {
                wiphy_warn(local->hw.wiphy,
                           "Failed to select rate control algorithm\n");
                return -ENOENT;
        }

        old = local->rate_ctrl;
        local->rate_ctrl = ref;
        if (old) {
                rate_control_put(old);
                sta_info_flush(local, NULL);
        }

        wiphy_debug(local->hw.wiphy, "Selected rate control algorithm '%s'\n",
                    ref->ops->name);

        return 0;
}

void rate_control_deinitialize(struct ieee80211_local *local)
{
        struct rate_control_ref *ref;

        ref = local->rate_ctrl;

        if (!ref)
                return;

        local->rate_ctrl = NULL;
        rate_control_put(ref);
}