rt2x00queue.c

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/*
    Copyright (C) 2010 Willow Garage <http://www.willowgarage.com>
    Copyright (C) 2004 - 2010 Ivo van Doorn <[email protected]>
    Copyright (C) 2004 - 2009 Gertjan van Wingerde <[email protected]>
    <http://rt2x00.serialmonkey.com>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the
    Free Software Foundation, Inc.,
    59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/*
    Module: rt2x00lib
    Abstract: rt2x00 queue specific routines.
 */

#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/dma-mapping.h>

#include "rt2x00.h"
#include "rt2x00lib.h"

struct sk_buff *rt2x00queue_alloc_rxskb(struct queue_entry *entry, gfp_t gfp)
{
    struct rt2x00_dev *rt2x00dev = entry->queue->rt2x00dev;
    struct sk_buff *skb;
    struct skb_frame_desc *skbdesc;
    unsigned int frame_size;
    unsigned int head_size = 0;
    unsigned int tail_size = 0;

    /*
     * The frame size includes descriptor size, because the
     * hardware directly receive the frame into the skbuffer.
     */
    frame_size = entry->queue->data_size + entry->queue->desc_size;

    /*
     * The payload should be aligned to a 4-byte boundary,
     * this means we need at least 3 bytes for moving the frame
     * into the correct offset.
     */
    head_size = 4;

    /*
     * For IV/EIV/ICV assembly we must make sure there is
     * at least 8 bytes bytes available in headroom for IV/EIV
     * and 8 bytes for ICV data as tailroon.
     */
    if (test_bit(CAPABILITY_HW_CRYPTO, &rt2x00dev->cap_flags)) {
        head_size += 8;
        tail_size += 8;
    }

    /*
     * Allocate skbuffer.
     */
    skb = __dev_alloc_skb(frame_size + head_size + tail_size, gfp);
    if (!skb)
        return NULL;

    /*
     * Make sure we not have a frame with the requested bytes
     * available in the head and tail.
     */
    skb_reserve(skb, head_size);
    skb_put(skb, frame_size);

    /*
     * Populate skbdesc.
     */
    skbdesc = get_skb_frame_desc(skb);
    memset(skbdesc, 0, sizeof(*skbdesc));
    skbdesc->entry = entry;

    if (test_bit(REQUIRE_DMA, &rt2x00dev->cap_flags)) {
        skbdesc->skb_dma = dma_map_single(rt2x00dev->dev,
                          skb->data,
                          skb->len,
                          DMA_FROM_DEVICE);
        skbdesc->flags |= SKBDESC_DMA_MAPPED_RX;
    }

    return skb;
}

void rt2x00queue_map_txskb(struct queue_entry *entry)
{
    struct device *dev = entry->queue->rt2x00dev->dev;
    struct skb_frame_desc *skbdesc = get_skb_frame_desc(entry->skb);

    skbdesc->skb_dma =
        dma_map_single(dev, entry->skb->data, entry->skb->len, DMA_TO_DEVICE);
    skbdesc->flags |= SKBDESC_DMA_MAPPED_TX;
}
EXPORT_SYMBOL_GPL(rt2x00queue_map_txskb);

void rt2x00queue_unmap_skb(struct queue_entry *entry)
{
    struct device *dev = entry->queue->rt2x00dev->dev;
    struct skb_frame_desc *skbdesc = get_skb_frame_desc(entry->skb);

    if (skbdesc->flags & SKBDESC_DMA_MAPPED_RX) {
        dma_unmap_single(dev, skbdesc->skb_dma, entry->skb->len,
                 DMA_FROM_DEVICE);
        skbdesc->flags &= ~SKBDESC_DMA_MAPPED_RX;
    } else if (skbdesc->flags & SKBDESC_DMA_MAPPED_TX) {
        dma_unmap_single(dev, skbdesc->skb_dma, entry->skb->len,
                 DMA_TO_DEVICE);
        skbdesc->flags &= ~SKBDESC_DMA_MAPPED_TX;
    }
}
EXPORT_SYMBOL_GPL(rt2x00queue_unmap_skb);

void rt2x00queue_free_skb(struct queue_entry *entry)
{
    if (!entry->skb)
        return;

    rt2x00queue_unmap_skb(entry);
    dev_kfree_skb_any(entry->skb);
    entry->skb = NULL;
}

void rt2x00queue_align_frame(struct sk_buff *skb)
{
    unsigned int frame_length = skb->len;
    unsigned int align = ALIGN_SIZE(skb, 0);

    if (!align)
        return;

    skb_push(skb, align);
    memmove(skb->data, skb->data + align, frame_length);
    skb_trim(skb, frame_length);
}

void rt2x00queue_insert_l2pad(struct sk_buff *skb, unsigned int header_length)
{
    unsigned int payload_length = skb->len - header_length;
    unsigned int header_align = ALIGN_SIZE(skb, 0);
    unsigned int payload_align = ALIGN_SIZE(skb, header_length);
    unsigned int l2pad = payload_length ? L2PAD_SIZE(header_length) : 0;

    /*
     * Adjust the header alignment if the payload needs to be moved more
     * than the header.
     */
    if (payload_align > header_align)
        header_align += 4;

    /* There is nothing to do if no alignment is needed */
    if (!header_align)
        return;

    /* Reserve the amount of space needed in front of the frame */
    skb_push(skb, header_align);

    /*
     * Move the header.
     */
    memmove(skb->data, skb->data + header_align, header_length);

    /* Move the payload, if present and if required */
    if (payload_length && payload_align)
        memmove(skb->data + header_length + l2pad,
            skb->data + header_length + l2pad + payload_align,
            payload_length);

    /* Trim the skb to the correct size */
    skb_trim(skb, header_length + l2pad + payload_length);
}

void rt2x00queue_remove_l2pad(struct sk_buff *skb, unsigned int header_length)
{
    /*
     * L2 padding is only present if the skb contains more than just the
     * IEEE 802.11 header.
     */
    unsigned int l2pad = (skb->len > header_length) ?
                L2PAD_SIZE(header_length) : 0;

    if (!l2pad)
        return;

    memmove(skb->data + l2pad, skb->data, header_length);
    skb_pull(skb, l2pad);
}

static void rt2x00queue_create_tx_descriptor_seq(struct rt2x00_dev *rt2x00dev,
                         struct sk_buff *skb,
                         struct txentry_desc *txdesc)
{
    struct ieee80211_tx_info *tx_info = IEEE80211_SKB_CB(skb);
    struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
    struct rt2x00_intf *intf = vif_to_intf(tx_info->control.vif);
    u16 seqno;

    if (!(tx_info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ))
        return;

    __set_bit(ENTRY_TXD_GENERATE_SEQ, &txdesc->flags);

    if (!test_bit(REQUIRE_SW_SEQNO, &rt2x00dev->cap_flags)) {
        /*
         * rt2800 has a H/W (or F/W) bug, device incorrectly increase
         * seqno on retransmited data (non-QOS) frames. To workaround
         * the problem let's generate seqno in software if QOS is
         * disabled.
         */
        if (test_bit(CONFIG_QOS_DISABLED, &rt2x00dev->flags))
            __clear_bit(ENTRY_TXD_GENERATE_SEQ, &txdesc->flags);
        else
            /* H/W will generate sequence number */
            return;
    }

    /*
     * The hardware is not able to insert a sequence number. Assign a
     * software generated one here.
     *
     * This is wrong because beacons are not getting sequence
     * numbers assigned properly.
     *
     * A secondary problem exists for drivers that cannot toggle
     * sequence counting per-frame, since those will override the
     * sequence counter given by mac80211.
     */
    if (test_bit(ENTRY_TXD_FIRST_FRAGMENT, &txdesc->flags))
        seqno = atomic_add_return(0x10, &intf->seqno);
    else
        seqno = atomic_read(&intf->seqno);

    hdr->seq_ctrl &= cpu_to_le16(IEEE80211_SCTL_FRAG);
    hdr->seq_ctrl |= cpu_to_le16(seqno);
}

static void rt2x00queue_create_tx_descriptor_plcp(struct rt2x00_dev *rt2x00dev,
                          struct sk_buff *skb,
                          struct txentry_desc *txdesc,
                          const struct rt2x00_rate *hwrate)
{
    struct ieee80211_tx_info *tx_info = IEEE80211_SKB_CB(skb);
    struct ieee80211_tx_rate *txrate = &tx_info->control.rates[0];
    unsigned int data_length;
    unsigned int duration;
    unsigned int residual;

    /*
     * Determine with what IFS priority this frame should be send.
     * Set ifs to IFS_SIFS when the this is not the first fragment,
     * or this fragment came after RTS/CTS.
     */
    if (test_bit(ENTRY_TXD_FIRST_FRAGMENT, &txdesc->flags))
        txdesc->u.plcp.ifs = IFS_BACKOFF;
    else
        txdesc->u.plcp.ifs = IFS_SIFS;

    /* Data length + CRC + Crypto overhead (IV/EIV/ICV/MIC) */
    data_length = skb->len + 4;
    data_length += rt2x00crypto_tx_overhead(rt2x00dev, skb);

    /*
     * PLCP setup
     * Length calculation depends on OFDM/CCK rate.
     */
    txdesc->u.plcp.signal = hwrate->plcp;
    txdesc->u.plcp.service = 0x04;

    if (hwrate->flags & DEV_RATE_OFDM) {
        txdesc->u.plcp.length_high = (data_length >> 6) & 0x3f;
        txdesc->u.plcp.length_low = data_length & 0x3f;
    } else {
        /*
         * Convert length to microseconds.
         */
        residual = GET_DURATION_RES(data_length, hwrate->bitrate);
        duration = GET_DURATION(data_length, hwrate->bitrate);

        if (residual != 0) {
            duration++;

            /*
             * Check if we need to set the Length Extension
             */
            if (hwrate->bitrate == 110 && residual <= 30)
                txdesc->u.plcp.service |= 0x80;
        }

        txdesc->u.plcp.length_high = (duration >> 8) & 0xff;
        txdesc->u.plcp.length_low = duration & 0xff;

        /*
         * When preamble is enabled we should set the
         * preamble bit for the signal.
         */
        if (txrate->flags & IEEE80211_TX_RC_USE_SHORT_PREAMBLE)
            txdesc->u.plcp.signal |= 0x08;
    }
}

static void rt2x00queue_create_tx_descriptor_ht(struct rt2x00_dev *rt2x00dev,
                        struct sk_buff *skb,
                        struct txentry_desc *txdesc,
                        struct ieee80211_sta *sta,
                        const struct rt2x00_rate *hwrate)
{
    struct ieee80211_tx_info *tx_info = IEEE80211_SKB_CB(skb);
    struct ieee80211_tx_rate *txrate = &tx_info->control.rates[0];
    struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
    struct rt2x00_sta *sta_priv = NULL;

    if (sta) {
        txdesc->u.ht.mpdu_density =
            sta->ht_cap.ampdu_density;

        sta_priv = sta_to_rt2x00_sta(sta);
        txdesc->u.ht.wcid = sta_priv->wcid;
    }

    /*
     * If IEEE80211_TX_RC_MCS is set txrate->idx just contains the
     * mcs rate to be used
     */
    if (txrate->flags & IEEE80211_TX_RC_MCS) {
        txdesc->u.ht.mcs = txrate->idx;

        /*
         * MIMO PS should be set to 1 for STA's using dynamic SM PS
         * when using more then one tx stream (>MCS7).
         */
        if (sta && txdesc->u.ht.mcs > 7 &&
            ((sta->ht_cap.cap &
              IEEE80211_HT_CAP_SM_PS) >>
             IEEE80211_HT_CAP_SM_PS_SHIFT) ==
            WLAN_HT_CAP_SM_PS_DYNAMIC)
            __set_bit(ENTRY_TXD_HT_MIMO_PS, &txdesc->flags);
    } else {
        txdesc->u.ht.mcs = rt2x00_get_rate_mcs(hwrate->mcs);
        if (txrate->flags & IEEE80211_TX_RC_USE_SHORT_PREAMBLE)
            txdesc->u.ht.mcs |= 0x08;
    }

    if (test_bit(CONFIG_HT_DISABLED, &rt2x00dev->flags)) {
        if (!(tx_info->flags & IEEE80211_TX_CTL_FIRST_FRAGMENT))
            txdesc->u.ht.txop = TXOP_SIFS;
        else
            txdesc->u.ht.txop = TXOP_BACKOFF;

        /* Left zero on all other settings. */
        return;
    }

    txdesc->u.ht.ba_size = 7;   /* FIXME: What value is needed? */

    /*
     * Only one STBC stream is supported for now.
     */
    if (tx_info->flags & IEEE80211_TX_CTL_STBC)
        txdesc->u.ht.stbc = 1;

    /*
     * This frame is eligible for an AMPDU, however, don't aggregate
     * frames that are intended to probe a specific tx rate.
     */
    if (tx_info->flags & IEEE80211_TX_CTL_AMPDU &&
        !(tx_info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE))
        __set_bit(ENTRY_TXD_HT_AMPDU, &txdesc->flags);

    /*
     * Set 40Mhz mode if necessary (for legacy rates this will
     * duplicate the frame to both channels).
     */
    if (txrate->flags & IEEE80211_TX_RC_40_MHZ_WIDTH ||
        txrate->flags & IEEE80211_TX_RC_DUP_DATA)
        __set_bit(ENTRY_TXD_HT_BW_40, &txdesc->flags);
    if (txrate->flags & IEEE80211_TX_RC_SHORT_GI)
        __set_bit(ENTRY_TXD_HT_SHORT_GI, &txdesc->flags);

    /*
     * Determine IFS values
     * - Use TXOP_BACKOFF for management frames except beacons
     * - Use TXOP_SIFS for fragment bursts
     * - Use TXOP_HTTXOP for everything else
     *
     * Note: rt2800 devices won't use CTS protection (if used)
     * for frames not transmitted with TXOP_HTTXOP
     */
    if (ieee80211_is_mgmt(hdr->frame_control) &&
        !ieee80211_is_beacon(hdr->frame_control))
        txdesc->u.ht.txop = TXOP_BACKOFF;
    else if (!(tx_info->flags & IEEE80211_TX_CTL_FIRST_FRAGMENT))
        txdesc->u.ht.txop = TXOP_SIFS;
    else
        txdesc->u.ht.txop = TXOP_HTTXOP;
}

static void rt2x00queue_create_tx_descriptor(struct rt2x00_dev *rt2x00dev,
                         struct sk_buff *skb,
                         struct txentry_desc *txdesc,
                         struct ieee80211_sta *sta)
{
    struct ieee80211_tx_info *tx_info = IEEE80211_SKB_CB(skb);
    struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
    struct ieee80211_tx_rate *txrate = &tx_info->control.rates[0];
    struct ieee80211_rate *rate;
    const struct rt2x00_rate *hwrate = NULL;

    memset(txdesc, 0, sizeof(*txdesc));

    /*
     * Header and frame information.
     */
    txdesc->length = skb->len;
    txdesc->header_length = ieee80211_get_hdrlen_from_skb(skb);

    /*
     * Check whether this frame is to be acked.
     */
    if (!(tx_info->flags & IEEE80211_TX_CTL_NO_ACK))
        __set_bit(ENTRY_TXD_ACK, &txdesc->flags);

    /*
     * Check if this is a RTS/CTS frame
     */
    if (ieee80211_is_rts(hdr->frame_control) ||
        ieee80211_is_cts(hdr->frame_control)) {
        __set_bit(ENTRY_TXD_BURST, &txdesc->flags);
        if (ieee80211_is_rts(hdr->frame_control))
            __set_bit(ENTRY_TXD_RTS_FRAME, &txdesc->flags);
        else
            __set_bit(ENTRY_TXD_CTS_FRAME, &txdesc->flags);
        if (tx_info->control.rts_cts_rate_idx >= 0)
            rate =
                ieee80211_get_rts_cts_rate(rt2x00dev->hw, tx_info);
    }

    /*
     * Determine retry information.
     */
    txdesc->retry_limit = tx_info->control.rates[0].count - 1;
    if (txdesc->retry_limit >= rt2x00dev->long_retry)
        __set_bit(ENTRY_TXD_RETRY_MODE, &txdesc->flags);

    /*
     * Check if more fragments are pending
     */
    if (ieee80211_has_morefrags(hdr->frame_control)) {
        __set_bit(ENTRY_TXD_BURST, &txdesc->flags);
        __set_bit(ENTRY_TXD_MORE_FRAG, &txdesc->flags);
    }

    /*
     * Check if more frames (!= fragments) are pending
     */
    if (tx_info->flags & IEEE80211_TX_CTL_MORE_FRAMES)
        __set_bit(ENTRY_TXD_BURST, &txdesc->flags);

    /*
     * Beacons and probe responses require the tsf timestamp
     * to be inserted into the frame.
     */
    if (ieee80211_is_beacon(hdr->frame_control) ||
        ieee80211_is_probe_resp(hdr->frame_control))
        __set_bit(ENTRY_TXD_REQ_TIMESTAMP, &txdesc->flags);

    if ((tx_info->flags & IEEE80211_TX_CTL_FIRST_FRAGMENT) &&
        !test_bit(ENTRY_TXD_RTS_FRAME, &txdesc->flags))
        __set_bit(ENTRY_TXD_FIRST_FRAGMENT, &txdesc->flags);

    /*
     * Determine rate modulation.
     */
    if (txrate->flags & IEEE80211_TX_RC_GREEN_FIELD)
        txdesc->rate_mode = RATE_MODE_HT_GREENFIELD;
    else if (txrate->flags & IEEE80211_TX_RC_MCS)
        txdesc->rate_mode = RATE_MODE_HT_MIX;
    else {
        rate = ieee80211_get_tx_rate(rt2x00dev->hw, tx_info);
        hwrate = rt2x00_get_rate(rate->hw_value);
        if (hwrate->flags & DEV_RATE_OFDM)
            txdesc->rate_mode = RATE_MODE_OFDM;
        else
            txdesc->rate_mode = RATE_MODE_CCK;
    }

    /*
     * Apply TX descriptor handling by components
     */
    rt2x00crypto_create_tx_descriptor(rt2x00dev, skb, txdesc);
    rt2x00queue_create_tx_descriptor_seq(rt2x00dev, skb, txdesc);

    if (test_bit(REQUIRE_HT_TX_DESC, &rt2x00dev->cap_flags))
        rt2x00queue_create_tx_descriptor_ht(rt2x00dev, skb, txdesc,
                           sta, hwrate);
    else
        rt2x00queue_create_tx_descriptor_plcp(rt2x00dev, skb, txdesc,
                              hwrate);
}

static int rt2x00queue_write_tx_data(struct queue_entry *entry,
                     struct txentry_desc *txdesc)
{
    struct rt2x00_dev *rt2x00dev = entry->queue->rt2x00dev;

    /*
     * This should not happen, we already checked the entry
     * was ours. When the hardware disagrees there has been
     * a queue corruption!
     */
    if (unlikely(rt2x00dev->ops->lib->get_entry_state &&
             rt2x00dev->ops->lib->get_entry_state(entry))) {
        ERROR(rt2x00dev,
              "Corrupt queue %d, accessing entry which is not ours.\n"
              "Please file bug report to %s.\n",
              entry->queue->qid, DRV_PROJECT);
        return -EINVAL;
    }

    /*
     * Add the requested extra tx headroom in front of the skb.
     */
    skb_push(entry->skb, rt2x00dev->ops->extra_tx_headroom);
    memset(entry->skb->data, 0, rt2x00dev->ops->extra_tx_headroom);

    /*
     * Call the driver's write_tx_data function, if it exists.
     */
    if (rt2x00dev->ops->lib->write_tx_data)
        rt2x00dev->ops->lib->write_tx_data(entry, txdesc);

    /*
     * Map the skb to DMA.
     */
    if (test_bit(REQUIRE_DMA, &rt2x00dev->cap_flags))
        rt2x00queue_map_txskb(entry);

    return 0;
}

static void rt2x00queue_write_tx_descriptor(struct queue_entry *entry,
                        struct txentry_desc *txdesc)
{
    struct data_queue *queue = entry->queue;

    queue->rt2x00dev->ops->lib->write_tx_desc(entry, txdesc);

    /*
     * All processing on the frame has been completed, this means
     * it is now ready to be dumped to userspace through debugfs.
     */
    rt2x00debug_dump_frame(queue->rt2x00dev, DUMP_FRAME_TX, entry->skb);
}

static void rt2x00queue_kick_tx_queue(struct data_queue *queue,
                      struct txentry_desc *txdesc)
{
    /*
     * Check if we need to kick the queue, there are however a few rules
     *  1) Don't kick unless this is the last in frame in a burst.
     *     When the burst flag is set, this frame is always followed
     *     by another frame which in some way are related to eachother.
     *     This is true for fragments, RTS or CTS-to-self frames.
     *  2) Rule 1 can be broken when the available entries
     *     in the queue are less then a certain threshold.
     */
    if (rt2x00queue_threshold(queue) ||
        !test_bit(ENTRY_TXD_BURST, &txdesc->flags))
        queue->rt2x00dev->ops->lib->kick_queue(queue);
}

int rt2x00queue_write_tx_frame(struct data_queue *queue, struct sk_buff *skb,
                   bool local)
{
    struct ieee80211_tx_info *tx_info;
    struct queue_entry *entry;
    struct txentry_desc txdesc;
    struct skb_frame_desc *skbdesc;
    u8 rate_idx, rate_flags;
    int ret = 0;

    /*
     * Copy all TX descriptor information into txdesc,
     * after that we are free to use the skb->cb array
     * for our information.
     */
    rt2x00queue_create_tx_descriptor(queue->rt2x00dev, skb, &txdesc, NULL);

    /*
     * All information is retrieved from the skb->cb array,
     * now we should claim ownership of the driver part of that
     * array, preserving the bitrate index and flags.
     */
    tx_info = IEEE80211_SKB_CB(skb);
    rate_idx = tx_info->control.rates[0].idx;
    rate_flags = tx_info->control.rates[0].flags;
    skbdesc = get_skb_frame_desc(skb);
    memset(skbdesc, 0, sizeof(*skbdesc));
    skbdesc->tx_rate_idx = rate_idx;
    skbdesc->tx_rate_flags = rate_flags;

    if (local)
        skbdesc->flags |= SKBDESC_NOT_MAC80211;

    /*
     * When hardware encryption is supported, and this frame
     * is to be encrypted, we should strip the IV/EIV data from
     * the frame so we can provide it to the driver separately.
     */
    if (test_bit(ENTRY_TXD_ENCRYPT, &txdesc.flags) &&
        !test_bit(ENTRY_TXD_ENCRYPT_IV, &txdesc.flags)) {
        if (test_bit(REQUIRE_COPY_IV, &queue->rt2x00dev->cap_flags))
            rt2x00crypto_tx_copy_iv(skb, &txdesc);
        else
            rt2x00crypto_tx_remove_iv(skb, &txdesc);
    }

    /*
     * When DMA allocation is required we should guarantee to the
     * driver that the DMA is aligned to a 4-byte boundary.
     * However some drivers require L2 padding to pad the payload
     * rather then the header. This could be a requirement for
     * PCI and USB devices, while header alignment only is valid
     * for PCI devices.
     */
    if (test_bit(REQUIRE_L2PAD, &queue->rt2x00dev->cap_flags))
        rt2x00queue_insert_l2pad(skb, txdesc.header_length);
    else if (test_bit(REQUIRE_DMA, &queue->rt2x00dev->cap_flags))
        rt2x00queue_align_frame(skb);

    /*
     * That function must be called with bh disabled.
     */
    spin_lock(&queue->tx_lock);

    if (unlikely(rt2x00queue_full(queue))) {
        ERROR(queue->rt2x00dev,
              "Dropping frame due to full tx queue %d.\n", queue->qid);
        ret = -ENOBUFS;
        goto out;
    }

    entry = rt2x00queue_get_entry(queue, Q_INDEX);

    if (unlikely(test_and_set_bit(ENTRY_OWNER_DEVICE_DATA,
                      &entry->flags))) {
        ERROR(queue->rt2x00dev,
              "Arrived at non-free entry in the non-full queue %d.\n"
              "Please file bug report to %s.\n",
              queue->qid, DRV_PROJECT);
        ret = -EINVAL;
        goto out;
    }

    skbdesc->entry = entry;
    entry->skb = skb;

    /*
     * It could be possible that the queue was corrupted and this
     * call failed. Since we always return NETDEV_TX_OK to mac80211,
     * this frame will simply be dropped.
     */
    if (unlikely(rt2x00queue_write_tx_data(entry, &txdesc))) {
        clear_bit(ENTRY_OWNER_DEVICE_DATA, &entry->flags);
        entry->skb = NULL;
        ret = -EIO;
        goto out;
    }

    set_bit(ENTRY_DATA_PENDING, &entry->flags);

    rt2x00queue_index_inc(entry, Q_INDEX);
    rt2x00queue_write_tx_descriptor(entry, &txdesc);
    rt2x00queue_kick_tx_queue(queue, &txdesc);

out:
    spin_unlock(&queue->tx_lock);
    return ret;
}

int rt2x00queue_clear_beacon(struct rt2x00_dev *rt2x00dev,
                 struct ieee80211_vif *vif)
{
    struct rt2x00_intf *intf = vif_to_intf(vif);

    if (unlikely(!intf->beacon))
        return -ENOBUFS;

    mutex_lock(&intf->beacon_skb_mutex);

    /*
     * Clean up the beacon skb.
     */
    rt2x00queue_free_skb(intf->beacon);

    /*
     * Clear beacon (single bssid devices don't need to clear the beacon
     * since the beacon queue will get stopped anyway).
     */
    if (rt2x00dev->ops->lib->clear_beacon)
        rt2x00dev->ops->lib->clear_beacon(intf->beacon);

    mutex_unlock(&intf->beacon_skb_mutex);

    return 0;
}

int rt2x00queue_update_beacon_locked(struct rt2x00_dev *rt2x00dev,
                     struct ieee80211_vif *vif)
{
    struct rt2x00_intf *intf = vif_to_intf(vif);
    struct skb_frame_desc *skbdesc;
    struct txentry_desc txdesc;

    if (unlikely(!intf->beacon))
        return -ENOBUFS;

    /*
     * Clean up the beacon skb.
     */
    rt2x00queue_free_skb(intf->beacon);

    intf->beacon->skb = ieee80211_beacon_get(rt2x00dev->hw, vif);
    if (!intf->beacon->skb)
        return -ENOMEM;

    /*
     * Copy all TX descriptor information into txdesc,
     * after that we are free to use the skb->cb array
     * for our information.
     */
    rt2x00queue_create_tx_descriptor(rt2x00dev, intf->beacon->skb, &txdesc, NULL);

    /*
     * Fill in skb descriptor
     */
    skbdesc = get_skb_frame_desc(intf->beacon->skb);
    memset(skbdesc, 0, sizeof(*skbdesc));
    skbdesc->entry = intf->beacon;

    /*
     * Send beacon to hardware.
     */
    rt2x00dev->ops->lib->write_beacon(intf->beacon, &txdesc);

    return 0;

}

int rt2x00queue_update_beacon(struct rt2x00_dev *rt2x00dev,
                  struct ieee80211_vif *vif)
{
    struct rt2x00_intf *intf = vif_to_intf(vif);
    int ret;

    mutex_lock(&intf->beacon_skb_mutex);
    ret = rt2x00queue_update_beacon_locked(rt2x00dev, vif);
    mutex_unlock(&intf->beacon_skb_mutex);

    return ret;
}

bool rt2x00queue_for_each_entry(struct data_queue *queue,
                enum queue_index start,
                enum queue_index end,
                bool (*fn)(struct queue_entry *entry))
{
    unsigned long irqflags;
    unsigned int index_start;
    unsigned int index_end;
    unsigned int i;

    if (unlikely(start >= Q_INDEX_MAX || end >= Q_INDEX_MAX)) {
        ERROR(queue->rt2x00dev,
              "Entry requested from invalid index range (%d - %d)\n",
              start, end);
        return true;
    }

    /*
     * Only protect the range we are going to loop over,
     * if during our loop a extra entry is set to pending
     * it should not be kicked during this run, since it
     * is part of another TX operation.
     */
    spin_lock_irqsave(&queue->index_lock, irqflags);
    index_start = queue->index[start];
    index_end = queue->index[end];
    spin_unlock_irqrestore(&queue->index_lock, irqflags);

    /*
     * Start from the TX done pointer, this guarantees that we will
     * send out all frames in the correct order.
     */
    if (index_start < index_end) {
        for (i = index_start; i < index_end; i++) {
            if (fn(&queue->entries[i]))
                return true;
        }
    } else {
        for (i = index_start; i < queue->limit; i++) {
            if (fn(&queue->entries[i]))
                return true;
        }

        for (i = 0; i < index_end; i++) {
            if (fn(&queue->entries[i]))
                return true;
        }
    }

    return false;
}
EXPORT_SYMBOL_GPL(rt2x00queue_for_each_entry);

struct queue_entry *rt2x00queue_get_entry(struct data_queue *queue,
                      enum queue_index index)
{
    struct queue_entry *entry;
    unsigned long irqflags;

    if (unlikely(index >= Q_INDEX_MAX)) {
        ERROR(queue->rt2x00dev,
              "Entry requested from invalid index type (%d)\n", index);
        return NULL;
    }

    spin_lock_irqsave(&queue->index_lock, irqflags);

    entry = &queue->entries[queue->index[index]];

    spin_unlock_irqrestore(&queue->index_lock, irqflags);

    return entry;
}
EXPORT_SYMBOL_GPL(rt2x00queue_get_entry);

void rt2x00queue_index_inc(struct queue_entry *entry, enum queue_index index)
{
    struct data_queue *queue = entry->queue;
    unsigned long irqflags;

    if (unlikely(index >= Q_INDEX_MAX)) {
        ERROR(queue->rt2x00dev,
              "Index change on invalid index type (%d)\n", index);
        return;
    }

    spin_lock_irqsave(&queue->index_lock, irqflags);

    queue->index[index]++;
    if (queue->index[index] >= queue->limit)
        queue->index[index] = 0;

    entry->last_action = jiffies;

    if (index == Q_INDEX) {
        queue->length++;
    } else if (index == Q_INDEX_DONE) {
        queue->length--;
        queue->count++;
    }

    spin_unlock_irqrestore(&queue->index_lock, irqflags);
}

void rt2x00queue_pause_queue(struct data_queue *queue)
{
    if (!test_bit(DEVICE_STATE_PRESENT, &queue->rt2x00dev->flags) ||
        !test_bit(QUEUE_STARTED, &queue->flags) ||
        test_and_set_bit(QUEUE_PAUSED, &queue->flags))
        return;

    switch (queue->qid) {
    case QID_AC_VO:
    case QID_AC_VI:
    case QID_AC_BE:
    case QID_AC_BK:
        /*
         * For TX queues, we have to disable the queue
         * inside mac80211.
         */
        ieee80211_stop_queue(queue->rt2x00dev->hw, queue->qid);
        break;
    default:
        break;
    }
}
EXPORT_SYMBOL_GPL(rt2x00queue_pause_queue);

void rt2x00queue_unpause_queue(struct data_queue *queue)
{
    if (!test_bit(DEVICE_STATE_PRESENT, &queue->rt2x00dev->flags) ||
        !test_bit(QUEUE_STARTED, &queue->flags) ||
        !test_and_clear_bit(QUEUE_PAUSED, &queue->flags))
        return;

    switch (queue->qid) {
    case QID_AC_VO:
    case QID_AC_VI:
    case QID_AC_BE:
    case QID_AC_BK:
        /*
         * For TX queues, we have to enable the queue
         * inside mac80211.
         */
        ieee80211_wake_queue(queue->rt2x00dev->hw, queue->qid);
        break;
    case QID_RX:
        /*
         * For RX we need to kick the queue now in order to
         * receive frames.
         */
        queue->rt2x00dev->ops->lib->kick_queue(queue);
    default:
        break;
    }
}
EXPORT_SYMBOL_GPL(rt2x00queue_unpause_queue);

void rt2x00queue_start_queue(struct data_queue *queue)
{
    mutex_lock(&queue->status_lock);

    if (!test_bit(DEVICE_STATE_PRESENT, &queue->rt2x00dev->flags) ||
        test_and_set_bit(QUEUE_STARTED, &queue->flags)) {
        mutex_unlock(&queue->status_lock);
        return;
    }

    set_bit(QUEUE_PAUSED, &queue->flags);

    queue->rt2x00dev->ops->lib->start_queue(queue);

    rt2x00queue_unpause_queue(queue);

    mutex_unlock(&queue->status_lock);
}
EXPORT_SYMBOL_GPL(rt2x00queue_start_queue);

void rt2x00queue_stop_queue(struct data_queue *queue)
{
    mutex_lock(&queue->status_lock);

    if (!test_and_clear_bit(QUEUE_STARTED, &queue->flags)) {
        mutex_unlock(&queue->status_lock);
        return;
    }

    rt2x00queue_pause_queue(queue);

    queue->rt2x00dev->ops->lib->stop_queue(queue);

    mutex_unlock(&queue->status_lock);
}
EXPORT_SYMBOL_GPL(rt2x00queue_stop_queue);

void rt2x00queue_flush_queue(struct data_queue *queue, bool drop)
{
    bool started;
    bool tx_queue =
        (queue->qid == QID_AC_VO) ||
        (queue->qid == QID_AC_VI) ||
        (queue->qid == QID_AC_BE) ||
        (queue->qid == QID_AC_BK);

    mutex_lock(&queue->status_lock);

    /*
     * If the queue has been started, we must stop it temporarily
     * to prevent any new frames to be queued on the device. If
     * we are not dropping the pending frames, the queue must
     * only be stopped in the software and not the hardware,
     * otherwise the queue will never become empty on its own.
     */
    started = test_bit(QUEUE_STARTED, &queue->flags);
    if (started) {
        /*
         * Pause the queue
         */
        rt2x00queue_pause_queue(queue);

        /*
         * If we are not supposed to drop any pending
         * frames, this means we must force a start (=kick)
         * to the queue to make sure the hardware will
         * start transmitting.
         */
        if (!drop && tx_queue)
            queue->rt2x00dev->ops->lib->kick_queue(queue);
    }

    /*
     * Check if driver supports flushing, if that is the case we can
     * defer the flushing to the driver. Otherwise we must use the
     * alternative which just waits for the queue to become empty.
     */
    if (likely(queue->rt2x00dev->ops->lib->flush_queue))
        queue->rt2x00dev->ops->lib->flush_queue(queue, drop);

    /*
     * The queue flush has failed...
     */
    if (unlikely(!rt2x00queue_empty(queue)))
        WARNING(queue->rt2x00dev, "Queue %d failed to flush\n", queue->qid);

    /*
     * Restore the queue to the previous status
     */
    if (started)
        rt2x00queue_unpause_queue(queue);

    mutex_unlock(&queue->status_lock);
}
EXPORT_SYMBOL_GPL(rt2x00queue_flush_queue);

void rt2x00queue_start_queues(struct rt2x00_dev *rt2x00dev)
{
    struct data_queue *queue;

    /*
     * rt2x00queue_start_queue will call ieee80211_wake_queue
     * for each queue after is has been properly initialized.
     */
    tx_queue_for_each(rt2x00dev, queue)
        rt2x00queue_start_queue(queue);

    rt2x00queue_start_queue(rt2x00dev->rx);
}
EXPORT_SYMBOL_GPL(rt2x00queue_start_queues);

void rt2x00queue_stop_queues(struct rt2x00_dev *rt2x00dev)
{
    struct data_queue *queue;

    /*
     * rt2x00queue_stop_queue will call ieee80211_stop_queue
     * as well, but we are completely shutting doing everything
     * now, so it is much safer to stop all TX queues at once,
     * and use rt2x00queue_stop_queue for cleaning up.
     */
    ieee80211_stop_queues(rt2x00dev->hw);

    tx_queue_for_each(rt2x00dev, queue)
        rt2x00queue_stop_queue(queue);

    rt2x00queue_stop_queue(rt2x00dev->rx);
}
EXPORT_SYMBOL_GPL(rt2x00queue_stop_queues);

void rt2x00queue_flush_queues(struct rt2x00_dev *rt2x00dev, bool drop)
{
    struct data_queue *queue;

    tx_queue_for_each(rt2x00dev, queue)
        rt2x00queue_flush_queue(queue, drop);

    rt2x00queue_flush_queue(rt2x00dev->rx, drop);
}
EXPORT_SYMBOL_GPL(rt2x00queue_flush_queues);

static void rt2x00queue_reset(struct data_queue *queue)
{
    unsigned long irqflags;
    unsigned int i;

    spin_lock_irqsave(&queue->index_lock, irqflags);

    queue->count = 0;
    queue->length = 0;

    for (i = 0; i < Q_INDEX_MAX; i++)
        queue->index[i] = 0;

    spin_unlock_irqrestore(&queue->index_lock, irqflags);
}

void rt2x00queue_init_queues(struct rt2x00_dev *rt2x00dev)
{
    struct data_queue *queue;
    unsigned int i;

    queue_for_each(rt2x00dev, queue) {
        rt2x00queue_reset(queue);

        for (i = 0; i < queue->limit; i++)
            rt2x00dev->ops->lib->clear_entry(&queue->entries[i]);
    }
}

static int rt2x00queue_alloc_entries(struct data_queue *queue,
                     const struct data_queue_desc *qdesc)
{
    struct queue_entry *entries;
    unsigned int entry_size;
    unsigned int i;

    rt2x00queue_reset(queue);

    queue->limit = qdesc->entry_num;
    queue->threshold = DIV_ROUND_UP(qdesc->entry_num, 10);
    queue->data_size = qdesc->data_size;
    queue->desc_size = qdesc->desc_size;

    /*
     * Allocate all queue entries.
     */
    entry_size = sizeof(*entries) + qdesc->priv_size;
    entries = kcalloc(queue->limit, entry_size, GFP_KERNEL);
    if (!entries)
        return -ENOMEM;

#define QUEUE_ENTRY_PRIV_OFFSET(__base, __index, __limit, __esize, __psize) \
    (((char *)(__base)) + ((__limit) * (__esize)) + \
        ((__index) * (__psize)))

    for (i = 0; i < queue->limit; i++) {
        entries[i].flags = 0;
        entries[i].queue = queue;
        entries[i].skb = NULL;
        entries[i].entry_idx = i;
        entries[i].priv_data =
            QUEUE_ENTRY_PRIV_OFFSET(entries, i, queue->limit,
                        sizeof(*entries), qdesc->priv_size);
    }

#undef QUEUE_ENTRY_PRIV_OFFSET

    queue->entries = entries;

    return 0;
}

static void rt2x00queue_free_skbs(struct data_queue *queue)
{
    unsigned int i;

    if (!queue->entries)
        return;

    for (i = 0; i < queue->limit; i++) {
        rt2x00queue_free_skb(&queue->entries[i]);
    }
}

static int rt2x00queue_alloc_rxskbs(struct data_queue *queue)
{
    unsigned int i;
    struct sk_buff *skb;

    for (i = 0; i < queue->limit; i++) {
        skb = rt2x00queue_alloc_rxskb(&queue->entries[i], GFP_KERNEL);
        if (!skb)
            return -ENOMEM;
        queue->entries[i].skb = skb;
    }

    return 0;
}

int rt2x00queue_initialize(struct rt2x00_dev *rt2x00dev)
{
    struct data_queue *queue;
    int status;

    status = rt2x00queue_alloc_entries(rt2x00dev->rx, rt2x00dev->ops->rx);
    if (status)
        goto exit;

    tx_queue_for_each(rt2x00dev, queue) {
        status = rt2x00queue_alloc_entries(queue, rt2x00dev->ops->tx);
        if (status)
            goto exit;
    }

    status = rt2x00queue_alloc_entries(rt2x00dev->bcn, rt2x00dev->ops->bcn);
    if (status)
        goto exit;

    if (test_bit(REQUIRE_ATIM_QUEUE, &rt2x00dev->cap_flags)) {
        status = rt2x00queue_alloc_entries(rt2x00dev->atim,
                           rt2x00dev->ops->atim);
        if (status)
            goto exit;
    }

    status = rt2x00queue_alloc_rxskbs(rt2x00dev->rx);
    if (status)
        goto exit;

    return 0;

exit:
    ERROR(rt2x00dev, "Queue entries allocation failed.\n");

    rt2x00queue_uninitialize(rt2x00dev);

    return status;
}

void rt2x00queue_uninitialize(struct rt2x00_dev *rt2x00dev)
{
    struct data_queue *queue;

    rt2x00queue_free_skbs(rt2x00dev->rx);

    queue_for_each(rt2x00dev, queue) {
        kfree(queue->entries);
        queue->entries = NULL;
    }
}

static void rt2x00queue_init(struct rt2x00_dev *rt2x00dev,
                 struct data_queue *queue, enum data_queue_qid qid)
{
    mutex_init(&queue->status_lock);
    spin_lock_init(&queue->tx_lock);
    spin_lock_init(&queue->index_lock);

    queue->rt2x00dev = rt2x00dev;
    queue->qid = qid;
    queue->txop = 0;
    queue->aifs = 2;
    queue->cw_min = 5;
    queue->cw_max = 10;
}

int rt2x00queue_allocate(struct rt2x00_dev *rt2x00dev)
{
    struct data_queue *queue;
    enum data_queue_qid qid;
    unsigned int req_atim =
        !!test_bit(REQUIRE_ATIM_QUEUE, &rt2x00dev->cap_flags);

    /*
     * We need the following queues:
     * RX: 1
     * TX: ops->tx_queues
     * Beacon: 1
     * Atim: 1 (if required)
     */
    rt2x00dev->data_queues = 2 + rt2x00dev->ops->tx_queues + req_atim;

    queue = kcalloc(rt2x00dev->data_queues, sizeof(*queue), GFP_KERNEL);
    if (!queue) {
        ERROR(rt2x00dev, "Queue allocation failed.\n");
        return -ENOMEM;
    }

    /*
     * Initialize pointers
     */
    rt2x00dev->rx = queue;
    rt2x00dev->tx = &queue[1];
    rt2x00dev->bcn = &queue[1 + rt2x00dev->ops->tx_queues];
    rt2x00dev->atim = req_atim ? &queue[2 + rt2x00dev->ops->tx_queues] : NULL;

    /*
     * Initialize queue parameters.
     * RX: qid = QID_RX
     * TX: qid = QID_AC_VO + index
     * TX: cw_min: 2^5 = 32.
     * TX: cw_max: 2^10 = 1024.
     * BCN: qid = QID_BEACON
     * ATIM: qid = QID_ATIM
     */
    rt2x00queue_init(rt2x00dev, rt2x00dev->rx, QID_RX);

    qid = QID_AC_VO;
    tx_queue_for_each(rt2x00dev, queue)
        rt2x00queue_init(rt2x00dev, queue, qid++);

    rt2x00queue_init(rt2x00dev, rt2x00dev->bcn, QID_BEACON);
    if (req_atim)
        rt2x00queue_init(rt2x00dev, rt2x00dev->atim, QID_ATIM);

    return 0;
}

void rt2x00queue_free(struct rt2x00_dev *rt2x00dev)
{
    kfree(rt2x00dev->rx);
    rt2x00dev->rx = NULL;
    rt2x00dev->tx = NULL;
    rt2x00dev->bcn = NULL;
}