Re: [ath9k-devel] Override Minstrel HT RC to set an MCS bitrate (mask)

["M. A." <jdiq123@googlemail.com>]

Dear all,
Can anyone help in fixing/ overriding MCS rates as described above,


Thank you all!

On Tue, Mar 15, 2011 at 5:02 AM, Mohammed Shafi <shafi.ath9k@gmail.com> wrote:
> On Tue, Mar 8, 2011 at 11:10 PM, M. A. <jdiq123@googlemail.com> wrote:
>> Hi all,
>>
>> My question is how can I modify Minstrel HT rate control to be able to
>> override it (by a boolean or otherwise) to select an MCS or specific
>> rate index from user space (such that once set it driver will only try
>> sending at that rate until unset then driver will resort back to
>> Minstrel RC).
>
> I don't think we can fix the MCS rate index from user space, may be we
> need a hack.
> iw  dev <devname> set bitrates [legacy-<2.4|5> <legacy rate in Mbps>*]
> and this is only for legacy rates.
>
>
>>
>> I have been able to change other kernel parameters at runtime(echo
>> /sys/kernel/debug/ieee80211/...) by passing them through (fops) to
>> DebugFs. however I am unsure of what parameters to pass through in the
>> case of MCS rate fixing and what modifications to the code are
>> required to achieve this.
>
> don't know and I am not sure whether this can be easily done.
>
>>
>>
>> Also I have been told that these sections of code facilitate the
>> masking of rates;
>>
>> =========================================================================
>> include/net/cfg80211.h: cfg80211_bitrate_mask
>> -------------------------------------------------------------------------------------------------------
>> /*
>>  * cfg80211_bitrate_mask - masks for bitrate control
>>  */
>> struct cfg80211_bitrate_mask {
>>        struct {
>>                u32 legacy;
>>                /* TODO: add support for masking MCS rates; e.g.: */
>>                /* u8 mcs[IEEE80211_HT_MCS_MASK_LEN]; */
>>        } control[IEEE80211_NUM_BANDS];
>> };
>> -------------------------------------------------------------------------------------------------------
>> net/mac80211/cfg.c ieee80211_set_bitrate_mask
>> -------------------------------------------------------------------------------------------------------
>> static int ieee80211_set_bitrate_mask(struct wiphy *wiphy,
>>                                      struct net_device *dev,
>>                                      const u8 *addr,
>>                                      const struct cfg80211_bitrate_mask *mask)
>> {
>>        struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
>>        struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
>>        int i;
>>
>>        /*
>>         * This _could_ be supported by providing a hook for
>>         * drivers for this function, but at this point it
>>         * doesn't seem worth bothering.
>>         */
>>        if (local->hw.flags & IEEE80211_HW_HAS_RATE_CONTROL)
>>                return -EOPNOTSUPP;
>>
>>
>>        for (i = 0; i < IEEE80211_NUM_BANDS; i++)
>>                sdata->rc_rateidx_mask[i] = mask->control[i].legacy;
>>
>>        return 0;
>> }
>> -------------------------------------------------------------------------------------------------------
>> net/wireless/nl80211.c: nl80211_set_tx_bitrate_mask
>> -------------------------------------------------------------------------------------------------------
>> static int nl80211_set_tx_bitrate_mask(struct sk_buff *skb,
>>                                       struct genl_info *info)
>> {
>>        struct nlattr *tb[NL80211_TXRATE_MAX + 1];
>>        struct cfg80211_registered_device *rdev = info->user_ptr[0];
>>        struct cfg80211_bitrate_mask mask;
>>        int rem, i;
>>        struct net_device *dev = info->user_ptr[1];
>>        struct nlattr *tx_rates;
>>        struct ieee80211_supported_band *sband;
>>
>>        if (info->attrs[NL80211_ATTR_TX_RATES] == NULL)
>>                return -EINVAL;
>>
>>        if (!rdev->ops->set_bitrate_mask)
>>                return -EOPNOTSUPP;
>>
>>        memset(&mask, 0, sizeof(mask));
>>        /* Default to all rates enabled */
>>        for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
>>                sband = rdev->wiphy.bands[i];
>>                mask.control[i].legacy =
>>                        sband ? (1 << sband->n_bitrates) - 1 : 0;
>>        }
>>
>>        /*
>>         * The nested attribute uses enum nl80211_band as the index. This maps
>>         * directly to the enum ieee80211_band values used in cfg80211.
>>         */
>>        nla_for_each_nested(tx_rates, info->attrs[NL80211_ATTR_TX_RATES], rem)
>>        {
>>                enum ieee80211_band band = nla_type(tx_rates);
>>                if (band < 0 || band >= IEEE80211_NUM_BANDS)
>>                        return -EINVAL;
>>                sband = rdev->wiphy.bands[band];
>>                if (sband == NULL)
>>                        return -EINVAL;
>>                nla_parse(tb, NL80211_TXRATE_MAX, nla_data(tx_rates),
>>                          nla_len(tx_rates), nl80211_txattr_policy);
>>                if (tb[NL80211_TXRATE_LEGACY]) {
>>                        mask.control[band].legacy = rateset_to_mask(
>>                                sband,
>>                                nla_data(tb[NL80211_TXRATE_LEGACY]),
>>                                nla_len(tb[NL80211_TXRATE_LEGACY]));
>>                        if (mask.control[band].legacy == 0)
>>                                return -EINVAL;
>>                }
>>        }
>>
>>        return rdev->ops->set_bitrate_mask(&rdev->wiphy, dev, NULL, &mask);
>> }
>
> As you see everything is for legacy thing and for MCS it's a TODO section.
>
>> ====================================================================================================================
>>
>>
>> Any help is much appreciated!
>>
>> Thank you all very much
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>