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

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

Hi all,

I would be grateful if anyone can advise on setting/masking a fixed
MCS HT rate (ath9k) at runtime, as I am only able to mask legacy
rates..

If this is not yet implemented, can anyone please advise on how to
implement this as I am in urgent need of this functionality.

Thank you all in advance!


> 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
>>> _______________________________________________
>>> ath9k-devel mailing list
>>> ath9k-devel@lists.ath9k.org
>>> https://lists.ath9k.org/mailman/listinfo/ath9k-devel
>>>
>>
>