On Thu, Jul 14, 2011 at 12:15:49PM +0200, Johannes Berg wrote:
> On Wed, 2011-07-13 at 17:54 +0530, Rajkumar Manoharan wrote:
> > This patch adds support for 40MHz intolerance handling in STA
> > mode. STA should report of any 40MHz intolerance in case if it
> > finds a non-HT AP or a HT AP which prohibits 40MHz transmission
> > (i.e 40MHz intolerant bit is set in HT capabilities IE).
> >
> > STA shall report this condition using 20/40 BSS coexistence
> > action frame.
>
> I think it'd be smarter to add this logic to cfg80211, the scan parsing
> stuff can be generic, and even the action frame can be transmitted
> generically.
>
> Heck, come to think of it, why not do this in wpa_supplicant?
>
I prefer to go with the common layer for both wpa_s and iw. But cfg80211
seems to be better.
> > --- a/net/mac80211/mlme.c
> > +++ b/net/mac80211/mlme.c
> > @@ -206,6 +206,7 @@ static u32 ieee80211_enable_ht(struct ieee80211_sub_if_data *sdata,
> > channel_type = NL80211_CHAN_HT20;
> >
> > if (!(ap_ht_cap_flags & IEEE80211_HT_CAP_40MHZ_INTOLERANT) &&
> > + !(sband->ht_cap.cap & IEEE80211_HT_CAP_40MHZ_INTOLERANT) &&
> > (sband->ht_cap.cap & IEEE80211_HT_CAP_SUP_WIDTH_20_40) &&
> > (hti->ht_param & IEEE80211_HT_PARAM_CHAN_WIDTH_ANY)) {
> > switch(hti->ht_param & IEEE80211_HT_PARAM_CHA_SEC_OFFSET) {
> > diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
> > index 08a45ac..29d50dd 100644
> > --- a/net/mac80211/scan.c
> > +++ b/net/mac80211/scan.c
> > @@ -74,6 +74,31 @@ static bool is_uapsd_supported(struct ieee802_11_elems *elems)
> > return qos_info & IEEE80211_WMM_IE_AP_QOSINFO_UAPSD;
> > }
> >
> > +static void ieee80211_check_40mhz_intolerance(
> > + struct ieee80211_sub_if_data *sdata,
> > + struct ieee80211_channel *channel,
> > + struct ieee802_11_elems *elems)
> > +{
> > + struct ieee80211_local *local = sdata->local;
> > +
> > + if ((local->_oper_channel_type != NL80211_CHAN_HT40MINUS) ||
> > + (local->_oper_channel_type != NL80211_CHAN_HT40PLUS))
> > + return;
> > +
> > + if (local->oper_channel->band != channel->band)
> > + return;
> > +
> > + if (!elems->ht_cap_elem ||
> > + (le16_to_cpu(elems->ht_cap_elem->cap_info) &
> > + IEEE80211_HT_CAP_40MHZ_INTOLERANT)) {
> > + sdata->found_40mhz_intolerant = true;
> > + if (!channel->is_40mhz_intolerant) {
> > + channel->is_40mhz_intolerant = true;
>
> I don't like mac80211 changing cfg80211 data structures much.
>
> > + sdata->intol_channels++;
>
> If that's a counter, why is it a u8?
>
> > @@ -434,6 +462,8 @@ static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
> > else
> > __set_bit(SCAN_SW_SCANNING, &local->scanning);
> >
> > + sdata->found_40mhz_intolerant = false;
> > + sdata->intol_channels = 0;
>
> This makes no sense, the scan could be on only some channels, but you're
> resetting all info.
>
> > ieee80211_recalc_idle(local);
> >
> > if (local->ops->hw_scan) {
> > diff --git a/net/mac80211/util.c b/net/mac80211/util.c
> > index 652e569..9ad5361 100644
> > --- a/net/mac80211/util.c
> > +++ b/net/mac80211/util.c
> > @@ -1334,6 +1334,93 @@ int ieee80211_reconfig(struct ieee80211_local *local)
> > return 0;
> > }
> >
> > +static void ieee80211_send_public_action_frame(
> > + struct ieee80211_sub_if_data *sdata)
>
> Kidding, right?
> "send_public_action_frame", but then it creates a 40 intolerant frame?
>
Hmm.. 20/40 BSS coexistence management messages are exchanged by action frame
with public category. That why I named like that.
Forgive my poor naming convention.
> > +void ieee80211_process_40mhz_intolerance(struct ieee80211_local *local)
> > +{
> > + struct ieee80211_hw *hw = &local->hw;
> > + struct ieee80211_conf *conf = &hw->conf;
> > + struct ieee80211_supported_band *sband =
> > + local->hw.wiphy->bands[local->oper_channel->band];
> > + struct ieee80211_sub_if_data *sdata;
> > + int i;
> > +
> > + mutex_lock(&local->iflist_mtx);
> > + list_for_each_entry(sdata, &local->interfaces, list) {
> > + if (!ieee80211_sdata_running(sdata))
> > + continue;
> > + if (!sdata->found_40mhz_intolerant)
> > + continue;
> > + if (!conf_is_ht40(conf))
> > + continue;
> > + ieee80211_send_public_action_frame(sdata);
>
> What if the AP is HT40, we find the intolerant AP, but we're only 20 MHz
> capable? IOW -- this logic doesn't seem to make sense?
>
> I really don't see why we can't do all of this in wpa_s.
>
I really appriciate your review comments. Will comeup with cfg80211 logic.
--
Rajkumar
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