Re: [PATCH] mac80211: adapt slot time in IBSS mode

[Nicolas Cavallari <Nicolas.Cavallari@lri.fr>]

On 04/12/2012 00:00, Julian Calaby wrote:
> Hi Simon,
> 
> On Tue, Dec 4, 2012 at 8:21 AM, Simon Wunderlich
> <simon.wunderlich@s2003.tu-chemnitz.de> wrote:
>> In 5GHz/802.11a, we are allowed to use short slot times. Doing this
>> may increases performance by 20% for legacy connections (54 MBit/s).
>> I can confirm this in my tests (27% more throughput using iperf), and
>> also have a small positive effect (5% more throughput) for HT rates,
>> tested on 1 stream.
>>
>> Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
>> Signed-off-by: Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
>> ---
>>  net/mac80211/ibss.c |   13 +++++++++++++
>>  1 file changed, 13 insertions(+)
>>
>> diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
>> index fa862b2..1a5d29c 100644
>> --- a/net/mac80211/ibss.c
>> +++ b/net/mac80211/ibss.c
>> @@ -201,6 +201,19 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
>>         bss_change |= BSS_CHANGED_BASIC_RATES;
>>         bss_change |= BSS_CHANGED_HT;
>>         bss_change |= BSS_CHANGED_IBSS;
>> +
>> +       /* In 5 GHz/802.11a, we can always use short slot time.
>> +        * (IEEE 802.11-2012 18.3.8.7)
>> +        *
>> +        * In 2.4GHz, we must always use long slots in IBSS for compatibility
>> +        * reasons.
>> +        * (IEEE 802.11-2012 19.4.5)
>> +        *
>> +        * HT follows these specifications (IEEE 802.11-2012 20.3.18)
>> +        */
>> +       sdata->vif.bss_conf.use_short_slot = chan->band == IEEE80211_BAND_5GHZ;
>> +       bss_change |= BSS_CHANGED_ERP_SLOT;
>> +
> 
> I don't know if this is done elsewhere, but this code doesn't match
> the comment - there is no test for IBSS mode.
> 
> Thanks,
> 

Do you happen to know any code path that calls
__ieee80211_sta_join_ibss() without being in IBSS mode ?