[PATCH] wpa_supplicant: Enable HT40 support for AP mode

[Arik Nemtsov]

On Mon, Jul 9, 2012 at 9:42 PM, Jouni Malinen <j at w1.fi> wrote:
> On Mon, Jul 09, 2012 at 08:30:23PM +0300, Arik Nemtsov wrote:
>> On Mon, Jul 9, 2012 at 8:15 PM, Rajkumar Manoharan
>> <rmanohar at qca.qualcomm.com> wrote:
>> > On Mon, Jul 09, 2012 at 10:41:39PM +0530, Rajkumar Manoharan wrote:
>> >> On Mon, Jul 09, 2012 at 07:33:23PM +0300, Arik Nemtsov wrote:
>> >> > On Mon, Jul 9, 2012 at 7:15 PM, Rajkumar Manoharan
>> >> > <rmanohar at qca.qualcomm.com> wrote:
>> >> > > On Mon, Jul 09, 2012 at 06:50:04PM +0300, Arik Nemtsov wrote:
>> >> > >> Can you tell me why HT_CAP_INFO_SUPP_CHANNEL_WIDTH_SET is not enabled
>> >> > >> in the capabilities white-list?
>> >> > >> (just below this code).
>
> It does not sound like a good idea to enable 40 MHz channels
> unconditionally especially for 2.4 GHz band. I guess it could be
> considered for 5 GHz, but even there, I would rather have this
> configurable or even better, set with p2p_connect/p2p_group_add commands
> on the GO.

The p2p_connect/p2p_group_add approach sounds reasonable.

>
>> A question for Jouni - are you against enabling 2.4Ghz 40mhz support
>> for STA (CLI) only as well?
>
> No. I thought we already enabled that (and probably do with some
> drivers). Does this get somehow disabled with mac80211-based drivers?
> I'm only concerned about unconditionally (or even by default) enabling
> 40 MHz channels on the AP/GO. The P2P client should follow whatever
> parameters the GO has set for the network.

I haven't tested it, only assumed the table was used by both sides for
channel type. What you're saying makes sense. I'll be testing this in
the following days (and will report).

>
>> This will require a different trick because we don't know what we are
>> yet. How about enabling the 2Ghz operating classes and disabling the
>> HT40 support just before starting the GO (if it's in 2Ghz)?
>
> The GO can switch to 40 MHz channel even after having negotiated group
> with the 20 MHz operating class. I don't see why the operating class
> table would need to be modified for this to work.

Well extended channel switch is not really tested in today's
certification tests, so it's likely to cause interoperability issues.
Probably negotiating an HT40 channel in the first place would work
better.
But if 2.4g 40mhz CLI can be enabled without touching these operating
classes, it would be great. I agree 2.4g 40mhz GO is problematic.

Arik