Re: [PATCH 1/2] nl80211: add support for mcs masks

[Ben Greear <greearb@candelatech.com>]

On 12/19/2011 01:14 PM, Simon Wunderlich wrote:
> Hello Ben,
>
> On Mon, Dec 19, 2011 at 07:28:52AM -0800, Ben Greear wrote:
>> On 12/19/2011 06:14 AM, Simon Wunderlich wrote:
>>> Allow to set mcs masks through nl80211. We also allow to set MCS
>>> rates but no legacy rates (and vice versa).
>>
>> Can you not use the ht-caps logic that went in recently?  I was able
>> to successfully set station MCS rates with it.  It only works for
>> station devices at this point...but AP support could probably be
>> added without too much trouble.
>
> I have not tried that out yet, but one important side effect we are
> using here is to force HT mode, also for No Ack packets which are
> usually sent with the lowest (legacy) rate. We are building fixed
> links and want to set a fixed HT rate there, and only this rate should
> be used whenever possible (and no legacy rates).

The ht-caps patch gives the ability to specify the available MCS rates
(again, for stations only at this point).  I didn't try forcing speeds
higher, but I did test that it could force speeds lower.  It requires
a patch to hostapd that I've posted, but it has not yet been accepted.

There is no way to disable legacy rates in the current code, as far
as I know.

>
> As far as I understand, the ht caps overrides will only override
> HT configurations, but what I want is to also let the rate matcher
> consider HT rates too and to disable legacy rates completely.
>
> As the mcs masks support has been prepared a long time ago in iw and
> mac80211, it did not seem to be the worst idea to finally fill this
> gap and implement it. :)

I haven't read your patch in detail, and at the least, the ht-caps code
would need some additional work to support your needs.  So, I'm not
sure whether working on top of the ht-caps logic is useful or not.

Likely Johannes will have more useful feedback when he gets the time.

I will try to read your patch in more detail when I get a chance.

Thanks,
Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com