Re: [PATCH v4 1/3] cfg80211: Add nl80211 antenna configuration

["Luis R. Rodriguez" <lrodriguez@atheros.com>]

On Wed, Jul 28, 2010 at 03:05:45PM -0700, Felix Fietkau wrote:
> On 2010-07-28 11:39 PM, Luis R. Rodriguez wrote:
> > On Wed, Jul 28, 2010 at 02:26:35PM -0700, Felix Fietkau wrote:
> >> We don't need any special case handling for this at all. Drivers already
> >> calculate their HT capabilities based on the number of available chains.
> >> Once the antenna selection stuff is actually used, they will have some
> >> internal information about which chains have how many antennas.
> >> 
> >> The reason why we can ignore *all* of this stuff for the API is simple:
> >> We only need to refactor the code to calculate these settings based on
> >> effective chainmask / antenna mask instead of pure hardware capability.
> >> 
> >> The effective chainmask / antenna mask is basically the same as the
> >> hardware settings, except that it gets masked with the values that are
> >> configured through this API. That leaves us with something that's easy
> >> to configure, easy to implement for drivers, and doesn't need special
> >> case stuff for various 802.11n features.
> > 
> > Consider the case of an already associated STA in 3x3 mode, and someone
> > uses this API to limit it to a 1 stream 1x1 chaimask setting using
> > only one antenna. How would the AP find out about this RX setting
> > from the STA? Are we going to deny mucking with this prior to association?
> > What about if you're the AP?
> > 
> > If you are using STBC and the user tunes the device to 1 stream 1x1 chainmask
> > settings, who deals with the required adaptations?
> I think we should simply not accept runtime modifications of this stuff.
> The user should bring down the interface, change the value, then bring
> it back up again. That allows the driver to recalculate all the HT stuff
> based on the updated chainmask/antenna mask without special cases.

Works with me.

Would we keep two values for some of these settings, an "actual hw"
capablity and then also a "configured" values? Would this be exposed
and visible through iw?

  Luis