On Tue, Aug 25, 2015 at 2:36 AM, Johannes Berg
[off-list ref] wrote:

It's ... complicated. First of all, it's currently not supported I
believe, in general, since there's no parsing code. Obviously, parsing
code can be changed, and I think there might even be patches floating
around for that.

Adding this into the parse_tx_radiotap() is pretty trivial, I've added
MCS and legacy bitrate, FEC, SGI and STBC controls already.  I just
don't quite know where to put transmit power.

However, not all hardware supports per-frame TX power control. Some
might, most will not. Until fairly recently, there was also no API with
drivers to allow setting TX power per frame. This changed with the
addition of TX power control to rate control, of course.

I'm currently working with ath9k.  It appears that it supports
per-frame power control, although I'm still familiarizing myself.

Where would I stick the transmit power control?  In the
ieee80211_tx_info->control somewhere, or maybe in the
ieee80211_tx_info->rate_driver_data?