You use value '0' to mean set to default values, as far as I can
tell.

I think you're confusing the internal API and the userspace API - at a
userspace level you have to set NL80211_ATTR_STA_TX_POWER_SETTING to
NL80211_TX_POWER_AUTOMATIC to revert back to defaults, no?

For perfect backwards compatibility we should ignore it if not
supported, but that doesn't really make sense - I think we should
reject it and handle errors elsewhere in the not supported case.

johannes