On 2013-10-01 1:50 PM, Johannes Berg wrote: > On Tue, 2013-10-01 at 13:14 +0200, Felix Fietkau wrote: >> On 2013-10-01 1:05 PM, Johannes Berg wrote: >> > On Fri, 2013-09-06 at 15:06 +0200, Felix Fietkau wrote: >> >> Report the maximum allowable extra antenna gain to the driver to allow >> >> it to reduce the tx power even further based on internal data >> > >> > I don't quite understand the maximum thing here - what's a user to do >> > who has an antenna that goes over? Is that then intended to not be >> > supported? That seems odd. A very high gain antenna might just result in >> > signal distortions, but what's the reason for limiting it this way? >> Very high gain antennas are useful for long distance links. >> The signal is not distorted, but focused directionally, which can easily >> make it exceed regulatory EIRP limits, unless tx power is reduced >> appropriately. > > Sure. > >> If the user explicitly configures the gain of the directional antenna >> using this patch, mac80211 will reduce the maximum allowed tx power >> setting to stay within the legal limit. > > I understand. I don't understand the pieces about "max_antenna_gain". Right now ath9k has an antenna gain value in the EEPROM, and it compares it against the channel max_antenna_gain value. Let's assume we have configured the tx power to the maximum value, the regdb allows 3 dB antenna gain, and the ath9k EEPROM contains an antenna gain of 3 dB as well. If we now add another 3 dB of user-configured antenna gain, it first starts tapping into the regulatory-allowed antenna gain before reducing tx power in mac80211. The driver needs to know about this, so I put the calculated maximum antenna gain into the hw conf as well. - Felix -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
