Message-ID: <52495798.1030408@openwrt.org> (sfid-20130930_125110_522371_CDDFA6FE)
Date: Mon, 30 Sep 2013 12:51:04 +0200
From: Felix Fietkau <nbd@openwrt.org>
MIME-Version: 1.0
To: Johannes Berg <johannes@sipsolutions.net>
CC: linux-wireless@vger.kernel.org
Subject: Re: [PATCH 3.12] mac80211: fix a tx power handling regression
References: <1380458883-19862-1-git-send-email-nbd@openwrt.org>  <1380532158.14467.3.camel@jlt4.sipsolutions.net>  <524947C0.7060607@openwrt.org> <1380537498.14467.10.camel@jlt4.sipsolutions.net>
In-Reply-To: <1380537498.14467.10.camel@jlt4.sipsolutions.net>
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On 2013-09-30 12:38 PM, Johannes Berg wrote:
> On Mon, 2013-09-30 at 11:43 +0200, Felix Fietkau wrote:
>> On 2013-09-30 11:09 AM, Johannes Berg wrote:
>> > On Sun, 2013-09-29 at 14:48 +0200, Felix Fietkau wrote:
>> >> commit 1ea6f9c0d48b11b6ec3ec4b5579ec74fc3951cf8
>> >> "mac80211: handle TX power per virtual interface"
>> >> 
>> >> This commit added support for tracking tx power configuration for
>> >> multiple interfaces, however instead of using the maximum value of all
>> >> virtual interfaces, it uses the minimum.
>> > 
>> > I'm not sure it should be using the maximum? What if the AP required
>> > lowering TX power by way of TPC for example?
>> Shouldn't that only affect the virtual interface that is connected to
>> that AP?
> Yes, but not all drivers support per-interface TX power I guess?
> 
>> If there's a regulatory requirement to use lower tx power, it should be
>> tracked as a limit somewhere else instead of implicitly being handled
>> via vif tx power configuration.
> 
> Not sure I see why? It's an absolute value after we do the calculations
> in that interface that has the TPC.
Maybe we need to rework this somehow, but in the mean time, this patch
fixes a serious regression that I've been looking into for a while now.
I haven't worked out the exact conditions that trigger this yet, but
often when an AP VLAN gets destroyed and recreated, or when a new
temporary interface is brought up and then down again, the tx power for
*all* interfaces gets reset to the lowest possible level.

- Felix