From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.candelatech.com ([208.74.158.172]:50097 "EHLO ns3.lanforge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755898Ab1KDQ1a (ORCPT ); Fri, 4 Nov 2011 12:27:30 -0400 Message-ID: <4EB4126E.1020802@candelatech.com> (sfid-20111104_172734_236559_0184BD8C) Date: Fri, 04 Nov 2011 09:27:26 -0700 From: Ben Greear MIME-Version: 1.0 To: Johannes Berg CC: linux-wireless@vger.kernel.org Subject: Re: [PATCH v3 3/3] mac80211: Allow overriding some HT information. References: <1320299722-30113-1-git-send-email-greearb@candelatech.com> <1320299722-30113-3-git-send-email-greearb@candelatech.com> (sfid-20111103_065549_863747_7FFD5818) <1320310045.3950.23.camel@jlt3.sipsolutions.net> <4EB2CBCC.6080709@candelatech.com> <1320417690.3969.88.camel@jlt3.sipsolutions.net> <4EB41014.6000002@candelatech.com> <1320423893.3969.104.camel@jlt3.sipsolutions.net> In-Reply-To: <1320423893.3969.104.camel@jlt3.sipsolutions.net> Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: On 11/04/2011 09:24 AM, Johannes Berg wrote: > On Fri, 2011-11-04 at 09:17 -0700, Ben Greear wrote: > >>>>> The AMPDU density should only allow increasing. >>>>> >>>>> I think a lot of this validation should live in cfg80211 so if another >>>>> driver wants to implement it, this kind of thing is already covered. >>>> >>>> The ath9k driver supports 0, and then every value that corresponds to 1us or higher. >>>> If you set it to 1/2us, for instance, it just quietly rounds up to 1us. It defaults >>>> to 8, so it appears valid to decrease or increase this value. >>> >>> What quietly rounds up? >>> >>> If it defaults to 8 then I'm sure there's a reason for it, such as the >>> crypto engine not being fast enough and needing 8us buffer between >>> frames. As such, I really don't think decreasing it is valid. >> >> See this code in ath9k, top of main.c. It appears to support more >> than the default of 8. I tested it out, and it appears to work >> when set to lower values. I am disabling hw-crypt since I need >> multiple VIFS, but not sure that matters or not. >> >> static u8 parse_mpdudensity(u8 mpdudensity) > > Well, this is used for TX. You're advertising the value for RX. > Advertising a smaller value may work for you -- but only if the AP uses > something larger anyway. It's free to do this. The code you quoted > implements this -- it looks at what the min spacing is the peer wants, > and then uses something bigger. > > So I still stand by what I said earlier -- you should not allow > advertising a smaller value than the hardware wanted to use initially. > If the AP doesn't use that smaller value, all is well, but if it > actually uses a smaller value then the hardware might fall over. Ok, I'll add that restriction. When this all settles, maybe I can get some info from the ath9k folks about what their hardware can actually support. Thanks, Ben > > johannes -- Ben Greear Candela Technologies Inc http://www.candelatech.com