Return-path: Received: from mail-wg0-f45.google.com ([74.125.82.45]:34285 "EHLO mail-wg0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932098AbaJVKkE convert rfc822-to-8bit (ORCPT ); Wed, 22 Oct 2014 06:40:04 -0400 Received: by mail-wg0-f45.google.com with SMTP id m15so3389418wgh.28 for ; Wed, 22 Oct 2014 03:40:03 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: Date: Wed, 22 Oct 2014 12:40:03 +0200 Message-ID: (sfid-20141022_124010_013078_376C8A05) Subject: Re: Change channel bandwidth without iw command From: Michal Kazior To: Okhwan Lee Cc: "ath10k@lists.infradead.org" , linux-wireless Content-Type: text/plain; charset=UTF-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 22 October 2014 12:14, Okhwan Lee wrote: > Hi, > > We are trying to implement a protocol to evaluate the performance our > algorithm using QCA9880. > > To implement our protocol, a receiver have to change the bandwidth > when a Action frame (what we define) is successfully received. > We know that the QCA9880 can change bandwidth by using iw command in > monitor mode. > So, we use similar function path used by "iw dev set freq ..." > When the receiver detects the reception of the Action frame we call > "ieee80211_set_monitor_channel" at the end of ieee80211_rx as follows: > > /*************** net/mac80211/rx.c ******************/ > > // receive action frame, change bandwidth 80 -> 20 > > rtnl_lock(); //lock rtnetlink used in pre_doit of nl80211 > chandef = local->monitor_chandef; // copy current chandef > chandef.width = NL80211_CHAN_WIDTH_20; // set bandwidth > chandef.center_freq1 = 5180; // set center freq... > ieee80211_set_monitor_channel(wiphy, &chandef); > rtnl_unlock(); > > /********************************************************/ If my understanding is correct you're doing it wrong. You probably want to modify chanctx of a vif the frame is associated with and notify the driver via appropriate mac80211 helpers instead of the hack above. Remember to get your locking right. > However, the receiver invokes kernel panic when receives the Action frame. > As fas as we know, the panic is occurred in ath10k_config_chan of > ath10k device driver. The panic printout would be most helpful. My best guess is this crashes in ath10k_dbg() at the very beginning of ath10k_config_chan because ar->chandef.chan is NULL. This is probably the case since you use monitor_chandef which is probably "empty" at the point you invoke your code. > To the best our knowledge, our implementation exploits same function > path of iw command in nl80211, cfg80211, mac80211 and ath10k. > Moreover, we confirm that the input parameters (wiphy, chandef) in our > implementation are identical to the parameters used by iw command. > > Is there any reason why we cannot change bandwidth? > Of course, iw command work correctly. The iw set channel is for monitor interfaces only so trying to make it work with, e.g. a station interface will bring you pain. Michał