On Fri, Feb 08, 2013 at 10:03:32AM +0100, Johannes Berg wrote: > On Thu, 2013-02-07 at 11:54 -0600, Seth Forshee wrote: > > Scans currently work by stopping the netdev tx queues but leaving the > > mac80211 queues active. This stops the flow of incoming packets while > > still allowing mac80211 to transmit nullfunc and probe request frames to > > facilitate scanning. However, the driver may try to wake the mac80211 > > queues while in this state, which will also wake the netdev queues. > > > > To prevent this, add a new queue stop reason, > > IEEE80211_QUEUE_STOP_REASON_OFFCHANNEL, to be used when stopping the tx > > queues for off-channel operation. This prevents the netdev queues from > > waking when a driver wakes the mac80211 queues. > > > > This also stops all frames from being transmitted, even those required > > for scanning. To get around this, add a new offchan_tx_ok argument to > > most of the tx interfaces. This flag can be set for frames which need to > > be transmitted during off-channel operation, allowing off-channel frames > > to be passed down to the driver if the queues have only been stopped for > > off-channel. Add ieee80211_tx_skb_offchannel() for transmitting > > off-channel frames with this flag set. > > I started wondering -- is there a reason to modify the entire TX path? > Could we maybe bypass it instead and call the driver's TX op almost > directly? The frames in question don't really need much TX handling, the > only thing that might be relevant _could_ be rate control but even that > I'd argue isn't really needed, just using rate_control_send_low() should > be ok (by setting IEEE80211_TX_CTL_USE_MINRATE it will always return > true). For the null data packets the sta pointer is also obvious, the AP > station (BSSID) ... we don't need any of the extra monitor/whatever > handling either. > > That might be simpler overall? Okay, I'll take a look at this. Another option that might simplify things a bit would be to use a ieee80211_tx_data flag. If I added another interface into tx.c for offchannel frames then the offchan argument would only be needed for ieee80211_xmit() and ieee80211_tx(). Though it would be nice to avoid adding an argument to ieee80211_xmit(). Seth -- 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
