Re: [RFC] nl80211: allow multiple active scheduled scan requests

[Johannes Berg <johannes@sipsolutions.net>]

On Tue, 2017-01-03 at 13:25 +0100, Arend Van Spriel wrote:
> On 2-1-2017 11:44, Johannes Berg wrote:
> > 
> > > +	/*
> > > +	 * allow only one legacy scheduled scan if user-space
> > > +	 * does not indicate multiple scheduled scan support.
> > > +	 */
> > > +	if (!info->attrs[NL80211_ATTR_SCHED_SCAN_MULTI] &&
> > > +	    cfg80211_legacy_sched_scan_active(rdev))
> > >  		return -EINPROGRESS;
> > 
> > That probably doesn't go far enough - if legacy one is active then
> > we
> > probably shouldn't allow a new MULTI one either (or abandon the
> > legacy
> > one) so that older userspace doesn't get confused with multiple
> > notifications from sched scans it didn't start.
> 
> I considered that although not taking the notifications into account.
> Will change it. Abandoning the legacy one would be a behavioral
> change so probably not acceptable, right?

Well, it would be acceptable since it's documented that it's possible
it might stop for any reason. However, we need to prefer something -
always preferring the new sched scan could lead to bounces, so we can
prefer (1) existing, (2) legacy-single type or (3) new-multi type, but
not (4) new sched scan.

I think preferring the existing would probably be best, i.e. refuse
legacy if any sched scan is running, and refuse multi if legacy is
running?

> I guess your remark means this clarifies your earlier question about
> the request id, right?

yeah.

johannes