Re: [RFC V2 1/5] nl80211: allow multiple active scheduled scan requests

[Johannes Berg <johannes@sipsolutions.net>]

On Tue, 2017-02-14 at 13:35 +0100, Arend Van Spriel wrote:
> On 24-1-2017 10:40, Johannes Berg wrote:
> > 
> > > + * @max_sched_scan_reqs: maximum number of scheduled scan
> > > requests
> > > that
> > > + *	the device can run concurrently.
> > 
> > Perhaps we should get rid of WIPHY_FLAG_SUPPORTS_SCHED_SCAN and
> > just
> > set this to 1 for such devices? Otherwise we have two different
> > requirements, and we need to track that 0 is an invalid value here
> > if
> > WIPHY_FLAG_SUPPORTS_SCHED_SCAN is set, or something like that?
> 
> Ok. Doesn't that cause issues in user-space. Or do you only want to
> get rid of it in cfg80211 api and report the flag to user-space when
> max_sched_scan_reqs equals 1?

WIPHY_FLAG_* aren't directly reported to userspace at all.

> > This might break older userspace - you'll have to put it in a later
> > portion of the code.
> > 
> > I'm also a bit surprised the attributes aren't actually optional
> > for when sched scan isn't supported, I'd make the new one optional
> > and I guess we can fix the others later too, if desired.
> 
> Why would it break user-space. Is the order in which attributes are
> added into the stream something user-space relies on.

No. But there was a size limit on how much older userspace could
process before we did the splitting.

> > > +static struct cfg80211_sched_scan_request *
> > > +cfg80211_find_sched_scan_req(struct cfg80211_registered_device
> > > *rdev, u64 reqid)
> > > +{
> > > +	struct cfg80211_sched_scan_request *pos;
> > > +
> > > +	list_for_each_entry(pos, &rdev->sched_scan_req_list,
> > > list) {
> > > +		if (pos->reqid == reqid)
> > > +			return pos;
> > > +	}
> > > +	return ERR_PTR(-ENOENT);
> > > +}
> > 
> > Here too, I guess, since you don't actually use RCU.
> 
> So should I use RCU here? Not sure what is the better choice here.

No no, I just meant to add locking assertions :)

johannes