Re: [PATCH v4] mac80211_hwsim: claim CSA support for AP

[Johannes Berg <johannes@sipsolutions.net>]

On Thu, 2013-12-05 at 18:26 +0100, Karl Beldan wrote:

> > Overall it seems ok, but all the purpose of csa_finished is not very
> > clear..
> > It looks that this patch tries to avoid extra beaconing on the previous
> > channel/hitting the warning..
> Yes, it avoids extra beacons.
> 
> > But the problem is much bigger here, it means that we didn't switch in
> > time (before the next beacon) so it's ok to hit the warning here and
> > transmit extra beacon with count==1.

> Precisely what I discussed in the previous emails.
> However, I'd expect WARN*s to trigger on unexpected conditions .. though
> I haven't seen any warning, the codepath nearly seems to beg for it.
> 
> > So if we see a lot of such warnings, maybe we need to fix
> > ieee80211_csa_finish instead (not using work for example)

> The replies I got from the race I detailed felt like ppl wanted to
> prevent this in-driver, now we agree this race prone work is a flaw.
> Maybe I'll send a v5 for hwsim relying on future in-stack improvement to
> avoid extra beacon instead of doing this in-driver, with some
> appropriate comments.

Generally, I think I'd prefer simpler code in the driver(s) over simpler
code in the stack, since the former tends to get duplicated a lot.

johannes