Re: [PATCH] ath9k: fix DFS detector synchronization

[Timothy Redaelli <tredaelli@redhat.com>]

On Fri, 09 Feb 2018 10:01:09 +0200
Kalle Valo <kvalo@codeaurora.org> wrote:

> Timothy Redaelli <tredaelli@redhat.com> writes:
> 
> > The code currently syncronize the DFS region only if curchan != 0,
> > but hostapd launch DFS before the channel is set and so
> > set_dfs_domain is never executed.
> >
> > CC: Felix Fietkau <nbd@nbd.name>
> > Signed-off-by: Timothy Redaelli <tredaelli@redhat.com>  
> 
> What kind of bug does this fix? Please describe the symptoms from
> user's point of view.

With the current code radar detection (CAC) doesn't work on ath9k
since "dpd_set_domain" is only called once with NL80211_DFS_UNSET (0) as
region and so "dpd_add_pulse" always returns true (radar detected)
without doing a real scan.

You can test it easily with a kernel built with
CONFIG_ATH9K_DFS_CERTIFIED and by using a simple hostapd configuration:

interface=wlp1s0
hw_mode=a
channel=acs_survey
chanlist=100 104 108 112 116 120 124 128 132 136 140
ieee80211d=1
ieee80211h=1
country_code=US
ieee80211n=1
wmm_enabled=1
ssid=testwifi