linux-kernel - Re: [PATCH 02/31] staging: wfx: do not send CAB while scanning

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Date:   Fri, 10 Sep 2021 18:54:36 +0200
From:   Jérôme Pouiller <jerome.pouiller@...abs.com>
To:     Kari Argillander <kari.argillander@...il.com>
Cc:     devel@...verdev.osuosl.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH 02/31] staging: wfx: do not send CAB while scanning

On Friday 10 September 2021 18:31:00 CEST Kari Argillander wrote:
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
> 
> 
> On Fri, Sep 10, 2021 at 06:04:35PM +0200, Jerome Pouiller wrote:
> > From: Jérôme Pouiller <jerome.pouiller@...abs.com>
> >
> > During the scan requests, the Tx traffic is suspended. This lock is
> > shared by all the network interfaces. So, a scan request on one
> > interface will block the traffic on a second interface. This causes
> > trouble when the queued traffic contains CAB (Content After DTIM Beacon)
> > since this traffic cannot be delayed.
> >
> > It could be possible to make the lock local to each interface. But It
> > would only push the problem further. The device won't be able to send
> > the CAB before the end of the scan.
> >
> > So, this patch just ignore the DTIM indication when a scan is in
> > progress. The firmware will send another indication on the next DTIM and
> > this time the system will be able to send the traffic just behind the
> > beacon.
> >
> > The only drawback of this solution is that the stations connected to
> > the AP will wait for traffic after the DTIM for nothing. But since the
> > case is really rare it is not a big deal.
> >
> > Signed-off-by: Jérôme Pouiller <jerome.pouiller@...abs.com>
> > ---
> >  drivers/staging/wfx/sta.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> >
> > diff --git a/drivers/staging/wfx/sta.c b/drivers/staging/wfx/sta.c
> > index a236e5bb6914..d901588237a4 100644
> > --- a/drivers/staging/wfx/sta.c
> > +++ b/drivers/staging/wfx/sta.c
> > @@ -629,8 +629,18 @@ int wfx_set_tim(struct ieee80211_hw *hw, struct ieee80211_sta *sta, bool set)
> >
> >  void wfx_suspend_resume_mc(struct wfx_vif *wvif, enum sta_notify_cmd notify_cmd)
> >  {
> > +     struct wfx_vif *wvif_it;
> > +
> >       if (notify_cmd != STA_NOTIFY_AWAKE)
> >               return;
> > +
> > +     // Device won't be able to honor CAB if a scan is in progress on any
> > +     // interface. Prefer to skip this DTIM and wait for the next one.
> 
> In one patch you drop // comments but you introduce some of your self.

Indeed. When I wrote this patch, I didn't yet care to this issue. Is it
a big deal since it is fixed in patch 27?



-- 
Jérôme Pouiller