Re: [PATCH] mac80211: enable IBSS merging

[Ivo van Doorn <ivdoorn@gmail.com>]

Hi,

> > > > Then there is a problem for rt2x00. Since the mactime isn't known.
> > > > rt2400pci is the _only_ device which has a RX_END_TIME field in the
> > > > RX descriptor.
> > >
> > > one workaround could be to simply use the current TSF at the time in the
> > > tasklet or interrupt handler (to be more close to the actual rx time). this
> > > should be sufficient to catch most cases where an IBSS merge is necessary -
> > > usually the beacon's TSF will be much higher than the local TSF.
> >
> > Should the driver to this, or should mac80211 handle that?
> 
> The driver should if it has access to some the mactime of the received
> packet otherwise yes -- I think mac80211 can handle this using the
> supplied get_tsf().
> 
> > Personally I think it is something for the mac80211 layer since the driver will
> > give what it can, and can be sure that it is what mac80211 expects instead of
> > drivers interpreting what mac80211 might want as replacement.
> > If mac80211 needs the TSF value when no mac time is given, it could just
> > use the get_tsf() callback function to the driver to get the substitute. When the
> > get_tsf() callback is not provided, then mac80211 can complain about missing
> > information.
> 
> Agreed, how about something like this modified to Bruno's patch:
> 
> +               if (rx_status->flag & RX_FLAG_TSFT)
> +                       mactime = rx_status->mactime;
> +               else {
> +                       if (!local->ops->get_tsf) {
> +                          WARN_ON(1);
> +                          mactime = -1LLU;
> +                          if (net_ratelimit())
> +                             printk(KERN_WARNING "%s: cannot determine if "
> +                                   "IBSS merge is required", dev->name);
> +                      }
> +                      else {
> +                           if (net_ratelimit())
> +                             printk("Could not get detailed timestamp
> of beacon "
> +                                          during reception, using the
> driver's TSF timer for mactime\n")
> +                           mactime = local->ops->get_tsf(local_to_hw(local));
> +                   }
> +               }
> 
> We could just not support IBSS for driver's without a get_tsf(). Thoughts?

I am not sure if we should print error warning messages when the mactime is
not provided. But other then that I agree with the above change, as it would
allow rt2x00 to use the IBSS syncing. :)

Ivo