Re: [RFC 1/2] nl80211: specify RSSI threshold when scanning

[Johannes Berg <johannes@sipsolutions.net>]

On Thu, 2012-06-07 at 12:18 -0700, Pedersen, Thomas wrote:
> On Thu, Jun 07, 2012 at 09:53:20PM +0300, Kalle Valo wrote:
> > On 06/07/2012 09:38 PM, Pedersen, Thomas wrote:
> > >>> +	WIPHY_FLAG_SUPPORTS_RSSI_SCAN		= BIT(22),
> > >>> > >  };
> > >> > 
> > >> > Is this flag really needed? For me this looks like an optimisation more
> > >> > than a functional change. If the driver supports this, that's great and
> > >> > we can save some power. But if the driver does not support it does it
> > >> > really make any difference for the user space? Would user space act
> > >> > differently if this feature is not supported by the driver?
> > >
> > > Well, this allows cfg80211 to return an error if this feature is
> > > requested but not supported by the driver / fw.
> > 
> > But do we want to return an error when the driver doesn't support this?
> > I was thinking that driver should just ignore the attribute in that case
> > and let user space filter the results.
> > 
> > Kalle
> 
> Sure, we can just let userspace unconditionally filter the results when
> we do something like:
> 
> iw wlan0 scan rssi -40
> 
> Johannes, does this look OK to you?

I don't see a need to filter in iw, but I agree with Kalle that we
shouldn't impose any restrictions on a performance optimisation.

johannes