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

["Pedersen, Thomas" <c_tpeder@qca.qualcomm.com>]

On Thu, Jun 07, 2012 at 10:23:57AM +0300, Kalle Valo wrote:
> On 06/07/2012 05:43 AM, Thomas Pedersen wrote:
> > Support configuring an RSSI threshold in dBm (s32) when scanning,
> > below which a BSS won't be reported by the cfg80211 driver.
> > 
> > Signed-off-by: Thomas Pedersen <c_tpeder@qca.qualcomm.com>
> 
> [...]
> 
> > + * @NL80211_ATTR_SCAN_RSSI: rssi threshold (in s32 dBm) below which a BSS is
> > + *	not reported in scan results. Will be disabled if 0 or not specified.
> > + *	Supported in %NL80211_CMD_START_SCHED_SCAN and %NL80211_TRIGGER_SCAN.
> > + *
> >   * @NL80211_ATTR_MAX: highest attribute number currently defined
> >   * @__NL80211_ATTR_AFTER_LAST: internal use
> >   */
> > @@ -1473,6 +1477,8 @@ enum nl80211_attrs {
> >  
> >  	NL80211_ATTR_BG_SCAN_PERIOD,
> >  
> > +	NL80211_ATTR_SCAN_RSSI,
> 
> NL80211_ATTR_SCAN_RSSI_THRESHOLD? Or is limit a better term? Or
> something else?
> 
> My english sucks anyway...

No you're probably right, thanks :)

> > @@ -935,6 +936,7 @@ struct cfg80211_scan_request {
> >  	struct net_device *dev;
> >  	bool aborted;
> >  	bool no_cck;
> > +	s32 rssi;
> 
> rssi_threshold?

Yes.

> >  
> >  	/* keep last */
> >  	struct ieee80211_channel *channels[0];
> > @@ -966,6 +968,7 @@ struct cfg80211_match_set {
> >   * @wiphy: the wiphy this was for
> >   * @dev: the interface
> >   * @channels: channels to scan
> > + * @rssi: don't report scan results below this threshold
> >   */
> >  struct cfg80211_sched_scan_request {
> >  	struct cfg80211_ssid *ssids;
> > @@ -976,6 +979,7 @@ struct cfg80211_sched_scan_request {
> >  	size_t ie_len;
> >  	struct cfg80211_match_set *match_sets;
> >  	int n_match_sets;
> > +	s32 rssi;
> 
> rssi_threshold?

Ditto.

> > @@ -1794,6 +1798,8 @@ struct cfg80211_ops {
> >   *	responds to probe-requests in hardware.
> >   * @WIPHY_FLAG_OFFCHAN_TX: Device supports direct off-channel TX.
> >   * @WIPHY_FLAG_HAS_REMAIN_ON_CHANNEL: Device supports remain-on-channel call.
> > + * @WIPHY_FLAG_SUPPORTS_RSSI_SCAN: Device supports filtering scan results by
> > + *	 RSSI (in dBm).
> >   */
> >  enum wiphy_flags {
> >  	WIPHY_FLAG_CUSTOM_REGULATORY		= BIT(0),
> > @@ -1817,6 +1823,7 @@ enum wiphy_flags {
> >  	WIPHY_FLAG_AP_PROBE_RESP_OFFLOAD	= BIT(19),
> >  	WIPHY_FLAG_OFFCHAN_TX			= BIT(20),
> >  	WIPHY_FLAG_HAS_REMAIN_ON_CHANNEL	= BIT(21),
> > +	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.

Thomas