Disabling SMPS (Spatial multiplexing power save) when 802.11n is not used

Johannes Berg johannes at sipsolutions.net
Fri Mar 18 05:33:33 PDT 2016

On Fri, 2016-03-18 at 09:20 +0100, Jose Blanquicet wrote:
> Hello,
> SMPS (Spatial multiplexing power save) is a feature proposed in
> 802.11n 
> to reduce power consumption. When device is playing in Access Point
> and 
> 802.11n mode is disable setting disable_ht = 1, the HT Capabilities 
> (conf->ht_capab) are "cleaned" (Set to zero) in function 
> wpa_supplicant_conf_ap_ht, but the value 0 does not actually clean
> the
> capabilities, instead it is being set to use SMPS_STATIC:
> 	#define HT_CAP_INFO_SMPS_STATIC			((u16)
> 0)
> 	#define HT_CAP_INFO_SMPS_DYNAMIC		((u16) BIT(2))
> 	#define HT_CAP_INFO_SMPS_DISABLED		((u16) (BIT(2)
> | BIT(3)))
> Therefore, when the beacons parameters are configured, it results in
> an 
> error because SMPS is set to SMPS_STATIC mode in a non-802.11n
> configuration:
> 	nl80211: Beacon set failed: -22 (Invalid argument)

Hm. Sounds a bit more like nl80211 driver shouldn't have this attribute
at all if it's not actually going to do HT?


More information about the Hostap mailing list