On Mon, Dec 29, 2008 at 6:29 PM, Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote: > On Mon, 2008-12-29 at 18:25 +0200, Ville Nuorvala wrote: >> The IWSPY ioctls and netlink events were supported in the old ieee80211 >> stack. This patch adds them to mac80211. > > missing very long explanation as to why this is needed Hello Johannes, to my knowledge it is currently the only way to get a realtime indication that the wireless link quality has changed, please correct me if I'm wrong. Such a feature can be used as an early indication that the link is going down, and may help prepare a vertical IP layer handover to for example 3G or just another WLAN interface. The predictive nature of the event allows you (most of the time) to set up the other link before the WLAN link is down, which allows a make-before-break handover without packet loss. In fact such events are described in the IEEE 802.21 Media Independent Handover document. Ideally these events might be produced by the 802.11 firmware or at least somewhere lower in the stack, but lacking that, it can at least be emulated by the IWSPY interface. Also, as an added bonus for using IWSPY, you can choose the trigger signal levels yourself and don't have to rely on any preset levels chosen by the device manufacturer. > As far as I can tell, nobody uses iwspy support or could possibly want > it the way it is done. The IOCTL interface is horrible, but it's already there and there is a tool that supports it; iwspy. I'm not bringing any new functionality to the wireless stack, I'm just reintroducing a feature that got lost when the wireless stack was changed. Sure a pure netlink interface without any ugly IOCTL hacks would be nice, but last time I checked the documentation for nl80211 and cfg80211 was nonexistent, and even driver_nl80211.c straight from the hostap GIT repository uses WEXT IOCTLs internally for several different purposes. To me at least it seems like the nl80211 interface is still far from ready. As my resources are currently very limited, I don't have time to implement the necessary netlink API and userspace tools at the moment. The logical conclusion for me was therefore to just use the old WEXT interface for now. Regards, Ville -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
