On Fri, 2006-03-24 at 08:28 -0800, Jouni Malinen wrote: > On Thu, Mar 23, 2006 at 08:16:04PM -0500, Dan Williams wrote: > > > fixed it. Active scanning has been out of vogue as the default scan > > method for like 2 years with wireless-tools/WE, I'm not sure why softmac > > thinks it should be different here. Active scanning takes more power > > anyway, since you have to power up the card to transmit the probe > > requests. That's why wireless-tools and Wireless Extensions switched to > > passive scanning. > > Can you please point to some documentation/email thread/etc. describing > this preference to use passive scanning? I was not aware of such a > preference and have assumed that active scanning would be the preferred > default because it is quite a bit faster and provides more complete > results. > > > I'd have issues with softmac doing active scanning unless _specifically_ > > requested to do so, by using the SIOCGIWMLME with a iw_scan_req > > structure requesting IW_SCAN_TYPE_ACTIVE. But _only_ then... Normal > > SIOCGIWSCAN shouldn't do active scanning. > > SIOCGIWSCAN does not request scanning, SIOCSIWSCAN does.. I don't
Right, typo on my part. Had considered sending mail correcting this, but that would have been pointless for 1 word. > understand what SIOCGIWMLME would have to do with this. SIOCSIWSCAN can > use an optional iw_scan_req to control scan request. If this data is not > present, I would assume that the drivers would do whatever they want and > in many cases I would expect this to be active scan. My fault here too. In my quick reading of wireless.h, I confused some of the comments regarding iw_scan_req and SIOCSIWSCAN. So you're correct here, that iw_scan_req should be used with SIOCSIWSCAN, and my comments about MLME are wrong. However, the problem with active scanning is that you have to power up the transmit components of the radio, while passive scanning, even though it takes a bit longer, doesn't necessarily require that. Active scanning takes more power. So what I'm arguing for here is that drivers should _default_ to passive scanning when given a scan request with no scan type information. But they should be able to do so when they get a request for an active scan using IW_SCAN_TYPE_ACTIVE. Drivers should default to using less power, and more only when the app requests so. However: It's somewhat unfortunate that wireless.h defines ACTIVE scan type as 0 since then, that's what non-WE-18 apps would inadvertently set. And apps that are power-aware would be setting that bit anyway. Most drivers that are FullMAC do passive scanning without sending probe requests, AFAIK, and so do OK here. In short, since WE already defines ACTIVE to be 0, and we're not going to change that, consider my arguments here withdrawn. We should just note that if an application wants the card to be power-conservative, that the _app_ needs to set the correct bits in the scan. Were ACTIVE defined as 1, the story would be different, but it's not. So be it. Dan - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
