Johannes Berg <johannes@xxxxxxxxxxxxxxxx> writes: > On Wed, 2009-06-10 at 17:22 +0200, Gábor Stefanik wrote: >> On Wed, Jun 10, 2009 at 3:39 PM, Hin-Tak Leung<hintak.leung@xxxxxxxxx> wrote: > >> (Note that I'm also for allowing such "buggy" AP mode on devices >> without a HW multicast buffer, perhaps with hostapd spitting out a >> big, fat warning on startup; but Johannes has the final say in >> mac80211-related questions.) >> >> (To Johannes: exactly why is it required for the multicast buffer to >> be in hardware?) > > It isn't required, ath5k/9k don't have it there, they have the notorious > "CAB" queue for sending frames directly after the beacon. So does b43, > and probably other designs. The problem really is that powersave mode is > very important for small clients like your mobile phone or digital > camera, or even bluetooth3 device, and not doing multicast buffering > correctly means that either those devices get into weird unreachable > states, or you need to turn off powersaving features on them which makes > the battery drain unbearable. Not only mobile clients, but as we are talking about enabling power save by default, also Linux laptops would have problems. > Now, it may or may not be possible to work around this in software by > sending out the multicast frames on a high-priority queue right after > the beacon, And the DTIM beacon should have the broadcast/multicast TIM bit set before sending the frames. > or something like that, but frankly I'm not interested in working on > zd1211rw myself, so that will have to be somebody who is (a) familiar > with 802.11 powersaving and multicast buffering, (b) wants zd1211rw to > work, and finally (c) has a lot of time to play with the device. If someone really has that much time, I think it's better to spend it on more important issues than this. -- Kalle Valo -- 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
