linux-wireless spam filter rejected our school's google appliance mail, trying again as plain text. Sorry, Dan ---------- Forwarded message ---------- From: Daniel Halperin <dhalperi@xxxxxxxxxxxxxxxxx> Date: Sun, Jan 2, 2011 at 11:13 PM Subject: mac80211+iwlwifi bug with HT rates? To: ipw3945-devel@xxxxxxxxxxxxxxxxxxxxx, linux-wireless@xxxxxxxxxxxxxxx Cc: Swati Rallapalli <swati@xxxxxxxxxxxxx> I'm trying to track down an anomaly with a 3-stream 802.11n AP. iwlwifi is saying that a single antenna should be sufficient even when the AP supports 3 streams. Here's what I've tracked down: Code in iwl-agn-rxon.c uses the ht_cap TX MCS parameters to determine how many streams the other side supports: <http://git.kernel.org/?p=linux/kernel/git/iwlwifi/iwlwifi-2.6.git;a=blob;f=drivers/net/wireless/iwlwifi/iwl-agn-rxon.c;h=d33e4db7e56cab88abc3281d04adf32162b8020e;hb=HEAD#l470> Yet, it looks like mac80211 doesn't actually set those variables at all! In net/mac80211/ht.c, when converting the IE to the Station HT cap: <http://git.kernel.org/?p=linux/kernel/git/iwlwifi/iwlwifi-2.6.git;a=blob;f=net/mac80211/ht.c;h=75d679d75e63e92143d55a47601a1dfc1377ba03;hb=HEAD#l21> we first zero out the HT CAP (line 30) and then never actually set the ht_cap->mcs.tx_params variables at all. Grep says that's the only use of mcs.tx_params in that directory, so I'm pretty confident mac80211 just never does that. Thus iwlwifi thinks it only needs to have 1 RX antenna enabled (though it defaults to a minimum of 2 when possible) and basically fails to receive 3 stream packets. Is this a bug in iwlwifi or mac80211? Thanks, Dan -- 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
