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Date: Mon, 4 Apr 2022 22:52:12 +0200 From: Peter Seiderer <ps.report@....net> To: Toke Høiland-Jørgensen <toke@...e.dk> Cc: linux-wireless@...r.kernel.org, Kalle Valo <kvalo@...nel.org>, "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Johannes Berg <johannes@...solutions.net>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v1 1/2] ath9k: fix ath_get_rate_txpower() to respect the rate list end tag Hello Toke, On Mon, 04 Apr 2022 20:19:39 +0200, Toke Høiland-Jørgensen <toke@...e.dk> wrote: > Peter Seiderer <ps.report@....net> writes: > > > Stop reading (and copying) from ieee80211_tx_rate to ath_tx_info.rates > > after list end tag (count == 0, idx < 0), prevents copying of garbage > > to card registers. > > In the normal case I don't think this patch does anything, since any > invalid rate entries will already be skipped (just one at a time instead > of all at once). So this comment is a bit misleading. Save some (minimal) compute time? Found it something misleading while debugging to see random values written out to the card and found this comment in net/mac80211/rate.c: 648 /* 649 * make sure there's no valid rate following 650 * an invalid one, just in case drivers don't 651 * take the API seriously to stop at -1. 652 */ and multiple places doing the same check (count == 0, idx < 0) for validation e.g.: 723 if (i < ARRAY_SIZE(info->control.rates) && 724 info->control.rates[i].idx >= 0 && 725 info->control.rates[i].count) { or 742 if (rates[i].idx < 0 || !rates[i].count) 743 break; > > Also, Minstrel could in principle produce a rate sequence where the > indexes are all positive, but there's one in the middle with a count of > 0, couldn't it? With this patch, the last entries of such a sequence > would now be skipped... According to net/mac80211/rc80211_minstrel_ht.c: 1128 static bool 1129 minstrel_ht_txstat_valid(struct minstrel_priv *mp, struct minstrel_ht_sta * mi, 1130 struct ieee80211_tx_rate *rate) 1131 { 1132 int i; 1133 1134 if (rate->idx < 0) 1135 return false; 1136 1137 if (!rate->count) 1138 return false; 1139 minstrel although evaluates a rate count of zero as invalid... Regards, Peter > > -Toke
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