Hello Toke,
On Mon, 04 Apr 2022 20:19:39 +0200, Toke Høiland-Jørgensen <toke@xxxxxxx> wrote:
> Peter Seiderer <ps.report@xxxxxxx> 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
