On Sat, 2013-11-30 at 21:08 +0100, Johannes Berg wrote: > On Sat, 2013-11-30 at 22:02 +0800, Chen Gang wrote: > > > >>> case NL80211_IFTYPE_AP: > > >>> - if (sdata->vif.type == NL80211_IFTYPE_AP) > > >>> - chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf); > > >>> + chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf); > > >>> if (!chanctx_conf) > > >>> goto fail_rcu; > > >>> +try_next: > > >> > > >> I don't think that's better than the (fairly obvious) fall-through, and > > >> has a pretty odd goto. Also, depending on the compiler, it still knows > > >> the previous case label and doesn't warn. > > >> > > > > > > Yeah, fall-through is obvious. But check 'A' again just near by "case A" > > > seems a little strange, and some of compilers (or some of versions) are > > > really not quit smart enough to know it is not a warning. > > > > > > > Sorry, the paragraph above may lead misunderstanding, I repeated again: > > > > - fall-through is obvious (although I did not notice it, originally). > > > > - Check 'A' again just near by "case A" seems a little strange. > > > > - Some compilers aren't quit smart enough to know 'chanctx_conf' is OK. > > I know. If you have any good ideas of how to make it more obvious to the > compiler, I'm all ears, I just don't like any of the solutions offered > so far (and you aren't the first to do so either) :-) > > FWIW, I find the label to be odd because if you're familiar with the > code then AP/AP_VLAN *should* be identical except for two special things > that are now linearly & neatly handled in the code (the first being the > 4-addr station, the second the chanctx assignment which always has to be > done regardless of 4-addr). IMHO the == check after case should be > enough to make a human reader take a closer look. I understand that you > didn't and that's OK since you were just trying to squelch compile > warnings, but I don't see that this one warrants much attention. The label/test could be moved to save a couple of lines of duplicated code. Maybe: net/mac80211/tx.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c index 70b5a05..b2160f4 100644 --- a/net/mac80211/tx.c +++ b/net/mac80211/tx.c @@ -1777,18 +1777,16 @@ netdev_tx_t ieee80211_subif_start_xmit(struct sk_buff *skb, } ap_sdata = container_of(sdata->bss, struct ieee80211_sub_if_data, u.ap); - chanctx_conf = rcu_dereference(ap_sdata->vif.chanctx_conf); - if (!chanctx_conf) - goto fail_rcu; - band = chanctx_conf->def.chan->band; - if (sta) - break; /* fall through */ case NL80211_IFTYPE_AP: - if (sdata->vif.type == NL80211_IFTYPE_AP) - chanctx_conf = rcu_dereference(sdata->vif.chanctx_conf); + chanctx_conf = rcu_dereference(ap_sdata->vif.chanctx_conf); if (!chanctx_conf) goto fail_rcu; + if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN) { + band = chanctx_conf->def.chan->band; + if (sta) + break; + } fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS); /* DA BSSID SA */ memcpy(hdr.addr1, skb->data, ETH_ALEN); -- 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