Re: [RFC PATCH 4/8] mac80211: Use PS module for managed mode powersave

Johannes Berg
2013-12-17T08:25:19Z

On Mon, 2013-12-16 at 16:00 -0600, Seth Forshee wrote:

> --- a/net/mac80211/iface.c
> +++ b/net/mac80211/iface.c
> @@ -682,7 +682,7 @@ int ieee80211_do_open(struct wireless_dev *wdev, bool coming_up)
> if (hw_reconf_flags)
> ieee80211_hw_config(local, hw_reconf_flags);
>
> - ieee80211_recalc_ps(local, -1);
> + ieee80211_ps_vif_open(sdata);

I have a feeling that now that we have very regular join/leave code, and
are guaranteed to go through disassoc when the interface is stopped, we
probably don't need all the hooks in this file at all any more.

> @@ -1609,6 +1609,7 @@ int ieee80211_if_add(struct ieee80211_local *local, const char *name,
> strlcpy(sdata->name, name, IFNAMSIZ);
> ieee80211_assign_perm_addr(local, wdev->address, type);
> memcpy(sdata->vif.addr, wdev->address, ETH_ALEN);
> + ieee80211_ps_init_vif(sdata);

That doesn't really seem like the right place? Shouldn't it somehow be
specific for managed interfaces, and be reset when the interface changes
type, for example?

> --- a/net/mac80211/status.c
> +++ b/net/mac80211/status.c
> @@ -732,15 +732,16 @@ void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb)
> local->dot11FailedCount++;
> }
>
> + sdata = IEEE80211_DEV_TO_SUB_IF(skb->dev);

This isn't safe, the interface can go away while the SKB is on some
hardware queue. Look at what we do in ieee80211_report_used_skb() and
maybe refactor that somehow.

> - if (local->hw.conf.flags & IEEE80211_CONF_PS) {
> + if (sdata->vif.ps_mode == IEEE80211_VIF_PS_DOZE) {
> ieee80211_stop_queues_by_reason(&local->hw,
> IEEE80211_MAX_QUEUE_MAP,
> IEEE80211_QUEUE_STOP_REASON_PS);

This is a bit odd now - shouldn't you only stop the queues for that
interface? Or is this still assuming only a single interface?

> + list_for_each_entry(sdata, &local->interfaces, list) {
> + if (sdata->vif.type != NL80211_IFTYPE_STATION)
> + continue;
> + if (!sdata->u.mgd.associated)
> + continue;
> + if (sdata->vif.ps_mode != IEEE80211_VIF_PS_AWAKE)
> + continue;
>
> - ieee80211_send_nullfunc(local, sdata, 0);
> - }
> + ieee80211_send_nullfunc(local, sdata, 0);

Unrelated to your patch, but we should probably send a nullfunc(PM=1)
packet for the other cases to detect if we got disconnected. Or wake up
briefly, and go back to sleep later or something ...

> +void ieee80211_recalc_ps(struct ieee80211_sub_if_data *sdata)
> +{
> + switch (sdata->vif.type) {
> + case NL80211_IFTYPE_STATION:
> + ieee80211_mgd_recalc_ps(sdata);
> + break;
> + default:
> + break;
> + }
> +}

Would that make more sense in ps.c now?

> +int ieee80211_max_network_latency(struct notifier_block *nb,
> + unsigned long data, void *dummy)

ditto?

> + mutex_lock(&local->iflist_mtx);
> + list_for_each_entry_rcu(sdata, &local->interfaces, list) {

locking mutex & then rcu seems weird.
johannes