linux-next: build failure after merge of the mac80211-next tree

Hi Johannes,

After merging the mac80211-next tree, today's linux-next build (x86_64
allmodconfig) failed like this:

drivers/net/wireless/mediatek/mt76/mt76x2_main.c:539:19: error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types]
  .wake_tx_queue = mt76_wake_tx_queue,
                   ^
drivers/net/wireless/mediatek/mt76/mt76x2_main.c:539:19: note: (near initialization for 'mt76x2_ops.wake_tx_queue')

Caused by commits

  17f1de56df05 ("mt76: add common code shared between multiple chipsets")
  7bc04215a66b ("mt76: add driver code for MT76x2e")

from the wireless-drivers-next tree interacting with commit

  e937b8da5a59 ("mac80211: Add TXQ scheduling API")

from the mac80211-next tree.

I applied the below hack merge fix ... please let me know if something
more/better is required.  Someone needs to remember to tell Dave when
these trees meet in his tree.

From: Stephen Rothwell <redacted>
Date: Tue, 12 Dec 2017 12:50:40 +1100
Subject: [PATCH] mt76: fix up for "mac80211: Add TXQ scheduling API"

Signed-off-by: Stephen Rothwell <redacted>
---
 drivers/net/wireless/mediatek/mt76/mt76.h |  2 +-
 drivers/net/wireless/mediatek/mt76/tx.c   | 10 +++++++---
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt76.h b/drivers/net/wireless/mediatek/mt76/mt76.h
index aa0880bbea7f..e395d3859212 100644
--- a/drivers/net/wireless/mediatek/mt76/mt76.h
+++ b/drivers/net/wireless/mediatek/mt76/mt76.h

@@ -338,7 +338,7 @@ void mt76_tx(struct mt76_dev *dev, struct ieee80211_sta *sta,
 	     struct mt76_wcid *wcid, struct sk_buff *skb);
 void mt76_txq_init(struct mt76_dev *dev, struct ieee80211_txq *txq);
 void mt76_txq_remove(struct mt76_dev *dev, struct ieee80211_txq *txq);
-void mt76_wake_tx_queue(struct ieee80211_hw *hw, struct ieee80211_txq *txq);
+void mt76_wake_tx_queue(struct ieee80211_hw *hw);
 void mt76_stop_tx_queues(struct mt76_dev *dev, struct ieee80211_sta *sta,
 			 bool send_bar);
 void mt76_txq_schedule(struct mt76_dev *dev, struct mt76_queue *hwq);

diff --git a/drivers/net/wireless/mediatek/mt76/tx.c b/drivers/net/wireless/mediatek/mt76/tx.c
index 4eef69bd8a9e..ad414af0750f 100644
--- a/drivers/net/wireless/mediatek/mt76/tx.c
+++ b/drivers/net/wireless/mediatek/mt76/tx.c

@@ -463,12 +463,16 @@ void mt76_stop_tx_queues(struct mt76_dev *dev, struct ieee80211_sta *sta,
 }
 EXPORT_SYMBOL_GPL(mt76_stop_tx_queues);
 
-void mt76_wake_tx_queue(struct ieee80211_hw *hw, struct ieee80211_txq *txq)
+void mt76_wake_tx_queue(struct ieee80211_hw *hw)
 {
+	struct ieee80211_txq *txq;
 	struct mt76_dev *dev = hw->priv;
-	struct mt76_txq *mtxq = (struct mt76_txq *) txq->drv_priv;
-	struct mt76_queue *hwq = mtxq->hwq;
+	struct mt76_txq *mtxq;
+	struct mt76_queue *hwq;
 
+	txq = ieee80211_next_txq(hw);
+	mtxq = (struct mt76_txq *) txq->drv_priv;
+	hwq = mtxq->hwq;
 	spin_lock_bh(&hwq->lock);
 	if (list_empty(&mtxq->list))
 		list_add_tail(&mtxq->list, &hwq->swq);

-- 
2.15.0

-- 
Cheers,
Stephen Rothwell

Hi Stephen,

Thanks!

Felix made me aware of this yesterday evening and said he's going to
work out the required changes to mt76.

Kalle and I will make sure to submit the trees to Dave one by one so he
doesn't have to deal with it :)

Unfortunately, this might take a few days to resolve.

Looks pretty much right to me - perhaps for safety there should be a
NULL check on txq, but OTOH when you get here it should be non-NULL.

Sorry for the inconvenience, I hadn't realized mt76 went in now.

johannes

Johannes Berg [off-list ref] writes:

Hi Stephen,

Thanks!

Felix made me aware of this yesterday evening and said he's going to
work out the required changes to mt76.

Kalle and I will make sure to submit the trees to Dave one by one so he
doesn't have to deal with it :)

Unfortunately, this might take a few days to resolve.

quoted

-void mt76_wake_tx_queue(struct ieee80211_hw *hw, struct ieee80211_txq *txq)
+void mt76_wake_tx_queue(struct ieee80211_hw *hw)
 {
+	struct ieee80211_txq *txq;
 	struct mt76_dev *dev = hw->priv;
-	struct mt76_txq *mtxq = (struct mt76_txq *) txq->drv_priv;
-	struct mt76_queue *hwq = mtxq->hwq;
+	struct mt76_txq *mtxq;
+	struct mt76_queue *hwq;
 
+	txq = ieee80211_next_txq(hw);
+	mtxq = (struct mt76_txq *) txq->drv_priv;
+	hwq = mtxq->hwq;

Looks pretty much right to me - perhaps for safety there should be a
NULL check on txq, but OTOH when you get here it should be non-NULL.

Note that while this will fix compilation it probably won't work right.
next_txq() is not guaranteed to return the same txq as was previously
passed in the wake_tx_queue() argument, so if this is the only place the
driver calls next_txq(), things are likely going to break.

Rather, the driver should call next_txq() whenever it schedules queues
instead of doing its own internal scheduling.

Sorry for the inconvenience, I hadn't realized mt76 went in now.

Yeah, hadn't expected these streams to cross either. If Felix is looking
into this that is great; let me know if you need me to do anything else
on the mac80211 side. :)

-Toke