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 <sfr@canb.auug.org.au>
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 <sfr@canb.auug.org.au>
---
 drivers/net/wireless/mediatek/mt76/mt76.h |  2 +-
 drivers/net/wireless/mediatek/mt76/tx.c   | 10 +++++++---
 2 files changed, 8 insertions(+), 4 deletions(-)

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.

> -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.

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

johannes

Johannes Berg <johannes@sipsolutions.net> 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.
>
>> -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

Toke Høiland-Jørgensen <toke@toke.dk> writes:

>> Sorry for the inconvenience, I hadn't realized mt76 went in now.
>
> Yeah, hadn't expected these streams to cross either.

I did ask[1] if everyone are ok that I apply mt76 and I didn't get any
comments, I guess I need to make more noise next time when I'm applying
a new driver.

[1] https://lkml.kernel.org/r/87wp22jzzb.fsf@purkki.adurom.net

Kalle Valo <kvalo@codeaurora.org> writes:

> Toke Høiland-Jørgensen <toke@toke.dk> writes:
>
>>> Sorry for the inconvenience, I hadn't realized mt76 went in now.
>>
>> Yeah, hadn't expected these streams to cross either.
>
> I did ask[1] if everyone are ok that I apply mt76 and I didn't get any
> comments,

Huh, did actually see that. But was not aware that Johannes had already
merged my patches; have been caught up in other stuff since netdev, so
have not been paying that close attention... Sorry about that, should
have pointed out the potential conflict :)

> I guess I need to make more noise next time when I'm applying a new
> driver.

Yeah, I would like to request a marching band to my apartment next time,
please. I'll send you my address off list... ;)

-Toke