netdev - Re: [PATCH] bgmac: driver for GBit MAC core on BCMA bus

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Message-ID: <CACna6ry4fQCvh_hSKooNi1Lq=ftjVD=tNeDijnfW1gnnvGzLeQ@mail.gmail.com>
Date:	Sat, 5 Jan 2013 13:08:37 +0100
From:	Rafał Miłecki <zajec5@...il.com>
To:	Francois Romieu <romieu@...zoreil.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] bgmac: driver for GBit MAC core on BCMA bus

2013/1/3 Francois Romieu <romieu@...zoreil.com>:
> Rafał Miłecki <zajec5@...il.com> :
>> > The driver should stop queueing after its processing if it detects that
>> > it can't handle more requests.
>>
>> I think it's what the code does... netif_stop_queue and return
>> NETDEV_TX_BUSY. Anything wrong about it?
>
> The driver does not hold its promise to send the packet. It should
> netif_stop_queue and return NETDEV_TX_OK after the last transmitted
> packet.

We really need some good explanation for NETDEV_TX_BUSY somewhere
(documentation!).

I've checked some drivers and:

1) b44.c
In case of:
> if (unlikely(TX_BUFFS_AVAIL(bp) < 1)) {
it does netif_stop_queue and returns NETDEV_TX_BUSY

2) sky2.c
In case of:
> if (unlikely(tx_avail(sky2) < tx_le_req(skb)))
it just returns NETDEV_TX_BUSY

3) jme.2
In case of:
> if (unlikely(idx < 0)) {
it does netif_stop_queue and returns NETDEV_TX_BUSY

4) de2104x.c
In case of:
> if (tx_free == 0) {
it does netif_stop_queue and returns NETDEV_TX_BUSY

So there are many drivers doing the same mistake I did.

-- 
Rafał
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