netdev - Re: [PATCH 3/4] net: w5100: enable to support sleepable register access interface

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Date:	Sat, 2 Apr 2016 01:42:44 +0900
From:	Akinobu Mita <akinobu.mita@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>,
	Mike Sinkovsky <msink@...monline.ru>
Subject: Re: [PATCH 3/4] net: w5100: enable to support sleepable register
 access interface

2016-04-01 4:30 GMT+09:00 David Miller <davem@...emloft.net>:
> From: Akinobu Mita <akinobu.mita@...il.com>
> Date: Thu, 31 Mar 2016 01:38:39 +0900
>
>> +     struct sk_buff_head tx_queue;
>
> The way the queueing works in this driver is that it is only possible
> to have one SKB being transmitted at one time.
>
> This is evident by how the driver immediately stops the TX queue when
> it is given a new packet to transmit, and this is woken up by the TX
> completion IRQ.
>
> So don't use a queue here, just use a plain single pointer.
>
> The SKB queue you're using here is going to also do locking which is
> even more unnecessary overhead.

Thanks for spotting this.  Using a single pointer works fine.

Maybe we can support sending multiple packets at a time, but it should be
another separated patch.