linux-kernel - Re: [Linux-zigbee-devel] [PATCH 1/6] mac802154: Immediately retry sending failed packets

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Message-Id: <20130402.220315.1782012687105065631.davem@davemloft.net>
Date:	Tue, 02 Apr 2013 22:03:15 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	alan@...nal11.us
Cc:	werner@...esberger.net, netdev@...r.kernel.org,
	linux-zigbee-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [Linux-zigbee-devel] [PATCH 1/6] mac802154: Immediately retry
 sending failed packets

From: Alan Ott <alan@...nal11.us>
Date: Tue, 02 Apr 2013 21:59:37 -0400

> On 04/02/2013 09:56 PM, David Miller wrote:
>> From: Alan Ott <alan@...nal11.us>
>> Date: Tue, 02 Apr 2013 21:24:59 -0400
>>
>>> I like it for a couple of reasons.
>>> 1. Most supported devices have only single packet output buffer, so
>>> blocking in the driver is the most straight-forward way to handle it.
>>> The alternative is to make each driver have a workqueue for xmit() (to
>>> lift the blocking out from atomic context). This makes each driver simpler.
>>>
>>> 2. All of the flow control can be handled one time in the mac802154 layer.
>> We have a perfectly working flow control mechanism in the generic
>> networking queuing layer.  Please use it instead of inventing things.
> 
> I'm pretty sure that's what I'm doing in [1]. When I say "flow control
> can be handled," I mean managing calls to netif_stop_queue() and
> netif_wake_queue(). Is there something else I should be doing instead?

Then you shouldn't need workqueues if the generic netdev facilities
can do the flow control properly.

There are several ethernet devices that have a single transmit buffer
and function just fine, and optimally, solely using the transmit queue
stop/start/wake infrastructure.
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