netdev - Re: [PATCH 3/6] pkt_sched: sch_generic: Add generic qdisc->ops->peek() implementation.

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Message-ID: <48F7AB16.6000101@gmail.com>
Date:	Thu, 16 Oct 2008 22:59:02 +0200
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Patrick McHardy <kaber@...sh.net>
CC:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [PATCH 3/6] pkt_sched: sch_generic: Add generic qdisc->ops->peek()
   implementation.

Patrick McHardy wrote, On 10/16/2008 02:45 PM:

> Jarek Poplawski wrote:
>> On Thu, Oct 16, 2008 at 02:19:37PM +0200, Patrick McHardy wrote:
>>> Jarek Poplawski wrote:
>>>> pkt_sched: sch_generic: Add generic qdisc->ops->peek() implementation.
>>>>
>>>> +	if (qops->peek == NULL)
>>>> +		qops->peek = noop_qdisc_ops.peek;
>>>>  	if (qops->dequeue == NULL)
>>>>  		qops->dequeue = noop_qdisc_ops.dequeue;
>>> ->dequeue and ->peek are somewhat tied together, so I think we should
>>> only use the noop variants if both are unset. Whether this should be
>>> checked here of before merging new qdiscs is a different question of
>>> course :)
>> Actually, there is much less users of ->peek. Do you mean to always check
>> for NULL before using? It was meant mainly for these non-work-conserving
>> qdisc in case patch 6/6 isn't merged. Of course, IMHO it should be enough
>> to implement this always (while merging), but this code above could be
>> misleading what is optional/mandatory. (Please make it clear which way do
>> you prefer and I'll redo, no problem.)
> 
> No, I meant that peek = noop_qdisc_ops.peek and dequeue = something_else
> doesn't make much sense. But I think declaring this an API usage error
> and catching it during review is fine.

As a matter of fact I treated this more symbolically: to declare the methods
which don't need checking. Is it possible to forget about ->dequeue()? And
after all, all qdisc but ingress declare this, so logically this could be
removed.

Jarek P.
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