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Date: Tue, 06 Aug 2002 13:09:16 +0200
From: Marcin Dalecki <dalecki@evision.ag>
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To: Jens Axboe <axboe@suse.de>
CC: martin@dalecki.de, Petr Vandrovec <VANDROVE@vc.cvut.cz>,
       linux-kernel@vger.kernel.org, torvalds@transmeta.com
Subject: Re: [PATCH] 2.5.30 IDE 113
References: <13A77E76028@vcnet.vc.cvut.cz> <3D4FA2F8.2050305@evision.ag> <20020806104238.GB1132@suse.de> <3D4FA845.90702@evision.ag> <20020806105450.GD1323@suse.de> <3D4FAA87.8040303@evision.ag> <20020806110548.GF1323@suse.de>
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Uz.ytkownik Jens Axboe napisa?:
> On Tue, Aug 06 2002, Marcin Dalecki wrote:
> 
>>Uz.ytkownik Jens Axboe napisa?:
>>
>>>On Tue, Aug 06 2002, Marcin Dalecki wrote:
>>>
>>>
>>>>Uz.ytkownik Jens Axboe napisa?:
>>>>
>>>>
>>>>>On Tue, Aug 06 2002, Marcin Dalecki wrote:
>>>>>
>>>>>
>>>>>
>>>>>>device not per channel! If q->request_fn would properly return the
>>>>>>error count instead of void, we could even get rid ot the
>>>>>>checking for rq->errors after finishment... But well that's
>>>>>>entierly different story.
>>>>>
>>>>>
>>>>>That's nonsense! What exactly would you return from a request_fn after
>>>>>having queued, eg, 20 commands? Error count is per request, anything
>>>>>else would be stupid.
>>>>
>>>>Returning the error count in the case q->request_fn is called for
>>>>a self submitted request like for example REQ_SPECIAL would be handy and 
>>>>well defined. For the cumulative case it would of course make sense to 
>>>>return the cumulative error count. Tough not very meaningfull, it would
>>>>indicate the occurrence of the error very fine.
>>>
>>>
>>>It's much nicer to maintain a sane API that doesn't depend on stuff like
>>>the above. Cumulative error count, come on, you can't possibly be
>>>serious?!
>>
>>Hey don't get me wrong - I *do not* suggest adding it becouse I don't 
>>think we are going to change the "eat as many as possible requests" 
>>instead of "eat one request" semantics of the q->reuqest_fn().
>>OK?
> 
> 
> You look from the IDE perspective, I look from the interface
> perspective. There's is no "eat one request" semantic of request_fn(),
> in fact there's just the opposite. If you quit after having just
> consumed one request, you must make sure to invoke request_fn _yourself_
> later on -- or use the recent blk_start/stop_queue helpers.

Yes of course I know that there is not "eat one request" semantic of
request_fn(). However looking at the interface perspective (out of my
small corner) I think the above is precisely what leads to ugly things
(and I think you will agree that this is ugly) like calling 
do_ide_request() back out from ata_irq_handler() - shrug.

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