linux-kernel - Re: snd-usb: "delay: estimated 0, actual 352"

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Date:	Thu, 06 Sep 2012 16:40:18 +0200
From:	Daniel Mack <zonque@...il.com>
To:	Takashi Iwai <tiwai@...e.de>
CC:	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, alsa-devel@...a-project.org,
	Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Subject: Re: snd-usb: "delay: estimated 0, actual 352"

On 06.09.2012 16:31, Takashi Iwai wrote:
> At Thu, 6 Sep 2012 15:17:58 +0200,
> Markus Trippelsdorf wrote:
>>
>> On 2012.09.06 at 15:08 +0200, Takashi Iwai wrote:
>>> At Thu, 6 Sep 2012 11:43:48 +0200,
>>> Markus Trippelsdorf wrote:
>>>>
>>>> On 2012.09.06 at 10:21 +0200, Takashi Iwai wrote:
>>>>> At Thu, 06 Sep 2012 09:35:26 +0200,
>>>>> Takashi Iwai wrote:
>>>>>
>>>>> In short, a patch like below may fix the issue (note: completely
>>>>> untested!)
>>>>
>>>> No it doesn't, unfortunately...
>>>
>>> OK, I start tracking down the problem a bit more deeply now.
>>>
>>> The issue happens when the first two URBs are passed to
>>> retire_playback_urb().  These are URBs filled before start_endpoints()
>>> are set, so they contain actually zero size.  Even though these are
>>> a sort of dummy packets, the driver still tries to check with the
>>> queued delay account, and gives bogus errors.
>>>
>>> So, essentially the messages are harmless and nothing to worry too
>>> much, but surely it doesn't look sexy.
>>>
>>> The patch below should fix the problem.  Please give it a try.
>>
>> Yes, your patch finally fixes the problem. 
>> Thank you Takashi-san.
> 
> Thanks for your quick test!
> 
> If Daniel has no objection with that patch, I'm going to merge it.

No objections from my side. I also gave it a quick test, and even though
I never saw the problem Markus was seeing, I agree to your findings.

Many thanks, everyone :)


Daniel

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