From: Clemens Ladisch <clemens@ladisch.de>
To: Takashi Iwai <tiwai@suse.de>
Cc: Jiada Wang <jiada_wang@mentor.com>,
alsa-devel@alsa-project.org, apape@de.adit-jv.com,
linux-kernel@vger.kernel.org, Mark_Craske@mentor.com
Subject: Re: [alsa-devel] [PATCH 1/3 v1] ALSA: usb-audio: more tolerant packetsize
Date: Thu, 1 Dec 2016 12:50:39 +0100 [thread overview]
Message-ID: <c503960d-7a94-c9ef-d98a-72945c2a44a9@ladisch.de> (raw)
In-Reply-To: <s5heg1r28rp.wl-tiwai@suse.de>
Takashi Iwai wrote:
> Clemens Ladisch wrote:
>> Takashi Iwai wrote:
>>> [...]
>>> In the commit mentioned above, we changed the logic to take +25%
>>> frequency as the basis, and it my *reduce* if ep->maxpacksize is lower
>>> than that.
>>>
>>> OTOH, if ep->maxpacksize is sane, we can rely on it rather than the
>>> implicit +25% frequency. That said, maybe we can check
>>> ep->maxpacksize whether it fits within the expected range, then adapt
>>> it, or take +25% freq as fallback?
>>
>> You are describing how the current code behaves. The +25% limit _is_
>> what the code takes as the expected range.
>
> Well, the question is what is the "sane" range. +25% doesn't fit for
> some devices.
The USB audio specification _requires_ that there is as little jitter
as possible.
It's no surprise that some device violates the specification. But
we don't know what the actual error is; whether we could adjust the
packet size for this particular device only, or increase the limit
for all devices, or use a completely different workaround.
> If maxpacksize fits without +100% as this patch suggests, can we rely
> on it instead?
The packet size affect the following computations, like the number of
packets per URB. I don't know how bad the effects would be.
Regards,
Clemens
next prev parent reply other threads:[~2016-12-01 11:50 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-30 7:59 [PATCH 0/3 v1] usb-misc fix Jiada Wang
2016-11-30 7:59 ` [PATCH 1/3 v1] ALSA: usb-audio: more tolerant packetsize Jiada Wang
2016-11-30 8:54 ` Takashi Iwai
2016-12-01 7:04 ` Jiada Wang
2016-12-01 7:41 ` [alsa-devel] " Clemens Ladisch
2016-12-01 8:58 ` Takashi Iwai
2016-12-01 11:16 ` Clemens Ladisch
2016-12-01 11:23 ` Takashi Iwai
2016-12-01 11:50 ` Clemens Ladisch [this message]
[not found] ` <58400B3A.7080806@mentor.com>
2016-12-01 12:15 ` Clemens Ladisch
2016-11-30 7:59 ` [PATCH 2/3 v2] ALSA: usb-audio: avoid setting of sample rate multiple times on bus Jiada Wang
2016-11-30 8:51 ` Takashi Iwai
2016-12-01 7:07 ` Jiada Wang
2016-11-30 10:45 ` Takashi Sakamoto
2016-11-30 22:19 ` Takashi Sakamoto
2016-12-05 7:32 ` Jiada Wang
2016-12-05 9:58 ` Takashi Sakamoto
2016-11-30 7:59 ` [PATCH 3/3 v3] ALSA: usb-audio: fix race in snd_usb_endpoint_stop Jiada Wang
2016-11-30 9:00 ` Takashi Iwai
2016-12-05 10:10 ` Jiada Wang
2016-12-05 10:30 ` Takashi Iwai
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