From: Clemens Ladisch <clemens@ladisch.de>
To: Monty Montgomery <xiphmont@gmail.com>
Cc: alsa-devel@alsa-project.org
Subject: Re: A problem with USB audio devices and the UHCI scheduler
Date: Tue, 03 Jul 2012 19:47:04 +0200 [thread overview]
Message-ID: <4FF33018.2050701@ladisch.de> (raw)
In-Reply-To: <CACrD=+8BOOb=17Qs5k_2jZeEf_+N3U1dq2sm0PtwrWxkrouRLw@mail.gmail.com>
Monty Montgomery wrote:
> UHCI (and EHCI) use the endpoint's wMaxPacketSize for all bandwidth
> allocation. My device supports all of its sample rates on the same
> altset, with a wMaxPacketSize matching the highest (96kHz) rate. So,
> the HCD is reserving most of the USB bus's bandwidth regardless of the
> actual requirements.
>
> How should I approach fixing this in the driver?
You cannot fix it in the audio driver; bandwidth allocation is done in
the controller driver, and that one doesn't know that your device lies
about its bandwidth requirements.
> There's currently no means to communicate a desired bandwidth
> reservation to the HCD from USB audio, so I'd have to extend even the
> quirks.
The device is supposed to use alternate settings for this.
Can't you change its firmware?
Regards,
Clemens
next prev parent reply other threads:[~2012-07-03 17:47 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-30 1:05 A problem with USB audio devices and the UHCI scheduler Monty Montgomery
2012-07-03 17:47 ` Clemens Ladisch [this message]
2012-07-03 18:13 ` Monty Montgomery
2012-07-04 13:43 ` Clemens Ladisch
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