From mboxrd@z Thu Jan 1 00:00:00 1970 From: Clemens Ladisch Subject: Re: A problem with USB audio devices and the UHCI scheduler Date: Tue, 03 Jul 2012 19:47:04 +0200 Message-ID: <4FF33018.2050701@ladisch.de> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from out3-smtp.messagingengine.com (out3-smtp.messagingengine.com [66.111.4.27]) by alsa0.perex.cz (Postfix) with ESMTP id 7730E103F3B for ; Tue, 3 Jul 2012 19:47:45 +0200 (CEST) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: Monty Montgomery Cc: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org 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