From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Keith A. Milner" Subject: Re: Attempting to understand odd snd-usb-audio code and behavior Date: Wed, 23 Aug 2017 23:43:49 +0100 Message-ID: <2465148.6KUvh8QIGJ@kamdesktop> References: <2006820.TBXnYHJvYE@kamdesktop> <1954362.aJMGcWAYHc@kamdesktop> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-wr0-f173.google.com (mail-wr0-f173.google.com [209.85.128.173]) by alsa0.perex.cz (Postfix) with ESMTP id A6C0F266A7C for ; Thu, 24 Aug 2017 00:43:52 +0200 (CEST) Received: by mail-wr0-f173.google.com with SMTP id f8so4645438wrf.3 for ; Wed, 23 Aug 2017 15:43:52 -0700 (PDT) Received: from kamdesktop.localnet (e.5.5.f.4.0.b.1.0.d.6.9.3.d.9.8.d.a.9.2.a.0.e.b.0.b.8.0.1.0.0.2.ip6.arpa. [2001:8b0:be0a:29ad:89d3:96d0:1b04:f55e]) by smtp.gmail.com with ESMTPSA id b96sm5016967wrd.94.2017.08.23.15.43.50 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 23 Aug 2017 15:43:50 -0700 (PDT) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org On Wednesday 23 Aug 2017 14:52:43 Clemens Ladisch wrote: > Keith A. Milner wrote: > >>> kernel: [ 1987.452947] usb 1-1: Unable to change format on ep #8e: > >>> already in use> > > So the error messages are due to a userspace app trying to open playback > > and capture at the same time? > > For this device, playback requires a running capture stream to determine > the rate of packets. This error happens when the application tries to > open the capture stream after the playback stream. (If the format does > not actually need to change, the error message is misleading.) > > Your actual problem is that the device does not send any capture packets. Thank you for the clarification. Hopefully I will find some time to explore this further. Cheers, Keith