From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Mack Subject: Re: [PATCH v5] ALSA: usb: Work around CM6631 sample rate change bug Date: Wed, 27 Mar 2013 12:52:14 +0100 Message-ID: <5152DD6E.6040707@gmail.com> References: <20130326211004.GD18838@pvv.ntnu.no> <5152C53D.5060604@ladisch.de> <20130327114703.GE18838@pvv.ntnu.no> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-we0-f173.google.com (mail-we0-f173.google.com [74.125.82.173]) by alsa0.perex.cz (Postfix) with ESMTP id C597F265162 for ; Wed, 27 Mar 2013 12:52:10 +0100 (CET) Received: by mail-we0-f173.google.com with SMTP id t57so2988046wey.32 for ; Wed, 27 Mar 2013 04:52:10 -0700 (PDT) In-Reply-To: <20130327114703.GE18838@pvv.ntnu.no> 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: Torstein Hegge Cc: Takashi Iwai , alsa-devel@alsa-project.org, Clemens Ladisch List-Id: alsa-devel@alsa-project.org On 27.03.2013 12:47, Torstein Hegge wrote: > On Wed, Mar 27, 2013 at 11:09:01 +0100, Clemens Ladisch wrote: >> Torstein Hegge wrote: >>> The C-Media CM6631 USB receiver doesn't respond to changes in sample rate >>> while the interface is active. The same behavior is observed in other UAC2 >>> hardware like the VIA VT1731. >> >> Might it be possible that these devices have reset the interface (see >> UAC2 section 3.16.3), and that the driver hasn't noticed this because it >> doesn't handle Active Alternate Setting Control interrupts? > > If that was the case, wouldn't the device be in altsetting zero after > the sample rate set and not be able to output sound at all? And as long > as the current altsetting supports the target sample rate as reported in > /proc/asound/card1/stream0, Active Alternate Setting Control shouldn't > have to be invoked. You could just try and catch that currently unhandled interrupt. We should support that anyway at some point ... Daniel