From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.16]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8F2647FBDF; Thu, 9 May 2024 19:56:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.16 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715284579; cv=none; b=X43Nk7gWBfCoV76OpeOQaBlZqNpWPiJ9HurT+4duJl6qIWlcedBpwGhKcQCptaJ2cmpKmp7xVqRrH3H/W5Z7K+woViuc8dujBMdCjMKh9ygNZhdnFNWfeekUkbpG+pGZpwf/GzyxkpROs3t1Ho3bfl30Ghz6xh2/cvD6NgUG2WU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715284579; c=relaxed/simple; bh=pqJGDudG3EtP+HKlIxczhzYllZ6fjisuemy8gyrPPqI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ClqJ5JACDxdYpLrHPERr8+tC2bF4AaSJliDANwcCVMojsfbRWNTestkQh6dHKAZ1qr1mJ1fm20KOGdHTzt8+p8qbXfSyzyoh4Lq6SF1Eu0RA+ftJU5AWKIAu6IieFJbfPwaXzIJhTmMB0/6IFMznprapXVi8fEAE+ifhDsCc6P0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=buzW5gge; arc=none smtp.client-ip=192.198.163.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="buzW5gge" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1715284578; x=1746820578; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=pqJGDudG3EtP+HKlIxczhzYllZ6fjisuemy8gyrPPqI=; b=buzW5ggew0mIN4l14a1zTP/tvPY7cs+Mc1UPn3H2eK6SZQo45OIGD1wz wkPYJSrtnAE0j4K5d1TJRXajkA8QXLX3UAmVgvIE+jxomacVtXXRwNNEu MolQXtEd+DK6aRsBkaswydCLTPBgXDfRnuXHyV00Tx5nNufwXQsb1QjF2 FXn4g+aW0zQHkJlfAmoQ0xBFDrQGCiaEDWP/ryxbN/A4eRjkZgEw+zAzu 1VnFllnIXdWtX6TimbQSYDt8pLF4BVR8xjWNZ80qmd91OTpmFRENV1IxW TOazwWVmKKfIzM20sPudChAtkAI1lxKr8AcRrcL74aicJqyrE++zRvG4d w==; X-CSE-ConnectionGUID: v90NA5gIRP6jZuPJLAcYDQ== X-CSE-MsgGUID: xb4zGuPQQEelwF022qCJiQ== X-IronPort-AV: E=McAfee;i="6600,9927,11068"; a="11454254" X-IronPort-AV: E=Sophos;i="6.08,148,1712646000"; d="scan'208";a="11454254" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by fmvoesa110.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 May 2024 12:56:17 -0700 X-CSE-ConnectionGUID: hRhLxpRCQlCZGrFg1s62Zg== X-CSE-MsgGUID: m1N3f5RbQ+yjnemil+4Tng== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.08,148,1712646000"; d="scan'208";a="34213076" Received: from ajunnare-mobl.amr.corp.intel.com (HELO [10.213.181.85]) ([10.213.181.85]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 May 2024 12:56:14 -0700 Message-ID: Date: Thu, 9 May 2024 08:01:04 -0500 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v21 22/39] ALSA: usb-audio: Prevent starting of audio stream if in use To: Wesley Cheng , srinivas.kandagatla@linaro.org, mathias.nyman@intel.com, perex@perex.cz, conor+dt@kernel.org, corbet@lwn.net, lgirdwood@gmail.com, andersson@kernel.org, krzk+dt@kernel.org, gregkh@linuxfoundation.org, Thinh.Nguyen@synopsys.com, broonie@kernel.org, bgoswami@quicinc.com, tiwai@suse.com, bagasdotme@gmail.com, robh@kernel.org, konrad.dybcio@linaro.org Cc: linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-sound@vger.kernel.org, linux-usb@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-doc@vger.kernel.org, alsa-devel@alsa-project.org References: <20240507195116.9464-1-quic_wcheng@quicinc.com> <20240507195116.9464-23-quic_wcheng@quicinc.com> <1e98935e-e35a-49e0-bbbf-ff326d40b581@linux.intel.com> <066fe096-a9d3-2498-275d-185f709e9a02@quicinc.com> Content-Language: en-US From: Pierre-Louis Bossart In-Reply-To: <066fe096-a9d3-2498-275d-185f709e9a02@quicinc.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 5/8/24 18:40, Wesley Cheng wrote: > Hi Pierre, > > On 5/7/2024 2:20 PM, Pierre-Louis Bossart wrote: >> >>> If a PCM device is already in use, the check will return an error to >>> userspace notifying that the stream is currently busy.  This ensures >>> that >>> only one path is using the USB substream. >> >> What was the point of having a "USB Mixer" then? > > The USB mixer is intended to enable/route the USB offloading path to the > audio DSP, and is for controlling the ASoC specific entities.  This > change is needed to resolve any contention between the USB SND PCM > device (non offload path) and the ASoC USB BE DAI (offload path). Not following, sorry. Is the "USB Mixer" some sort of hardware entity related to USB offload or just a pure DAPM processing widget handling volume and actual mixing between streams? I was trying to get clarity on whether there can be multiple streams mixed before going to the USB endpoint. The commit message "only one path is using the USB substream" is ambiguous, not sure if you are referring to mutual exclusion between offloaded and non-offloaded paths, or number of streams when offloaded is supported. Different concepts/levels.