From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 339DB2033E; Thu, 19 Oct 2023 13:03:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="J59Fvaoj" Received: from mgamail.intel.com (mgamail.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4002181; Thu, 19 Oct 2023 06:03:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1697720588; x=1729256588; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=VgSvxH67qt9LKjm5+c5G2G8wQo6a1gXmEAilB1I2dfg=; b=J59FvaojU1bLb52ZkemRWNSr2TKWEa6heGKHIxtRL7pWr497hF41kZ02 zX/nm8+i662p0+nI+A64m9GY28SrghRQhW1TEHFTHir8lrlsBAgOcCnRD mfylpcFwUjdw1lN7iKMDogrbOsBTBXUvC7anSeHyahCWQa7aM8MCmr7bz QJYWs8ra9nkm7LCYNHou7Ued6Ob4JMDHS3Q/ks/ahhleQsuSGwQ3orX5f 9dfq7JI8qwNsGo4feX+NJKAfP0HiRJziRrvI0fIXYziRznmTerMtRJI99 CLwXU5hO2RU9HQqI18amuJVd995IVSCZihfdt0oIhkA3kIKf6E0PU12KP A==; X-IronPort-AV: E=McAfee;i="6600,9927,10868"; a="385115720" X-IronPort-AV: E=Sophos;i="6.03,237,1694761200"; d="scan'208";a="385115720" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Oct 2023 06:01:48 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10868"; a="757014468" X-IronPort-AV: E=Sophos;i="6.03,237,1694761200"; d="scan'208";a="757014468" Received: from mttran4-mobl2.amr.corp.intel.com (HELO [10.213.160.204]) ([10.213.160.204]) by orsmga002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Oct 2023 06:01:45 -0700 Message-ID: Date: Wed, 18 Oct 2023 20:00:00 -0500 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 09/34] ASoC: qcom: qdsp6: Introduce USB AFE port to q6dsp To: Wesley Cheng , mathias.nyman@intel.com, gregkh@linuxfoundation.org, lgirdwood@gmail.com, broonie@kernel.org, perex@perex.cz, tiwai@suse.com, agross@kernel.org, andersson@kernel.org, konrad.dybcio@linaro.org, robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org, srinivas.kandagatla@linaro.org, bgoswami@quicinc.com, Thinh.Nguyen@synopsys.com Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org References: <20231017200109.11407-1-quic_wcheng@quicinc.com> <20231017200109.11407-10-quic_wcheng@quicinc.com> <7aa4ea87-9d1f-400a-bcc5-b56e5b4500c6@linux.intel.com> <2f05708e-3ee8-472e-a24f-6f3eb118133c@linux.intel.com> Content-Language: en-US From: Pierre-Louis Bossart In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit >>>>> Specifically, the QC ADSP can support all potential endpoints that are >>>>> exposed by the audio data interface.  This includes, feedback >>>>> endpoints >>>>> (both implicit and explicit) as well as the isochronous (data) >>>>> endpoints. >>>> >>>> implicit feedback means support for capture. This is confusing... >>>> >>> >>> I mean, a USB device can expose a capture path, but as of now, we won't >>> enable the offloading to the audio DSP for it.  However, if we're >>> executing playback, and device does support implicit feedback, we will >>> pass that along to the audio DSP to utilize. >> >> Not following. Implicit feedback means a capture stream *SHALL* be >> started. Are you saying this capture stream is hidden and handled at the >> DSP level only? If yes, what prevents you from exposing the capture >> stream to userspace as well? >> >> I must be missing something. >> > > My understanding is that with implicit feedback endpoints, it allows for > another data endpoint in the opposite direction to be utilized as a > feedback endpoint (versus having to expose another EP, such as in the > case of explicit feedback).  For example, if we are enabling the > playback path (and the device does have a capture data ep) then the data > ep used for the capture path can be used. That's right, so all the plumbing is enabled for the capture path... Making a decision to discard the data is very odd, all the work has already been done at lower levels, so why not expose the captured data?