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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 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 Message-ID-Hash: 3BOFIPSPOZ6AND7PLCDCHTWIOM5QRVHQ X-Message-ID-Hash: 3BOFIPSPOZ6AND7PLCDCHTWIOM5QRVHQ X-MailFrom: pierre-louis.bossart@linux.intel.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-alsa-devel.alsa-project.org-0; header-match-alsa-devel.alsa-project.org-1; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.8 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: >>>>> 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?