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08 May 2024 06:16:12 -0700 Message-ID: <1e98935e-e35a-49e0-bbbf-ff326d40b581@linux.intel.com> Date: Tue, 7 May 2024 16:20:26 -0500 Precedence: bulk X-Mailing-List: linux-kernel@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> Content-Language: en-US From: Pierre-Louis Bossart In-Reply-To: <20240507195116.9464-23-quic_wcheng@quicinc.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit > 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?