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Message-ID: <54b79b7b-49e6-418e-9a6b-11bcbada8398@linux.intel.com>
Date: Tue, 7 May 2024 16:26:09 -0500
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Subject: Re: [PATCH v21 27/39] ASoC: Introduce SND kcontrols to select sound
 card and PCM device
To: Wesley Cheng <quic_wcheng@quicinc.com>, 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>
 <20240507195116.9464-28-quic_wcheng@quicinc.com>
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From: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
In-Reply-To: <20240507195116.9464-28-quic_wcheng@quicinc.com>
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On 5/7/24 14:51, Wesley Cheng wrote:
> Add SND kcontrol to SOC USB, which will allow for userpsace to determine
> which USB card number and PCM device to offload.  This allows for userspace
> to potentially tag an alternate path for a specific USB SND card and PCM
> device.  Previously, control was absent, and the offload path would be
> enabled on the last USB SND device which was connected.  This logic will
> continue to be applicable if no mixer input is received for specific device
> selection.
> 
> An example to configure the offload device using tinymix:
> tinymix -D 0 set 'USB Offload Playback Route Select' 1 0
> 
> The above command will configure the offload path to utilize card#1 and PCM
> stream#0.

I don't know how this is usable in practice. Using card indices is
really hard to do, it depends on the order in which devices are
plugged-in...