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Date: Sun, 11 Feb 2024 23:58:31 -0800
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Subject: Re: [PATCH v14 20/53] ASoC: Add SOC USB APIs for adding an USB
 backend
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To: Takashi Iwai <tiwai@suse.de>
CC: <srinivas.kandagatla@linaro.org>, <mathias.nyman@intel.com>,
        <perex@perex.cz>, <conor+dt@kernel.org>, <corbet@lwn.net>,
        <lgirdwood@gmail.com>, <andersson@kernel.org>,
        <krzysztof.kozlowski+dt@linaro.org>, <gregkh@linuxfoundation.org>,
        <Thinh.Nguyen@synopsys.com>, <broonie@kernel.org>,
        <bgoswami@quicinc.com>, <tiwai@suse.com>, <robh+dt@kernel.org>,
        <konrad.dybcio@linaro.org>, <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: <20240208231406.27397-1-quic_wcheng@quicinc.com>
 <20240208231406.27397-21-quic_wcheng@quicinc.com>
 <87r0hl29ha.wl-tiwai@suse.de>
 <b007a78c-b8fb-83bc-3be6-963708182cee@quicinc.com>
 <875xywzqpp.wl-tiwai@suse.de>
From: Wesley Cheng <quic_wcheng@quicinc.com>
In-Reply-To: <875xywzqpp.wl-tiwai@suse.de>
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Hi Takashi,

On 2/10/2024 12:08 AM, Takashi Iwai wrote:
> On Fri, 09 Feb 2024 21:34:39 +0100,
> Wesley Cheng wrote:
>>
>> Hi Takashi,
>>
>> On 2/9/2024 2:54 AM, Takashi Iwai wrote:
>>> On Fri, 09 Feb 2024 00:13:33 +0100,
>>> Wesley Cheng wrote:
>>>>
>>>> Some platforms may have support for offloading USB audio devices to a
>>>> dedicated audio DSP.  Introduce a set of APIs that allow for management of
>>>> USB sound card and PCM devices enumerated by the USB SND class driver.
>>>> This allows for the ASoC components to be aware of what USB devices are
>>>> available for offloading.
>>>>
>>>> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
>>> (snip)
>>>> --- a/sound/soc/Makefile
>>>> +++ b/sound/soc/Makefile
>>>> @@ -1,5 +1,5 @@
>>>>    # SPDX-License-Identifier: GPL-2.0
>>>> -snd-soc-core-objs := soc-core.o soc-dapm.o soc-jack.o soc-utils.o soc-dai.o soc-component.o
>>>> +snd-soc-core-objs := soc-core.o soc-dapm.o soc-jack.o soc-usb.o soc-utils.o soc-dai.o soc-component.o
>>>>    snd-soc-core-objs += soc-pcm.o soc-devres.o soc-ops.o soc-link.o soc-card.o
>>>>    snd-soc-core-$(CONFIG_SND_SOC_COMPRESS) += soc-compress.o
>>>
>>> Do we really want to build this into ASoC core unconditionally?
>>> This is very specific to Qualcomm USB-offload stuff, so it's better to
>>> factor out.
>>>
>>
>> Ideally, the SOC USB part shouldn't be Qualcomm specific.  Since I
>> don't have access or insight into how other vendors are achieving the
>> same thing, I can only base the soc-usb layer to work with the
>> information that is required to get the audio stream up and running on
>> the QC platforms.  In its simplest form, its basically just a SW
>> entity that notifies ASoC components about changes occurring from USB
>> SND, and I think all vendors that have an ASoC based platform card
>> handling the offload will need this notification.
> 
> Yes, but it's not necessarily built into the snd-soc-core module at
> all, but can be split to another module, right?  Otherwise all
> machines must load this code even if it doesn't use at all.
> If this were common among various chips, it'd be worth to be merged
> into the default common module.  But I don't think that's the case.
> 

That's fair.  I'll make it a separate module and upload v15 tomorrow. 
Thanks for the explanation.

Thanks
Wesley Cheng