linux-kernel - Re: [PATCH v20 33/41] ASoC: usb: Create SOC USB SND jack kcontrol

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Message-ID: <c8bd16e8-b204-471b-a702-36e14c8695c5@linux.intel.com>
Date: Fri, 26 Apr 2024 15:26:44 +0200
From: Amadeusz Sławiński
 <amadeuszx.slawinski@...ux.intel.com>
To: Wesley Cheng <quic_wcheng@...cinc.com>, srinivas.kandagatla@...aro.org,
 mathias.nyman@...el.com, perex@...ex.cz, conor+dt@...nel.org,
 corbet@....net, lgirdwood@...il.com, andersson@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, gregkh@...uxfoundation.org,
 Thinh.Nguyen@...opsys.com, broonie@...nel.org, bgoswami@...cinc.com,
 tiwai@...e.com, robh@...nel.org, konrad.dybcio@...aro.org
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
 linux-sound@...r.kernel.org, linux-usb@...r.kernel.org,
 linux-arm-msm@...r.kernel.org, linux-doc@...r.kernel.org,
 alsa-devel@...a-project.org
Subject: Re: [PATCH v20 33/41] ASoC: usb: Create SOC USB SND jack kcontrol

On 4/25/2024 11:51 PM, Wesley Cheng wrote:
> Expose API for creation of a jack control for notifying of available
> devices that are plugged in/discovered, and that support offloading.  This
> allows for control names to be standardized across implementations of USB
> audio offloading.
> 
> Signed-off-by: Wesley Cheng <quic_wcheng@...cinc.com>
> ---

(...)

>   /* SOC USB sound kcontrols */
> +/**
> + * snd_soc_usb_setup_offload_jack() - Create USB offloading jack
> + * @component: USB DPCM backend DAI component
> + * @jack: jack structure to create
> + *
> + * Creates a jack device for notifying userspace of the availability
> + * of an offload capable device.
> + *
> + * Returns 0 on success, negative on error.
> + *
> + */
> +int snd_soc_usb_setup_offload_jack(struct snd_soc_component *component,
> +					struct snd_soc_jack *jack)
> +{
> +	int ret;
> +
> +	ret = snd_soc_card_jack_new(component->card, "USB Offload Playback Jack",
> +					SND_JACK_HEADPHONE, jack);
> +	if (ret < 0) {
> +		dev_err(component->card->dev, "Unable to add USB offload jack\n");
> +		return ret;
> +	}
> +
> +	ret = snd_soc_component_set_jack(component, jack, NULL);
> +	if (ret) {
> +		dev_warn(component->card->dev, "Failed to set jack: %d\n", ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(snd_soc_usb_setup_offload_jack);
> +
>   static int snd_soc_usb_get_offload_card_status(struct snd_kcontrol *kcontrol,
>   				   struct snd_ctl_elem_value *ucontrol)
>   {
> 

I'm not sure if this should be handled in generic USB API, this feels 
like something that should be handled in specific device driver side, 
like all users currently do.

Anyway I think there should also be some function that tears jack down, 
by calling:
snd_soc_component_set_jack(component, NULL, NULL);
so it can get cleaned up properly?