linux-kernel - Re: [PATCH v26 29/33] ALSA: usb-audio: qcom: Don't allow USB offload path if PCM device is in use

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Message-ID: <2a64c924-9957-4c53-bf93-a651d19c733f@quicinc.com>
Date: Tue, 3 Sep 2024 16:43:36 -0700
From: Wesley Cheng <quic_wcheng@...cinc.com>
To: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        <srinivas.kandagatla@...aro.org>, <mathias.nyman@...el.com>,
        <perex@...ex.cz>, <conor+dt@...nel.org>, <dmitry.torokhov@...il.com>,
        <corbet@....net>, <broonie@...nel.org>, <lgirdwood@...il.com>,
        <tiwai@...e.com>, <krzk+dt@...nel.org>, <Thinh.Nguyen@...opsys.com>,
        <bgoswami@...cinc.com>, <robh@...nel.org>,
        <gregkh@...uxfoundation.org>
CC: <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-sound@...r.kernel.org>, <linux-input@...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 v26 29/33] ALSA: usb-audio: qcom: Don't allow USB offload
 path if PCM device is in use

Hi Pierre,

On 8/30/2024 2:55 AM, Pierre-Louis Bossart wrote:
>
> On 8/29/24 21:41, Wesley Cheng wrote:
>> Add proper checks and updates to the USB substream once receiving a USB QMI
>> stream enable request.  If the substream is already in use from the non
>> offload path, reject the stream enable request.  In addition, update the
>> USB substream opened parameter when enabling the offload path, so the
>> non offload path can be blocked.
>>
>> Signed-off-by: Wesley Cheng <quic_wcheng@...cinc.com>
>> ---
>>  sound/usb/qcom/qc_audio_offload.c | 15 ++++++++++++++-
>>  1 file changed, 14 insertions(+), 1 deletion(-)
>>
>> diff --git a/sound/usb/qcom/qc_audio_offload.c b/sound/usb/qcom/qc_audio_offload.c
>> index e9f2fd6bbb41..0bd533f539e4 100644
>> --- a/sound/usb/qcom/qc_audio_offload.c
>> +++ b/sound/usb/qcom/qc_audio_offload.c
>> @@ -1482,12 +1482,17 @@ static void handle_uaudio_stream_req(struct qmi_handle *handle,
>>  		goto response;
>>  	}
>>  
>> +	mutex_lock(&chip->mutex);
>>  	if (req_msg->enable) {
>> -		if (info_idx < 0 || chip->system_suspend) {
>> +		if (info_idx < 0 || chip->system_suspend || subs->opened) {
>>  			ret = -EBUSY;
>> +			mutex_unlock(&chip->mutex);
>> +
>>  			goto response;
>>  		}
>> +		subs->opened = 1;
>>  	}
>> +	mutex_unlock(&chip->mutex);
>>  
>>  	if (req_msg->service_interval_valid) {
>>  		ret = get_data_interval_from_si(subs,
>> @@ -1509,6 +1514,11 @@ static void handle_uaudio_stream_req(struct qmi_handle *handle,
>>  		if (!ret)
>>  			ret = prepare_qmi_response(subs, req_msg, &resp,
>>  						   info_idx);
>> +		if (ret < 0) {
>> +			mutex_lock(&chip->mutex);
>> +			subs->opened = 0;
>> +			mutex_unlock(&chip->mutex);
>> +		}
>>  	} else {
>>  		info = &uadev[pcm_card_num].info[info_idx];
>>  		if (info->data_ep_pipe) {
>> @@ -1532,6 +1542,9 @@ static void handle_uaudio_stream_req(struct qmi_handle *handle,
>>  		}
>>  
>>  		disable_audio_stream(subs);
>> +		mutex_lock(&chip->mutex);
>> +		subs->opened = 0;
>> +		mutex_unlock(&chip->mutex);
>>  	}
>>  
>
> This sounds ok but I wonder why all this needs to be done in
> Qualcomm-specific layers instead of soc-usb?
>
This is to prevent conflicts within the non-offload/legacy USB SND path and the USB SND offload vendor driver.  Don't think we need to involve anything with ASoC in these checks.

Thanks

Wesley Cheng