Re: [PATCH v24 26/34] ALSA: usb-audio: qcom: Don't allow USB offload path if PCM device is in use

[Wesley Cheng <quic_wcheng@xxxxxxxxxxx>]

On 8/1/2024 1:57 AM, Pierre-Louis Bossart wrote:
>
> On 8/1/24 03:17, 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.
> It's a bit weird that the mutual exclusion between the standard path and
> the offloaded path is handled at the vendor level. I would think this
> needs to be handled in the soc_usb framework, no?
>
Hmm...I guess that make sense.  In the end, the mutual exclusion check would need to either be handled by the vendor USB offload driver, or the USB backend DAI link.  I could consider adding another SOC USB API to query for the USB PCM status.  If it is open/active, then just return with an error, or maybe just rename the snd_soc_usb_find_format() API to something more generic which checks for parameters and current status before allowing offloading to start (ie snd_soc_check_offload_available())

Thanks

Wesley Cheng

>> Signed-off-by: Wesley Cheng <quic_wcheng@xxxxxxxxxxx>
>> ---
>>  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 8b0913b7256b..3b46d05f1421 100644
>> --- a/sound/usb/qcom/qc_audio_offload.c
>> +++ b/sound/usb/qcom/qc_audio_offload.c
>> @@ -1460,12 +1460,17 @@ 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,
>> @@ -1487,6 +1492,11 @@ 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) {
>> @@ -1510,6 +1520,9 @@ 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);
>>  	}
>>  
>>  response: