Re: [PATCH v9 27/34] ALSA: usb-audio: qcom: Populate PCM and USB chip information

[Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>]

On 10/17/23 15:01, Wesley Cheng wrote:
> Currently, only the index to the USB SND card array is passed to the USB
> backend.  Pass through more information, specifically the USB SND card
> number and the number of PCM devices available.  This allows for the DPCM
> backend to determine what USB resources are available during situations,
> such as USB audio offloading.
> 
> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
> ---
>  sound/usb/qcom/qc_audio_offload.c | 21 ++++++++++++++++++---
>  1 file changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/sound/usb/qcom/qc_audio_offload.c b/sound/usb/qcom/qc_audio_offload.c
> index bd6b84f72c74..ae74098b41f5 100644
> --- a/sound/usb/qcom/qc_audio_offload.c
> +++ b/sound/usb/qcom/qc_audio_offload.c
> @@ -173,6 +173,21 @@ enum usb_qmi_audio_format {
>  	USB_QMI_PCM_FORMAT_U32_BE,
>  };
>  
> +static int usb_qmi_get_pcm_num(struct snd_usb_audio *chip, int direction)
> +{
> +	struct snd_usb_substream *subs = NULL;
> +	struct snd_usb_stream *as;
> +	int count = 0;
> +
> +	list_for_each_entry(as, &chip->pcm_list, list) {
> +		subs = &as->substream[direction];
> +		if (subs->ep_num)
> +			count++;
> +	}
> +
> +	return count;
> +}
> +
>  static enum usb_qmi_audio_device_speed_enum_v01
>  get_speed_info(enum usb_device_speed udev_speed)
>  {
> @@ -1592,6 +1607,8 @@ static void qc_usb_audio_offload_probe(struct snd_usb_audio *chip)
>  
>  	sdev->card_idx = chip->card->number;
>  	sdev->chip_idx = chip->index;
> +	sdev->num_playback = usb_qmi_get_pcm_num(chip, 0);
> +	sdev->num_capture = usb_qmi_get_pcm_num(chip, 1);
>  	uadev[chip->card->number].sdev = sdev;
>  
>  	uaudio_qdev->last_card_num = chip->card->number;
> @@ -1706,10 +1723,8 @@ static void qc_usb_audio_offload_disconnect(struct snd_usb_audio *chip)
>  	mutex_unlock(&chip->mutex);
>  
>  	atomic_dec(&uaudio_qdev->qdev_in_use);
> -	if (!atomic_read(&uaudio_qdev->qdev_in_use)) {
> -		snd_soc_usb_disconnect(usb_get_usb_backend(udev));

this also feels like a patch split issue, removing this
snd_soc_usb_disconnect() has nothing to do with the "populate PCM and
USB chip information" ?

> +	if (!atomic_read(&uaudio_qdev->qdev_in_use))
>  		qc_usb_audio_cleanup_qmi_dev();
> -	}
>  	mutex_unlock(&qdev_mutex);
>  }
>