Re: [PATCH v4 26/32] sound: Pass USB SND card and PCM information to SOC USB

Hi Pierre,

On 7/25/2023 1:59 AM, Pierre-Louis Bossart wrote:

On 7/25/23 04:34, 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. The USB backend should know about which sound resources are being shared between the ASoC and USB SND paths. This can be utilized to properly select and maintain the offloading devices.

Signed-off-by: Wesley Cheng quic_wcheng@quicinc.com

include/sound/soc-usb.h | 9 +++++---- sound/soc/qcom/qdsp6/q6usb.c | 20 ++++++++++++++++++-- sound/soc/soc-usb.c | 12 +++++++----- sound/usb/qcom/qc_audio_offload.c | 9 +++++---- 4 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/include/sound/soc-usb.h b/include/sound/soc-usb.h index 71e6e75e600a..606128332044 100644 --- a/include/sound/soc-usb.h +++ b/include/sound/soc-usb.h @@ -19,20 +19,21 @@ struct snd_soc_usb { struct device *dev; struct snd_soc_component *component; int (*connection_status_cb)(struct snd_soc_usb *usb, int card_idx,

• 		int connected);
  

• 		int chip_idx, int num_pcm, int connected);
  

I don't know what 'chip_idx' is.

chip_idx is the index to the USB SND chip array which carries information about each udev (USB device) connected to USB SND)

The 'num_pcm' sounds problematic if there are different devices for playback and capture. I would guess this is for playback only, but this doesn't scale.

I agree. My plan is to address this by having another SND SOC USB structure that is created by the USB class driver, ie qc_usb_offload, which would populate the required parameters.

Main thing I wanted to avoid is to have to expose the main USB SND structure if we're only going to only have a few variables to check for.

...

void *priv_data; };

...

+struct q6usb_status {

• unsigned int num_pcm;
• unsigned int chip_index;
• unsigned int pcm_index;

+};

• struct q6usb_port_data { struct q6afe_usb_cfg usb_cfg; struct snd_soc_usb *usb; struct q6usb_offload priv;
• unsigned long available_card_slot;

what is a card slot?

Idea was just to have a bitmapped value of all offload capable audio devices that are currently connected. Then we can take the necessary actions when everything has been disconnected.

...

• struct q6usb_status status[SNDRV_CARDS]; int active_idx; };

@@ -97,7 +105,7 @@ static int q6usb_audio_ports_of_xlate_dai_name(struct snd_soc_component *compone }

static int q6usb_alsa_connection_cb(struct snd_soc_usb *usb, int card_idx,

• 	int connected)
  

• 	int chip_idx, int num_pcm, int connected)
  

  { struct snd_soc_dapm_context *dapm; struct q6usb_port_data *data;

@@ -109,8 +117,16 @@ static int q6usb_alsa_connection_cb(struct snd_soc_usb *usb, int card_idx, snd_soc_dapm_enable_pin(dapm, "USB_RX_BE"); /* We only track the latest USB headset plugged in */ data->active_idx = card_idx;

• set_bit(card_idx, &data->available_card_slot);
  

• data->status[card_idx].num_pcm = num_pcm;
  

• data->status[card_idx].chip_index = chip_idx;
  

  } else {

• snd_soc_dapm_disable_pin(dapm, "USB_RX_BE");
  

• clear_bit(card_idx, &data->available_card_slot);
  

• data->status[card_idx].num_pcm = 0;
  

• data->status[card_idx].chip_index = 0;
  

• if (!data->available_card_slot)
  

• 	snd_soc_dapm_disable_pin(dapm, "USB_RX_BE");
  

not able to follow what this does, this patch is rather unclear and lacks comments.

I will add comments, but it basically will populate some of the limits that we'll end up using for controlling the ksndcontrols.

Thanks Wesley Cheng