In case the USB backend device has not been initialized/probed, USB SND device connections can still occur. When the USB backend is eventually made available, previous USB SND device connections are not communicated to the USB backend. Call snd_usb_rediscover_devices() to generate the connect callbacks for all USB SND devices connected. This will allow for the USB backend to be updated with the current set of devices available.
The chip array entries are all populated and removed while under the register_mutex, so going over potential race conditions:
Thread#1: q6usb_component_probe() --> snd_soc_usb_add_port() --> snd_usb_rediscover_devices() --> mutex_lock(register_mutex)
Thread#2 --> usb_audio_disconnect() --> mutex_lock(register_mutex)
So either thread#1 or thread#2 will complete first. If
Thread#1 completes before thread#2: SOC USB will notify DPCM backend of the device connection. Shortly after, once thread#2 runs, we will get a disconnect event for the connected device.
Thread#2 completes before thread#1: Then during snd_usb_rediscover_devices() it won't notify of any connection for that particular chip index.
Signed-off-by: Wesley Cheng quic_wcheng@quicinc.com --- sound/soc/soc-usb.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/sound/soc/soc-usb.c b/sound/soc/soc-usb.c index 619f9bfd6999..7df7f93cf5a2 100644 --- a/sound/soc/soc-usb.c +++ b/sound/soc/soc-usb.c @@ -115,6 +115,8 @@ struct snd_soc_usb *snd_soc_usb_add_port(struct device *dev, void *priv, list_add_tail(&usb->list, &usb_ctx_list); mutex_unlock(&ctx_mutex);
+ snd_usb_rediscover_devices(); + return usb; } EXPORT_SYMBOL_GPL(snd_soc_usb_add_port);