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 e56826f1df71..ee566ca7c675 100644 --- a/sound/soc/soc-usb.c +++ b/sound/soc/soc-usb.c @@ -279,6 +279,8 @@ void snd_soc_usb_add_port(struct snd_soc_usb *usb) mutex_lock(&ctx_mutex); list_add_tail(&usb->list, &usb_ctx_list); mutex_unlock(&ctx_mutex); + + snd_usb_rediscover_devices(); } EXPORT_SYMBOL_GPL(snd_soc_usb_add_port);