Commit 722f7911 authored by Wesley Cheng's avatar Wesley Cheng Committed by Greg Kroah-Hartman
Browse files

ALSA: usb-audio: Allow for rediscovery of connected USB SND devices 



In case of notifying SND platform drivers of connection events, some of
these use cases, such as offloading, require an ASoC USB backend device to
be initialized before the events can be handled.  If the USB backend device
has not yet been probed, this leads to missing initial USB audio device
connection events.

Expose an API that traverses the usb_chip array for connected devices, and
to call the respective connection callback registered to the SND platform
driver.

Signed-off-by: default avatarWesley Cheng <quic_wcheng@quicinc.com>
Acked-by: default avatarMark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20250409194804.3773260-14-quic_wcheng@quicinc.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 74914dc1

sound/usb/card.c

+21 −0
Original line number Diff line number Diff line
@@ -155,6 +155,27 @@ int snd_usb_unregister_platform_ops(void) 
}

EXPORT_SYMBOL_GPL(snd_usb_unregister_platform_ops);



/*

 * in case the platform driver was not ready at the time of USB SND

 * device connect, expose an API to discover all connected USB devices

 * so it can populate any dependent resources/structures.

 */

void snd_usb_rediscover_devices(void)

{

	int i;



	guard(mutex)(&register_mutex);



	if (!platform_ops || !platform_ops->connect_cb)

		return;



	for (i = 0; i < SNDRV_CARDS; i++) {

		if (usb_chip[i])

			platform_ops->connect_cb(usb_chip[i]);

	}

}

EXPORT_SYMBOL_GPL(snd_usb_rediscover_devices);



/*

 * Checks to see if requested audio profile, i.e sample rate, # of

 * channels, etc... is supported by the substream associated to the

sound/usb/card.h

+2 −0
Original line number Diff line number Diff line
@@ -222,4 +222,6 @@ snd_usb_find_suppported_substream(int card_idx, struct snd_pcm_hw_params *params 


int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops);

int snd_usb_unregister_platform_ops(void);



void snd_usb_rediscover_devices(void);

#endif /* __USBAUDIO_CARD_H */