Commit fca9c850 authored by Cássio Gabriel's avatar Cássio Gabriel Committed by Takashi Iwai
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ALSA: usb-audio: Avoid false E-MU sample-rate notifications 



snd_emuusb_set_samplerate() unconditionally notifies the E-MU
SampleRate Extension Unit control after issuing SET_CUR.

If snd_usb_mixer_set_ctl_value() fails, the control value has not
changed, yet snd_usb_mixer_notify_id() still invalidates the cache and
emits a value-change event to userspace.

Notify the control only after a successful write.

Fixes: 7d2b451e ("ALSA: usb-audio - Added functionality for E-mu 0404USB/0202USB/TrackerPre")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarCássio Gabriel <cassiogabrielcontato@gmail.com>
Link: https://patch.msgid.link/20260421-alsa-emuusb-samplerate-notify-v1-1-8b63bbc1d7f1@gmail.com


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent eacda758

sound/usb/mixer_quirks.c

+6 −4
Original line number Diff line number Diff line
@@ -1538,14 +1538,16 @@ void snd_emuusb_set_samplerate(struct snd_usb_audio *chip, 
{

	struct usb_mixer_interface *mixer;

	struct usb_mixer_elem_info *cval;

	int err;

	int unitid = 12; /* SampleRate ExtensionUnit ID */



	list_for_each_entry(mixer, &chip->mixer_list, list) {

		if (mixer->id_elems[unitid]) {

			cval = mixer_elem_list_to_info(mixer->id_elems[unitid]);

			snd_usb_mixer_set_ctl_value(cval, UAC_SET_CUR,

			err = snd_usb_mixer_set_ctl_value(cval, UAC_SET_CUR,

							  cval->control << 8,

							  samplerate_id);

			if (!err)

				snd_usb_mixer_notify_id(mixer, unitid);

			break;

		}