[PATCH 2/2] ALSA: usb-audio: Update Babyface Pro control caches only after successful writes

["Cássio Gabriel" <cassiogabrielcontato@gmail.com>]

snd_bbfpro_ctl_put() and snd_bbfpro_vol_put()
cache the requested packed control state in
kcontrol->private_value before issuing the USB write.

Their get and resume paths use that cached value directly,
so a failed write can leave the driver reporting and later
replaying a setting the hardware never accepted.

Update the cached state only after a successful USB write.

Fixes: 3e8f3bd04716 ("ALSA: usb-audio: RME Babyface Pro mixer patch")
Cc: stable@vger.kernel.org
Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
---
 sound/usb/mixer_quirks.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c
index 229be55e9158..99975c3240a5 100644
--- a/sound/usb/mixer_quirks.c
+++ b/sound/usb/mixer_quirks.c
@@ -3027,12 +3027,14 @@ static int snd_bbfpro_ctl_put(struct snd_kcontrol *kcontrol,
 	if (val == old_value)
 		return 0;
 
+	err = snd_bbfpro_ctl_update(mixer, reg, idx, val);
+	if (err < 0)
+		return err;
+
 	kcontrol->private_value = reg
 		| ((idx & SND_BBFPRO_CTL_IDX_MASK) << SND_BBFPRO_CTL_IDX_SHIFT)
 		| ((val & SND_BBFPRO_CTL_VAL_MASK) << SND_BBFPRO_CTL_VAL_SHIFT);
-
-	err = snd_bbfpro_ctl_update(mixer, reg, idx, val);
-	return err < 0 ? err : 1;
+	return 1;
 }
 
 static int snd_bbfpro_ctl_resume(struct usb_mixer_elem_list *list)
@@ -3217,11 +3219,13 @@ static int snd_bbfpro_vol_put(struct snd_kcontrol *kcontrol,
 
 	new_val = uvalue & SND_BBFPRO_MIXER_VAL_MASK;
 
+	err = snd_bbfpro_vol_update(mixer, idx, new_val);
+	if (err < 0)
+		return err;
+
 	kcontrol->private_value = idx
 		| (new_val << SND_BBFPRO_MIXER_VAL_SHIFT);
-
-	err = snd_bbfpro_vol_update(mixer, idx, new_val);
-	return err < 0 ? err : 1;
+	return 1;
 }
 
 static int snd_bbfpro_vol_resume(struct usb_mixer_elem_list *list)

-- 
2.54.0