[PATCH] ALSA: usb-audio: Disable sample read check if firmware doesn't give back

[Takashi Iwai]

Some buggy firmware don't give the current sample rate but leaves
zero.  Handle this case more gracefully without warning but just skip
the current rate verification from the next time.

Cc: <stable at vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 sound/usb/clock.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/sound/usb/clock.c b/sound/usb/clock.c
index e940dcee792b..31051f2be46d 100644
--- a/sound/usb/clock.c
+++ b/sound/usb/clock.c
@@ -534,6 +534,12 @@ static int set_sample_rate_v1(struct snd_usb_audio *chip,
 	}
 
 	crate = data[0] | (data[1] << 8) | (data[2] << 16);
+	if (!crate) {
+		dev_info(&dev->dev, "failed to read current rate; disabling the check\n");
+		chip->sample_rate_read_error = 3; /* three strikes, see above */
+		return 0;
+	}
+
 	if (crate != rate) {
 		dev_warn(&dev->dev, "current rate %d is different from the runtime rate %d\n", crate, rate);
 		// runtime->rate = crate;
-- 
2.26.2