ALSA: usb-audio - Fix non-continuous rate detection

The detection of non-continuous rates (given via rate tables) isn't
processed properly (e.g. for type II).

This patch fixes and simplifies the detection code.

Tested-by: Joris van Rantwijk <jorispubl@xs4all.nl>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/usbaudio.c

@@ -2524,32 +2524,33 @@ static int parse_audio_format_rates(struct snd_usb_audio *chip, struct audioform
 		 * build the rate table and bitmap flags
 		 */
 		int r, idx;
-		unsigned int nonzero_rates = 0;
 
 		fp->rate_table = kmalloc(sizeof(int) * nr_rates, GFP_KERNEL);
 		if (fp->rate_table == NULL) {
 			snd_printk(KERN_ERR "cannot malloc\n");
 			return -1;
 		}
 
-		fp->nr_rates = nr_rates;
-		fp->rate_min = fp->rate_max = combine_triple(&fmt[8]);
+		fp->nr_rates = 0;
+		fp->rate_min = fp->rate_max = 0;
 		for (r = 0, idx = offset + 1; r < nr_rates; r++, idx += 3) {
 			unsigned int rate = combine_triple(&fmt[idx]);
+			if (!rate)
+				continue;
 			/* C-Media CM6501 mislabels its 96 kHz altsetting */
 			if (rate == 48000 && nr_rates == 1 &&
 			    chip->usb_id == USB_ID(0x0d8c, 0x0201) &&
 			    fp->altsetting == 5 && fp->maxpacksize == 392)
 				rate = 96000;
-			fp->rate_table[r] = rate;
-			nonzero_rates |= rate;
-			if (rate < fp->rate_min)
+			fp->rate_table[fp->nr_rates] = rate;
+			if (!fp->rate_min || rate < fp->rate_min)
 				fp->rate_min = rate;
-			else if (rate > fp->rate_max)
+			if (!fp->rate_max || rate > fp->rate_max)
 				fp->rate_max = rate;
 			fp->rates |= snd_pcm_rate_to_rate_bit(rate);
+			fp->nr_rates++;
 		}
-		if (!nonzero_rates) {
+		if (!fp->nr_rates) {
 			hwc_debug("All rates were zero. Skipping format!\n");
 			return -1;
 		}