+/*
+ * Helper function to walk the array of sample rate triplets reported by
+ * the device. The problem is that we need to parse whole array first to
+ * get to know how many sample rates we have to expect.
+ * Then fp->rate_table can be allocated and filled.
+ */
+static int parse_uac2_sample_rate_range(struct audioformat *fp, int nr_triplets,
+ const unsigned char *data)
+{
+ int i, nr_rates = 0;
+
+ fp->rates = fp->rate_min = fp->rate_max = 0;
+
+ for (i = 0; i < nr_triplets; i++) {
+ int min = combine_quad(&data[2 + 12 * i]);
+ int max = combine_quad(&data[6 + 12 * i]);
+ int res = combine_quad(&data[10 + 12 * i]);
+ int rate;
+
+ if ((max < 0) || (min < 0) || (res < 0) || (max < min))
+ continue;
+
+ /*
+ * for ranges with res == 1, we announce a continuous sample
+ * rate range, and this function should return 0 for no further
+ * parsing.
+ */
+ if (res == 1) {
+ fp->rate_min = min;
+ fp->rate_max = max;
+ fp->rates = SNDRV_PCM_RATE_CONTINUOUS;
+ return 0;
+ }
+
+ for (rate = min; rate <= max; rate += res) {
+ if (fp->rate_table)
+ fp->rate_table[nr_rates] = rate;
+ if (!fp->rate_min || rate < fp->rate_min)
+ fp->rate_min = rate;
+ if (!fp->rate_max || rate > fp->rate_max)
+ fp->rate_max = rate;
+ fp->rates |= snd_pcm_rate_to_rate_bit(rate);
+
+ nr_rates++;
+
+ /* avoid endless loop */
+ if (res == 0)
+ break;
+ }
+ }
+
+ return nr_rates;
+}
+