1 files changed, 99 insertions, 7 deletions

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 769821c30031..c6593101c049 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -454,6 +454,103 @@ add_sync_ep:
 }
 
 /*
+ * Return the score of matching two audioformats.
+ * Veto the audioformat if:
+ * - It has no channels for some reason.
+ * - Requested PCM format is not supported.
+ * - Requested sample rate is not supported.
+ */
+static int match_endpoint_audioformats(struct audioformat *fp,
+        struct audioformat *match, int rate,
+        snd_pcm_format_t pcm_format)
+{
+        int i;
+        int score = 0;
+
+        if (fp->channels < 1) {
+                snd_printdd("%s: (fmt @%p) no channels\n", __func__, fp);
+                return 0;
+        }
+
+        if (!(fp->formats & (1ULL << pcm_format))) {
+                snd_printdd("%s: (fmt @%p) no match for format %d\n", __func__,
+                        fp, pcm_format);
+                return 0;
+        }
+
+        for (i = 0; i < fp->nr_rates; i++) {
+                if (fp->rate_table[i] == rate) {
+                        score++;
+                        break;
+                }
+        }
+        if (!score) {
+                snd_printdd("%s: (fmt @%p) no match for rate %d\n", __func__,
+                        fp, rate);
+                return 0;
+        }
+
+        if (fp->channels == match->channels)
+                score++;
+
+        snd_printdd("%s: (fmt @%p) score %d\n", __func__, fp, score);
+
+        return score;
+}
+
+/*
+ * Configure the sync ep using the rate and pcm format of the data ep.
+ */
+static int configure_sync_endpoint(struct snd_usb_substream *subs)
+{
+        int ret;
+        struct audioformat *fp;
+        struct audioformat *sync_fp = NULL;
+        int cur_score = 0;
+        int sync_period_bytes = subs->period_bytes;
+        struct snd_usb_substream *sync_subs =
+                &subs->stream->substream[subs->direction ^ 1];
+
+        /* Try to find the best matching audioformat. */
+        list_for_each_entry(fp, &sync_subs->fmt_list, list) {
+                int score = match_endpoint_audioformats(fp, subs->cur_audiofmt,
+                        subs->cur_rate, subs->pcm_format);
+
+                if (score > cur_score) {
+                        sync_fp = fp;
+                        cur_score = score;
+                }
+        }
+
+        if (unlikely(sync_fp == NULL)) {
+                snd_printk(KERN_ERR "%s: no valid audioformat for sync ep %x found\n",
+                        __func__, sync_subs->ep_num);
+                return -EINVAL;
+        }
+
+        /*
+         * Recalculate the period bytes if channel number differ between
+         * data and sync ep audioformat.
+         */
+        if (sync_fp->channels != subs->channels) {
+                sync_period_bytes = (subs->period_bytes / subs->channels) *
+                        sync_fp->channels;
+                snd_printdd("%s: adjusted sync ep period bytes (%d -> %d)\n",
+                        __func__, subs->period_bytes, sync_period_bytes);
+        }
+
+        ret = snd_usb_endpoint_set_params(subs->sync_endpoint,
+                                          subs->pcm_format,
+                                          sync_fp->channels,
+                                          sync_period_bytes,
+                                          subs->cur_rate,
+                                          sync_fp,
+                                          NULL);
+
+        return ret;
+}
+
+/*
  * configure endpoint params
  *
  * called  during initial setup and upon resume
@@ -475,13 +572,8 @@ static int configure_endpoint(struct snd_usb_substream *subs)
                 return ret;
 
         if (subs->sync_endpoint)
-                ret = snd_usb_endpoint_set_params(subs->sync_endpoint,
-                                                  subs->pcm_format,
-                                                  subs->channels,
-                                                  subs->period_bytes,
-                                                  subs->cur_rate,
-                                                  subs->cur_audiofmt,
-                                                  NULL);
+                ret = configure_sync_endpoint(subs);
+
         return ret;
 }