diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h
index 7eecc99..0aa955aa8 100644
--- a/include/uapi/sound/asound.h
+++ b/include/uapi/sound/asound.h
@@ -429,9 +429,14 @@ struct snd_pcm_sw_params {
 	snd_pcm_uframes_t avail_min;		/* min avail frames for wakeup */
 	snd_pcm_uframes_t xfer_align;		/* obsolete: xfer size need to be a multiple */
 	snd_pcm_uframes_t start_threshold;	/* min hw_avail frames for automatic start */
-	snd_pcm_uframes_t stop_threshold;	/* min avail frames for automatic stop */
-	snd_pcm_uframes_t silence_threshold;	/* min distance from noise for silence filling */
-	snd_pcm_uframes_t silence_size;		/* silence block size */
+	/*
+	 * The following two thresholds alleviate playback buffer underruns; when
+	 * hw_avail drops below the threshold, the respective action is triggered:
+	 */
+	snd_pcm_uframes_t stop_threshold;	/* - stop playback */
+	snd_pcm_uframes_t silence_threshold;	/* - pre-fill buffer with silence */
+	snd_pcm_uframes_t silence_size;		/* max size of silence pre-fill; when >= boundary,
+						 * fill played area with silence immediately */
 	snd_pcm_uframes_t boundary;		/* pointers wrap point */
 	unsigned int proto;			/* protocol version */
 	unsigned int tstamp_type;		/* timestamp type (req. proto >= 2.0.12) */