1 files changed, 87 insertions, 2 deletions

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 2e51fb031ae0..6fa9115e322b 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -659,6 +659,9 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
 #define hwc_debug(fmt, args...) do { } while(0)
 #endif
 
+#define MAX_BUFFER_BYTES	(1024 * 1024)
+#define MAX_PERIOD_BYTES	(512 * 1024)
+
 static const struct snd_pcm_hardware snd_usb_hardware =
 {
 	.info =			SNDRV_PCM_INFO_MMAP |
@@ -669,9 +672,9 @@ static const struct snd_pcm_hardware snd_usb_hardware =
 				SNDRV_PCM_INFO_PAUSE,
 	.channels_min =		1,
 	.channels_max =		256,
-	.buffer_bytes_max =	1024 * 1024,
+	.buffer_bytes_max =	MAX_BUFFER_BYTES,
 	.period_bytes_min =	64,
-	.period_bytes_max =	512 * 1024,
+	.period_bytes_max =	MAX_PERIOD_BYTES,
 	.periods_min =		2,
 	.periods_max =		1024,
 };
@@ -971,6 +974,78 @@ static int hw_rule_periods_implicit_fb(struct snd_pcm_hw_params *params,
 				      ep->cur_buffer_periods);
 }
 
+/* get the adjusted max buffer (or period) bytes that can fit with the
+ * paired format for implicit fb
+ */
+static unsigned int
+get_adjusted_max_bytes(struct snd_usb_substream *subs,
+		       struct snd_usb_substream *pair,
+		       struct snd_pcm_hw_params *params,
+		       unsigned int max_bytes,
+		       bool reverse_map)
+{
+	const struct audioformat *fp, *pp;
+	unsigned int rmax = 0, r;
+
+	list_for_each_entry(fp, &subs->fmt_list, list) {
+		if (!fp->implicit_fb)
+			continue;
+		if (!reverse_map &&
+		    !hw_check_valid_format(subs, params, fp))
+			continue;
+		list_for_each_entry(pp, &pair->fmt_list, list) {
+			if (pp->iface != fp->sync_iface ||
+			    pp->altsetting != fp->sync_altsetting ||
+			    pp->ep_idx != fp->sync_ep_idx)
+				continue;
+			if (reverse_map &&
+			    !hw_check_valid_format(pair, params, pp))
+				break;
+			if (!reverse_map && pp->channels > fp->channels)
+				r = max_bytes * fp->channels / pp->channels;
+			else if (reverse_map && pp->channels < fp->channels)
+				r = max_bytes * pp->channels / fp->channels;
+			else
+				r = max_bytes;
+			rmax = max(rmax, r);
+			break;
+		}
+	}
+	return rmax;
+}
+
+/* Reduce the period or buffer bytes depending on the paired substream;
+ * when a paired configuration for implicit fb has a higher number of channels,
+ * we need to reduce the max size accordingly, otherwise it may become unusable
+ */
+static int hw_rule_bytes_implicit_fb(struct snd_pcm_hw_params *params,
+				     struct snd_pcm_hw_rule *rule)
+{
+	struct snd_usb_substream *subs = rule->private;
+	struct snd_usb_substream *pair;
+	struct snd_interval *it;
+	unsigned int max_bytes;
+	unsigned int rmax;
+
+	pair = &subs->stream->substream[!subs->direction];
+	if (!pair->ep_num)
+		return 0;
+
+	if (rule->var == SNDRV_PCM_HW_PARAM_PERIOD_BYTES)
+		max_bytes = MAX_PERIOD_BYTES;
+	else
+		max_bytes = MAX_BUFFER_BYTES;
+
+	rmax = get_adjusted_max_bytes(subs, pair, params, max_bytes, false);
+	if (!rmax)
+		rmax = get_adjusted_max_bytes(pair, subs, params, max_bytes, true);
+	if (!rmax)
+		return 0;
+
+	it = hw_param_interval(params, rule->var);
+	return apply_hw_params_minmax(it, 0, rmax);
+}
+
 /*
  * set up the runtime hardware information.
  */
@@ -1085,6 +1160,16 @@ static int setup_hw_info(struct snd_pcm_runtime *runtime, struct snd_usb_substre
 				  SNDRV_PCM_HW_PARAM_PERIODS, -1);
 	if (err < 0)
 		return err;
+	err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_BUFFER_BYTES,
+				  hw_rule_bytes_implicit_fb, subs,
+				  SNDRV_PCM_HW_PARAM_BUFFER_BYTES, -1);
+	if (err < 0)
+		return err;
+	err = snd_pcm_hw_rule_add(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_BYTES,
+				  hw_rule_bytes_implicit_fb, subs,
+				  SNDRV_PCM_HW_PARAM_PERIOD_BYTES, -1);
+	if (err < 0)
+		return err;
 
 	return 0;
 }