From 7d297da104318d18ff6a219b94b0add10f705e99 Mon Sep 17 00:00:00 2001
From: Clemens Ladisch <clemens@ladisch.de>
Date: Mon, 26 Jan 2009 08:09:28 +0100
Subject: [PATCH] --- yaml --- r: 133210 b: refs/heads/master c:
 4d788e040b72d2a46ea3ba726b7fa0b65de06c88 h: refs/heads/master v: v3

---
 [refs]                     | 2 +-
 trunk/sound/usb/usbaudio.c | 9 ++++++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/[refs] b/[refs]
index 8538aa2fb0a5..331156dae4ce 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: b7eb4a06e9980973755b7e95a6d97fb8decbf8fd
+refs/heads/master: 4d788e040b72d2a46ea3ba726b7fa0b65de06c88
diff --git a/trunk/sound/usb/usbaudio.c b/trunk/sound/usb/usbaudio.c
index 417d557ed641..f3d4de23fedf 100644
--- a/trunk/sound/usb/usbaudio.c
+++ b/trunk/sound/usb/usbaudio.c
@@ -108,6 +108,7 @@ MODULE_PARM_DESC(ignore_ctl_error,
 #define MAX_URBS	8
 #define SYNC_URBS	4	/* always four urbs for sync */
 #define MIN_PACKS_URB	1	/* minimum 1 packet per urb */
+#define MAX_QUEUE	24	/* try not to exceed this queue length, in ms */
 
 struct audioformat {
 	struct list_head list;
@@ -1079,7 +1080,7 @@ static int init_substream_urbs(struct snd_usb_substream *subs, unsigned int peri
 
 	/* decide how many packets to be used */
 	if (is_playback) {
-		unsigned int minsize;
+		unsigned int minsize, maxpacks;
 		/* determine how small a packet can be */
 		minsize = (subs->freqn >> (16 - subs->datainterval))
 			  * (frame_bits >> 3);
@@ -1094,6 +1095,12 @@ static int init_substream_urbs(struct snd_usb_substream *subs, unsigned int peri
 		/* we need at least two URBs for queueing */
 		if (total_packs < 2 * MIN_PACKS_URB * packs_per_ms)
 			total_packs = 2 * MIN_PACKS_URB * packs_per_ms;
+		else {
+			/* and we don't want too long a queue either */
+			maxpacks = max((unsigned int)MAX_QUEUE, urb_packs * 2);
+			if (total_packs > maxpacks * packs_per_ms)
+				total_packs = maxpacks * packs_per_ms;
+		}
 	} else {
 		total_packs = MAX_URBS * urb_packs;
 	}