Index: drivers/dahdi/dahdi-base.c
===================================================================
--- drivers/dahdi/dahdi-base.c	(revision 9205)
+++ drivers/dahdi/dahdi-base.c	(working copy)
@@ -2053,13 +2053,33 @@
 	int res, rv;
 	int oldbuf,x;
 	unsigned long flags;
+	static int last_badchan_count = 0;
 
 	/* Make sure count never exceeds 65k, and make sure it's unsigned */
 	count &= 0xffff;
 
-	if (!chan)
+	if (!chan) {
+		if (++last_badchan_count > 3) {
+			/* Give userspace something to work with, if it's not going to pay attention to our -EINVAL */
+			char nothing[128] = {
+				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+				-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+			};
+			if (copy_to_user(usrbuf, nothing, count < 128 ? count : 128))
+				return -EFAULT;
+			return count < 128 ? count : 128;
+		}
 		return -EINVAL;
+	}
 
+	last_badchan_count = 0;
+
 	if (count < 1)
 		return -EINVAL;
 
@@ -2177,12 +2197,18 @@
 	unsigned long flags;
 	struct dahdi_chan *chan = chans[unit];
 	int res, amnt, oldbuf, rv, x;
+	static int last_badchan_count = 0;
 
 	/* Make sure count never exceeds 65k, and make sure it's unsigned */
 	count &= 0xffff;
 
-	if (!chan)
+	if (!chan) {
+		if (++last_badchan_count > 3) {
+			/* If userspace is going to ignore our -EINVAL, then tell it what it wants to hear. */
+			return count;
+		}
 		return -EINVAL;
+	}
 
 	if (count < 1) {
 		return -EINVAL;