diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index ac7d277..5276b99 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -223,8 +223,10 @@
 			int quote = *buf++;
 			for (end = buf; *end && *end != quote; end++)
 				;
-			if (!*end)
+			if (!*end) {
+				pr_err("unclosed quote: %s\n", buf);
 				return -EINVAL;	/* unclosed quote */
+			}
 		} else {
 			for (end = buf; *end && !isspace(*end); end++)
 				;
@@ -232,8 +234,10 @@
 		}
 
 		/* `buf' is start of word, `end' is one past its end */
-		if (nwords == maxwords)
+		if (nwords == maxwords) {
+			pr_err("too many words, legal max <=%d\n", maxwords);
 			return -EINVAL;	/* ran out of words[] before bytes */
+		}
 		if (*end)
 			*end++ = '\0';	/* terminate the word */
 		words[nwords++] = buf;
@@ -265,7 +269,11 @@
 		return 0;
 	}
 	*val = simple_strtoul(str, &end, 10);
-	return end == NULL || end == str || *end != '\0' ? -EINVAL : 0;
+	if (end == NULL || end == str || *end != '\0') {
+		pr_err("bad line-number: %s\n", str);
+		return -EINVAL;
+	}
+	return 0;
 }
 
 /*
@@ -345,8 +353,10 @@
 	int rc;
 
 	/* check we have an even number of words */
-	if (nwords % 2 != 0)
+	if (nwords % 2 != 0) {
+		pr_err("expecting pairs of match-spec <value>\n");
 		return -EINVAL;
+	}
 	memset(query, 0, sizeof(*query));
 
 	if (modname)
@@ -367,18 +377,22 @@
 			char *first = words[i+1];
 			char *last = strchr(first, '-');
 			if (query->first_lineno || query->last_lineno) {
-				pr_err("match-spec:line given 2 times\n");
+				pr_err("match-spec: line used 2x\n");
 				return -EINVAL;
 			}
 			if (last)
 				*last++ = '\0';
-			if (parse_lineno(first, &query->first_lineno) < 0)
+			if (parse_lineno(first, &query->first_lineno) < 0) {
+				pr_err("line-number is <0\n");
 				return -EINVAL;
+			}
 			if (last) {
 				/* range <first>-<last> */
 				if (parse_lineno(last, &query->last_lineno)
 				    < query->first_lineno) {
-					pr_err("last-line < 1st-line\n");
+					pr_err("last-line:%d < 1st-line:%d\n",
+						query->last_lineno,
+						query->first_lineno);
 					return -EINVAL;
 				}
 			} else {
@@ -414,6 +428,7 @@
 		op = *str++;
 		break;
 	default:
+		pr_err("bad flag-op %c, at start of %s\n", *str, str);
 		return -EINVAL;
 	}
 	vpr_info("op='%c'\n", op);
@@ -425,8 +440,10 @@
 				break;
 			}
 		}
-		if (i < 0)
+		if (i < 0) {
+			pr_err("unknown flag '%c' in \"%s\"\n", *str, str);
 			return -EINVAL;
+		}
 	}
 	vpr_info("flags=0x%x\n", flags);
 
@@ -458,13 +475,19 @@
 	char *words[MAXWORDS];
 
 	nwords = ddebug_tokenize(query_string, words, MAXWORDS);
-	if (nwords <= 0)
+	if (nwords <= 0) {
+		pr_err("tokenize failed\n");
 		return -EINVAL;
-	if (ddebug_parse_query(words, nwords-1, &query, modname))
+	}
+	/* check flags 1st (last arg) so query is pairs of spec,val */
+	if (ddebug_parse_flags(words[nwords-1], &flags, &mask)) {
+		pr_err("flags parse failed\n");
 		return -EINVAL;
-	if (ddebug_parse_flags(words[nwords-1], &flags, &mask))
+	}
+	if (ddebug_parse_query(words, nwords-1, &query, modname)) {
+		pr_err("query parse failed\n");
 		return -EINVAL;
-
+	}
 	/* actually go and implement the change */
 	nfound = ddebug_change(&query, flags, mask);
 	vpr_info_dq(&query, nfound ? "applied" : "no-match");