Index: uspace/lib/math/generic/trunc.c
===================================================================
--- uspace/lib/math/generic/trunc.c	(revision a11bcb1624f1a81c389f476489618ef6bcb2ad17)
+++ uspace/lib/math/generic/trunc.c	(revision 47f7390f53c3d64fcfcb8712911ccf9c35f0c9fb)
@@ -27,5 +27,5 @@
  */
 
-/** @addtogroup libc
+/** @addtogroup libmath
  * @{
  */
@@ -36,4 +36,19 @@
 #include <trunc.h>
 
+/** Truncate fractional part (round towards zero)
+ *
+ * Truncate the fractional part of IEEE 754 double
+ * precision floating point number by zeroing fraction
+ * bits, effectively rounding the number towards zero
+ * to the nearest whole number.
+ *
+ * If the argument is infinity or NaN, an exception
+ * should be indicated. This is not implemented yet.
+ *
+ * @param val Floating point number.
+ *
+ * @return Number rounded towards zero.
+ *
+ */
 float64 trunc_float64(float64 val)
 {