Index: uspace/lib/libfs/libfs.c
===================================================================
--- uspace/lib/libfs/libfs.c	(revision d2c1fd53579d1a567dfae1eae22cce29947a9f5f)
+++ uspace/lib/libfs/libfs.c	(revision a61d1fc3aa43e7a55cd4864d7eb1669c9e1f12f4)
@@ -334,8 +334,23 @@
 #define RD_READ_BLOCK	(RD_BASE + 1)
 
-bool libfs_blockread(int phone, void *buffer, size_t *bufpos, size_t *buflen,
-    size_t *pos, void *dst, size_t size, size_t block_size)
+/** Read data from a block device.
+ *
+ * @param phone		Phone to be used to communicate with the device.
+ * @param buffer	Communication buffer shared with the device.
+ * @param bufpos	Pointer to the first unread valid offset within the
+ * 			communication buffer.
+ * @param buflen	Pointer to the number of unread bytes that are ready in
+ * 			the communication buffer.
+ * @param pos		Device position to be read.
+ * @param dst		Destination buffer.
+ * @param size		Size of the destination buffer.
+ * @param block_size	Block size to be used for the transfer.
+ *
+ * @return		True on success, false on failure.
+ */
+bool libfs_blockread(int phone, void *buffer, off_t *bufpos, size_t *buflen,
+    off_t *pos, void *dst, size_t size, size_t block_size)
 {
-	size_t offset = 0;
+	off_t offset = 0;
 	size_t left = size;
 	
@@ -349,4 +364,8 @@
 		
 		if (rd > 0) {
+			/*
+			 * Copy the contents of the communication buffer to the
+			 * destination buffer.
+			 */
 			memcpy(dst + offset, buffer + *bufpos, rd);
 			offset += rd;
@@ -357,4 +376,5 @@
 		
 		if (*bufpos == *buflen) {
+			/* Refill the communication buffer with a new block. */
 			ipcarg_t retval;
 			int rc = async_req_2_1(phone, RD_READ_BLOCK,
Index: uspace/lib/libfs/libfs.h
===================================================================
--- uspace/lib/libfs/libfs.h	(revision d2c1fd53579d1a567dfae1eae22cce29947a9f5f)
+++ uspace/lib/libfs/libfs.h	(revision a61d1fc3aa43e7a55cd4864d7eb1669c9e1f12f4)
@@ -70,5 +70,5 @@
 extern void libfs_lookup(libfs_ops_t *, fs_handle_t, ipc_callid_t, ipc_call_t *);
 
-extern bool libfs_blockread(int, void *, size_t *, size_t *, size_t *, void *,
+extern bool libfs_blockread(int, void *, off_t *, size_t *, off_t *, void *,
     size_t, size_t);