Index: uspace/lib/c/generic/as.c
===================================================================
--- uspace/lib/c/generic/as.c	(revision 27833d82536aab87f18f2072179b5d4defc41c5b)
+++ uspace/lib/c/generic/as.c	(revision af430ce799faa0cd9d8ef17bb2196baca244a2a7)
@@ -35,4 +35,5 @@
 #include <as.h>
 #include <libc.h>
+#include <errno.h>
 #include <unistd.h>
 #include <align.h>
@@ -114,4 +115,30 @@
 }
 
+/** Find mapping to physical address.
+ *
+ * @param address Virtual address in question (virtual).
+ * @param[out] frame Frame address (physical).
+ * @return Error code.
+ * @retval EOK No error, @p frame holds the translation.
+ * @retval ENOENT Mapping not found.
+ */
+int as_get_physical_mapping(void *address, uintptr_t *frame)
+{
+	uintptr_t tmp_frame;
+	uintptr_t virt = (uintptr_t) address;
+	
+	int rc = (int) __SYSCALL2(SYS_PAGE_FIND_MAPPING,
+	    (sysarg_t) virt, (sysarg_t) &tmp_frame);
+	if (rc != EOK) {
+		return rc;
+	}
+	
+	if (frame != NULL) {
+		*frame = tmp_frame;
+	}
+	
+	return EOK;
+}
+
 /** @}
  */
Index: uspace/lib/c/generic/async.c
===================================================================
--- uspace/lib/c/generic/async.c	(revision 27833d82536aab87f18f2072179b5d4defc41c5b)
+++ uspace/lib/c/generic/async.c	(revision af430ce799faa0cd9d8ef17bb2196baca244a2a7)
@@ -1567,4 +1567,18 @@
 }
 
+/** Start IPC_M_DATA_READ using the async framework.
+ *
+ * @param phoneid Phone that will be used to contact the receiving side.
+ * @param dst Address of the beginning of the destination buffer.
+ * @param size Size of the destination buffer (in bytes).
+ * @param dataptr Storage of call data (arg 2 holds actual data size).
+ * @return Hash of the sent message or 0 on error.
+ */
+aid_t async_data_read(int phoneid, void *dst, size_t size, ipc_call_t *dataptr)
+{
+	return async_send_2(phoneid, IPC_M_DATA_READ, (sysarg_t) dst,
+	    (sysarg_t) size, dataptr);
+}
+
 /** Wrapper for IPC_M_DATA_READ calls using the async framework.
  *
Index: uspace/lib/c/generic/str_error.c
===================================================================
--- uspace/lib/c/generic/str_error.c	(revision 27833d82536aab87f18f2072179b5d4defc41c5b)
+++ uspace/lib/c/generic/str_error.c	(revision af430ce799faa0cd9d8ef17bb2196baca244a2a7)
@@ -33,4 +33,5 @@
  */
 
+#include <errno.h>
 #include <str_error.h>
 #include <stdio.h>
@@ -63,10 +64,24 @@
 static fibril_local char noerr[NOERR_LEN];
 
-const char *str_error(const int errno)
+const char *str_error(const int e)
 {
-	if ((errno <= 0) && (errno >= MIN_ERRNO))
-		return err_desc[-errno];
+	if ((e <= 0) && (e >= MIN_ERRNO))
+		return err_desc[-e];
 	
-	snprintf(noerr, NOERR_LEN, "Unkown error code %d", errno);
+	/* Ad hoc descriptions of error codes interesting for USB. */
+	switch (e) {
+		case EBADCHECKSUM:
+			return "Bad checksum";
+		case ESTALL:
+			return "Operation stalled";
+		case EAGAIN:
+			return "Resource temporarily unavailable";
+		case EEMPTY:
+			return "Resource is empty";
+		default:
+			break;
+	}
+
+	snprintf(noerr, NOERR_LEN, "Unkown error code %d", e);
 	return noerr;
 }