Index: uspace/drv/bus/usb/usbdiag/device.c
===================================================================
--- uspace/drv/bus/usb/usbdiag/device.c	(revision eb862fddddc297494d90b7923161a1a84c8291de)
+++ uspace/drv/bus/usb/usbdiag/device.c	(revision 7cba9f73d4bf1357e8b015cf70d85178e89a2c01)
@@ -54,7 +54,7 @@
 };
 
-static int device_init(usbdiag_dev_t *dev, const usb_endpoint_description_t **endpoints)
+static errno_t device_init(usbdiag_dev_t *dev, const usb_endpoint_description_t **endpoints)
 {
-	int rc;
+	errno_t rc;
 	ddf_fun_t *fun = usb_device_ddf_fun_create(dev->usb_dev, fun_exposed, "tmon");
 	if (!fun) {
@@ -104,5 +104,5 @@
 }
 
-int usbdiag_dev_create(usb_device_t *dev, usbdiag_dev_t **out_diag_dev, const usb_endpoint_description_t **endpoints)
+errno_t usbdiag_dev_create(usb_device_t *dev, usbdiag_dev_t **out_diag_dev, const usb_endpoint_description_t **endpoints)
 {
 	assert(dev);
@@ -115,5 +115,5 @@
 	diag_dev->usb_dev = dev;
 
-	int err;
+	errno_t err;
 	if ((err = device_init(diag_dev, endpoints)))
 		goto err_init;
Index: uspace/drv/bus/usb/usbdiag/device.h
===================================================================
--- uspace/drv/bus/usb/usbdiag/device.h	(revision eb862fddddc297494d90b7923161a1a84c8291de)
+++ uspace/drv/bus/usb/usbdiag/device.h	(revision 7cba9f73d4bf1357e8b015cf70d85178e89a2c01)
@@ -77,5 +77,5 @@
 } usbdiag_dev_t;
 
-int usbdiag_dev_create(usb_device_t *, usbdiag_dev_t **, const usb_endpoint_description_t **);
+errno_t usbdiag_dev_create(usb_device_t *, usbdiag_dev_t **, const usb_endpoint_description_t **);
 void usbdiag_dev_destroy(usbdiag_dev_t *);
 
Index: uspace/drv/bus/usb/usbdiag/main.c
===================================================================
--- uspace/drv/bus/usb/usbdiag/main.c	(revision eb862fddddc297494d90b7923161a1a84c8291de)
+++ uspace/drv/bus/usb/usbdiag/main.c	(revision 7cba9f73d4bf1357e8b015cf70d85178e89a2c01)
@@ -47,7 +47,7 @@
 static const usb_endpoint_description_t *diag_endpoints[];
 
-static int device_add(usb_device_t *dev)
-{
-	int rc;
+static errno_t device_add(usb_device_t *dev)
+{
+	errno_t rc;
 	usb_log_info("Adding device '%s'", usb_device_get_name(dev));
 
@@ -79,5 +79,5 @@
 }
 
-static int device_cleanup(usbdiag_dev_t *diag_dev)
+static errno_t device_cleanup(usbdiag_dev_t *diag_dev)
 {
 	/* TODO: Join some fibrils? */
@@ -88,7 +88,7 @@
 }
 
-static int device_remove(usb_device_t *dev)
-{
-	int rc;
+static errno_t device_remove(usb_device_t *dev)
+{
+	errno_t rc;
 	usb_log_info("Removing device '%s'", usb_device_get_name(dev));
 
@@ -109,7 +109,7 @@
 }
 
-static int device_gone(usb_device_t *dev)
-{
-	int rc;
+static errno_t device_gone(usb_device_t *dev)
+{
+	errno_t rc;
 	usb_log_info("Device '%s' gone.", usb_device_get_name(dev));
 
@@ -129,10 +129,10 @@
 }
 
-static int function_online(ddf_fun_t *fun)
+static errno_t function_online(ddf_fun_t *fun)
 {
 	return ddf_fun_online(fun);
 }
 
-static int function_offline(ddf_fun_t *fun)
+static errno_t function_offline(ddf_fun_t *fun)
 {
 	return ddf_fun_offline(fun);
Index: uspace/drv/bus/usb/usbdiag/tests.c
===================================================================
--- uspace/drv/bus/usb/usbdiag/tests.c	(revision eb862fddddc297494d90b7923161a1a84c8291de)
+++ uspace/drv/bus/usb/usbdiag/tests.c	(revision 7cba9f73d4bf1357e8b015cf70d85178e89a2c01)
@@ -46,5 +46,5 @@
 static const uint32_t test_data_src = 0xDEADBEEF;
 
-static int test_in(usb_pipe_t *pipe, const usbdiag_test_params_t *params, usbdiag_test_results_t *results)
+static errno_t test_in(usb_pipe_t *pipe, const usbdiag_test_params_t *params, usbdiag_test_results_t *results)
 {
 	if (!pipe)
@@ -69,5 +69,5 @@
 	usb_log_info("Performing %s IN test with duration %ld ms.", usb_str_transfer_type(pipe->desc.transfer_type), params->min_duration);
 
-	int rc = EOK;
+	errno_t rc = EOK;
 	uint32_t transfer_count = 0;
 
@@ -138,5 +138,5 @@
 }
 
-static int test_out(usb_pipe_t *pipe, const usbdiag_test_params_t *params, usbdiag_test_results_t *results)
+static errno_t test_out(usb_pipe_t *pipe, const usbdiag_test_params_t *params, usbdiag_test_results_t *results)
 {
 	if (!pipe)
@@ -167,5 +167,5 @@
 	usb_log_info("Performing %s OUT test.", usb_str_transfer_type(pipe->desc.transfer_type));
 
-	int rc = EOK;
+	errno_t rc = EOK;
 	uint32_t transfer_count = 0;
 
@@ -203,5 +203,5 @@
 }
 
-int usbdiag_dev_test_in(ddf_fun_t *fun, const usbdiag_test_params_t *params, usbdiag_test_results_t *results)
+errno_t usbdiag_dev_test_in(ddf_fun_t *fun, const usbdiag_test_params_t *params, usbdiag_test_results_t *results)
 {
 	usbdiag_dev_t *dev = ddf_fun_to_usbdiag_dev(fun);
@@ -228,5 +228,5 @@
 }
 
-int usbdiag_dev_test_out(ddf_fun_t *fun, const usbdiag_test_params_t *params, usbdiag_test_results_t *results)
+errno_t usbdiag_dev_test_out(ddf_fun_t *fun, const usbdiag_test_params_t *params, usbdiag_test_results_t *results)
 {
 	usbdiag_dev_t *dev = ddf_fun_to_usbdiag_dev(fun);
Index: uspace/drv/bus/usb/usbdiag/tests.h
===================================================================
--- uspace/drv/bus/usb/usbdiag/tests.h	(revision eb862fddddc297494d90b7923161a1a84c8291de)
+++ uspace/drv/bus/usb/usbdiag/tests.h	(revision 7cba9f73d4bf1357e8b015cf70d85178e89a2c01)
@@ -39,6 +39,6 @@
 #include <ddf/driver.h>
 
-int usbdiag_dev_test_in(ddf_fun_t *, const usbdiag_test_params_t *, usbdiag_test_results_t *);
-int usbdiag_dev_test_out(ddf_fun_t *, const usbdiag_test_params_t *, usbdiag_test_results_t *);
+errno_t usbdiag_dev_test_in(ddf_fun_t *, const usbdiag_test_params_t *, usbdiag_test_results_t *);
+errno_t usbdiag_dev_test_out(ddf_fun_t *, const usbdiag_test_params_t *, usbdiag_test_results_t *);
 
 #endif /* USBDIAG_TESTS_H_ */