svn commit: r348688 - head/sys/sys

[Andriy Gapon]

Author: avg
Date: Wed Jun  5 13:18:00 2019
New Revision: 348688
URL: https://svnweb.freebsd.org/changeset/base/348688

Log:
  first step towards enforcing must-succeed semantics for bus accessors
  
  Unlike BUS_READ_IVAR / BUS_WRITE_IVAR, bus accessors do not have a
  return code.  It is assumed that there is a tight coupling between a bus
  driver and a driver for a device on the bus with respect to instance
  variables that the bus defines for its children.  So, the driver is
  supposed to have only valid accesses to the variables and, thus, the
  accessors must always succeed.
  
  Of course, programming errors sometimes happen.  At present, such errors
  go completely unnoticed.  The idea of this change is to start catching
  them.  As a first step, there will be a warning about a failed accessor
  call.  This is to give developers a heads-up.  I plan to replace the
  printf with a KASSERT a week later, so that the warning is harder to
  ignore.
  
  Reviewed by:	cem, imp, ian
  MFC after:	2 weeks
  Differential Revision: https://reviews.freebsd.org/D20458

Modified:
  head/sys/sys/bus.h

Modified: head/sys/sys/bus.h
==============================================================================
--- head/sys/sys/bus.h	Wed Jun  5 13:08:21 2019	(r348687)
+++ head/sys/sys/bus.h	Wed Jun  5 13:18:00 2019	(r348688)
@@ -810,16 +810,30 @@ DECLARE_MODULE(name##_##busname, name##_##busname##_mo
 static __inline type varp ## _get_ ## var(device_t dev)			\
 {									\
 	uintptr_t v;							\
-	BUS_READ_IVAR(device_get_parent(dev), dev,			\
+	int e;								\
+	e = BUS_READ_IVAR(device_get_parent(dev), dev,			\
 	    ivarp ## _IVAR_ ## ivar, &v);				\
+	if (e != 0) {							\
+		device_printf(dev, "failed to read ivar "		\
+		    __XSTRING(ivarp ## _IVAR_ ## ivar) " on bus %s, "	\
+		    "error = %d\n",					\
+		    device_get_nameunit(device_get_parent(dev)), e);	\
+	}								\
 	return ((type) v);						\
 }									\
 									\
 static __inline void varp ## _set_ ## var(device_t dev, type t)		\
 {									\
 	uintptr_t v = (uintptr_t) t;					\
-	BUS_WRITE_IVAR(device_get_parent(dev), dev,			\
+	int e;								\
+	e = BUS_WRITE_IVAR(device_get_parent(dev), dev,			\
 	    ivarp ## _IVAR_ ## ivar, v);				\
+	if (e != 0) {							\
+		device_printf(dev, "failed to write ivar "		\
+		    __XSTRING(ivarp ## _IVAR_ ## ivar) " on bus %s, "	\
+		    "error = %d\n",					\
+		    device_get_nameunit(device_get_parent(dev)), e);	\
+	}								\
 }
 
 /**