3 files changed, 28 insertions, 2 deletions

diff --git a/sys/dev/acpica/acpi.c b/sys/dev/acpica/acpi.c
index d402274..b31f1e7 100644
--- a/sys/dev/acpica/acpi.c
+++ b/sys/dev/acpica/acpi.c
@@ -2244,6 +2244,28 @@ acpi_SetIntrModel(int model)
 }
 
 /*
+ * Walk subtables of a table and call a callback routine for each
+ * subtable.  The caller should provide the first subtable and a
+ * pointer to the end of the table.  This can be used to walk tables
+ * such as MADT and SRAT that use subtable entries.
+ */
+void
+acpi_walk_subtables(void *first, void *end, acpi_subtable_handler *handler,
+    void *arg)
+{
+    ACPI_SUBTABLE_HEADER *entry;
+
+    for (entry = first; (void *)entry < end; ) {
+	/* Avoid an infinite loop if we hit a bogus entry. */
+	if (entry->Length < sizeof(ACPI_SUBTABLE_HEADER))
+	    return;
+
+	handler(entry, arg);
+	entry = ACPI_ADD_PTR(ACPI_SUBTABLE_HEADER, entry, entry->Length);
+    }
+}
+
+/*
  * DEPRECATED.  This interface has serious deficiencies and will be
  * removed.
  *
diff --git a/sys/dev/acpica/acpi_video.c b/sys/dev/acpica/acpi_video.c
index c095a40..e7e7d66 100644
--- a/sys/dev/acpica/acpi_video.c
+++ b/sys/dev/acpica/acpi_video.c
@@ -282,8 +282,7 @@ acpi_video_detach(device_t dev)
 				acpi_video_notify_handler);
 
 	ACPI_SERIAL_BEGIN(video);
-	for (vo = STAILQ_FIRST(&sc->vid_outputs); vo != NULL; vo = vn) {
-		vn = STAILQ_NEXT(vo, vo_next);
+	STAILQ_FOREACH_SAFE(vo, &sc->vid_outputs, vo_next, vn) {
 		acpi_video_vo_destroy(vo);
 	}
 	ACPI_SERIAL_END(video);
diff --git a/sys/dev/acpica/acpivar.h b/sys/dev/acpica/acpivar.h
index 63eadea..f4d27e4 100644
--- a/sys/dev/acpica/acpivar.h
+++ b/sys/dev/acpica/acpivar.h
@@ -307,6 +307,9 @@ void		acpi_EnterDebugger(void);
 	ACPI_DEVINFO_PRESENT(x, ACPI_STA_PRESENT | ACPI_STA_FUNCTIONAL | \
 	    ACPI_STA_BATT_PRESENT)
 
+/* Callback function type for walking subtables within a table. */
+typedef void acpi_subtable_handler(ACPI_SUBTABLE_HEADER *, void *);
+
 BOOLEAN		acpi_DeviceIsPresent(device_t dev);
 BOOLEAN		acpi_BatteryIsPresent(device_t dev);
 ACPI_STATUS	acpi_GetHandleInScope(ACPI_HANDLE parent, char *path,
@@ -340,6 +343,8 @@ void		acpi_UserNotify(const char *subsystem, ACPI_HANDLE h,
 int		acpi_bus_alloc_gas(device_t dev, int *type, int *rid,
 		    ACPI_GENERIC_ADDRESS *gas, struct resource **res,
 		    u_int flags);
+void		acpi_walk_subtables(void *first, void *end,
+		    acpi_subtable_handler *handler, void *arg);
 
 struct acpi_parse_resource_set {
     void	(*set_init)(device_t dev, void *arg, void **context);