bus_if: Add a default implementation of get_property

There are multiple buses that pretend to be ofw compatible,
e.g ofw_pci, mii_fdt. We now need to provide an implementation
of BUS_GET_PROPERTY for every one of them. Instead of modifying
them one by one it's better to just provide a default
implementation that simply traverses up the device tree.
Remove the now unneeded BUS_GET_PROPERTY implementation in mii_fdt.

Reviewed by: andrew, bz
Obtained from: Semihalf
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D34031

4 files changed, 21 insertions, 22 deletions

diff --git a/sys/dev/mii/mii_fdt.c b/sys/dev/mii/mii_fdt.c
index 387b02f69504..9cf3fd2fab37 100644
--- a/sys/dev/mii/mii_fdt.c
+++ b/sys/dev/mii/mii_fdt.c
@@ -326,20 +326,6 @@ miibus_fdt_get_devinfo(device_t bus, device_t child)
 	return (&ma->obd);
 }
 
-static ssize_t
-miibus_fdt_get_property(device_t bus, device_t child, const char *propname,
-    void *buf, size_t size)
-{
-	struct mii_attach_args *ma;
-
-	ma = device_get_ivars(child);
-
-	if (ma->obd.obd_node == 0)
-		return (-1);
-
-	return (OF_getencprop(ma->obd.obd_node, propname, buf, size));
-}
-
 static device_method_t miibus_fdt_methods[] = {
 	DEVMETHOD(device_probe,		miibus_fdt_probe),
 	DEVMETHOD(device_attach,	miibus_fdt_attach),
@@ -362,7 +348,6 @@ static device_method_t miibus_fdt_methods[] = {
 	DEVMETHOD(bus_get_resource,		bus_generic_rl_get_resource),
 	DEVMETHOD(bus_set_resource,		bus_generic_rl_set_resource),
 	DEVMETHOD(bus_get_resource_list,	miibus_fdt_get_resource_list),
-	DEVMETHOD(bus_get_property,		miibus_fdt_get_property),
 
 	DEVMETHOD_END
 };
diff --git a/sys/kern/bus_if.m b/sys/kern/bus_if.m
index ef0f5e9eb65a..cf6470c220ef 100644
--- a/sys/kern/bus_if.m
+++ b/sys/kern/bus_if.m
@@ -77,12 +77,6 @@ CODE {
 		return (0);
 	}
 
-	static ssize_t
-	null_get_property(device_t dev, device_t child, const char *propname,
-	    void *propvalue, size_t size)
-	{
-		return (-1);
-	}
 };
 
 /**
@@ -944,7 +938,7 @@ METHOD ssize_t get_property {
 	const char *_propname;
 	void *_propvalue;
 	size_t _size;
-} DEFAULT null_get_property;
+} DEFAULT bus_generic_get_property;
 
 /**
  * @brief Gets a child's full path to the device
diff --git a/sys/kern/subr_bus.c b/sys/kern/subr_bus.c
index 5e6cfa162f4c..8a05c28c96b1 100644
--- a/sys/kern/subr_bus.c
+++ b/sys/kern/subr_bus.c
@@ -4126,6 +4126,23 @@ bus_generic_write_ivar(device_t dev, device_t child, int index,
 }
 
 /**
+ * @brief Helper function for implementing BUS_GET_PROPERTY().
+ *
+ * This simply calls the BUS_GET_PROPERTY of the parent of dev,
+ * until a non-default implementation is found.
+ */
+ssize_t
+bus_generic_get_property(device_t dev, device_t child, const char *propname,
+    void *propvalue, size_t size)
+{
+	if (device_get_parent(dev) != NULL)
+		return (BUS_GET_PROPERTY(device_get_parent(dev), child,
+		    propname, propvalue, size));
+
+	return (-1);
+}
+
+/**
  * @brief Stub function for implementing BUS_GET_RESOURCE_LIST().
  *
  * @returns NULL
diff --git a/sys/sys/bus.h b/sys/sys/bus.h
index d31eb31a362a..0b4f85a7fd0d 100644
--- a/sys/sys/bus.h
+++ b/sys/sys/bus.h
@@ -444,6 +444,9 @@ bus_dma_tag_t
 bus_space_tag_t
 	bus_generic_get_bus_tag(device_t dev, device_t child);
 int	bus_generic_get_domain(device_t dev, device_t child, int *domain);
+ssize_t bus_generic_get_property(device_t dev, device_t child,
+				 const char *propname, void *propvalue,
+				 size_t size);
 struct resource_list *
 	bus_generic_get_resource_list(device_t, device_t);
 int	bus_generic_map_resource(device_t dev, device_t child, int type,