[PATCH v2] of: Keep track of populated platform devices

On Wed, 2014-05-14 at 11:56 +0100, Grant Likely wrote:

quoted

Agreed, but, unless I'm missing some fundamental issue, I believe we can
solve the flag clearing problem in a generic way:

--8<-----------

diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
index 3cf61a1..0f489fb 100644
--- a/drivers/amba/bus.c
+++ b/drivers/amba/bus.c

@@ -17,6 +17,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/amba/bus.h>
 #include <linux/sizes.h>
+#include <linux/of_device.h>
 
 #include <asm/irq.h>
 

@@ -268,6 +269,7 @@ static void amba_device_release(struct device *dev)
 {
 	struct amba_device *d = to_amba_device(dev);
 
+	of_device_node_put(dev);
 	if (d->res.parent)
 		release_resource(&d->res);
 	kfree(d);

diff --git a/include/linux/of_device.h b/include/linux/of_device.h
index ef37021..fd14d46 100644
--- a/include/linux/of_device.h
+++ b/include/linux/of_device.h

@@ -41,6 +41,8 @@ extern int of_device_uevent_modalias(struct device *dev, struct kobj_uevent_env
 
 static inline void of_device_node_put(struct device *dev)
 {
+	if (dev->of_node)
+		of_node_clear_flag(dev->of_node, OF_POPULATED);
 	of_node_put(dev->of_node);
 }
--8<-----------

This will work even if one manually unregisters a DT-originating device,
because of_device_node_put() would be called in both amba and platform
device (kobj) release path.

Doing it that way will also catch platform_devices that were created
apart from of_platform_populate() and manually attached to an of_node,
which is done some times. It will also break whenever multiple devices
reference the same node if they call of_device_node_put().

For example, a platform device providing an i2c bus will have a child
device that represents the i2c bus, and that i2c device will point to
the same node.

Yes, can I see it doing this. Without 

The flag clear really does need to be kept in the
platform_device_unpopulate path because it is only to be used internally
by of_platform_{populate,depopulate}

Ok, will move it there.
 

quoted

By the way, the fact that today amba_device_release() doesn't do
of_device_node_put() seems like a bug to me? (node's reference counter
won't be decremented)

Yes, that is a bug. I want to get some unittests added to the DT code to
verify that reference counts are being tracked correctly. Right now it
is an utter mess.

Ok. If I move the flag, this bit is not longer an integral part of the
patch so will split it into a separate one, but merge the _depopulate()
one instead.

Thanks!

Pawe?