mfd: Only unregister platform devices allocated by the mfd core

mfd_remove_devices would iterate over all devices sharing a parent with
an mfd device regardless of whether they were allocated by the mfd core
or not. This especially caused problems when the device structure was
not contained within a platform_device, because to_platform_device is
used on each device pointer.

This patch defines a device_type for mfd devices and checks this is
present from mfd_remove_devices_fn before processing the device.

Cc: stable@vger.kernel.org
Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Tested-by: Peter Tyser <ptyser@xes-inc.com>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

Author: charleskeepax

drivers/mfd/mfd-core.c

@@ -21,6 +21,10 @@
 #include <linux/irqdomain.h>
 #include <linux/of.h>
 
+static struct device_type mfd_dev_type = {
+	.name	= "mfd_device",
+};
+
 int mfd_cell_enable(struct platform_device *pdev)
 {
 	const struct mfd_cell *cell = mfd_get_cell(pdev);
@@ -91,6 +95,7 @@ static int mfd_add_device(struct device *parent, int id,
 		goto fail_device;
 
 	pdev->dev.parent = parent;
+	pdev->dev.type = &mfd_dev_type;
 
 	if (parent->of_node && cell->of_compatible) {
 		for_each_child_of_node(parent->of_node, np) {
@@ -204,10 +209,16 @@ EXPORT_SYMBOL(mfd_add_devices);
 
 static int mfd_remove_devices_fn(struct device *dev, void *c)
 {
-	struct platform_device *pdev = to_platform_device(dev);
-	const struct mfd_cell *cell = mfd_get_cell(pdev);
+	struct platform_device *pdev;
+	const struct mfd_cell *cell;
 	atomic_t **usage_count = c;
 
+	if (dev->type != &mfd_dev_type)
+		return 0;
+
+	pdev = to_platform_device(dev);
+	cell = mfd_get_cell(pdev);
+
 	/* find the base address of usage_count pointers (for freeing) */
 	if (!*usage_count || (cell->usage_count < *usage_count))
 		*usage_count = cell->usage_count;