Add helper functions to create a device on the auxiliary bus.

This is meant for fairly simple usage of the auxiliary bus, to avoid having
the same code repeated in the different drivers.

Suggested-by: Stephen Boyd <sboyd@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
---
 drivers/base/auxiliary.c      | 108 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/auxiliary_bus.h |  17 +++++++
 2 files changed, 125 insertions(+)

diff --git a/drivers/base/auxiliary.c b/drivers/base/auxiliary.c
index afa4df4c5a3f371b91d8dd8c4325495d32ad1291..a6d46c2759be81a0739f07528d5959c2a76eb8a8 100644
--- a/drivers/base/auxiliary.c
+++ b/drivers/base/auxiliary.c

@@ -385,6 +385,114 @@ void auxiliary_driver_unregister(struct auxiliary_driver *auxdrv)
 }
 EXPORT_SYMBOL_GPL(auxiliary_driver_unregister);
 
+static void auxiliary_device_release(struct device *dev)
+{
+	struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
+
+	kfree(auxdev);
+}
+
+/**
+ * auxiliary_device_create - create a device on the auxiliary bus
+ * @dev: parent device
+ * @modname: module name used to create the auxiliary driver name.
+ * @devname: auxiliary bus device name
+ * @platform_data: auxiliary bus device platform data
+ * @id: auxiliary bus device id
+ *
+ * Helper to create an auxiliary bus device.
+ * The device created matches driver 'modname.devname' on the auxiliary bus.
+ */
+struct auxiliary_device *auxiliary_device_create(struct device *dev,
+						 const char *modname,
+						 const char *devname,
+						 void *platform_data,
+						 int id)
+{
+	struct auxiliary_device *auxdev;
+	int ret;
+
+	auxdev = kzalloc(sizeof(*auxdev), GFP_KERNEL);
+	if (!auxdev)
+		return NULL;
+
+	auxdev->id = id;
+	auxdev->name = devname;
+	auxdev->dev.parent = dev;
+	auxdev->dev.platform_data = platform_data;
+	auxdev->dev.release = auxiliary_device_release;
+	device_set_of_node_from_dev(&auxdev->dev, dev);
+
+	ret = auxiliary_device_init(auxdev);
+	if (ret) {
+		kfree(auxdev);
+		return NULL;
+	}
+
+	ret = __auxiliary_device_add(auxdev, modname);
+	if (ret) {