linux-kernel - [PATCH v2 1/7] driver core: auxiliary bus: add device creation helper

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Message-ID: <20250206-aux-device-create-helper-v2-1-fa6a0f326527@baylibre.com>
Date: Thu,  6 Feb 2025 19:23:11 +0100
From: Jerome Brunet <jbrunet@...libre.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dave Ertman <david.m.ertman@...el.com>,
	Ira Weiny <ira.weiny@...el.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Stephen Boyd <sboyd@...nel.org>,
	Arnd Bergmann <arnd@...db.de>
Cc: Jerome Brunet <jbrunet@...libre.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/7] driver core: auxiliary bus: add device creation helper

Add a function helper 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@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
---
 drivers/base/auxiliary.c      | 88 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/auxiliary_bus.h |  6 +++
 2 files changed, 94 insertions(+)

diff --git a/drivers/base/auxiliary.c b/drivers/base/auxiliary.c
index afa4df4c5a3f371b91d8dd8c4325495d32ad1291..2594ec9a2d6f1696e064989b2bd5145a73beb159 100644
--- a/drivers/base/auxiliary.c
+++ b/drivers/base/auxiliary.c
@@ -385,6 +385,94 @@ 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);
+}
+
+static 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 ERR_PTR(-ENOMEM);
+
+	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 ERR_PTR(ret);
+	}
+
+	ret = __auxiliary_device_add(auxdev, modname);
+	if (ret) {
+		/*
+		 * NOTE: It may look odd but auxdev should not be freed
+		 * here. auxiliary_device_uninit() calls device_put()
+		 * which call the device release function, freeing auxdev.
+		 */
+		auxiliary_device_uninit(auxdev);
+		return ERR_PTR(ret);
+	}
+
+	return auxdev;
+}
+
+static void auxiliary_device_destroy(void *_auxdev)
+{
+	struct auxiliary_device *auxdev = _auxdev;
+
+	auxiliary_device_delete(auxdev);
+	auxiliary_device_uninit(auxdev);
+}
+
+/**
+ * devm_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
+ *
+ * Device managed helper to create an auxiliary bus device.
+ * The device create matches driver 'modname.devname' on the auxiliary bus.
+ */
+struct auxiliary_device *devm_auxiliary_device_create(struct device *dev,
+						      const char *modname,
+						      const char *devname,
+						      void *platform_data,
+						      int id)
+{
+	struct auxiliary_device *auxdev;
+	int ret;
+
+	auxdev = auxiliary_device_create(dev, modname, devname, platform_data, id);
+	if (IS_ERR(auxdev))
+		return auxdev;
+
+	ret = devm_add_action_or_reset(dev, auxiliary_device_destroy,
+				       auxdev);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return auxdev;
+}
+EXPORT_SYMBOL_GPL(devm_auxiliary_device_create);
+
 void __init auxiliary_bus_init(void)
 {
 	WARN_ON(bus_register(&auxiliary_bus_type));
diff --git a/include/linux/auxiliary_bus.h b/include/linux/auxiliary_bus.h
index 65dd7f15437474468acf0e28f6932a7ff2cfff2c..c9ba8e718304c0ce27e16cdf53b18d81a290e4da 100644
--- a/include/linux/auxiliary_bus.h
+++ b/include/linux/auxiliary_bus.h
@@ -254,6 +254,12 @@ int __auxiliary_driver_register(struct auxiliary_driver *auxdrv, struct module *
 
 void auxiliary_driver_unregister(struct auxiliary_driver *auxdrv);
 
+struct auxiliary_device *devm_auxiliary_device_create(struct device *dev,
+						      const char *modname,
+						      const char *devname,
+						      void *platform_data,
+						      int id);
+
 /**
  * module_auxiliary_driver() - Helper macro for registering an auxiliary driver
  * @__auxiliary_driver: auxiliary driver struct

-- 
2.45.2