platform/x86: lenovo-wmi-helpers: Add helper for creating per-device debugfs dir

We are about to add debugfs support for lenovo-wmi-capdata. Let's setup
a debugfs directory called "lenovo_wmi" for tidiness, so that any
lenovo-wmi-* device can put its subdirectory under the directory.
Subdirectories will be named after the corresponding WMI devices.

Signed-off-by: Rong Zhang <i@rong.moe>
Signed-off-by: Derek J. Clark <derekjohn.clark@gmail.com>

Author: Rongronggg9

drivers/platform/x86/lenovo/wmi-helpers.c

@@ -17,6 +17,8 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/debugfs.h>
+#include <linux/device.h>
 #include <linux/cleanup.h>
 #include <linux/errno.h>
 #include <linux/export.h>
@@ -186,6 +188,38 @@ int lwmi_tm_notifier_call(enum thermal_mode *mode)
 }
 EXPORT_SYMBOL_NS_GPL(lwmi_tm_notifier_call, "LENOVO_WMI_HELPERS");
 
+static struct dentry *lwmi_debugfs_dir;
+
+/**
+ * lwmi_debugfs_create_dir() - Helper function for creating a debugfs directory
+ * for a device.
+ * @wdev: Pointer to the WMI device to be called.
+ *
+ * Caller must remove the directory with debugfs_remove_recursive() on device
+ * removal.
+ *
+ * Return: Pointer to the created directory.
+ */
+struct dentry *lwmi_debugfs_create_dir(struct wmi_device *wdev)
+{
+	return debugfs_create_dir(dev_name(&wdev->dev), lwmi_debugfs_dir);
+}
+EXPORT_SYMBOL_NS_GPL(lwmi_debugfs_create_dir, "LENOVO_WMI_HELPERS");
+
+static int __init lwmi_helpers_init(void)
+{
+	lwmi_debugfs_dir = debugfs_create_dir("lenovo_wmi", NULL);
+
+	return 0;
+}
+subsys_initcall(lwmi_helpers_init)
+
+static void __exit lwmi_helpers_exit(void)
+{
+	debugfs_remove_recursive(lwmi_debugfs_dir);
+}
+module_exit(lwmi_helpers_exit)
+
 MODULE_AUTHOR("Derek J. Clark <derekjohn.clark@gmail.com>");
 MODULE_DESCRIPTION("Lenovo WMI Helpers Driver");
 MODULE_LICENSE("GPL");

drivers/platform/x86/lenovo/wmi-helpers.h

@@ -16,6 +16,8 @@ struct wmi_method_args_32 {
 	u32 arg1;
 };
 
+struct dentry *lwmi_debugfs_create_dir(struct wmi_device *wdev);
+
 enum lwmi_event_type {
 	LWMI_GZ_GET_THERMAL_MODE = 0x01,
 };