ACPI: platform_profile: Add support for non-ACPI platforms

Currently the platform profile subsystem assumes that all supported
(i.e. ACPI-capable) platforms always run with ACPI being enabled.
However some ARM64 notebooks do not support ACPI and are instead
using devicetree for booting.

Do not register the legacy sysfs interface on such devices as it
depends on the acpi_kobj (/sys/firmware/acpi/) being present. Users
are encouraged to use the new platform-profile class interface
instead.

Signed-off-by: Armin Wolf <W_Armin@gmx.de>

Author: Wer-Wolf

drivers/acpi/platform_profile.c

@@ -190,6 +190,20 @@ static ssize_t profile_show(struct device *dev,
 	return sysfs_emit(buf, "%s\n", profile_names[profile]);
 }
 
+/**
+ * profile_notify_legacy - Notify the legacy sysfs interface
+ *
+ * This wrapper takes care of only notifying the legacy sysfs interface
+ * if it was registered during module initialization.
+ */
+static void profile_notify_legacy(void)
+{
+	if (!acpi_kobj)
+		return;
+
+	sysfs_notify(acpi_kobj, NULL, "platform_profile");
+}
+
 /**
  * profile_store - Set the profile for a class device
  * @dev: The device
@@ -215,7 +229,7 @@ static ssize_t profile_store(struct device *dev,
 			return ret;
 	}
 
-	sysfs_notify(acpi_kobj, NULL, "platform_profile");
+	profile_notify_legacy();
 
 	return count;
 }
@@ -435,7 +449,7 @@ static ssize_t platform_profile_store(struct kobject *kobj,
 			return ret;
 	}
 
-	sysfs_notify(acpi_kobj, NULL, "platform_profile");
+	profile_notify_legacy();
 
 	return count;
 }
@@ -472,6 +486,22 @@ static const struct attribute_group platform_profile_group = {
 	.is_visible = profile_class_is_visible,
 };
 
+/**
+ * profile_update_legacy - Update the legacy sysfs interface
+ *
+ * This wrapper takes care of only updating the legacy sysfs interface
+ * if it was registered during module initialization.
+ *
+ * Return: 0 on success or error code on failure.
+ */
+static int profile_update_legacy(void)
+{
+	if (!acpi_kobj)
+		return 0;
+
+	return sysfs_update_group(acpi_kobj, &platform_profile_group);
+}
+
 /**
  * platform_profile_notify - Notify class device and legacy sysfs interface
  * @dev: The class device
@@ -481,7 +511,7 @@ void platform_profile_notify(struct device *dev)
 	scoped_cond_guard(mutex_intr, return, &profile_lock) {
 		_notify_class_profile(dev, NULL);
 	}
-	sysfs_notify(acpi_kobj, NULL, "platform_profile");
+	profile_notify_legacy();
 }
 EXPORT_SYMBOL_GPL(platform_profile_notify);
 
@@ -529,7 +559,7 @@ int platform_profile_cycle(void)
 			return err;
 	}
 
-	sysfs_notify(acpi_kobj, NULL, "platform_profile");
+	profile_notify_legacy();
 
 	return 0;
 }
@@ -603,9 +633,9 @@ struct device *platform_profile_register(struct device *dev, const char *name,
 		goto cleanup_ida;
 	}
 
-	sysfs_notify(acpi_kobj, NULL, "platform_profile");
+	profile_notify_legacy();
 
-	err = sysfs_update_group(acpi_kobj, &platform_profile_group);
+	err = profile_update_legacy();
 	if (err)
 		goto cleanup_cur;
 
@@ -639,8 +669,8 @@ void platform_profile_remove(struct device *dev)
 	ida_free(&platform_profile_ida, pprof->minor);
 	device_unregister(&pprof->dev);
 
-	sysfs_notify(acpi_kobj, NULL, "platform_profile");
-	sysfs_update_group(acpi_kobj, &platform_profile_group);
+	profile_notify_legacy();
+	profile_update_legacy();
 }
 EXPORT_SYMBOL_GPL(platform_profile_remove);
 
@@ -692,16 +722,28 @@ static int __init platform_profile_init(void)
 	if (err)
 		return err;
 
-	err = sysfs_create_group(acpi_kobj, &platform_profile_group);
-	if (err)
-		class_unregister(&platform_profile_class);
+	/*
+	 * The ACPI kobject can be missing if ACPI was disabled during booting.
+	 * We thus skip the initialization of the legacy sysfs interface in such
+	 * cases to allow the platform profile class to work on ARM64 notebooks
+	 * without ACPI support.
+	 */
+	if (acpi_kobj) {
+		err = sysfs_create_group(acpi_kobj, &platform_profile_group);
+		if (err < 0) {
+			class_unregister(&platform_profile_class);
+			return err;
+		}
+	}
 
-	return err;
+	return 0;
 }
 
 static void __exit platform_profile_exit(void)
 {
-	sysfs_remove_group(acpi_kobj, &platform_profile_group);
+	if (acpi_kobj)
+		sysfs_remove_group(acpi_kobj, &platform_profile_group);
+
 	class_unregister(&platform_profile_class);
 }
 module_init(platform_profile_init);