platform/x86: firmware_attributes_class: Simplify API

[ Upstream commit d03cfde56f5cf9ec50b4cf099a42bf056fc80ddd ]

The module core already guarantees that a module can only be unloaded
after all other modules using its symbols have been unloaded.
As it's already the responsibility of the drivers using
firmware_attributes_class to clean up their devices before unloading,
the lifetime of the firmware_attributes_class can be bound to the
lifetime of the module.
This enables the direct usage of firmware_attributes_class from the
drivers, without having to go through the lifecycle functions,
leading to simplifications for both the subsystem and its users.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Armin Wolf <W_Armin@gmx.de>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Tested-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Link: https://lore.kernel.org/r/20250104-firmware-attributes-simplify-v1-2-949f9709e405@weissschuh.net
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Stable-dep-of: 5ff1fbb30597 ("platform/x86: think-lmi: Fix class device unregistration")
Signed-off-by: Sasha Levin <sashal@kernel.org>

2 files changed, 15 insertions, 26 deletions

diff --git a/drivers/platform/x86/firmware_attributes_class.c b/drivers/platform/x86/firmware_attributes_class.c
index cbc56e5db592..87672c49e86a 100644
--- a/drivers/platform/x86/firmware_attributes_class.c
+++ b/drivers/platform/x86/firmware_attributes_class.c
@@ -2,47 +2,35 @@
 
 /* Firmware attributes class helper module */
 
-#include <linux/mutex.h>
 #include <linux/module.h>
 #include "firmware_attributes_class.h"
 
-static DEFINE_MUTEX(fw_attr_lock);
-static int fw_attr_inuse;
-
-static const struct class firmware_attributes_class = {
+const struct class firmware_attributes_class = {
 	.name = "firmware-attributes",
 };
+EXPORT_SYMBOL_GPL(firmware_attributes_class);
+
+static __init int fw_attributes_class_init(void)
+{
+	return class_register(&firmware_attributes_class);
+}
+module_init(fw_attributes_class_init);
+
+static __exit void fw_attributes_class_exit(void)
+{
+	class_unregister(&firmware_attributes_class);
+}
+module_exit(fw_attributes_class_exit);
 
 int fw_attributes_class_get(const struct class **fw_attr_class)
 {
-	int err;
-
-	mutex_lock(&fw_attr_lock);
-	if (!fw_attr_inuse) { /*first time class is being used*/
-		err = class_register(&firmware_attributes_class);
-		if (err) {
-			mutex_unlock(&fw_attr_lock);
-			return err;
-		}
-	}
-	fw_attr_inuse++;
 	*fw_attr_class = &firmware_attributes_class;
-	mutex_unlock(&fw_attr_lock);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(fw_attributes_class_get);
 
 int fw_attributes_class_put(void)
 {
-	mutex_lock(&fw_attr_lock);
-	if (!fw_attr_inuse) {
-		mutex_unlock(&fw_attr_lock);
-		return -EINVAL;
-	}
-	fw_attr_inuse--;
-	if (!fw_attr_inuse) /* No more consumers */
-		class_unregister(&firmware_attributes_class);
-	mutex_unlock(&fw_attr_lock);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(fw_attributes_class_put);
diff --git a/drivers/platform/x86/firmware_attributes_class.h b/drivers/platform/x86/firmware_attributes_class.h
index 8e0f47cfdf92..ef6c3764a834 100644
--- a/drivers/platform/x86/firmware_attributes_class.h
+++ b/drivers/platform/x86/firmware_attributes_class.h
@@ -7,6 +7,7 @@
 
 #include <linux/device/class.h>
 
+extern const struct class firmware_attributes_class;
 int fw_attributes_class_get(const struct class **fw_attr_class);
 int fw_attributes_class_put(void);