platform/x86: firmware_attributes_class: Create helper file for handling firmware-attributes class registration events

This offers shared code for registering the firmware_attributes_class,
which is used by the Dell and Lenovo WMI management drivers.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Mark Pearson <markpearson@lenovo.com>
Link: https://lore.kernel.org/r/20210530223111.25929-1-markpearson@lenovo.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

1 files changed, 52 insertions, 0 deletions

diff --git a/drivers/platform/x86/firmware_attributes_class.c b/drivers/platform/x86/firmware_attributes_class.c
new file mode 100644
index 000000000000..d62ec3d71ede
--- /dev/null
+++ b/drivers/platform/x86/firmware_attributes_class.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/* Firmware attributes class helper module */
+
+#include <linux/mutex.h>
+#include <linux/device/class.h>
+#include <linux/module.h>
+#include "firmware_attributes_class.h"
+
+static DEFINE_MUTEX(fw_attr_lock);
+int fw_attr_inuse;
+
+static struct class firmware_attributes_class = {
+	.name = "firmware-attributes",
+};
+
+int fw_attributes_class_get(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);
+
+MODULE_AUTHOR("Mark Pearson <markpearson@lenovo.com>");
+MODULE_LICENSE("GPL");