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>

drivers/platform/x86/Kconfig

@@ -1077,6 +1077,10 @@ config TOUCHSCREEN_DMI
 	  the OS-image for the device. This option supplies the missing info.
 	  Enable this for x86 tablets with Silead or Chipone touchscreens.
 
+config FW_ATTR_CLASS
+	tristate
+	default n
+
 config INTEL_IMR
 	bool "Intel Isolated Memory Region support"
 	depends on X86_INTEL_QUARK && IOSF_MBI

drivers/platform/x86/Makefile

@@ -111,6 +111,7 @@ obj-$(CONFIG_SYSTEM76_ACPI)	+= system76_acpi.o
 obj-$(CONFIG_TOPSTAR_LAPTOP)	+= topstar-laptop.o
 
 # Platform drivers
+obj-$(CONFIG_FW_ATTR_CLASS)		+= firmware_attributes_class.o
 obj-$(CONFIG_I2C_MULTI_INSTANTIATE)	+= i2c-multi-instantiate.o
 obj-$(CONFIG_MLX_PLATFORM)		+= mlx-platform.o
 obj-$(CONFIG_TOUCHSCREEN_DMI)		+= touchscreen_dmi.o

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");

drivers/platform/x86/firmware_attributes_class.h

@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/* Firmware attributes class helper module */
+
+#ifndef FW_ATTR_CLASS_H
+#define FW_ATTR_CLASS_H
+
+int fw_attributes_class_get(struct class **fw_attr_class);
+int fw_attributes_class_put(void);
+
+#endif /* FW_ATTR_CLASS_H */