[PATCH v2 1/3] platform/x86: firmware_attributes_class: Create helper file for handling firmware-attributes class registration events

[Mark Pearson <markpearson@lenovo.com>]

This will be used by the Dell and Lenovo WMI management drivers to
prevent both drivers being active.

Signed-off-by: Mark Pearson <markpearson@lenovo.com>
---
Changes in v2:
 This is a new file requested as part of the review of the proposed
think_lmi.c driver. Labeling as V2 to keep series consistent (hope
that's correct).

 drivers/platform/x86/Kconfig                  |  6 +++
 drivers/platform/x86/Makefile                 |  1 +
 .../platform/x86/firmware_attributes_class.c  | 51 +++++++++++++++++++
 .../platform/x86/firmware_attributes_class.h  | 13 +++++
 4 files changed, 71 insertions(+)
 create mode 100644 drivers/platform/x86/firmware_attributes_class.c
 create mode 100644 drivers/platform/x86/firmware_attributes_class.h

diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index 2714f7c38..b0e1e5f65 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -1076,6 +1076,12 @@ 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 "Firmware attributes class helper module"
+	help
+	  This option should be enabled by any modules using the firmware
+	  attributes class.
+
 config INTEL_IMR
 	bool "Intel Isolated Memory Region support"
 	depends on X86_INTEL_QUARK && IOSF_MBI
diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
index dcc8cdb95..147573f69 100644
--- a/drivers/platform/x86/Makefile
+++ b/drivers/platform/x86/Makefile
@@ -115,6 +115,7 @@ obj-$(CONFIG_TOPSTAR_LAPTOP)	+= topstar-laptop.o
 obj-$(CONFIG_I2C_MULTI_INSTANTIATE)	+= i2c-multi-instantiate.o
 obj-$(CONFIG_MLX_PLATFORM)		+= mlx-platform.o
 obj-$(CONFIG_TOUCHSCREEN_DMI)		+= touchscreen_dmi.o
+obj-$(CONFIG_FW_ATTR_CLASS)             += firmware_attributes_class.o
 
 # Intel uncore drivers
 obj-$(CONFIG_INTEL_IPS)				+= intel_ips.o
diff --git a/drivers/platform/x86/firmware_attributes_class.c b/drivers/platform/x86/firmware_attributes_class.c
new file mode 100644
index 000000000..4ed959d6c
--- /dev/null
+++ b/drivers/platform/x86/firmware_attributes_class.c
@@ -0,0 +1,51 @@
+// 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>
+
+static DEFINE_MUTEX(fw_attr_lock);
+bool fw_attr_inuse;
+
+static struct class firmware_attributes_class = {
+	.name = "firmware-attributes",
+};
+
+int fw_attributes_class_register(struct class **fw_attr_class)
+{
+	int err;
+
+	mutex_lock(&fw_attr_lock);
+	/* We can only have one active FW attribute class */
+	if (fw_attr_inuse) {
+		mutex_unlock(&fw_attr_lock);
+		return -EEXIST;
+	}
+
+	err = class_register(&firmware_attributes_class);
+	if (err) {
+		mutex_unlock(&fw_attr_lock);
+		return err;
+	}
+	fw_attr_inuse = true;
+	*fw_attr_class = &firmware_attributes_class;
+	mutex_unlock(&fw_attr_lock);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fw_attributes_class_register);
+
+void fw_attributes_class_remove(void)
+{
+	mutex_lock(&fw_attr_lock);
+	fw_attr_inuse = false;
+	class_unregister(&firmware_attributes_class);
+	mutex_unlock(&fw_attr_lock);
+}
+EXPORT_SYMBOL_GPL(fw_attributes_class_remove);
+
+MODULE_AUTHOR("Mark Pearson <markpearson@lenovo.com>");
+MODULE_LICENSE("GPL");
+
+
diff --git a/drivers/platform/x86/firmware_attributes_class.h b/drivers/platform/x86/firmware_attributes_class.h
new file mode 100644
index 000000000..e479a5720
--- /dev/null
+++ b/drivers/platform/x86/firmware_attributes_class.h
@@ -0,0 +1,13 @@
+/* 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_register(struct class **fw_attr_class);
+void fw_attributes_class_remove(void);
+
+#endif /* FW_ATTR_CLASS_H */
+
+
-- 
2.31.1