platform/x86: Add Asus Wireless Radio Control driver

Some Asus notebooks like the Asus E202SA and the Asus X555UB have a
separate ACPI device for notifications from the airplane mode hotkey.
This device is called "Wireless Radio Control" in Asus websites and ASHS
in the DSDT, and its ACPI _HID is ATK4002 in the two models mentioned
above.

For these models, when the airplane mode hotkey (Fn+F2) is pressed, a
query 0x0B is started in the Embedded Controller, and all this query does
is a notify ASHS with the value 0x88 (for acpi_osi >= "Windows 2012"):

	Scope (_SB.PCI0.SBRG.EC0)
	{
		(...)
		Method (_Q0B, 0, NotSerialized)  // _Qxx: EC Query
		{
			If ((MSOS () >= OSW8))
			{
				Notify (ASHS, 0x88) // Device-Specific
			}
			Else
			{
				(...)
			}
		}
	}

Signed-off-by: João Paulo Rechi Vita <jprvita@endlessm.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>

MAINTAINERS

@@ -1791,6 +1791,12 @@ S:	Maintained
 F:	drivers/platform/x86/asus*.c
 F:	drivers/platform/x86/eeepc*.c
 
+ASUS WIRELESS RADIO CONTROL DRIVER
+M:	João Paulo Rechi Vita <jprvita@gmail.com>
+L:	platform-driver-x86@vger.kernel.org
+S:	Maintained
+F:	drivers/platform/x86/asus-wireless.c
+
 ASYNCHRONOUS TRANSFERS/TRANSFORMS (IOAT) API
 R:	Dan Williams <dan.j.williams@intel.com>
 W:	http://sourceforge.net/projects/xscaleiop

drivers/platform/x86/Kconfig

@@ -587,6 +587,20 @@ config EEEPC_WMI
 	  If you have an ACPI-WMI compatible Eee PC laptop (>= 1000), say Y or M
 	  here.
 
+config ASUS_WIRELESS
+	tristate "Asus Wireless Radio Control Driver"
+	depends on ACPI
+	depends on INPUT
+	---help---
+	  The Asus Wireless Radio Control handles the airplane mode hotkey
+	  present on some Asus laptops.
+
+	  Say Y or M here if you have an ASUS notebook with an airplane mode
+	  hotkey.
+
+	  If you choose to compile this driver as a module the module will be
+	  called asus-wireless.
+
 config ACPI_WMI
 	tristate "WMI"
 	depends on ACPI

drivers/platform/x86/Makefile

@@ -5,6 +5,7 @@
 obj-$(CONFIG_ASUS_LAPTOP)	+= asus-laptop.o
 obj-$(CONFIG_ASUS_WMI)		+= asus-wmi.o
 obj-$(CONFIG_ASUS_NB_WMI)	+= asus-nb-wmi.o
+obj-$(CONFIG_ASUS_WIRELESS)	+= asus-wireless.o
 obj-$(CONFIG_EEEPC_LAPTOP)	+= eeepc-laptop.o
 obj-$(CONFIG_EEEPC_WMI)		+= eeepc-wmi.o
 obj-$(CONFIG_MSI_LAPTOP)	+= msi-laptop.o

drivers/platform/x86/asus-wireless.c

@@ -0,0 +1,83 @@
+/*
+ * Asus Wireless Radio Control Driver
+ *
+ * Copyright (C) 2015-2016 Endless Mobile, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/acpi.h>
+#include <linux/input.h>
+#include <linux/pci_ids.h>
+
+struct asus_wireless_data {
+	struct input_dev *idev;
+};
+
+static void asus_wireless_notify(struct acpi_device *adev, u32 event)
+{
+	struct asus_wireless_data *data = acpi_driver_data(adev);
+
+	dev_dbg(&adev->dev, "event=%#x\n", event);
+	if (event != 0x88) {
+		dev_notice(&adev->dev, "Unknown ASHS event: %#x\n", event);
+		return;
+	}
+	input_report_key(data->idev, KEY_RFKILL, 1);
+	input_report_key(data->idev, KEY_RFKILL, 0);
+	input_sync(data->idev);
+}
+
+static int asus_wireless_add(struct acpi_device *adev)
+{
+	struct asus_wireless_data *data;
+
+	data = devm_kzalloc(&adev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+	adev->driver_data = data;
+
+	data->idev = devm_input_allocate_device(&adev->dev);
+	if (!data->idev)
+		return -ENOMEM;
+	data->idev->name = "Asus Wireless Radio Control";
+	data->idev->phys = "asus-wireless/input0";
+	data->idev->id.bustype = BUS_HOST;
+	data->idev->id.vendor = PCI_VENDOR_ID_ASUSTEK;
+	set_bit(EV_KEY, data->idev->evbit);
+	set_bit(KEY_RFKILL, data->idev->keybit);
+	return input_register_device(data->idev);
+}
+
+static int asus_wireless_remove(struct acpi_device *adev)
+{
+	return 0;
+}
+
+static const struct acpi_device_id device_ids[] = {
+	{"ATK4002", 0},
+	{"", 0},
+};
+MODULE_DEVICE_TABLE(acpi, device_ids);
+
+static struct acpi_driver asus_wireless_driver = {
+	.name = "Asus Wireless Radio Control Driver",
+	.class = "hotkey",
+	.ids = device_ids,
+	.ops = {
+		.add = asus_wireless_add,
+		.remove = asus_wireless_remove,
+		.notify = asus_wireless_notify,
+	},
+};
+module_acpi_driver(asus_wireless_driver);
+
+MODULE_DESCRIPTION("Asus Wireless Radio Control Driver");
+MODULE_AUTHOR("João Paulo Rechi Vita <jprvita@gmail.com>");
+MODULE_LICENSE("GPL");