surface pro 3: Add support driver for Surface Pro 3 buttons

Since Surface Pro 3 does not follow the specs of "Windows ACPI Design
Guide for SoC Platform", code in drivers/input/misc/soc_array.c can
not detect these buttons on it. According to bios implementation,
Surface Pro 3 encapsulates these buttons in a device named "VGBI",
with _HID "MSHW0028". When any of the buttons is pressed, a specify
ACPI notification code for this button will be delivered to "VGBI". For
example, if power button is pressed down, ACPI notification code of 0xc6
will be sent by Notify(VGBI, 0xc6).

This patch leverages "VGBI" to distinguish different ACPI notification
code from Power button, Home button, Volume button, then dispatches these
code to input layer. Lid is already covered by acpi button driver, so
there's no need to rewrite.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=84651
Tested-by: Ethan Schoonover <es@ethanschoonover.com>
Tested-by: Peter Amidon <psa.pub.0@picnicpark.org>
Tested-by: Donavan Lance <tusklahoma@gmail.com>
Tested-by: Stephen Just <stephenjust@gmail.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
[dvhart@linux.intel.com: Formatting corrections in MAINTAINERS and Intel (c)]
Signed-off-by: Darren Hart <dvhart@linux.intel.com>

MAINTAINERS

@@ -6709,6 +6709,12 @@ T:	git git://git.monstr.eu/linux-2.6-microblaze.git
 S:	Supported
 F:	arch/microblaze/
 
+MICROSOFT SURFACE PRO 3 BUTTON DRIVER
+M:	Chen Yu <yu.c.chen@intel.com>
+L:	platform-driver-x86@vger.kernel.org
+S:	Supported
+F:	drivers/platform/x86/surfacepro3_button.c
+
 MICROTEK X6 SCANNER
 M:	Oliver Neukum <oliver@neukum.org>
 S:	Maintained

drivers/platform/x86/Kconfig

@@ -919,4 +919,9 @@ config INTEL_PMC_IPC
 	The PMC is an ARC processor which defines IPC commands for communication
 	with other entities in the CPU.
 
+config SURFACE_PRO3_BUTTON
+	tristate "Power/home/volume buttons driver for Microsoft Surface Pro 3 tablet"
+	depends on ACPI && INPUT
+	---help---
+	  This driver handles the power/home/volume buttons on the Microsoft Surface Pro 3 tablet.
 endif # X86_PLATFORM_DEVICES

drivers/platform/x86/Makefile

@@ -60,3 +60,4 @@ obj-$(CONFIG_INTEL_SMARTCONNECT)	+= intel-smartconnect.o
 obj-$(CONFIG_PVPANIC)           += pvpanic.o
 obj-$(CONFIG_ALIENWARE_WMI)	+= alienware-wmi.o
 obj-$(CONFIG_INTEL_PMC_IPC)	+= intel_pmc_ipc.o
+obj-$(CONFIG_SURFACE_PRO3_BUTTON)	+= surfacepro3_button.o

drivers/platform/x86/surfacepro3_button.c

@@ -0,0 +1,216 @@
+/*
+ * power/home/volume button support for
+ * Microsoft Surface Pro 3 tablet.
+ *
+ * Copyright (c) 2015 Intel Corporation.
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/input.h>
+#include <linux/acpi.h>
+#include <acpi/button.h>
+
+#define SURFACE_BUTTON_HID		"MSHW0028"
+#define SURFACE_BUTTON_OBJ_NAME		"VGBI"
+#define SURFACE_BUTTON_DEVICE_NAME	"Surface Pro 3 Buttons"
+
+#define SURFACE_BUTTON_NOTIFY_PRESS_POWER	0xc6
+#define SURFACE_BUTTON_NOTIFY_RELEASE_POWER	0xc7
+
+#define SURFACE_BUTTON_NOTIFY_PRESS_HOME	0xc4
+#define SURFACE_BUTTON_NOTIFY_RELEASE_HOME	0xc5
+
+#define SURFACE_BUTTON_NOTIFY_PRESS_VOLUME_UP	0xc0
+#define SURFACE_BUTTON_NOTIFY_RELEASE_VOLUME_UP	0xc1
+
+#define SURFACE_BUTTON_NOTIFY_PRESS_VOLUME_DOWN	0xc2
+#define SURFACE_BUTTON_NOTIFY_RELEASE_VOLUME_DOWN	0xc3
+
+ACPI_MODULE_NAME("surface pro 3 button");
+
+MODULE_AUTHOR("Chen Yu");
+MODULE_DESCRIPTION("Surface Pro3 Button Driver");
+MODULE_LICENSE("GPL v2");
+
+/*
+ * Power button, Home button, Volume buttons support is supposed to
+ * be covered by drivers/input/misc/soc_button_array.c, which is implemented
+ * according to "Windows ACPI Design Guide for SoC Platforms".
+ * However surface pro3 seems not to obey the specs, instead it uses
+ * device VGBI(MSHW0028) for dispatching the events.
+ * We choose acpi_driver rather than platform_driver/i2c_driver because
+ * although VGBI has an i2c resource connected to i2c controller, it
+ * is not embedded in any i2c controller's scope, thus neither platform_device
+ * will be created, nor i2c_client will be enumerated, we have to use
+ * acpi_driver.
+ */
+static const struct acpi_device_id surface_button_device_ids[] = {
+	{SURFACE_BUTTON_HID,    0},
+	{"", 0},
+};
+MODULE_DEVICE_TABLE(acpi, surface_button_device_ids);
+
+struct surface_button {
+	unsigned int type;
+	struct input_dev *input;
+	char phys[32];			/* for input device */
+	unsigned long pushed;
+	bool suspended;
+};
+
+static void surface_button_notify(struct acpi_device *device, u32 event)
+{
+	struct surface_button *button = acpi_driver_data(device);
+	struct input_dev *input;
+	int key_code = KEY_RESERVED;
+	bool pressed = false;
+
+	switch (event) {
+	/* Power button press,release handle */
+	case SURFACE_BUTTON_NOTIFY_PRESS_POWER:
+		pressed = true;
+		/*fall through*/
+	case SURFACE_BUTTON_NOTIFY_RELEASE_POWER:
+		key_code = KEY_POWER;
+		break;
+	/* Home button press,release handle */
+	case SURFACE_BUTTON_NOTIFY_PRESS_HOME:
+		pressed = true;
+		/*fall through*/
+	case SURFACE_BUTTON_NOTIFY_RELEASE_HOME:
+		key_code = KEY_LEFTMETA;
+		break;
+	/* Volume up button press,release handle */
+	case SURFACE_BUTTON_NOTIFY_PRESS_VOLUME_UP:
+		pressed = true;
+		/*fall through*/
+	case SURFACE_BUTTON_NOTIFY_RELEASE_VOLUME_UP:
+		key_code = KEY_VOLUMEUP;
+		break;
+	/* Volume down button press,release handle */
+	case SURFACE_BUTTON_NOTIFY_PRESS_VOLUME_DOWN:
+		pressed = true;
+		/*fall through*/
+	case SURFACE_BUTTON_NOTIFY_RELEASE_VOLUME_DOWN:
+		key_code = KEY_VOLUMEDOWN;
+		break;
+	default:
+		dev_info_ratelimited(&device->dev,
+				  "Unsupported event [0x%x]\n", event);
+		break;
+	}
+	input = button->input;
+	if (KEY_RESERVED == key_code)
+		return;
+	if (pressed)
+		pm_wakeup_event(&device->dev, 0);
+	if (button->suspended)
+		return;
+	input_report_key(input, key_code, pressed?1:0);
+	input_sync(input);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int surface_button_suspend(struct device *dev)
+{
+	struct acpi_device *device = to_acpi_device(dev);
+	struct surface_button *button = acpi_driver_data(device);
+
+	button->suspended = true;
+	return 0;
+}
+
+static int surface_button_resume(struct device *dev)
+{
+	struct acpi_device *device = to_acpi_device(dev);
+	struct surface_button *button = acpi_driver_data(device);
+
+	button->suspended = false;
+	return 0;
+}
+#endif
+
+static int surface_button_add(struct acpi_device *device)
+{
+	struct surface_button *button;
+	struct input_dev *input;
+	const char *hid = acpi_device_hid(device);
+	char *name;
+	int error;
+
+	if (strncmp(acpi_device_bid(device), SURFACE_BUTTON_OBJ_NAME,
+	    strlen(SURFACE_BUTTON_OBJ_NAME)))
+		return -ENODEV;
+
+	button = kzalloc(sizeof(struct surface_button), GFP_KERNEL);
+	if (!button)
+		return -ENOMEM;
+
+	device->driver_data = button;
+	button->input = input = input_allocate_device();
+	if (!input) {
+		error = -ENOMEM;
+		goto err_free_button;
+	}
+
+	name = acpi_device_name(device);
+	strcpy(name, SURFACE_BUTTON_DEVICE_NAME);
+	snprintf(button->phys, sizeof(button->phys), "%s/buttons", hid);
+
+	input->name = name;
+	input->phys = button->phys;
+	input->id.bustype = BUS_HOST;
+	input->dev.parent = &device->dev;
+	input_set_capability(input, EV_KEY, KEY_POWER);
+	input_set_capability(input, EV_KEY, KEY_LEFTMETA);
+	input_set_capability(input, EV_KEY, KEY_VOLUMEUP);
+	input_set_capability(input, EV_KEY, KEY_VOLUMEDOWN);
+
+	error = input_register_device(input);
+	if (error)
+		goto err_free_input;
+	dev_info(&device->dev,
+			"%s [%s]\n", name, acpi_device_bid(device));
+	return 0;
+
+ err_free_input:
+	input_free_device(input);
+ err_free_button:
+	kfree(button);
+	return error;
+}
+
+static int surface_button_remove(struct acpi_device *device)
+{
+	struct surface_button *button = acpi_driver_data(device);
+
+	input_unregister_device(button->input);
+	kfree(button);
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(surface_button_pm,
+		surface_button_suspend, surface_button_resume);
+
+static struct acpi_driver surface_button_driver = {
+	.name = "surface_pro3_button",
+	.class = "SurfacePro3",
+	.ids = surface_button_device_ids,
+	.ops = {
+		.add = surface_button_add,
+		.remove = surface_button_remove,
+		.notify = surface_button_notify,
+	},
+	.drv.pm = &surface_button_pm,
+};
+
+module_acpi_driver(surface_button_driver);