intel-vbtn: new driver for Intel Virtual Button

This driver supports power button event in Intel Virtual Button currently.
New Dell XPS 13 requires this driver for the power button.

This driver is copied/modified from intel-hid.c
Most credit goes to the author of intel-hid.c,
Alex Hung <alex.hung@canonical.com>
Signed-off-by: AceLan Kao <acelan.kao@canonical.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>

MAINTAINERS

@@ -5903,6 +5903,12 @@ L:	platform-driver-x86@vger.kernel.org
 S:	Maintained
 F:	drivers/platform/x86/intel-hid.c
 
+INTEL VIRTUAL BUTTON DRIVER
+M:	AceLan Kao <acelan.kao@canonical.com>
+L:	platform-driver-x86@vger.kernel.org
+S:	Maintained
+F:	drivers/platform/x86/intel-vbtn.c
+
 INTEL IDLE DRIVER
 M:	Len Brown <lenb@kernel.org>
 L:	linux-pm@vger.kernel.org

drivers/platform/x86/Kconfig

@@ -774,6 +774,18 @@ config INTEL_HID_EVENT
 	  To compile this driver as a module, choose M here: the module will
 	  be called intel_hid.
 
+config INTEL_VBTN
+	tristate "INTEL VIRTUAL BUTTON"
+	depends on ACPI
+	depends on INPUT
+	select INPUT_SPARSEKMAP
+	help
+	  This driver provides support for the Intel Virtual Button interface.
+	  Some laptops require this driver for power button support.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called intel_vbtn.
+
 config INTEL_SCU_IPC
 	bool "Intel SCU IPC Support"
 	depends on X86_INTEL_MID

drivers/platform/x86/Makefile

@@ -44,6 +44,7 @@ obj-$(CONFIG_TOSHIBA_BT_RFKILL)	+= toshiba_bluetooth.o
 obj-$(CONFIG_TOSHIBA_HAPS)	+= toshiba_haps.o
 obj-$(CONFIG_TOSHIBA_WMI)	+= toshiba-wmi.o
 obj-$(CONFIG_INTEL_HID_EVENT)	+= intel-hid.o
+obj-$(CONFIG_INTEL_VBTN)	+= intel-vbtn.o
 obj-$(CONFIG_INTEL_SCU_IPC)	+= intel_scu_ipc.o
 obj-$(CONFIG_INTEL_SCU_IPC_UTIL) += intel_scu_ipcutil.o
 obj-$(CONFIG_INTEL_MFLD_THERMAL) += intel_mid_thermal.o

drivers/platform/x86/intel-vbtn.c

+/*
+ *  Intel Virtual Button driver for Windows 8.1+
+ *
+ *  Copyright (C) 2016 AceLan Kao <acelan.kao@canonical.com>
+ *  Copyright (C) 2016 Alex Hung <alex.hung@canonical.com>
+ *
+ *  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; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/input.h>
+#include <linux/platform_device.h>
+#include <linux/input/sparse-keymap.h>
+#include <linux/acpi.h>
+#include <acpi/acpi_bus.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("AceLan Kao");
+
+static const struct acpi_device_id intel_vbtn_ids[] = {
+	{"INT33D6", 0},
+	{"", 0},
+};
+
+/* In theory, these are HID usages. */
+static const struct key_entry intel_vbtn_keymap[] = {
+	{ KE_IGNORE, 0xC0, { KEY_POWER } },	/* power key press */
+	{ KE_KEY, 0xC1, { KEY_POWER } },	/* power key release */
+	{ KE_END },
+};
+
+struct intel_vbtn_priv {
+	struct input_dev *input_dev;
+};
+
+static int intel_vbtn_input_setup(struct platform_device *device)
+{
+	struct intel_vbtn_priv *priv = dev_get_drvdata(&device->dev);
+	int ret;
+
+	priv->input_dev = input_allocate_device();
+	if (!priv->input_dev)
+		return -ENOMEM;
+
+	ret = sparse_keymap_setup(priv->input_dev, intel_vbtn_keymap, NULL);
+	if (ret)
+		goto err_free_device;
+
+	priv->input_dev->dev.parent = &device->dev;
+	priv->input_dev->name = "Intel Virtual Button driver";
+	priv->input_dev->id.bustype = BUS_HOST;
+
+	ret = input_register_device(priv->input_dev);
+	if (ret)
+		goto err_free_device;
+
+	return 0;
+
+err_free_device:
+	input_free_device(priv->input_dev);
+	return ret;
+}
+
+static void intel_vbtn_input_destroy(struct platform_device *device)
+{
+	struct intel_vbtn_priv *priv = dev_get_drvdata(&device->dev);
+
+	input_unregister_device(priv->input_dev);
+}
+
+static void notify_handler(acpi_handle handle, u32 event, void *context)
+{
+	struct platform_device *device = context;
+	struct intel_vbtn_priv *priv = dev_get_drvdata(&device->dev);
+
+	if (!sparse_keymap_report_event(priv->input_dev, event, 1, true))
+		dev_info(&device->dev, "unknown event index 0x%x\n",
+			 event);
+}
+
+static int intel_vbtn_probe(struct platform_device *device)
+{
+	acpi_handle handle = ACPI_HANDLE(&device->dev);
+	struct intel_vbtn_priv *priv;
+	acpi_status status;
+	int err;
+
+	status = acpi_evaluate_object(handle, "VBDL", NULL, NULL);
+	if (!ACPI_SUCCESS(status)) {
+		dev_warn(&device->dev, "failed to read Intel Virtual Button driver\n");
+		return -ENODEV;
+	}
+
+	priv = devm_kzalloc(&device->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+	dev_set_drvdata(&device->dev, priv);
+
+	err = intel_vbtn_input_setup(device);
+	if (err) {
+		pr_err("Failed to setup Intel Virtual Button\n");
+		return err;
+	}
+
+	status = acpi_install_notify_handler(handle,
+					     ACPI_DEVICE_NOTIFY,
+					     notify_handler,
+					     device);
+	if (ACPI_FAILURE(status)) {
+		err = -EBUSY;
+		goto err_remove_input;
+	}
+
+	return 0;
+
+err_remove_input:
+	intel_vbtn_input_destroy(device);
+
+	return err;
+}
+
+static int intel_vbtn_remove(struct platform_device *device)
+{
+	acpi_handle handle = ACPI_HANDLE(&device->dev);
+
+	intel_vbtn_input_destroy(device);
+	acpi_remove_notify_handler(handle, ACPI_DEVICE_NOTIFY, notify_handler);
+
+	/*
+	 * Even if we failed to shut off the event stream, we can still
+	 * safely detach from the device.
+	 */
+	return 0;
+}
+
+static struct platform_driver intel_vbtn_pl_driver = {
+	.driver = {
+		.name = "intel-vbtn",
+		.acpi_match_table = intel_vbtn_ids,
+	},
+	.probe = intel_vbtn_probe,
+	.remove = intel_vbtn_remove,
+};
+MODULE_DEVICE_TABLE(acpi, intel_vbtn_ids);
+
+static acpi_status __init
+check_acpi_dev(acpi_handle handle, u32 lvl, void *context, void **rv)
+{
+	const struct acpi_device_id *ids = context;
+	struct acpi_device *dev;
+
+	if (acpi_bus_get_device(handle, &dev) != 0)
+		return AE_OK;
+
+	if (acpi_match_device_ids(dev, ids) == 0)
+		if (acpi_create_platform_device(dev))
+			dev_info(&dev->dev,
+				 "intel-vbtn: created platform device\n");
+
+	return AE_OK;
+}
+
+static int __init intel_vbtn_init(void)
+{
+	acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
+			    ACPI_UINT32_MAX, check_acpi_dev, NULL,
+			    (void *)intel_vbtn_ids, NULL);
+
+	return platform_driver_register(&intel_vbtn_pl_driver);
+}
+module_init(intel_vbtn_init);
+
+static void __exit intel_vbtn_exit(void)
+{
+	platform_driver_unregister(&intel_vbtn_pl_driver);
+}
+module_exit(intel_vbtn_exit);