platform/x86: peaq-wmi: Add new peaq-wmi driver

PEAQ is a new European OEM, I've bought one of their 2-in-1 x86 devices,
which is actually quite a nice device. Under Windows it has Dolby
software for "better" sound and you can select different equalizer
presets using a special button.

This WMI interface for this button is not really nice, as it does not do
notifies (it really does not I triple checked), but since I had already
figured out the entire WMI interface for this I decided to go the full
mile anyway and implement a WMI based input driver for this using
input_polldev since, well, we need to poll.

This commit adds support for this button making it report KEY_SOUND
input events. KEY_SOUND is already used in various places to switch
sound into theatre mode and things like that so it seems appropriate
here.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
[dvhart: minor declaration ordering and commit log typo fixes]
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

drivers/platform/x86/Kconfig

@@ -669,6 +669,13 @@ config MSI_WMI
 	 To compile this driver as a module, choose M here: the module will
 	 be called msi-wmi.
 
+config PEAQ_WMI
+	tristate "PEAQ 2-in-1 WMI hotkey driver"
+	depends on ACPI_WMI
+	depends on INPUT
+	help
+	 Say Y here if you want to support WMI-based hotkeys on PEAQ 2-in-1s.
+
 config TOPSTAR_LAPTOP
 	tristate "Topstar Laptop Extras"
 	depends on ACPI

drivers/platform/x86/Makefile

@@ -35,6 +35,7 @@ obj-$(CONFIG_PANASONIC_LAPTOP)	+= panasonic-laptop.o
 obj-$(CONFIG_INTEL_MENLOW)	+= intel_menlow.o
 obj-$(CONFIG_ACPI_WMI)		+= wmi.o
 obj-$(CONFIG_MSI_WMI)		+= msi-wmi.o
+obj-$(CONFIG_PEAQ_WMI)		+= peaq-wmi.o
 obj-$(CONFIG_SURFACE3_WMI)	+= surface3-wmi.o
 obj-$(CONFIG_TOPSTAR_LAPTOP)	+= topstar-laptop.o
 

drivers/platform/x86/peaq-wmi.c

+/*
+ * PEAQ 2-in-1 WMI hotkey driver
+ * Copyright (C) 2017 Hans de Goede <hdegoede@redhat.com>
+ *
+ * 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/acpi.h>
+#include <linux/input-polldev.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#define PEAQ_DOLBY_BUTTON_GUID		"ABBC0F6F-8EA1-11D1-00A0-C90629100000"
+#define PEAQ_DOLBY_BUTTON_METHOD_ID	5
+#define PEAQ_POLL_INTERVAL_MS		250
+#define PEAQ_POLL_IGNORE_MS		500
+#define PEAQ_POLL_MAX_MS		1000
+
+MODULE_ALIAS("wmi:"PEAQ_DOLBY_BUTTON_GUID);
+
+static unsigned int peaq_ignore_events_counter;
+static struct input_polled_dev *peaq_poll_dev;
+
+/*
+ * The Dolby button (yes really a Dolby button) causes an ACPI variable to get
+ * set on both press and release. The WMI method checks and clears that flag.
+ * So for a press + release we will get back One from the WMI method either once
+ * (if polling after the release) or twice (polling between press and release).
+ * We ignore events for 0.5s after the first event to avoid reporting 2 presses.
+ */
+static void peaq_wmi_poll(struct input_polled_dev *dev)
+{
+	union acpi_object obj;
+	acpi_status status;
+	u32 dummy = 0;
+
+	struct acpi_buffer input = { sizeof(dummy), &dummy };
+	struct acpi_buffer output = { sizeof(obj), &obj };
+
+	status = wmi_evaluate_method(PEAQ_DOLBY_BUTTON_GUID, 1,
+				     PEAQ_DOLBY_BUTTON_METHOD_ID,
+				     &input, &output);
+	if (ACPI_FAILURE(status))
+		return;
+
+	if (obj.type != ACPI_TYPE_INTEGER) {
+		dev_err(&peaq_poll_dev->input->dev,
+			"Error WMBC did not return an integer\n");
+		return;
+	}
+
+	if (peaq_ignore_events_counter && --peaq_ignore_events_counter > 0)
+		return;
+
+	if (obj.integer.value) {
+		input_event(peaq_poll_dev->input, EV_KEY, KEY_SOUND, 1);
+		input_sync(peaq_poll_dev->input);
+		input_event(peaq_poll_dev->input, EV_KEY, KEY_SOUND, 0);
+		input_sync(peaq_poll_dev->input);
+		peaq_ignore_events_counter = max(1u,
+			PEAQ_POLL_IGNORE_MS / peaq_poll_dev->poll_interval);
+	}
+}
+
+static int __init peaq_wmi_init(void)
+{
+	if (!wmi_has_guid(PEAQ_DOLBY_BUTTON_GUID))
+		return -ENODEV;
+
+	peaq_poll_dev = input_allocate_polled_device();
+	if (!peaq_poll_dev)
+		return -ENOMEM;
+
+	peaq_poll_dev->poll = peaq_wmi_poll;
+	peaq_poll_dev->poll_interval = PEAQ_POLL_INTERVAL_MS;
+	peaq_poll_dev->poll_interval_max = PEAQ_POLL_MAX_MS;
+	peaq_poll_dev->input->name = "PEAQ WMI hotkeys";
+	peaq_poll_dev->input->phys = "wmi/input0";
+	peaq_poll_dev->input->id.bustype = BUS_HOST;
+	input_set_capability(peaq_poll_dev->input, EV_KEY, KEY_SOUND);
+
+	return input_register_polled_device(peaq_poll_dev);
+}
+
+static void __exit peaq_wmi_exit(void)
+{
+	if (!wmi_has_guid(PEAQ_DOLBY_BUTTON_GUID))
+		return;
+
+	input_unregister_polled_device(peaq_poll_dev);
+}
+
+module_init(peaq_wmi_init);
+module_exit(peaq_wmi_exit);
+
+MODULE_DESCRIPTION("PEAQ 2-in-1 WMI hotkey driver");
+MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
+MODULE_LICENSE("GPL");