platform/x86: Introduce button support for the Surface 3

The Surface 3 is not following the ACPI spec for PNP0C40, but nearly.
The device is connected to a I2C device that might have some magic
but we don't know about.
Just create the device after the enumeration and use the declared GPIOs
to provide button support.

This driver is just an adaptation of drivers/input/misc/soc_button_array.c

The Surface Pro 3 is using an ACPI driver and matches against the bid
of the device ("VGBI"). To prevent this incompatible driver to be used
on the Surface Pro, we add a match on the Surface 3 bid "TEV2".

link: https://bugzilla.kernel.org/show_bug.cgi?id=102761Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/platform/x86/Kconfig

@@ -1023,6 +1023,12 @@ config SURFACE_PRO3_BUTTON
 	---help---
 	  This driver handles the power/home/volume buttons on the Microsoft Surface Pro 3/4 tablet.
 
+config SURFACE_3_BUTTON
+	tristate "Power/home/volume buttons driver for Microsoft Surface 3 tablet"
+	depends on ACPI && KEYBOARD_GPIO
+	---help---
+	  This driver handles the power/home/volume buttons on the Microsoft Surface 3 tablet.
+
 config INTEL_PUNIT_IPC
 	tristate "Intel P-Unit IPC Driver"
 	---help---

drivers/platform/x86/Makefile

@@ -67,6 +67,7 @@ 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
+obj-$(CONFIG_SURFACE_3_BUTTON)	+= surface3_button.o
 obj-$(CONFIG_INTEL_PUNIT_IPC)  += intel_punit_ipc.o
 obj-$(CONFIG_INTEL_TELEMETRY)	+= intel_telemetry_core.o \
 				   intel_telemetry_pltdrv.o \

drivers/platform/x86/surface3_button.c

+/*
+ * Supports for the button array on the Surface tablets.
+ *
+ * (C) Copyright 2016 Red Hat, Inc
+ *
+ * Based on soc_button_array.c:
+ *
+ * {C} Copyright 2014 Intel Corporation
+ *
+ * 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/module.h>
+#include <linux/input.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/i2c.h>
+#include <linux/slab.h>
+#include <linux/acpi.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio_keys.h>
+#include <linux/gpio.h>
+#include <linux/platform_device.h>
+
+
+#define SURFACE_BUTTON_OBJ_NAME		"TEV2"
+#define MAX_NBUTTONS			4
+
+/*
+ * Some of the buttons like volume up/down are auto repeat, while others
+ * are not. To support both, we register two platform devices, and put
+ * buttons into them based on whether the key should be auto repeat.
+ */
+#define BUTTON_TYPES			2
+
+/*
+ * 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 3 seems not to obey the specs, instead it uses
+ * device TEV2(MSHW0028) for declaring the GPIOs. The gpios are also slightly
+ * different in which the Home button is active high.
+ * Compared to surfacepro3_button.c which also handles MSHW0028, the Surface 3
+ * is a reduce platform and thus uses GPIOs, not ACPI events.
+ * We choose an I2C driver here because we need to access the resources
+ * declared under the device node, while surfacepro3_button.c only needs
+ * the ACPI companion node.
+ */
+static const struct acpi_device_id surface3_acpi_match[] = {
+	{ "MSHW0028", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, surface3_acpi_match);
+
+struct surface3_button_info {
+	const char *name;
+	int acpi_index;
+	unsigned int event_type;
+	unsigned int event_code;
+	bool autorepeat;
+	bool wakeup;
+	bool active_low;
+};
+
+struct surface3_button_data {
+	struct platform_device *children[BUTTON_TYPES];
+};
+
+/*
+ * Get the Nth GPIO number from the ACPI object.
+ */
+static int surface3_button_lookup_gpio(struct device *dev, int acpi_index)
+{
+	struct gpio_desc *desc;
+	int gpio;
+
+	desc = gpiod_get_index(dev, NULL, acpi_index, GPIOD_ASIS);
+	if (IS_ERR(desc))
+		return PTR_ERR(desc);
+
+	gpio = desc_to_gpio(desc);
+
+	gpiod_put(desc);
+
+	return gpio;
+}
+
+static struct platform_device *
+surface3_button_device_create(struct i2c_client *client,
+			      const struct surface3_button_info *button_info,
+			      bool autorepeat)
+{
+	const struct surface3_button_info *info;
+	struct platform_device *pd;
+	struct gpio_keys_button *gpio_keys;
+	struct gpio_keys_platform_data *gpio_keys_pdata;
+	int n_buttons = 0;
+	int gpio;
+	int error;
+
+	gpio_keys_pdata = devm_kzalloc(&client->dev,
+				       sizeof(*gpio_keys_pdata) +
+				       sizeof(*gpio_keys) * MAX_NBUTTONS,
+				       GFP_KERNEL);
+	if (!gpio_keys_pdata)
+		return ERR_PTR(-ENOMEM);
+
+	gpio_keys = (void *)(gpio_keys_pdata + 1);
+
+	for (info = button_info; info->name; info++) {
+		if (info->autorepeat != autorepeat)
+			continue;
+
+		gpio = surface3_button_lookup_gpio(&client->dev,
+						   info->acpi_index);
+		if (!gpio_is_valid(gpio))
+			continue;
+
+		gpio_keys[n_buttons].type = info->event_type;
+		gpio_keys[n_buttons].code = info->event_code;
+		gpio_keys[n_buttons].gpio = gpio;
+		gpio_keys[n_buttons].active_low = info->active_low;
+		gpio_keys[n_buttons].desc = info->name;
+		gpio_keys[n_buttons].wakeup = info->wakeup;
+		n_buttons++;
+	}
+
+	if (n_buttons == 0) {
+		error = -ENODEV;
+		goto err_free_mem;
+	}
+
+	gpio_keys_pdata->buttons = gpio_keys;
+	gpio_keys_pdata->nbuttons = n_buttons;
+	gpio_keys_pdata->rep = autorepeat;
+
+	pd = platform_device_alloc("gpio-keys", PLATFORM_DEVID_AUTO);
+	if (!pd) {
+		error = -ENOMEM;
+		goto err_free_mem;
+	}
+
+	error = platform_device_add_data(pd, gpio_keys_pdata,
+					 sizeof(*gpio_keys_pdata));
+	if (error)
+		goto err_free_pdev;
+
+	error = platform_device_add(pd);
+	if (error)
+		goto err_free_pdev;
+
+	return pd;
+
+err_free_pdev:
+	platform_device_put(pd);
+err_free_mem:
+	devm_kfree(&client->dev, gpio_keys_pdata);
+	return ERR_PTR(error);
+}
+
+static int surface3_button_remove(struct i2c_client *client)
+{
+	struct surface3_button_data *priv = i2c_get_clientdata(client);
+
+	int i;
+
+	for (i = 0; i < BUTTON_TYPES; i++)
+		if (priv->children[i])
+			platform_device_unregister(priv->children[i]);
+
+	return 0;
+}
+
+static struct surface3_button_info surface3_button_surface3[] = {
+	{ "power", 0, EV_KEY, KEY_POWER, false, true, true },
+	{ "home", 1, EV_KEY, KEY_LEFTMETA, false, true, false },
+	{ "volume_up", 2, EV_KEY, KEY_VOLUMEUP, true, false, true },
+	{ "volume_down", 3, EV_KEY, KEY_VOLUMEDOWN, true, false, true },
+	{ }
+};
+
+static int surface3_button_probe(struct i2c_client *client,
+				 const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct surface3_button_data *priv;
+	struct platform_device *pd;
+	int i;
+	int error;
+
+	if (strncmp(acpi_device_bid(ACPI_COMPANION(&client->dev)),
+		    SURFACE_BUTTON_OBJ_NAME,
+		    strlen(SURFACE_BUTTON_OBJ_NAME)))
+		return -ENODEV;
+
+	if (gpiod_count(dev, KBUILD_MODNAME) <= 0) {
+		dev_dbg(dev, "no GPIO attached, ignoring...\n");
+		return -ENODEV;
+	}
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, priv);
+
+	for (i = 0; i < BUTTON_TYPES; i++) {
+		pd = surface3_button_device_create(client,
+						   surface3_button_surface3,
+						   i == 0);
+		if (IS_ERR(pd)) {
+			error = PTR_ERR(pd);
+			if (error != -ENODEV) {
+				surface3_button_remove(client);
+				return error;
+			}
+			continue;
+		}
+
+		priv->children[i] = pd;
+	}
+
+	if (!priv->children[0] && !priv->children[1])
+		return -ENODEV;
+
+	return 0;
+}
+
+static const struct i2c_device_id surface3_id[] = {
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, surface3_id);
+
+static struct i2c_driver surface3_driver = {
+	.probe = surface3_button_probe,
+	.remove = surface3_button_remove,
+	.id_table = surface3_id,
+	.driver = {
+		.name = "surface3",
+		.acpi_match_table = ACPI_PTR(surface3_acpi_match),
+	},
+};
+module_i2c_driver(surface3_driver);
+
+MODULE_AUTHOR("Benjamin Tissoires <benjamin.tissoires@gmail.com>");
+MODULE_DESCRIPTION("surface3 button array driver");
+MODULE_LICENSE("GPL v2");