Input: add D-Link DIR-685 touchkeys driver

This adds support for the D-Link DIR-685 touchkeys found in the
router with this name.

The vendor code calles this a "touchpad" but we are registering
it here under its real name.

Signed-off-by: Linus Walleij <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

Documentation/devicetree/bindings/input/dlink,dir685-touchkeys.txt

···
+* D-Link DIR-685 Touchkeys
+
+This is a I2C one-off touchkey controller based on the Cypress Semiconductor
+CY8C214 MCU with some firmware in its internal 8KB flash. The circuit
+board inside the router is named E119921.
+
+The touchkey device node should be placed inside an I2C bus node.
+
+Required properties:
+- compatible: must be "dlink,dir685-touchkeys"
+- reg: the I2C address of the touchkeys
+- interrupts: reference to the interrupt number
+
+Example:
+
+touchkeys@26 {
+	compatible = "dlink,dir685-touchkeys";
+	reg = <0x26>;
+	interrupt-parent = <&gpio0>;
+	interrupts = <17 IRQ_TYPE_EDGE_FALLING>;
+};

MAINTAINERS

···
 F:	drivers/input/touchscreen/cyttsp*
 F:	include/linux/input/cyttsp.h
 
+D-LINK DIR-685 TOUCHKEYS DRIVER
+M:	Linus Walleij <[e-mail]>
+L:	[e-mail]
+S:	Supported
+F:	drivers/input/dlink-dir685-touchkeys.c
+
 DALLAS/MAXIM DS1685-FAMILY REAL TIME CLOCK
 M:	Joshua Kinard <[e-mail]>
 S:	Maintained

drivers/input/keyboard/Kconfig

···
 	  To compile this driver as a module, choose M here: the
 	  module will be called clps711x-keypad.
 
+config KEYBOARD_DLINK_DIR685
+	tristate "D-Link DIR-685 touchkeys support"
+	depends on I2C
+	default ARCH_GEMINI
+	help
+	  If you say yes here you get support for the D-Link DIR-685
+	  touchkeys.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called dlink-dir685-touchkeys.
+
 config KEYBOARD_LKKBD
 	tristate "DECstation/VAXstation LK201/LK401 keyboard"
 	select SERIO

drivers/input/keyboard/Makefile

···
 obj-$(CONFIG_KEYBOARD_CLPS711X)		+= clps711x-keypad.o
 obj-$(CONFIG_KEYBOARD_CROS_EC)		+= cros_ec_keyb.o
 obj-$(CONFIG_KEYBOARD_DAVINCI)		+= davinci_keyscan.o
+obj-$(CONFIG_KEYBOARD_DLINK_DIR685)	+= dlink-dir685-touchkeys.o
 obj-$(CONFIG_KEYBOARD_EP93XX)		+= ep93xx_keypad.o
 obj-$(CONFIG_KEYBOARD_GOLDFISH_EVENTS)	+= goldfish_events.o
 obj-$(CONFIG_KEYBOARD_GPIO)		+= gpio_keys.o

drivers/input/keyboard/dlink-dir685-touchkeys.c

···
+/*
+ * D-Link DIR-685 router I2C-based Touchkeys input driver
+ * Copyright (C) 2017 Linus Walleij <[e-mail]>
+ *
+ * This is a one-off touchkey controller based on the Cypress Semiconductor
+ * CY8C214 MCU with some firmware in its internal 8KB flash. The circuit
+ * board inside the router is named E119921
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+#include <linux/input.h>
+#include <linux/slab.h>
+#include <linux/bitops.h>
+
+struct dir685_touchkeys {
+	struct device		*dev;
+	struct i2c_client	*client;
+	struct input_dev	*input;
+	unsigned long		cur_key;
+	u16			codes[7];
+};
+
+static irqreturn_t dir685_tk_irq_thread(int irq, void *data)
+{
+	struct dir685_touchkeys *tk = data;
+	const int num_bits = min_t(int, ARRAY_SIZE(tk->codes), 16);
+	unsigned long changed;
+	u8 buf[6];
+	unsigned long key;
+	int i;
+	int err;
+
+	memset(buf, 0, sizeof(buf));
+	err = i2c_master_recv(tk->client, buf, sizeof(buf));
+	if (err != sizeof(buf)) {
+		dev_err(tk->dev, "short read %d\n", err);
+		return IRQ_HANDLED;
+	}
+
+	dev_dbg(tk->dev, "IN: %*ph\n", (int)sizeof(buf), buf);
+	key = be16_to_cpup((__be16 *) &buf[4]);
+
+	/* Figure out if any bits went high or low since last message */
+	changed = tk->cur_key ^ key;
+	for_each_set_bit(i, &changed, num_bits) {
+		dev_dbg(tk->dev, "key %d is %s\n", i,
+			test_bit(i, &key) ? "down" : "up");
+		input_report_key(tk->input, tk->codes[i], test_bit(i, &key));
+	}
+
+	/* Store currently down keys */
+	tk->cur_key = key;
+	input_sync(tk->input);
+
+	return IRQ_HANDLED;
+}
+
+static int dir685_tk_probe(struct i2c_client *client,
+			   const struct i2c_device_id *id)
+{
+	struct dir685_touchkeys *tk;
+	struct device *dev = &client->dev;
+	u8 bl_data[] = { 0xa7, 0x40 };
+	int err;
+	int i;
+
+	tk = devm_kzalloc(&client->dev, sizeof(*tk), GFP_KERNEL);
+	if (!tk)
+		return -ENOMEM;
+
+	tk->input = devm_input_allocate_device(dev);
+	if (!tk->input)
+		return -ENOMEM;
+
+	tk->client = client;
+	tk->dev = dev;
+
+	tk->input->keycodesize = sizeof(u16);
+	tk->input->keycodemax = ARRAY_SIZE(tk->codes);
+	tk->input->keycode = tk->codes;
+	tk->codes[0] = KEY_UP;
+	tk->codes[1] = KEY_DOWN;
+	tk->codes[2] = KEY_LEFT;
+	tk->codes[3] = KEY_RIGHT;
+	tk->codes[4] = KEY_ENTER;
+	tk->codes[5] = KEY_WPS_BUTTON;
+	/*
+	 * This key appears in the vendor driver, but I have
+	 * not been able to activate it.
+	 */
+	tk->codes[6] = KEY_RESERVED;
+
+	__set_bit(EV_KEY, tk->input->evbit);
+	for (i = 0; i < ARRAY_SIZE(tk->codes); i++)
+		__set_bit(tk->codes[i], tk->input->keybit);
+	__clear_bit(KEY_RESERVED, tk->input->keybit);
+
+	tk->input->name = "D-Link DIR-685 touchkeys";
+	tk->input->id.bustype = BUS_I2C;
+
+	err = input_register_device(tk->input);
+	if (err)
+		return err;
+
+	/* Set the brightness to max level */
+	err = i2c_master_send(client, bl_data, sizeof(bl_data));
+	if (err != sizeof(bl_data))
+		dev_warn(tk->dev, "error setting brightness level\n");
+
+	if (!client->irq) {
+		dev_err(dev, "no IRQ on the I2C device\n");
+		return -ENODEV;
+	}
+	err = devm_request_threaded_irq(dev, client->irq,
+					NULL, dir685_tk_irq_thread,
+					IRQF_ONESHOT,
+					"dir685-tk", tk);
+	if (err) {
+		dev_err(dev, "can't request IRQ\n");
+		return err;
+	}
+
+	return 0;
+}
+
+static const struct i2c_device_id dir685_tk_id[] = {
+	{ "dir685tk", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, dir685_tk_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id dir685_tk_of_match[] = {
+	{ .compatible = "dlink,dir685-touchkeys" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, dir685_tk_of_match);
+#endif
+
+static struct i2c_driver dir685_tk_i2c_driver = {
+	.driver = {
+		.name	= "dlin-dir685-touchkeys",
+		.of_match_table = of_match_ptr(dir685_tk_of_match),
+	},
+	.probe		= dir685_tk_probe,
+	.id_table	= dir685_tk_id,
+};
+module_i2c_driver(dir685_tk_i2c_driver);
+
+MODULE_AUTHOR("Linus Walleij <[e-mail]>");
+MODULE_DESCRIPTION("D-Link DIR-685 touchkeys driver");
+MODULE_LICENSE("GPL");