Re: [PATCH 2/2 v3] input: keyboard: 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 <redacted>
---
ChangeLog v2->v3:
- Switch "KEY_W" to "KEY_WPS_BUTTON" as apropriate.
- Add comment about the mysterious "KEY_O".
ChangeLog v1->v2:
- Change the whole touchpad->touchkey naming scheme, even in
  the device tree bindings.
- Embedd the keycodes directly into the state container and
  open code the key assignments.
- Use Dmitry's suggested XOR loop to detect key state changes.
- Drop <linux/mutex.h> add <linux/bitops.h>
- Drop dependency on the OF config symbol.
- Rename all "ret" to "err".
- Drop driver dev_info() announcement.
---
 MAINTAINERS                                     |   6 +
 drivers/input/keyboard/Kconfig                  |  11 ++
 drivers/input/keyboard/Makefile                 |   1 +
 drivers/input/keyboard/dlink-dir685-touchkeys.c | 157 ++++++++++++++++++++++++
 4 files changed, 175 insertions(+)
 create mode 100644 drivers/input/keyboard/dlink-dir685-touchkeys.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 96753be12026..eea776eec996 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS

@@ -3779,6 +3779,12 @@ S:	Supported
 F:	drivers/input/touchscreen/cyttsp*
 F:	include/linux/input/cyttsp.h
 
+D-LINK DIR-685 TOUCHKEYS DRIVER
+M:	Linus Walleij <linus.walleij@linaro.org>
+L:	linux-input@vger.kernel.org
+S:	Supported
+F:	drivers/input/dlink-dir685-touchkeys.c
+
 DALLAS/MAXIM DS1685-FAMILY REAL TIME CLOCK
 M:	Joshua Kinard <kumba@gentoo.org>
 S:	Maintained

diff --git a/drivers/input/keyboard/Kconfig b/drivers/input/keyboard/Kconfig
index 97acd6524ad7..4c4ab1ced235 100644
--- a/drivers/input/keyboard/Kconfig
+++ b/drivers/input/keyboard/Kconfig

@@ -178,6 +178,17 @@ config KEYBOARD_CLPS711X
 	  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

diff --git a/drivers/input/keyboard/Makefile b/drivers/input/keyboard/Makefile
index 7d9acff819a7..d2338bacdad1 100644
--- a/drivers/input/keyboard/Makefile
+++ b/drivers/input/keyboard/Makefile

@@ -17,6 +17,7 @@ obj-$(CONFIG_KEYBOARD_CAP11XX)		+= cap11xx.o
 obj-$(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

diff --git a/drivers/input/keyboard/dlink-dir685-touchkeys.c b/drivers/input/keyboard/dlink-dir685-touchkeys.c
new file mode 100644
index 000000000000..6d6f60963e3c
--- /dev/null
+++ b/drivers/input/keyboard/dlink-dir685-touchkeys.c

@@ -0,0 +1,157 @@
+/*
+ * D-Link DIR-685 router I2C-based Touchkeys input driver
+ * Copyright (C) 2017 Linus Walleij <linus.walleij@linaro.org>
+ *
+ * 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: %02x, %02x, %02x, %02x, %02x, %02x\n",
+		buf[0], buf[1], buf[2], buf[3], buf[4], buf[5]);