Date:	Tue,  3 May 2016 10:13:31 -0700
From:	Grant Grundler <grundler@...omium.org>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	linux-input <linux-input@...r.kernel.org>,
	Grant Likely <grant.likely@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>, devicetree@...r.kernel.org,
	Hung-yu Wu <hywu@...gle.com>,
	Grant Grundler <grundler@...omium.org>
Subject: Input: add Atmel Atmegaxx captouch driver

Add I2C driver for AtmegaXX capacitive touch device.

Signed-off-by: Hung-yu Wu <hywu@...gle.com>
Signed-off-by: Grant Grundler <grundler@...omium.org>
---
 .../bindings/input/atmel,atmegaxx_captouch.txt     |  34 +++
 drivers/input/misc/Kconfig                         |  11 +
 drivers/input/misc/Makefile                        |   1 +
 drivers/input/misc/atmegaxx_captouch.c             | 278 +++++++++++++++++++++
 4 files changed, 324 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/input/atmel,atmegaxx_captouch.txt
 create mode 100644 drivers/input/misc/atmegaxx_captouch.c

For those that like to know how sausage is made, ChromeOS code review history here:
   https://chromium-review.googlesource.com/339950

Driver was tested with prototype HW and it reliably reports events correctly.
Manual testing was just using "evtest /dev/input/event0" and watch for events.

diff --git a/Documentation/devicetree/bindings/input/atmel,atmegaxx_captouch.txt b/Documentation/devicetree/bindings/input/atmel,atmegaxx_captouch.txt
new file mode 100644
index 0000000..07a4b0b
--- /dev/null
+++ b/Documentation/devicetree/bindings/input/atmel,atmegaxx_captouch.txt
@@ -0,0 +1,34 @@
+Device tree bindings for Atmel AtmegaXX capacitive touch sensor
+
+The node for this device must be a child of a I2C controller node, as the
+device communicates via I2C.
+
+Required properties:
+
+	compatible:	Must be "atmel,atmegaxx_captouch".
+	reg:		The I2C slave address of the device.
+	interrupts:	Property describing the interrupt line the device
+			is connected to. The device only has one interrupt
+			source.
+	linux,keycodes:	Specifies an array of numeric keycode values to
+			be used for reporting button presses. The array can
+			contain up to 8 entries.
+
+Optional properties:
+
+	autorepeat:	Enables the Linux input system's autorepeat
+			feature on the input device.
+
+Example:
+
+	atmegaxx_captouch@51 {
+		compatible = "atmel,atmegaxx_captouch";
+		reg = <0x51>;
+		interrupt-parent = <&tlmm>;
+		interrupts = <67 IRQ_TYPE_EDGE_FALLING>;
+		linux,keycodes = <BTN_0>, <BTN_1>,
+			<BTN_2>, <BTN_3>,
+			<BTN_4>, <BTN_5>,
+			<BTN_6>, <BTN_7>;
+		autorepeat;
+	};
diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
index 838824b..4cee1ac 100644
--- a/drivers/input/misc/Kconfig
+++ b/drivers/input/misc/Kconfig
@@ -82,6 +82,17 @@ config INPUT_ARIZONA_HAPTICS
 	  To compile this driver as a module, choose M here: the
 	  module will be called arizona-haptics.
 
+config INPUT_ATMEGAXX_CAPTOUCH
+	tristate "Atmel AtmegaXX Capacitive Touch"
+	depends on OF || COMPILE_TEST
+	help
+	  Say Y here if an Atmel Capacitive Touch device is connected to
+	  an I2C bus. One should find "atmel,atmegaxx_captouch" node in
+	  the board specific DTS.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called atmegaxx_captouch.
+
 config INPUT_BMA150
 	tristate "BMA150/SMB380 acceleration sensor support"
 	depends on I2C
diff --git a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
index f77268e..7254bd6c 100644
--- a/drivers/input/misc/Makefile
+++ b/drivers/input/misc/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_INPUT_APANEL)		+= apanel.o
 obj-$(CONFIG_INPUT_ARIZONA_HAPTICS)	+= arizona-haptics.o
 obj-$(CONFIG_INPUT_ATI_REMOTE2)		+= ati_remote2.o
 obj-$(CONFIG_INPUT_ATLAS_BTNS)		+= atlas_btns.o
+obj-$(CONFIG_INPUT_ATMEGAXX_CAPTOUCH)	+= atmegaxx_captouch.o
 obj-$(CONFIG_INPUT_BFIN_ROTARY)		+= bfin_rotary.o
 obj-$(CONFIG_INPUT_BMA150)		+= bma150.o
 obj-$(CONFIG_INPUT_CM109)		+= cm109.o
diff --git a/drivers/input/misc/atmegaxx_captouch.c b/drivers/input/misc/atmegaxx_captouch.c
new file mode 100644
index 0000000..bd886c1
--- /dev/null
+++ b/drivers/input/misc/atmegaxx_captouch.c
@@ -0,0 +1,278 @@
+/*
+ * Atmel Atmegaxx Capacitive Touch Driver
+ *
+ * Copyright (C) 2016 Google, inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * 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.
+ */
+
+/*
+ * For raw i2c access from userspace, use i2cset/i2cget
+ * to poke at /dev/i2c-N devices.
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/slab.h>
+
+/* Maximum number of buttons supported */
+#define MAX_NUM_OF_BUTTONS		8
+
+/* Registers */
+#define REG_KEY1_THRESHOLD		0x02
+#define REG_KEY2_THRESHOLD		0x03
+#define REG_KEY3_THRESHOLD		0x04
+#define REG_KEY4_THRESHOLD		0x05
+
+#define REG_KEY1_REF_H			0x20
+#define REG_KEY1_REF_L			0x21
+#define REG_KEY2_REF_H			0x22
+#define REG_KEY2_REF_L			0x23
+#define REG_KEY3_REF_H			0x24
+#define REG_KEY3_REF_L			0x25
+#define REG_KEY4_REF_H			0x26
+#define REG_KEY4_REF_L			0x27
+
+#define REG_KEY1_DLT_H			0x30
+#define REG_KEY1_DLT_L			0x31
+#define REG_KEY2_DLT_H			0x32
+#define REG_KEY2_DLT_L			0x33
+#define REG_KEY3_DLT_H			0x34
+#define REG_KEY3_DLT_L			0x35
+#define REG_KEY4_DLT_H			0x36
+#define REG_KEY4_DLT_L			0x37
+
+#define REG_KEY_STATE			0x3C
+
+/*
+ * @i2c_client: I2C slave device client pointer
+ * @input: Input device pointer
+ * @num_btn: Number of buttons
+ * @keycodes: map of button# to KeyCode
+ * @prev_btn: Previous key state to detect button "press" or "release"
+ * @xfer_buf: I2C transfer buffer
+ */
+struct atmegaxx_captouch_device {
+	struct i2c_client *client;
+	struct input_dev *input;
+	u32 num_btn;
+	u32 keycodes[MAX_NUM_OF_BUTTONS];
+	u8 prev_btn;
+	u8 xfer_buf[8] ____cacheline_aligned;
+};
+
+/*
+ * Read from I2C slave device
+ * The protocol is that the client has to provide both the register address
+ * and the length, and while reading back the device would prepend the data
+ * with address and length for verification.
+ */
+static int atmegaxx_read(struct atmegaxx_captouch_device *atmegaxx,
+			 u8 reg, u8 *data, size_t len)
+{
+	struct i2c_client *client = atmegaxx->client;
+	struct device *dev = &client->dev;
+	struct i2c_msg msg[2];
+	int err;
+
+	if (len > sizeof(atmegaxx->xfer_buf) - 2)
+		return -EINVAL;
+
+	atmegaxx->xfer_buf[0] = reg;
+	atmegaxx->xfer_buf[1] = len;
+
+	msg[0].addr = client->addr;
+	msg[0].flags = 0;
+	msg[0].buf = atmegaxx->xfer_buf;
+	msg[0].len = 2;
+
+	msg[1].addr = client->addr;
+	msg[1].flags = I2C_M_RD;
+	msg[1].buf = atmegaxx->xfer_buf;
+	msg[1].len = len + 2;
+
+	err = i2c_transfer(client->adapter, msg, ARRAY_SIZE(msg));
+	if (err != ARRAY_SIZE(msg))
+		return err < 0 ? err : -EIO;
+
+	if (atmegaxx->xfer_buf[0] != reg) {
+		dev_err(dev, "I2C read error: register address does not match\n");
+		return -ECOMM;
+	}
+
+	memcpy(data, &atmegaxx->xfer_buf[2], len);
+
+	return 0;
+}
+
+/*
+ * Handle interrupt and report the key changes to the input system.
+ * Multi-touch can be supported; however, it really depends on whether
+ * the device can multi-touch.
+ */
+static irqreturn_t atmegaxx_captouch_isr(int irq, void *data)
+{
+	struct atmegaxx_captouch_device *atmegaxx = data;
+	struct device *dev = &atmegaxx->client->dev;
+	int error;
+	int i;
+	u8 new_btn;
+	u8 changed_btn;
+
+	error = atmegaxx_read(atmegaxx, REG_KEY_STATE, &new_btn, 1);
+	if (error) {
+		dev_err(dev, "failed to read button state: %d\n", error);
+		goto out;
+	}
+
+	dev_dbg(dev, "%s: button state %#02x\n", __func__, new_btn);
+
+	changed_btn = new_btn ^ atmegaxx->prev_btn;
+	atmegaxx->prev_btn = new_btn;
+
+	for (i = 0; i < atmegaxx->num_btn; i++) {
+		if (changed_btn & BIT(i))
+			input_report_key(atmegaxx->input,
+					 atmegaxx->keycodes[i],
+					 new_btn & BIT(i));
+	}
+
+	input_sync(atmegaxx->input);
+
+out:
+	return IRQ_HANDLED;
+}
+
+/*
+ * Probe function to setup the device, input system and interrupt
+ */
+static int atmegaxx_captouch_probe(struct i2c_client *client,
+		const struct i2c_device_id *id)
+{
+	struct atmegaxx_captouch_device *atmegaxx;
+	struct device *dev = &client->dev;
+	struct device_node *node;
+	int i;
+	int err;
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_BYTE_DATA |
+					I2C_FUNC_SMBUS_WORD_DATA |
+					I2C_FUNC_SMBUS_I2C_BLOCK)) {
+		dev_err(dev, "needed i2c functionality is not supported\n");
+		return -EINVAL;
+	}
+
+	atmegaxx = devm_kzalloc(dev, sizeof(*atmegaxx), GFP_KERNEL);
+	if (!atmegaxx)
+		return -ENOMEM;
+
+	atmegaxx->client = client;
+	i2c_set_clientdata(client, atmegaxx);
+
+	err = atmegaxx_read(atmegaxx, REG_KEY_STATE,
+			    &atmegaxx->prev_btn, sizeof(atmegaxx->prev_btn));
+	if (err) {
+		dev_err(dev, "failed to read initial button state: %d\n", err);
+		return err;
+	}
+
+	atmegaxx->input = devm_input_allocate_device(dev);
+	if (!atmegaxx->input) {
+		dev_err(dev, "failed to allocate input device\n");
+		return -ENOMEM;
+	}
+
+	atmegaxx->input->id.bustype = BUS_I2C;
+	atmegaxx->input->id.product = 0x880A;
+	atmegaxx->input->id.version = 0;
+	atmegaxx->input->name = "ATMegaXX Capacitive Button Controller";
+	__set_bit(EV_KEY, atmegaxx->input->evbit);
+
+	node = dev->of_node;
+	if (!node) {
+		dev_err(dev, "failed to find matching node in device tree\n");
+		return -EINVAL;
+	}
+
+	if (of_property_read_bool(node, "autorepeat"))
+		__set_bit(EV_REP, atmegaxx->input->evbit);
+
+	atmegaxx->num_btn = of_property_count_u32_elems(node, "linux,keymap");
+	if (atmegaxx->num_btn > MAX_NUM_OF_BUTTONS)
+		atmegaxx->num_btn = MAX_NUM_OF_BUTTONS;
+
+	err = of_property_read_u32_array(node, "linux,keycodes",
+					 atmegaxx->keycodes,
+					 atmegaxx->num_btn);
+	if (err) {
+		dev_err(dev,
+			"failed to read linux,keycode property: %d\n", err);
+		return err;
+	}
+
+	for (i = 0; i < atmegaxx->num_btn; i++)
+		__set_bit(atmegaxx->keycodes[i], atmegaxx->input->keybit);
+
+	atmegaxx->input->keycode = atmegaxx->keycodes;
+	atmegaxx->input->keycodesize = sizeof(atmegaxx->keycodes[0]);
+	atmegaxx->input->keycodemax = atmegaxx->num_btn;
+
+	err = input_register_device(atmegaxx->input);
+	if (err)
+		return err;
+
+	err = devm_request_threaded_irq(dev, client->irq, NULL,
+				atmegaxx_captouch_isr, IRQF_ONESHOT,
+				"atmegaxx_captouch", atmegaxx);
+	if (err) {
+		dev_err(dev, "failed to request irq %d: %d\n",
+			client->irq, err);
+		return err;
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id atmegaxx_captouch_of_id[] = {
+	{
+		.compatible = "atmel,atmegaxx_captouch",
+	},
+	{ /* sentinel */ }
+}
+MODULE_DEVICE_TABLE(of, atmegaxx_captouch_of_id);
+#endif
+
+static const struct i2c_device_id atmegaxx_captouch_id[] = {
+	{ "atmegaxx_captouch", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, atmegaxx_captouch_id);
+
+static struct i2c_driver atmegaxx_captouch_driver = {
+	.probe		= atmegaxx_captouch_probe,
+	.id_table	= atmegaxx_captouch_id,
+	.driver		= {
+		.name	= "atmegaxx_captouch",
+		.of_match_table = of_match_ptr(atmegaxx_captouch_of_id),
+	},
+};
+module_i2c_driver(atmegaxx_captouch_driver);
+
+/* Module information */
+MODULE_AUTHOR("Hung-yu Wu <hywu@...gle.com>");
+MODULE_DESCRIPTION("Atmel ATmegaXX Capacitance Touch Sensor I2C Driver");
+MODULE_LICENSE("GPL v2");
-- 
2.1.2

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