[PATCH 2/2 V4] Input: add Atmel Captouch Button driver

[Grant Grundler]

From: Daniel Hung-yu Wu <hywu@xxxxxxxxxx>

Add I2C driver for Atmel Capacitive Touch Button device.

Signed-off-by: Hung-yu Wu <hywu@xxxxxxxxxx>
Signed-off-by: Grant Grundler <grundler@xxxxxxxxxxxx>
---
 drivers/input/misc/Kconfig          |  13 ++
 drivers/input/misc/Makefile         |   1 +
 drivers/input/misc/atmel_captouch.c | 287 ++++++++++++++++++++++++++++++++++++
 3 files changed, 299 insertions(+)
 create mode 100644 drivers/input/misc/atmel_captouch.c

V4: wordsmithing comments at top of file.
    Added missing semicolon to CONFIG_OF data struct.

V3: use dash, not underscore in nodename. Wordsmith Kconfig help text.

V2: split Documentation/devicetree/bindings from driver patch.
    rename "atmel,atmegaxx_captouch" to "atmel,captouch" since it's irrelevant
    which controller implements the register set/controller.

V1: posted https://lkml.org/lkml/2016/5/3/613

diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
index 838824b..d8b6620 100644
--- a/drivers/input/misc/Kconfig
+++ b/drivers/input/misc/Kconfig
@@ -82,6 +82,19 @@ config INPUT_ARIZONA_HAPTICS
 	  To compile this driver as a module, choose M here: the
 	  module will be called arizona-haptics.
 
+config INPUT_ATMEL_CAPTOUCH
+	tristate "Atmel Capacitive Touch Button Driver"
+	depends on OF || COMPILE_TEST
+	help
+	  Say Y here if an Atmel Capacitive Touch Button device which
+	  implements "captouch" protocol is connected to I2C bus. Typically
+	  this device consists of Atmel Touch sensor controlled by AtMegaXX
+	  MCU running firmware based on Qtouch library.
+	  One should find "atmel,captouch" node in the board specific DTS.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called atmel_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..b5ec626 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-$(CONFIG_INPUT_ATMEL_CAPTOUCH)	+= atmel_captouch.o
 obj-$(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/atmel_captouch.c b/drivers/input/misc/atmel_captouch.c
new file mode 100644
index 0000000..91bfc73
--- /dev/null
+++ b/drivers/input/misc/atmel_captouch.c
@@ -0,0 +1,287 @@
+/*
+ * Atmel Capacitive Touch Button 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.
+ */
+
+/*
+ * It's irrelevant the HW used to develop captouch driver is based
+ * on Atmega88PA part and uses QtouchADC parts for sensing touch.
+ * Calling this driver "captouch" is an arbitrary way to distinguish
+ * the protocol this driver supports from other atmel/qtouch drivers.
+ *
+ * captouch driver supports a newer/different version of the I2C
+ * registers/commands than the qt1070.c driver.
+ * Don't let the similarity of the general driver structure fool you. :)
+ *
+ * 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 atmel_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 atmel_read(struct atmel_captouch_device *capdev,
+			 u8 reg, u8 *data, size_t len)
+{
+	struct i2c_client *client = capdev->client;
+	struct device *dev = &client->dev;
+	struct i2c_msg msg[2];
+	int err;
+
+	if (len > sizeof(capdev->xfer_buf) - 2)
+		return -EINVAL;
+
+	capdev->xfer_buf[0] = reg;
+	capdev->xfer_buf[1] = len;
+
+	msg[0].addr = client->addr;
+	msg[0].flags = 0;
+	msg[0].buf = capdev->xfer_buf;
+	msg[0].len = 2;
+
+	msg[1].addr = client->addr;
+	msg[1].flags = I2C_M_RD;
+	msg[1].buf = capdev->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 (capdev->xfer_buf[0] != reg) {
+		dev_err(dev, "I2C read error: register address does not match\n");
+		return -ECOMM;
+	}
+
+	memcpy(data, &capdev->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 atmel_captouch_isr(int irq, void *data)
+{
+	struct atmel_captouch_device *capdev = data;
+	struct device *dev = &capdev->client->dev;
+	int error;
+	int i;
+	u8 new_btn;
+	u8 changed_btn;
+
+	error = atmel_read(capdev, 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 ^ capdev->prev_btn;
+	capdev->prev_btn = new_btn;
+
+	for (i = 0; i < capdev->num_btn; i++) {
+		if (changed_btn & BIT(i))
+			input_report_key(capdev->input,
+					 capdev->keycodes[i],
+					 new_btn & BIT(i));
+	}
+
+	input_sync(capdev->input);
+
+out:
+	return IRQ_HANDLED;
+}
+
+/*
+ * Probe function to setup the device, input system and interrupt
+ */
+static int atmel_captouch_probe(struct i2c_client *client,
+		const struct i2c_device_id *id)
+{
+	struct atmel_captouch_device *capdev;
+	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;
+	}
+
+	capdev = devm_kzalloc(dev, sizeof(*capdev), GFP_KERNEL);
+	if (!capdev)
+		return -ENOMEM;
+
+	capdev->client = client;
+	i2c_set_clientdata(client, capdev);
+
+	err = atmel_read(capdev, REG_KEY_STATE,
+			    &capdev->prev_btn, sizeof(capdev->prev_btn));
+	if (err) {
+		dev_err(dev, "failed to read initial button state: %d\n", err);
+		return err;
+	}
+
+	capdev->input = devm_input_allocate_device(dev);
+	if (!capdev->input) {
+		dev_err(dev, "failed to allocate input device\n");
+		return -ENOMEM;
+	}
+
+	capdev->input->id.bustype = BUS_I2C;
+	capdev->input->id.product = 0x880A;
+	capdev->input->id.version = 0;
+	capdev->input->name = "ATMegaXX Capacitive Button Controller";
+	__set_bit(EV_KEY, capdev->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, capdev->input->evbit);
+
+	capdev->num_btn = of_property_count_u32_elems(node, "linux,keymap");
+	if (capdev->num_btn > MAX_NUM_OF_BUTTONS)
+		capdev->num_btn = MAX_NUM_OF_BUTTONS;
+
+	err = of_property_read_u32_array(node, "linux,keycodes",
+					 capdev->keycodes,
+					 capdev->num_btn);
+	if (err) {
+		dev_err(dev,
+			"failed to read linux,keycode property: %d\n", err);
+		return err;
+	}
+
+	for (i = 0; i < capdev->num_btn; i++)
+		__set_bit(capdev->keycodes[i], capdev->input->keybit);
+
+	capdev->input->keycode = capdev->keycodes;
+	capdev->input->keycodesize = sizeof(capdev->keycodes[0]);
+	capdev->input->keycodemax = capdev->num_btn;
+
+	err = input_register_device(capdev->input);
+	if (err)
+		return err;
+
+	err = devm_request_threaded_irq(dev, client->irq, NULL,
+				atmel_captouch_isr, IRQF_ONESHOT,
+				"atmel_captouch", capdev);
+	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 atmel_captouch_of_id[] = {
+	{
+		.compatible = "atmel,captouch",
+	},
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, atmel_captouch_of_id);
+#endif
+
+static const struct i2c_device_id atmel_captouch_id[] = {
+	{ "atmel_captouch", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, atmel_captouch_id);
+
+static struct i2c_driver atmel_captouch_driver = {
+	.probe		= atmel_captouch_probe,
+	.id_table	= atmel_captouch_id,
+	.driver		= {
+		.name	= "atmel_captouch",
+		.of_match_table = of_match_ptr(atmel_captouch_of_id),
+	},
+};
+module_i2c_driver(atmel_captouch_driver);
+
+/* Module information */
+MODULE_AUTHOR("Hung-yu Wu <hywu@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Atmel ATmegaXX Capacitance Touch Sensor I2C Driver");
+MODULE_LICENSE("GPL v2");
-- 
2.1.2