[PATCH 2/2 V3] Input: add Atmel Captouch Button driver

From: Grant Grundler
Date: Mon May 16 2016 - 16:56:30 EST

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

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 Atmegaxx 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 supported by 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