blob: c4c0f4bb7627a001b360ba9e90b155e827e4017a [file] [log] [blame]
* 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
* GNU General Public License for more details.
* It's irrelevant that 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 */
/* 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) {
"I2C read error: register address does not match (%#02x vs %02x)\n",
capdev->xfer_buf[0], reg);
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))
new_btn & BIT(i));
* 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,
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;
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",
if (err) {
"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,
"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);
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 information */
MODULE_AUTHOR("Hung-yu Wu <>");
MODULE_DESCRIPTION("Atmel ATmegaXX Capacitance Touch Sensor I2C Driver");