Date:	Wed, 18 May 2016 14:59:42 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Grant Grundler <grundler@...omium.org>
Cc:	Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	devicetree <devicetree@...r.kernel.org>,
	linux-input <linux-input@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Hung-yu Wu <hywu@...gle.com>,
	Kumar Gala <galak@...eaurora.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Grant Likely <grant.likely@...aro.org>
Subject: Re: [PATCH 2/2 V4] Input: add Atmel Captouch Button driver

On Tue, May 17, 2016 at 12:29:32PM -0700, Grant Grundler wrote:
> From: Daniel Hung-yu Wu <hywu@...gle.com>
> 
> Add I2C driver for Atmel Capacitive Touch Button device.
> 
> Signed-off-by: Hung-yu Wu <hywu@...gle.com>
> Signed-off-by: Grant Grundler <grundler@...omium.org>

Applied, thank you.

> ---
>  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@...gle.com>");
> +MODULE_DESCRIPTION("Atmel ATmegaXX Capacitance Touch Sensor I2C Driver");
> +MODULE_LICENSE("GPL v2");
> -- 
> 2.1.2
> 

-- 
Dmitry

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