Subject: [PATCH v2 07/10] input: touchscreen: touch_adc: add generic resistive ADC touchscreen

From: [email-masked] (Jonathan Cameron)
Date: Fri, 30 Mar 2018 13:58:35 +0100

On Tue, 27 Mar 2018 15:32:40 +0300
Eugen Hristev <[email-masked]> wrote:

> This adds a generic resistive touchscreen (GRTS) driver, which is based
> on an IIO device (an ADC). It must be connected to the channels of an ADC
> to receive touch data. Then it will feed the data into the input subsystem
> where it registers an input device.
> It uses an IIO callback buffer to register to the IIO device
> 
> Some parts of this patch are based on initial original work by
> Mohamed Jamsheeth Hajanajubudeen and Bandaru Venkateswara Swamy
> 
> Signed-off-by: Eugen Hristev <[email-masked]>
I like this a lot!

A few minor bits and bobs inline.  Over to Dmitry for the input
side of things.

Jonathan

> ---
> Changes in v2:
>  - this is now a generic resistive adc touchscreen driver
> 
>  drivers/input/touchscreen/Kconfig     |  13 +++
>  drivers/input/touchscreen/Makefile    |   1 +
>  drivers/input/touchscreen/touch_adc.c | 199 ++++++++++++++++++++++++++++++++++
>  3 files changed, 213 insertions(+)
>  create mode 100644 drivers/input/touchscreen/touch_adc.c
> 
> diff --git a/drivers/input/touchscreen/Kconfig b/drivers/input/touchscreen/Kconfig
> index 4f15496..afd879f 100644
> --- a/drivers/input/touchscreen/Kconfig
> +++ b/drivers/input/touchscreen/Kconfig
> @@ -92,6 +92,19 @@ config TOUCHSCREEN_AD7879_SPI
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called ad7879-spi.
>  
> +config TOUCHSCREEN_ADC
> +	tristate "Generic ADC based resistive touchscreen"
> +	depends on IIO
> +	select IIO_BUFFER_CB
> +	help
> +	  Say Y here if you want to use the generic ADC
> +	  resistive touchscreen driver.
> +
> +	  If unsure, say N (but it's safe to say "Y").
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called touch_adc.ko.
> +
>  config TOUCHSCREEN_AR1021_I2C
>  	tristate "Microchip AR1020/1021 i2c touchscreen"
>  	depends on I2C && OF
> diff --git a/drivers/input/touchscreen/Makefile b/drivers/input/touchscreen/Makefile
> index dddae79..cbe6121 100644
> --- a/drivers/input/touchscreen/Makefile
> +++ b/drivers/input/touchscreen/Makefile
> @@ -13,6 +13,7 @@ obj-$(CONFIG_TOUCHSCREEN_AD7877)	+= ad7877.o
>  obj-$(CONFIG_TOUCHSCREEN_AD7879)	+= ad7879.o
>  obj-$(CONFIG_TOUCHSCREEN_AD7879_I2C)	+= ad7879-i2c.o
>  obj-$(CONFIG_TOUCHSCREEN_AD7879_SPI)	+= ad7879-spi.o
> +obj-$(CONFIG_TOUCHSCREEN_ADC)		+= touch_adc.o
>  obj-$(CONFIG_TOUCHSCREEN_ADS7846)	+= ads7846.o
>  obj-$(CONFIG_TOUCHSCREEN_AR1021_I2C)	+= ar1021_i2c.o
>  obj-$(CONFIG_TOUCHSCREEN_ATMEL_MXT)	+= atmel_mxt_ts.o
> diff --git a/drivers/input/touchscreen/touch_adc.c b/drivers/input/touchscreen/touch_adc.c
> new file mode 100644
> index 0000000..de4b929
> --- /dev/null
> +++ b/drivers/input/touchscreen/touch_adc.c
> @@ -0,0 +1,199 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * ADC generic resistive touchscreen (GRTS)
> + *
> + * Copyright (C) 2017,2018 Microchip Technology,
> + * Author: Eugen Hristev <[email-masked]>
> + *
> + */
> +#include <linux/input.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/iio/consumer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/module.h>
> +
> +#define DRIVER_NAME					"touch_adc"
> +#define GRTS_DEFAULT_PRESSURE_THRESHOLD			10000
> +#define MAX_POS_MASK					GENMASK(11, 0)
> +
> +/**
> + * grts_state - generic resistive touch screen information struct
> + * @pressure_threshold:	number representing the threshold for the pressure
> + * @pressure:		are we getting pressure info or not
> + * @iio_chans:		list of channels acquired
> + * @iio_cb:		iio_callback buffer for the data
> + * @input:		the input device structure that we register
> + */
> +struct grts_state {
> +	u32			pressure_threshold;
> +	bool			pressure;
> +	struct iio_channel	*iio_chans;
> +	struct iio_cb_buffer	*iio_cb;
> +	struct input_dev	*input;
> +};
> +
> +static int grts_cb(const void *data, void *private)
> +{
> +	const u16 *touch_info = data;
> +	struct grts_state *st = private;
> +
> +	unsigned int x, y, press = 0xFFFF;
> +
> +	/* channel data coming in buffer in the order below */
> +	x = touch_info[0];
> +	y = touch_info[1];
> +	if (st->pressure)
> +		press = touch_info[2];
> +
> +	if ((!x && !y) || (st->pressure && (press > st->pressure_threshold))) {
Ah, clearly pressure is the other way around to I assumed and gets larger as
the pressure is reduced.  hmm.

> +		/* report end of touch */
> +		input_report_key(st->input, BTN_TOUCH, 0);
> +		input_sync(st->input);
> +		return 0;
> +	}
> +
> +	/* report proper touch to subsystem*/
> +	input_report_abs(st->input, ABS_X, x);
> +	input_report_abs(st->input, ABS_Y, y);
> +	if (st->pressure)
> +		input_report_abs(st->input, ABS_PRESSURE, press);
> +	input_report_key(st->input, BTN_TOUCH, 1);
> +	input_sync(st->input);
blank line preferred here.

> +	return 0;
> +}
> +
> +static int grts_open(struct input_dev *dev)
> +{
> +	int ret;
> +	struct grts_state *st = input_get_drvdata(dev);
> +
> +	ret = iio_channel_start_all_cb(st->iio_cb);
> +	if (ret) {
> +		dev_err(dev->dev.parent, "failed to start callback buffer.\n");
> +		return ret;
Drop the return ret out of the brackets.

> +	}
> +	return 0;
> +}
> +
> +static void grts_close(struct input_dev *dev)
> +{
> +	struct grts_state *st = input_get_drvdata(dev);
> +
> +	iio_channel_stop_all_cb(st->iio_cb);
> +}
> +
> +static int grts_probe(struct platform_device *pdev)
> +{
> +	struct grts_state *st;
> +	struct input_dev *input;
> +	struct device *dev = &pdev->dev;
> +	struct device_node *node = dev->of_node;
> +	struct iio_channel *chan;
> +	int ret = 0;
> +
> +	st = devm_kzalloc(dev, sizeof(struct grts_state), GFP_KERNEL);
> +	if (!st)
> +		return -ENOMEM;
> +
> +	ret = of_property_read_u32(node,
> +			"generic-adc-resistive-touchscreen,pressure-threshold",
> +			&st->pressure_threshold);
> +	if (ret < 0) {
> +		dev_dbg(dev, "can't get touchscreen pressure threshold property.\n");
> +		st->pressure_threshold = GRTS_DEFAULT_PRESSURE_THRESHOLD;
> +	}
> +
> +	/* get the channels from IIO device */
> +	st->iio_chans = devm_iio_channel_get_all(dev);
> +
> +	if (IS_ERR(st->iio_chans)) {
> +		if (PTR_ERR(st->iio_chans) != -EPROBE_DEFER)
> +			dev_err(dev, "can't get iio channels.\n");
> +		return PTR_ERR(st->iio_chans);
> +	}
> +
> +	chan = &st->iio_chans[0];
> +	st->pressure = false;
> +	while (chan && chan->indio_dev) {
> +		if (!strcmp(chan->channel->datasheet_name, "pressure"))
> +			st->pressure = true;
> +		chan++;
> +	}
> +
> +	input = devm_input_allocate_device(dev);
> +	if (!input) {
> +		dev_err(dev, "failed to allocate input device.\n");
> +		return -ENOMEM;
> +	}
> +
> +	input->name = DRIVER_NAME;
> +	input->id.bustype = BUS_HOST;
> +	input->dev.parent = dev;
> +	input->open = grts_open;
> +	input->close = grts_close;
> +
> +	input_set_abs_params(input, ABS_X, 0, MAX_POS_MASK - 1, 0, 0);
> +	input_set_abs_params(input, ABS_Y, 0, MAX_POS_MASK - 1, 0, 0);
> +	if (st->pressure)
> +		input_set_abs_params(input, ABS_PRESSURE, 0, 0xffffff, 0, 0);
> +
> +	input->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
> +	input->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
> +
> +	st->input = input;
> +	input_set_drvdata(input, st);
> +
> +	ret = input_register_device(input);
> +	if (ret) {
> +		dev_err(dev, "failed to register input device.");
> +		return ret;
> +	}
> +
> +	st->iio_cb = iio_channel_get_all_cb(&pdev->dev, grts_cb, st);
> +
> +	if (IS_ERR(st->iio_cb)) {
> +		dev_err(dev, "failed to allocate callback buffer.\n");
> +		ret =  PTR_ERR(st->iio_cb);
> +		return ret;
> +	}
> +
> +	platform_set_drvdata(pdev, st);
> +
> +	return ret;
> +}
> +
> +static int grts_remove(struct platform_device *pdev)
> +{
> +	struct grts_state *st = platform_get_drvdata(pdev);
> +
> +	iio_channel_release_all_cb(st->iio_cb);
> +	input_unregister_device(st->input);
blank line preferred before simple returns.

> +	return 0;
> +}
> +
> +static const struct of_device_id grts_of_match[] = {
> +	{
> +		.compatible = "generic-resistive-adc-touch",
> +	}, {
> +		/* sentinel */
> +	},
> +};
> +
> +MODULE_DEVICE_TABLE(of, grts_of_match);
> +
> +static struct platform_driver grts_driver = {
> +	.probe = grts_probe,
> +	.remove = grts_remove,
> +	.driver = {
> +		   .name = DRIVER_NAME,
> +		   .of_match_table = of_match_ptr(grts_of_match),
> +	},
> +};
> +
> +module_platform_driver(grts_driver);
> +
> +MODULE_AUTHOR("Eugen Hristev <[email-masked]>");
> +MODULE_DESCRIPTION("Generic ADC Resistive Touch Driver");
> +MODULE_LICENSE("GPL v2");