// SPDX-License-Identifier: GPL-2.0
/*
* ADC generic resistive touchscreen (GRTS)
* This is a generic input driver that connects to an ADC
* given the channels in device tree, and reports events to the input
* subsystem.
*
* Copyright (C) 2017,2018 Microchip Technology,
* Author: Eugen Hristev <[email protected]>
*
*/
#include <linux/input.h>
#include <linux/input/touchscreen.h>
#include <linux/iio/consumer.h>
#include <linux/iio/iio.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#define DRIVER_NAME "resistive-adc-touch"
#define GRTS_DEFAULT_PRESSURE_MIN 50000
#define GRTS_DEFAULT_PRESSURE_MAX 65535
#define GRTS_MAX_POS_MASK GENMASK(11, 0)
#define GRTS_MAX_CHANNELS 4
enum grts_ch_type {
GRTS_CH_X,
GRTS_CH_Y,
GRTS_CH_PRESSURE,
GRTS_CH_Z1,
GRTS_CH_Z2,
GRTS_CH_MAX = GRTS_CH_Z2 + 1
};
/**
* struct grts_state - generic resistive touch screen information struct
* @x_plate_ohms: resistance of the X plate
* @pressure_min: number representing the minimum 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
* @prop: touchscreen properties struct
* @ch_map: map of channels that are defined for the touchscreen
*/
struct grts_state {
u32 x_plate_ohms;
u32 pressure_min;
bool pressure;
struct iio_channel *iio_chans;
struct iio_cb_buffer *iio_cb;
struct input_dev *input;
struct touchscreen_properties prop;
u8 ch_map[GRTS_CH_MAX];
};
static int grts_cb(const void *data, void *private)
{
const u16 *touch_info = data;
struct grts_state *st = private;
unsigned int x, y, press = 0;
x = touch_info[st->ch_map[GRTS_CH_X]];
y = touch_info[st->ch_map[GRTS_CH_Y]];
if (st->ch_map[GRTS_CH_PRESSURE] < GRTS_MAX_CHANNELS) {
press = touch_info[st->ch_map[GRTS_CH_PRESSURE]];
} else if (st->ch_map[GRTS_CH_Z1] < GRTS_MAX_CHANNELS) {
unsigned int z1 = touch_info[st->ch_map[GRTS_CH_Z1]];
unsigned int z2 = touch_info[st->ch_map[GRTS_CH_Z2]];
unsigned int Rt;
if (likely(x && z1)) {
Rt = z2;
Rt -= z1;
Rt *= st->x_plate_ohms;
Rt = DIV_ROUND_CLOSEST(Rt, 16);
Rt *= x;
Rt /= z1;
Rt = DIV_ROUND_CLOSEST(Rt, 256);
/*
* On increased pressure the resistance (Rt) is
* decreasing so, convert values to make it looks as
* real pressure.
*/
if (Rt < GRTS_DEFAULT_PRESSURE_MAX)
press = GRTS_DEFAULT_PRESSURE_MAX - Rt;
}
}
if ((!x && !y) || (st->pressure && (press < st->pressure_min))) {
/* report end of touch */
input_report_key(st->input, BTN_TOUCH, 0);
input_sync(st->input);
return 0;
}
/* report proper touch to subsystem*/
touchscreen_report_pos(st->input, &st->prop, x, y, false);
if (st->pressure)
input_report_abs(st->input, ABS_PRESSURE, press);
input_report_key(st->input, BTN_TOUCH, 1);
input_sync(st->input);
return 0;
}
static int grts_open(struct input_dev *dev)
{
int error;
struct grts_state *st = input_get_drvdata(dev);
error = iio_channel_start_all_cb(st->iio_cb);
if (error) {
dev_err(dev->dev.parent, "failed to start callback buffer.\n");
return error;
}
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 void grts_disable(void *data)
{
iio_channel_release_all_cb(data);
}
static int grts_map_channel(struct grts_state *st, struct device *dev,
enum grts_ch_type type, const char *name,
bool optional)
{
int idx;
idx = device_property_match_string(dev, "io-channel-names", name);
if (idx < 0) {
if (!optional)
return idx;
idx = GRTS_MAX_CHANNELS;
} else if (idx >= GRTS_MAX_CHANNELS) {
return -EOVERFLOW;
}
st->ch_map[type] = idx;
return 0;
}
static int grts_get_properties(struct grts_state *st, struct device *dev)
{
int error;
error = grts_map_channel(st, dev, GRTS_CH_X, "x", false);
if (error)
return error;
error = grts_map_channel(st, dev, GRTS_CH_Y, "y", false);
if (error)
return error;
/* pressure is optional */
error = grts_map_channel(st, dev, GRTS_CH_PRESSURE, "pressure", true);
if (error)
return error;
if (st->ch_map[GRTS_CH_PRESSURE] < GRTS_MAX_CHANNELS) {
st->pressure = true;
return 0;
}
/* if no pressure is defined, try optional z1 + z2 */
error = grts_map_channel(st, dev, GRTS_CH_Z1, "z1", true);
if (error)
return error;
if (st->ch_map[GRTS_CH_Z1] >= GRTS_MAX_CHANNELS)
return 0;
/* if z1 is provided z2 is not optional */
error = grts_map_channel(st, dev, GRTS_CH_Z2, "z2", true);
if (error)
return error;
error = device_property_read_u32(dev,
"touchscreen-x-plate-ohms",
&st->x_plate_ohms);
if (error) {
dev_err(dev, "can't get touchscreen-x-plate-ohms property\n");
return error;
}
st->pressure = true;
return 0;
}
static int grts_probe(struct platform_device *pdev)
{
struct grts_state *st;
struct input_dev *input;
struct device *dev = &pdev->dev;
int error;
st = devm_kzalloc(dev, sizeof(struct grts_state), GFP_KERNEL);
if (!st)
return -ENOMEM;
/* get the channels from IIO device */
st->iio_chans = devm_iio_channel_get_all(dev);
if (IS_ERR(st->iio_chans))
return dev_err_probe(dev, PTR_ERR(st->iio_chans), "can't get iio channels\n");
if (!device_property_present(dev, "io-channel-names"))
return -ENODEV;
error = grts_get_properties(st, dev);
if (error) {
dev_err(dev, "Failed to parse properties\n");
return error;
}
if (st->pressure) {
error = device_property_read_u32(dev,
"touchscreen-min-pressure",
&st->pressure_min);
if (error) {
dev_dbg(dev, "can't get touchscreen-min-pressure property.\n");
st->pressure_min = GRTS_DEFAULT_PRESSURE_MIN;
}
}
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->open = grts_open;
input->close = grts_close;
input_set_abs_params(input, ABS_X, 0, GRTS_MAX_POS_MASK - 1, 0, 0);
input_set_abs_params(input, ABS_Y, 0, GRTS_MAX_POS_MASK - 1, 0, 0);
if (st->pressure)
input_set_abs_params(input, ABS_PRESSURE, st->pressure_min,
GRTS_DEFAULT_PRESSURE_MAX, 0, 0);
input_set_capability(input, EV_KEY, BTN_TOUCH);
/* parse optional device tree properties */
touchscreen_parse_properties(input, false, &st->prop);
st->input = input;
input_set_drvdata(input, st);
error = input_register_device(input);
if (error) {
dev_err(dev, "failed to register input device.");
return error;
}
st->iio_cb = iio_channel_get_all_cb(dev, grts_cb, st);
if (IS_ERR(st->iio_cb)) {
dev_err(dev, "failed to allocate callback buffer.\n");
return PTR_ERR(st->iio_cb);
}
error = devm_add_action_or_reset(dev, grts_disable, st->iio_cb);
if (error) {
dev_err(dev, "failed to add disable action.\n");
return error;
}
return 0;
}
static const struct of_device_id grts_of_match[] = {
{
.compatible = "resistive-adc-touch",
}, {
/* sentinel */
},
};
MODULE_DEVICE_TABLE(of, grts_of_match);
static struct platform_driver grts_driver = {
.probe = grts_probe,
.driver = {
.name = DRIVER_NAME,
.of_match_table = grts_of_match,
},
};
module_platform_driver(grts_driver);
MODULE_AUTHOR("Eugen Hristev <[email protected]>");
MODULE_DESCRIPTION("Generic ADC Resistive Touch Driver");
MODULE_LICENSE("GPL v2");
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