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Diffstat (limited to 'drivers/input/touchscreen/resistive-adc-touch.c')
-rw-r--r--drivers/input/touchscreen/resistive-adc-touch.c307
1 files changed, 307 insertions, 0 deletions
diff --git a/drivers/input/touchscreen/resistive-adc-touch.c b/drivers/input/touchscreen/resistive-adc-touch.c
new file mode 100644
index 000000000..6f754a8d3
--- /dev/null
+++ b/drivers/input/touchscreen/resistive-adc-touch.c
@@ -0,0 +1,307 @@
+// 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 <eugen.hristev@microchip.com>
+ *
+ */
+#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)) {
+ error = PTR_ERR(st->iio_chans);
+ if (error != -EPROBE_DEFER)
+ dev_err(dev, "can't get iio channels.\n");
+ return error;
+ }
+
+ 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 <eugen.hristev@microchip.com>");
+MODULE_DESCRIPTION("Generic ADC Resistive Touch Driver");
+MODULE_LICENSE("GPL v2");