diff options
Diffstat (limited to 'drivers/input/touchscreen/resistive-adc-touch.c')
| -rw-r--r-- | drivers/input/touchscreen/resistive-adc-touch.c | 307 |
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"); |