drivers/input/touchscreen/resistive-adc-touch.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * ADC generic resistive touchscreen (GRTS)
   4  * This is a generic input driver that connects to an ADC
   5  * given the channels in device tree, and reports events to the input
   6  * subsystem.
   7  *
   8  * Copyright (C) 2017,2018 Microchip Technology,
   9  * Author: Eugen Hristev <eugen.hristev@microchip.com>
  10  *
  11  */
  12 #include <linux/input.h>
  13 #include <linux/input/touchscreen.h>
  14 #include <linux/iio/consumer.h>
  15 #include <linux/iio/iio.h>
  16 #include <linux/module.h>
  17 #include <linux/of.h>
  18 #include <linux/of_device.h>
  19 #include <linux/platform_device.h>
  20
  21 #define DRIVER_NAME                                     "resistive-adc-touch"
  22 #define GRTS_DEFAULT_PRESSURE_MIN                       50000
  23 #define GRTS_MAX_POS_MASK                               GENMASK(11, 0)
  24
  25 /**
  26  * grts_state - generic resistive touch screen information struct
  27  * @pressure_min:       number representing the minimum for the pressure
  28  * @pressure:           are we getting pressure info or not
  29  * @iio_chans:          list of channels acquired
  30  * @iio_cb:             iio_callback buffer for the data
  31  * @input:              the input device structure that we register
  32  * @prop:               touchscreen properties struct
  33  */
  34 struct grts_state {
  35         u32                             pressure_min;
  36         bool                            pressure;
  37         struct iio_channel              *iio_chans;
  38         struct iio_cb_buffer            *iio_cb;
  39         struct input_dev                *input;
  40         struct touchscreen_properties   prop;
  41 };
  42
  43 static int grts_cb(const void *data, void *private)
  44 {
  45         const u16 *touch_info = data;
  46         struct grts_state *st = private;
  47         unsigned int x, y, press = 0x0;
  48
  49         /* channel data coming in buffer in the order below */
  50         x = touch_info[0];
  51         y = touch_info[1];
  52         if (st->pressure)
  53                 press = touch_info[2];
  54
  55         if ((!x && !y) || (st->pressure && (press < st->pressure_min))) {
  56                 /* report end of touch */
  57                 input_report_key(st->input, BTN_TOUCH, 0);
  58                 input_sync(st->input);
  59                 return 0;
  60         }
  61
  62         /* report proper touch to subsystem*/
  63         touchscreen_report_pos(st->input, &st->prop, x, y, false);
  64         if (st->pressure)
  65                 input_report_abs(st->input, ABS_PRESSURE, press);
  66         input_report_key(st->input, BTN_TOUCH, 1);
  67         input_sync(st->input);
  68
  69         return 0;
  70 }
  71
  72 static int grts_open(struct input_dev *dev)
  73 {
  74         int error;
  75         struct grts_state *st = input_get_drvdata(dev);
  76
  77         error = iio_channel_start_all_cb(st->iio_cb);
  78         if (error) {
  79                 dev_err(dev->dev.parent, "failed to start callback buffer.\n");
  80                 return error;
  81         }
  82         return 0;
  83 }
  84
  85 static void grts_close(struct input_dev *dev)
  86 {
  87         struct grts_state *st = input_get_drvdata(dev);
  88
  89         iio_channel_stop_all_cb(st->iio_cb);
  90 }
  91
  92 static void grts_disable(void *data)
  93 {
  94         iio_channel_release_all_cb(data);
  95 }
  96
  97 static int grts_probe(struct platform_device *pdev)
  98 {
  99         struct grts_state *st;
 100         struct input_dev *input;
 101         struct device *dev = &pdev->dev;
 102         struct iio_channel *chan;
 103         int error;
 104
 105         st = devm_kzalloc(dev, sizeof(struct grts_state), GFP_KERNEL);
 106         if (!st)
 107                 return -ENOMEM;
 108
 109         /* get the channels from IIO device */
 110         st->iio_chans = devm_iio_channel_get_all(dev);
 111         if (IS_ERR(st->iio_chans)) {
 112                 error = PTR_ERR(st->iio_chans);
 113                 if (error != -EPROBE_DEFER)
 114                         dev_err(dev, "can't get iio channels.\n");
 115                 return error;
 116         }
 117
 118         chan = &st->iio_chans[0];
 119         st->pressure = false;
 120         while (chan && chan->indio_dev) {
 121                 if (!strcmp(chan->channel->datasheet_name, "pressure"))
 122                         st->pressure = true;
 123                 chan++;
 124         }
 125
 126         if (st->pressure) {
 127                 error = device_property_read_u32(dev,
 128                                                  "touchscreen-min-pressure",
 129                                                  &st->pressure_min);
 130                 if (error) {
 131                         dev_dbg(dev, "can't get touchscreen-min-pressure property.\n");
 132                         st->pressure_min = GRTS_DEFAULT_PRESSURE_MIN;
 133                 }
 134         }
 135
 136         input = devm_input_allocate_device(dev);
 137         if (!input) {
 138                 dev_err(dev, "failed to allocate input device.\n");
 139                 return -ENOMEM;
 140         }
 141
 142         input->name = DRIVER_NAME;
 143         input->id.bustype = BUS_HOST;
 144         input->open = grts_open;
 145         input->close = grts_close;
 146
 147         input_set_abs_params(input, ABS_X, 0, GRTS_MAX_POS_MASK - 1, 0, 0);
 148         input_set_abs_params(input, ABS_Y, 0, GRTS_MAX_POS_MASK - 1, 0, 0);
 149         if (st->pressure)
 150                 input_set_abs_params(input, ABS_PRESSURE, st->pressure_min,
 151                                      0xffff, 0, 0);
 152
 153         input_set_capability(input, EV_KEY, BTN_TOUCH);
 154
 155         /* parse optional device tree properties */
 156         touchscreen_parse_properties(input, false, &st->prop);
 157
 158         st->input = input;
 159         input_set_drvdata(input, st);
 160
 161         error = input_register_device(input);
 162         if (error) {
 163                 dev_err(dev, "failed to register input device.");
 164                 return error;
 165         }
 166
 167         st->iio_cb = iio_channel_get_all_cb(dev, grts_cb, st);
 168         if (IS_ERR(st->iio_cb)) {
 169                 dev_err(dev, "failed to allocate callback buffer.\n");
 170                 return PTR_ERR(st->iio_cb);
 171         }
 172
 173         error = devm_add_action_or_reset(dev, grts_disable, st->iio_cb);
 174         if (error) {
 175                 dev_err(dev, "failed to add disable action.\n");
 176                 return error;
 177         }
 178
 179         return 0;
 180 }
 181
 182 static const struct of_device_id grts_of_match[] = {
 183         {
 184                 .compatible = "resistive-adc-touch",
 185         }, {
 186                 /* sentinel */
 187         },
 188 };
 189
 190 MODULE_DEVICE_TABLE(of, grts_of_match);
 191
 192 static struct platform_driver grts_driver = {
 193         .probe = grts_probe,
 194         .driver = {
 195                 .name = DRIVER_NAME,
 196                 .of_match_table = of_match_ptr(grts_of_match),
 197         },
 198 };
 199
 200 module_platform_driver(grts_driver);
 201
 202 MODULE_AUTHOR("Eugen Hristev <eugen.hristev@microchip.com>");
 203 MODULE_DESCRIPTION("Generic ADC Resistive Touch Driver");
 204 MODULE_LICENSE("GPL v2");