1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Input driver for resistor ladder connected on ADC
  4 *
  5 * Copyright (c) 2016 Alexandre Belloni
  6 */
  7
  8#include <linux/err.h>
  9#include <linux/iio/consumer.h>
 10#include <linux/iio/types.h>
 11#include <linux/input.h>
 12#include <linux/kernel.h>
 13#include <linux/module.h>
 14#include <linux/of.h>
 15#include <linux/platform_device.h>
 16#include <linux/property.h>
 17#include <linux/slab.h>
 18
 19struct adc_keys_button {
 20	u32 voltage;
 21	u32 keycode;
 22};
 23
 24struct adc_keys_state {
 25	struct iio_channel *channel;
 26	u32 num_keys;
 27	u32 last_key;
 28	u32 keyup_voltage;
 29	const struct adc_keys_button *map;
 30};
 31
 32static void adc_keys_poll(struct input_dev *input)
 33{
 34	struct adc_keys_state *st = input_get_drvdata(input);
 35	int i, value, ret;
 36	u32 diff, closest = 0xffffffff;
 37	int keycode = 0;
 38
 39	ret = iio_read_channel_processed(st->channel, &value);
 40	if (unlikely(ret < 0)) {
 41		/* Forcibly release key if any was pressed */
 42		value = st->keyup_voltage;
 43	} else {
 44		for (i = 0; i < st->num_keys; i++) {
 45			diff = abs(st->map[i].voltage - value);
 46			if (diff < closest) {
 47				closest = diff;
 48				keycode = st->map[i].keycode;
 49			}
 50		}
 51	}
 52
 53	if (abs(st->keyup_voltage - value) < closest)
 54		keycode = 0;
 55
 56	if (st->last_key && st->last_key != keycode)
 57		input_report_key(input, st->last_key, 0);
 58
 59	if (keycode)
 60		input_report_key(input, keycode, 1);
 61
 62	input_sync(input);
 63	st->last_key = keycode;
 64}
 65
 66static int adc_keys_load_keymap(struct device *dev, struct adc_keys_state *st)
 67{
 68	struct adc_keys_button *map;
 69	struct fwnode_handle *child;
 70	int i;
 71
 72	st->num_keys = device_get_child_node_count(dev);
 73	if (st->num_keys == 0) {
 74		dev_err(dev, "keymap is missing\n");
 75		return -EINVAL;
 76	}
 77
 78	map = devm_kmalloc_array(dev, st->num_keys, sizeof(*map), GFP_KERNEL);
 79	if (!map)
 80		return -ENOMEM;
 81
 82	i = 0;
 83	device_for_each_child_node(dev, child) {
 84		if (fwnode_property_read_u32(child, "press-threshold-microvolt",
 85					     &map[i].voltage)) {
 86			dev_err(dev, "Key with invalid or missing voltage\n");
 87			fwnode_handle_put(child);
 88			return -EINVAL;
 89		}
 90		map[i].voltage /= 1000;
 91
 92		if (fwnode_property_read_u32(child, "linux,code",
 93					     &map[i].keycode)) {
 94			dev_err(dev, "Key with invalid or missing linux,code\n");
 95			fwnode_handle_put(child);
 96			return -EINVAL;
 97		}
 98
 99		i++;
100	}
101
102	st->map = map;
103	return 0;
104}
105
106static int adc_keys_probe(struct platform_device *pdev)
107{
108	struct device *dev = &pdev->dev;
109	struct adc_keys_state *st;
110	struct input_dev *input;
111	enum iio_chan_type type;
112	int i, value;
113	int error;
114
115	st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
116	if (!st)
117		return -ENOMEM;
118
119	st->channel = devm_iio_channel_get(dev, "buttons");
120	if (IS_ERR(st->channel))
121		return PTR_ERR(st->channel);
122
123	if (!st->channel->indio_dev)
124		return -ENXIO;
125
126	error = iio_get_channel_type(st->channel, &type);
127	if (error < 0)
128		return error;
129
130	if (type != IIO_VOLTAGE) {
131		dev_err(dev, "Incompatible channel type %d\n", type);
132		return -EINVAL;
133	}
134
135	if (device_property_read_u32(dev, "keyup-threshold-microvolt",
136				     &st->keyup_voltage)) {
137		dev_err(dev, "Invalid or missing keyup voltage\n");
138		return -EINVAL;
139	}
140	st->keyup_voltage /= 1000;
141
142	error = adc_keys_load_keymap(dev, st);
143	if (error)
144		return error;
145
146	input = devm_input_allocate_device(dev);
147	if (!input) {
148		dev_err(dev, "failed to allocate input device\n");
149		return -ENOMEM;
150	}
151
152	input_set_drvdata(input, st);
153
154	input->name = pdev->name;
155	input->phys = "adc-keys/input0";
156
157	input->id.bustype = BUS_HOST;
158	input->id.vendor = 0x0001;
159	input->id.product = 0x0001;
160	input->id.version = 0x0100;
161
162	__set_bit(EV_KEY, input->evbit);
163	for (i = 0; i < st->num_keys; i++)
164		__set_bit(st->map[i].keycode, input->keybit);
165
166	if (device_property_read_bool(dev, "autorepeat"))
167		__set_bit(EV_REP, input->evbit);
168
169
170	error = input_setup_polling(input, adc_keys_poll);
171	if (error) {
172		dev_err(dev, "Unable to set up polling: %d\n", error);
173		return error;
174	}
175
176	if (!device_property_read_u32(dev, "poll-interval", &value))
177		input_set_poll_interval(input, value);
178
179	error = input_register_device(input);
180	if (error) {
181		dev_err(dev, "Unable to register input device: %d\n", error);
182		return error;
183	}
184
185	return 0;
186}
187
188#ifdef CONFIG_OF
189static const struct of_device_id adc_keys_of_match[] = {
190	{ .compatible = "adc-keys", },
191	{ }
192};
193MODULE_DEVICE_TABLE(of, adc_keys_of_match);
194#endif
195
196static struct platform_driver adc_keys_driver = {
197	.driver = {
198		.name = "adc_keys",
199		.of_match_table = of_match_ptr(adc_keys_of_match),
200	},
201	.probe = adc_keys_probe,
202};
203module_platform_driver(adc_keys_driver);
204
205MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
206MODULE_DESCRIPTION("Input driver for resistor ladder connected on ADC");
207MODULE_LICENSE("GPL v2");