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");
208