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(dev: input);
35 int i, value, ret;
36 u32 diff, closest = 0xffffffff;
37 int keycode = 0;
38
39 ret = iio_read_channel_processed(chan: st->channel, val: &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(dev: input, code: st->last_key, value: 0);
58
59 if (keycode)
60 input_report_key(dev: input, code: keycode, value: 1);
61
62 input_sync(dev: 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 int i;
70
71 st->num_keys = device_get_child_node_count(dev);
72 if (st->num_keys == 0) {
73 dev_err(dev, "keymap is missing\n");
74 return -EINVAL;
75 }
76
77 map = devm_kmalloc_array(dev, n: st->num_keys, size: sizeof(*map), GFP_KERNEL);
78 if (!map)
79 return -ENOMEM;
80
81 i = 0;
82 device_for_each_child_node_scoped(dev, child) {
83 if (fwnode_property_read_u32(fwnode: child, propname: "press-threshold-microvolt",
84 val: &map[i].voltage)) {
85 dev_err(dev, "Key with invalid or missing voltage\n");
86 return -EINVAL;
87 }
88 map[i].voltage /= 1000;
89
90 if (fwnode_property_read_u32(fwnode: child, propname: "linux,code",
91 val: &map[i].keycode)) {
92 dev_err(dev, "Key with invalid or missing linux,code\n");
93 return -EINVAL;
94 }
95
96 i++;
97 }
98
99 st->map = map;
100 return 0;
101}
102
103static int adc_keys_probe(struct platform_device *pdev)
104{
105 struct device *dev = &pdev->dev;
106 struct adc_keys_state *st;
107 struct input_dev *input;
108 enum iio_chan_type type;
109 int i, value;
110 int error;
111
112 st = devm_kzalloc(dev, size: sizeof(*st), GFP_KERNEL);
113 if (!st)
114 return -ENOMEM;
115
116 st->channel = devm_iio_channel_get(dev, consumer_channel: "buttons");
117 if (IS_ERR(ptr: st->channel))
118 return PTR_ERR(ptr: st->channel);
119
120 if (!st->channel->indio_dev)
121 return -ENXIO;
122
123 error = iio_get_channel_type(channel: st->channel, type: &type);
124 if (error < 0)
125 return error;
126
127 if (type != IIO_VOLTAGE) {
128 dev_err(dev, "Incompatible channel type %d\n", type);
129 return -EINVAL;
130 }
131
132 if (device_property_read_u32(dev, propname: "keyup-threshold-microvolt",
133 val: &st->keyup_voltage)) {
134 dev_err(dev, "Invalid or missing keyup voltage\n");
135 return -EINVAL;
136 }
137 st->keyup_voltage /= 1000;
138
139 error = adc_keys_load_keymap(dev, st);
140 if (error)
141 return error;
142
143 input = devm_input_allocate_device(dev);
144 if (!input) {
145 dev_err(dev, "failed to allocate input device\n");
146 return -ENOMEM;
147 }
148
149 input_set_drvdata(dev: input, data: st);
150
151 input->name = pdev->name;
152 input->phys = "adc-keys/input0";
153
154 input->id.bustype = BUS_HOST;
155 input->id.vendor = 0x0001;
156 input->id.product = 0x0001;
157 input->id.version = 0x0100;
158
159 __set_bit(EV_KEY, input->evbit);
160 for (i = 0; i < st->num_keys; i++)
161 __set_bit(st->map[i].keycode, input->keybit);
162
163 if (device_property_read_bool(dev, propname: "autorepeat"))
164 __set_bit(EV_REP, input->evbit);
165
166
167 error = input_setup_polling(dev: input, poll_fn: adc_keys_poll);
168 if (error) {
169 dev_err(dev, "Unable to set up polling: %d\n", error);
170 return error;
171 }
172
173 if (!device_property_read_u32(dev, propname: "poll-interval", val: &value))
174 input_set_poll_interval(dev: input, interval: value);
175
176 error = input_register_device(input);
177 if (error) {
178 dev_err(dev, "Unable to register input device: %d\n", error);
179 return error;
180 }
181
182 return 0;
183}
184
185#ifdef CONFIG_OF
186static const struct of_device_id adc_keys_of_match[] = {
187 { .compatible = "adc-keys", },
188 { }
189};
190MODULE_DEVICE_TABLE(of, adc_keys_of_match);
191#endif
192
193static struct platform_driver adc_keys_driver = {
194 .driver = {
195 .name = "adc_keys",
196 .of_match_table = of_match_ptr(adc_keys_of_match),
197 },
198 .probe = adc_keys_probe,
199};
200module_platform_driver(adc_keys_driver);
201
202MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
203MODULE_DESCRIPTION("Input driver for resistor ladder connected on ADC");
204MODULE_LICENSE("GPL v2");
205

source code of linux/drivers/input/keyboard/adc-keys.c