1/*
2 * Input driver for resistor ladder connected on ADC
3 *
4 * Copyright (c) 2016 Alexandre Belloni
5 *
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 as published by
8 * the Free Software Foundation.
9 */
10
11#include <linux/err.h>
12#include <linux/iio/consumer.h>
13#include <linux/iio/types.h>
14#include <linux/input.h>
15#include <linux/input-polldev.h>
16#include <linux/kernel.h>
17#include <linux/module.h>
18#include <linux/of.h>
19#include <linux/platform_device.h>
20#include <linux/property.h>
21#include <linux/slab.h>
22
23struct adc_keys_button {
24 u32 voltage;
25 u32 keycode;
26};
27
28struct adc_keys_state {
29 struct iio_channel *channel;
30 u32 num_keys;
31 u32 last_key;
32 u32 keyup_voltage;
33 const struct adc_keys_button *map;
34};
35
36static void adc_keys_poll(struct input_polled_dev *dev)
37{
38 struct adc_keys_state *st = dev->private;
39 int i, value, ret;
40 u32 diff, closest = 0xffffffff;
41 int keycode = 0;
42
43 ret = iio_read_channel_processed(st->channel, &value);
44 if (unlikely(ret < 0)) {
45 /* Forcibly release key if any was pressed */
46 value = st->keyup_voltage;
47 } else {
48 for (i = 0; i < st->num_keys; i++) {
49 diff = abs(st->map[i].voltage - value);
50 if (diff < closest) {
51 closest = diff;
52 keycode = st->map[i].keycode;
53 }
54 }
55 }
56
57 if (abs(st->keyup_voltage - value) < closest)
58 keycode = 0;
59
60 if (st->last_key && st->last_key != keycode)
61 input_report_key(dev->input, st->last_key, 0);
62
63 if (keycode)
64 input_report_key(dev->input, keycode, 1);
65
66 input_sync(dev->input);
67 st->last_key = keycode;
68}
69
70static int adc_keys_load_keymap(struct device *dev, struct adc_keys_state *st)
71{
72 struct adc_keys_button *map;
73 struct fwnode_handle *child;
74 int i;
75
76 st->num_keys = device_get_child_node_count(dev);
77 if (st->num_keys == 0) {
78 dev_err(dev, "keymap is missing\n");
79 return -EINVAL;
80 }
81
82 map = devm_kmalloc_array(dev, st->num_keys, sizeof(*map), GFP_KERNEL);
83 if (!map)
84 return -ENOMEM;
85
86 i = 0;
87 device_for_each_child_node(dev, child) {
88 if (fwnode_property_read_u32(child, "press-threshold-microvolt",
89 &map[i].voltage)) {
90 dev_err(dev, "Key with invalid or missing voltage\n");
91 fwnode_handle_put(child);
92 return -EINVAL;
93 }
94 map[i].voltage /= 1000;
95
96 if (fwnode_property_read_u32(child, "linux,code",
97 &map[i].keycode)) {
98 dev_err(dev, "Key with invalid or missing linux,code\n");
99 fwnode_handle_put(child);
100 return -EINVAL;
101 }
102
103 i++;
104 }
105
106 st->map = map;
107 return 0;
108}
109
110static int adc_keys_probe(struct platform_device *pdev)
111{
112 struct device *dev = &pdev->dev;
113 struct adc_keys_state *st;
114 struct input_polled_dev *poll_dev;
115 struct input_dev *input;
116 enum iio_chan_type type;
117 int i, value;
118 int error;
119
120 st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
121 if (!st)
122 return -ENOMEM;
123
124 st->channel = devm_iio_channel_get(dev, "buttons");
125 if (IS_ERR(st->channel))
126 return PTR_ERR(st->channel);
127
128 if (!st->channel->indio_dev)
129 return -ENXIO;
130
131 error = iio_get_channel_type(st->channel, &type);
132 if (error < 0)
133 return error;
134
135 if (type != IIO_VOLTAGE) {
136 dev_err(dev, "Incompatible channel type %d\n", type);
137 return -EINVAL;
138 }
139
140 if (device_property_read_u32(dev, "keyup-threshold-microvolt",
141 &st->keyup_voltage)) {
142 dev_err(dev, "Invalid or missing keyup voltage\n");
143 return -EINVAL;
144 }
145 st->keyup_voltage /= 1000;
146
147 error = adc_keys_load_keymap(dev, st);
148 if (error)
149 return error;
150
151 poll_dev = devm_input_allocate_polled_device(dev);
152 if (!poll_dev) {
153 dev_err(dev, "failed to allocate input device\n");
154 return -ENOMEM;
155 }
156
157 if (!device_property_read_u32(dev, "poll-interval", &value))
158 poll_dev->poll_interval = value;
159
160 poll_dev->poll = adc_keys_poll;
161 poll_dev->private = st;
162
163 input = poll_dev->input;
164
165 input->name = pdev->name;
166 input->phys = "adc-keys/input0";
167
168 input->id.bustype = BUS_HOST;
169 input->id.vendor = 0x0001;
170 input->id.product = 0x0001;
171 input->id.version = 0x0100;
172
173 __set_bit(EV_KEY, input->evbit);
174 for (i = 0; i < st->num_keys; i++)
175 __set_bit(st->map[i].keycode, input->keybit);
176
177 if (device_property_read_bool(dev, "autorepeat"))
178 __set_bit(EV_REP, input->evbit);
179
180 error = input_register_polled_device(poll_dev);
181 if (error) {
182 dev_err(dev, "Unable to register input device: %d\n", error);
183 return error;
184 }
185
186 return 0;
187}
188
189#ifdef CONFIG_OF
190static const struct of_device_id adc_keys_of_match[] = {
191 { .compatible = "adc-keys", },
192 { }
193};
194MODULE_DEVICE_TABLE(of, adc_keys_of_match);
195#endif
196
197static struct platform_driver __refdata adc_keys_driver = {
198 .driver = {
199 .name = "adc_keys",
200 .of_match_table = of_match_ptr(adc_keys_of_match),
201 },
202 .probe = adc_keys_probe,
203};
204module_platform_driver(adc_keys_driver);
205
206MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
207MODULE_DESCRIPTION("Input driver for resistor ladder connected on ADC");
208MODULE_LICENSE("GPL v2");
209