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
19 struct adc_keys_button {
20 u32 voltage;
21 u32 keycode;
22 };
23
24 struct 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
adc_keys_poll(struct input_dev * input)32 static 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
adc_keys_load_keymap(struct device * dev,struct adc_keys_state * st)66 static 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
adc_keys_probe(struct platform_device * pdev)106 static 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
189 static const struct of_device_id adc_keys_of_match[] = {
190 { .compatible = "adc-keys", },
191 { }
192 };
193 MODULE_DEVICE_TABLE(of, adc_keys_of_match);
194 #endif
195
196 static struct platform_driver __refdata 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 };
203 module_platform_driver(adc_keys_driver);
204
205 MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
206 MODULE_DESCRIPTION("Input driver for resistor ladder connected on ADC");
207 MODULE_LICENSE("GPL v2");
208
