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 
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 
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 
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 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