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 
23 struct adc_keys_button {
24 	u32 voltage;
25 	u32 keycode;
26 };
27 
28 struct 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 
36 static 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 
70 static 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 
110 static 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 	platform_set_drvdata(pdev, st);
152 
153 	poll_dev = devm_input_allocate_polled_device(dev);
154 	if (!poll_dev) {
155 		dev_err(dev, "failed to allocate input device\n");
156 		return -ENOMEM;
157 	}
158 
159 	if (!device_property_read_u32(dev, "poll-interval", &value))
160 		poll_dev->poll_interval = value;
161 
162 	poll_dev->poll = adc_keys_poll;
163 	poll_dev->private = st;
164 
165 	input = poll_dev->input;
166 
167 	input->name = pdev->name;
168 	input->phys = "adc-keys/input0";
169 
170 	input->id.bustype = BUS_HOST;
171 	input->id.vendor = 0x0001;
172 	input->id.product = 0x0001;
173 	input->id.version = 0x0100;
174 
175 	__set_bit(EV_KEY, input->evbit);
176 	for (i = 0; i < st->num_keys; i++)
177 		__set_bit(st->map[i].keycode, input->keybit);
178 
179 	if (device_property_read_bool(dev, "autorepeat"))
180 		__set_bit(EV_REP, input->evbit);
181 
182 	error = input_register_polled_device(poll_dev);
183 	if (error) {
184 		dev_err(dev, "Unable to register input device: %d\n", error);
185 		return error;
186 	}
187 
188 	return 0;
189 }
190 
191 #ifdef CONFIG_OF
192 static const struct of_device_id adc_keys_of_match[] = {
193 	{ .compatible = "adc-keys", },
194 	{ }
195 };
196 MODULE_DEVICE_TABLE(of, adc_keys_of_match);
197 #endif
198 
199 static struct platform_driver __refdata adc_keys_driver = {
200 	.driver = {
201 		.name = "adc_keys",
202 		.of_match_table = of_match_ptr(adc_keys_of_match),
203 	},
204 	.probe = adc_keys_probe,
205 };
206 module_platform_driver(adc_keys_driver);
207 
208 MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
209 MODULE_DESCRIPTION("Input driver for resistor ladder connected on ADC");
210 MODULE_LICENSE("GPL v2");
211