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	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
192static const struct of_device_id adc_keys_of_match[] = {
193	{ .compatible = "adc-keys", },
194	{ }
195};
196MODULE_DEVICE_TABLE(of, adc_keys_of_match);
197#endif
198
199static 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};
206module_platform_driver(adc_keys_driver);
207
208MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@free-electrons.com>");
209MODULE_DESCRIPTION("Input driver for resistor ladder connected on ADC");
210MODULE_LICENSE("GPL v2");