1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com/
4 *
5 * A generic driver to read multiple gpio lines and translate the
6 * encoded numeric value into an input event.
7 */
8
9#include <linux/device.h>
10#include <linux/gpio/consumer.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
17struct gpio_decoder {
18	struct gpio_descs *input_gpios;
19	struct device *dev;
20	u32 axis;
21	u32 last_stable;
22};
23
24static int gpio_decoder_get_gpios_state(struct gpio_decoder *decoder)
25{
26	struct gpio_descs *gpios = decoder->input_gpios;
27	unsigned int ret = 0;
28	int i, val;
29
30	for (i = 0; i < gpios->ndescs; i++) {
31		val = gpiod_get_value_cansleep(gpios->desc[i]);
32		if (val < 0) {
33			dev_err(decoder->dev,
34				"Error reading gpio %d: %d\n",
35				desc_to_gpio(gpios->desc[i]), val);
36			return val;
37		}
38
39		val = !!val;
40		ret = (ret << 1) | val;
41	}
42
43	return ret;
44}
45
46static void gpio_decoder_poll_gpios(struct input_dev *input)
47{
48	struct gpio_decoder *decoder = input_get_drvdata(input);
49	int state;
50
51	state = gpio_decoder_get_gpios_state(decoder);
52	if (state >= 0 && state != decoder->last_stable) {
53		input_report_abs(input, decoder->axis, state);
54		input_sync(input);
55		decoder->last_stable = state;
56	}
57}
58
59static int gpio_decoder_probe(struct platform_device *pdev)
60{
61	struct device *dev = &pdev->dev;
62	struct gpio_decoder *decoder;
63	struct input_dev *input;
64	u32  max;
65	int err;
66
67	decoder = devm_kzalloc(dev, sizeof(*decoder), GFP_KERNEL);
68	if (!decoder)
69		return -ENOMEM;
70
71	decoder->dev = dev;
72	device_property_read_u32(dev, "linux,axis", &decoder->axis);
73
74	decoder->input_gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN);
75	if (IS_ERR(decoder->input_gpios)) {
76		dev_err(dev, "unable to acquire input gpios\n");
77		return PTR_ERR(decoder->input_gpios);
78	}
79
80	if (decoder->input_gpios->ndescs < 2) {
81		dev_err(dev, "not enough gpios found\n");
82		return -EINVAL;
83	}
84
85	if (device_property_read_u32(dev, "decoder-max-value", &max))
86		max = (1U << decoder->input_gpios->ndescs) - 1;
87
88	input = devm_input_allocate_device(dev);
89	if (!input)
90		return -ENOMEM;
91
92	input_set_drvdata(input, decoder);
93
94	input->name = pdev->name;
95	input->id.bustype = BUS_HOST;
96	input_set_abs_params(input, decoder->axis, 0, max, 0, 0);
97
98	err = input_setup_polling(input, gpio_decoder_poll_gpios);
99	if (err) {
100		dev_err(dev, "failed to set up polling\n");
101		return err;
102	}
103
104	err = input_register_device(input);
105	if (err) {
106		dev_err(dev, "failed to register input device\n");
107		return err;
108	}
109
110	return 0;
111}
112
113#ifdef CONFIG_OF
114static const struct of_device_id gpio_decoder_of_match[] = {
115	{ .compatible = "gpio-decoder", },
116	{ },
117};
118MODULE_DEVICE_TABLE(of, gpio_decoder_of_match);
119#endif
120
121static struct platform_driver gpio_decoder_driver = {
122	.probe		= gpio_decoder_probe,
123	.driver		= {
124		.name	= "gpio-decoder",
125		.of_match_table = of_match_ptr(gpio_decoder_of_match),
126	}
127};
128module_platform_driver(gpio_decoder_driver);
129
130MODULE_DESCRIPTION("GPIO decoder input driver");
131MODULE_AUTHOR("Vignesh R <vigneshr@ti.com>");
132MODULE_LICENSE("GPL v2");
133