1/*
2 * Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com/
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License as
6 * published by the Free Software Foundation version 2.
7 *
8 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
9 * kind, whether express or implied; without even the implied warranty
10 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU General Public License for more details.
12 *
13 * A generic driver to read multiple gpio lines and translate the
14 * encoded numeric value into an input event.
15 */
16
17#include <linux/device.h>
18#include <linux/gpio/consumer.h>
19#include <linux/input.h>
20#include <linux/input-polldev.h>
21#include <linux/kernel.h>
22#include <linux/module.h>
23#include <linux/of.h>
24#include <linux/platform_device.h>
25
26struct gpio_decoder {
27 struct input_polled_dev *poll_dev;
28 struct gpio_descs *input_gpios;
29 struct device *dev;
30 u32 axis;
31 u32 last_stable;
32};
33
34static int gpio_decoder_get_gpios_state(struct gpio_decoder *decoder)
35{
36 struct gpio_descs *gpios = decoder->input_gpios;
37 unsigned int ret = 0;
38 int i, val;
39
40 for (i = 0; i < gpios->ndescs; i++) {
41 val = gpiod_get_value_cansleep(gpios->desc[i]);
42 if (val < 0) {
43 dev_err(decoder->dev,
44 "Error reading gpio %d: %d\n",
45 desc_to_gpio(gpios->desc[i]), val);
46 return val;
47 }
48
49 val = !!val;
50 ret = (ret << 1) | val;
51 }
52
53 return ret;
54}
55
56static void gpio_decoder_poll_gpios(struct input_polled_dev *poll_dev)
57{
58 struct gpio_decoder *decoder = poll_dev->private;
59 int state;
60
61 state = gpio_decoder_get_gpios_state(decoder);
62 if (state >= 0 && state != decoder->last_stable) {
63 input_report_abs(poll_dev->input, decoder->axis, state);
64 input_sync(poll_dev->input);
65 decoder->last_stable = state;
66 }
67}
68
69static int gpio_decoder_probe(struct platform_device *pdev)
70{
71 struct device *dev = &pdev->dev;
72 struct gpio_decoder *decoder;
73 struct input_polled_dev *poll_dev;
74 u32 max;
75 int err;
76
77 decoder = devm_kzalloc(dev, sizeof(struct gpio_decoder), GFP_KERNEL);
78 if (!decoder)
79 return -ENOMEM;
80
81 device_property_read_u32(dev, "linux,axis", &decoder->axis);
82 decoder->input_gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN);
83 if (IS_ERR(decoder->input_gpios)) {
84 dev_err(dev, "unable to acquire input gpios\n");
85 return PTR_ERR(decoder->input_gpios);
86 }
87 if (decoder->input_gpios->ndescs < 2) {
88 dev_err(dev, "not enough gpios found\n");
89 return -EINVAL;
90 }
91
92 if (device_property_read_u32(dev, "decoder-max-value", &max))
93 max = (1U << decoder->input_gpios->ndescs) - 1;
94
95 decoder->dev = dev;
96 poll_dev = devm_input_allocate_polled_device(decoder->dev);
97 if (!poll_dev)
98 return -ENOMEM;
99
100 poll_dev->private = decoder;
101 poll_dev->poll = gpio_decoder_poll_gpios;
102 decoder->poll_dev = poll_dev;
103
104 poll_dev->input->name = pdev->name;
105 poll_dev->input->id.bustype = BUS_HOST;
106 input_set_abs_params(poll_dev->input, decoder->axis, 0, max, 0, 0);
107
108 err = input_register_polled_device(poll_dev);
109 if (err) {
110 dev_err(dev, "failed to register polled device\n");
111 return err;
112 }
113
114 return 0;
115}
116
117#ifdef CONFIG_OF
118static const struct of_device_id gpio_decoder_of_match[] = {
119 { .compatible = "gpio-decoder", },
120 { },
121};
122MODULE_DEVICE_TABLE(of, gpio_decoder_of_match);
123#endif
124
125static struct platform_driver gpio_decoder_driver = {
126 .probe = gpio_decoder_probe,
127 .driver = {
128 .name = "gpio-decoder",
129 .of_match_table = of_match_ptr(gpio_decoder_of_match),
130 }
131};
132module_platform_driver(gpio_decoder_driver);
133
134MODULE_DESCRIPTION("GPIO decoder input driver");
135MODULE_AUTHOR("Vignesh R <vigneshr@ti.com>");
136MODULE_LICENSE("GPL v2");
137