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
17 struct gpio_decoder {
18 struct gpio_descs *input_gpios;
19 struct device *dev;
20 u32 axis;
21 u32 last_stable;
22 };
23
gpio_decoder_get_gpios_state(struct gpio_decoder * decoder)24 static 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
gpio_decoder_poll_gpios(struct input_dev * input)46 static 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
gpio_decoder_probe(struct platform_device * pdev)59 static 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
114 static const struct of_device_id gpio_decoder_of_match[] = {
115 { .compatible = "gpio-decoder", },
116 { },
117 };
118 MODULE_DEVICE_TABLE(of, gpio_decoder_of_match);
119 #endif
120
121 static 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 };
128 module_platform_driver(gpio_decoder_driver);
129
130 MODULE_DESCRIPTION("GPIO decoder input driver");
131 MODULE_AUTHOR("Vignesh R <vigneshr@ti.com>");
132 MODULE_LICENSE("GPL v2");
133