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