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/kernel.h>
21 #include <linux/module.h>
22 #include <linux/of.h>
23 #include <linux/platform_device.h>
24 
25 struct gpio_decoder {
26 	struct gpio_descs *input_gpios;
27 	struct device *dev;
28 	u32 axis;
29 	u32 last_stable;
30 };
31 
32 static int gpio_decoder_get_gpios_state(struct gpio_decoder *decoder)
33 {
34 	struct gpio_descs *gpios = decoder->input_gpios;
35 	unsigned int ret = 0;
36 	int i, val;
37 
38 	for (i = 0; i < gpios->ndescs; i++) {
39 		val = gpiod_get_value_cansleep(gpios->desc[i]);
40 		if (val < 0) {
41 			dev_err(decoder->dev,
42 				"Error reading gpio %d: %d\n",
43 				desc_to_gpio(gpios->desc[i]), val);
44 			return val;
45 		}
46 
47 		val = !!val;
48 		ret = (ret << 1) | val;
49 	}
50 
51 	return ret;
52 }
53 
54 static void gpio_decoder_poll_gpios(struct input_dev *input)
55 {
56 	struct gpio_decoder *decoder = input_get_drvdata(input);
57 	int state;
58 
59 	state = gpio_decoder_get_gpios_state(decoder);
60 	if (state >= 0 && state != decoder->last_stable) {
61 		input_report_abs(input, decoder->axis, state);
62 		input_sync(input);
63 		decoder->last_stable = state;
64 	}
65 }
66 
67 static int gpio_decoder_probe(struct platform_device *pdev)
68 {
69 	struct device *dev = &pdev->dev;
70 	struct gpio_decoder *decoder;
71 	struct input_dev *input;
72 	u32  max;
73 	int err;
74 
75 	decoder = devm_kzalloc(dev, sizeof(*decoder), GFP_KERNEL);
76 	if (!decoder)
77 		return -ENOMEM;
78 
79 	decoder->dev = dev;
80 	device_property_read_u32(dev, "linux,axis", &decoder->axis);
81 
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 
88 	if (decoder->input_gpios->ndescs < 2) {
89 		dev_err(dev, "not enough gpios found\n");
90 		return -EINVAL;
91 	}
92 
93 	if (device_property_read_u32(dev, "decoder-max-value", &max))
94 		max = (1U << decoder->input_gpios->ndescs) - 1;
95 
96 	input = devm_input_allocate_device(dev);
97 	if (!input)
98 		return -ENOMEM;
99 
100 	input_set_drvdata(input, decoder);
101 
102 	input->name = pdev->name;
103 	input->id.bustype = BUS_HOST;
104 	input_set_abs_params(input, decoder->axis, 0, max, 0, 0);
105 
106 	err = input_setup_polling(input, gpio_decoder_poll_gpios);
107 	if (err) {
108 		dev_err(dev, "failed to set up polling\n");
109 		return err;
110 	}
111 
112 	err = input_register_device(input);
113 	if (err) {
114 		dev_err(dev, "failed to register input device\n");
115 		return err;
116 	}
117 
118 	return 0;
119 }
120 
121 #ifdef CONFIG_OF
122 static const struct of_device_id gpio_decoder_of_match[] = {
123 	{ .compatible = "gpio-decoder", },
124 	{ },
125 };
126 MODULE_DEVICE_TABLE(of, gpio_decoder_of_match);
127 #endif
128 
129 static struct platform_driver gpio_decoder_driver = {
130 	.probe		= gpio_decoder_probe,
131 	.driver		= {
132 		.name	= "gpio-decoder",
133 		.of_match_table = of_match_ptr(gpio_decoder_of_match),
134 	}
135 };
136 module_platform_driver(gpio_decoder_driver);
137 
138 MODULE_DESCRIPTION("GPIO decoder input driver");
139 MODULE_AUTHOR("Vignesh R <vigneshr@ti.com>");
140 MODULE_LICENSE("GPL v2");
141