projects/linux·blob 9e795d94 · refs

140 lines · 3.5 KiB

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
25struct gpio_decoder {
26 struct gpio_descs *input_gpios;
27 struct device *dev;
28 u32 axis;
29 u32 last_stable;
30};
31
32static 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
54static 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
67static 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
122static const struct of_device_id gpio_decoder_of_match[] = {
123 { .compatible = "gpio-decoder", },
124 { },
125};
126MODULE_DEVICE_TABLE(of, gpio_decoder_of_match);
127#endif
128
129static 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};
136module_platform_driver(gpio_decoder_driver);
137
138MODULE_DESCRIPTION("GPIO decoder input driver");
139MODULE_AUTHOR("Vignesh R <[email protected]>");
140MODULE_LICENSE("GPL v2");