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 <vigneshr@ti.com>");
140MODULE_LICENSE("GPL v2");