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/*
* Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com/
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation version 2.
*
* This program is distributed "as is" WITHOUT ANY WARRANTY of any
* kind, whether express or implied; without even the implied warranty
* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* A generic driver to read multiple gpio lines and translate the
* encoded numeric value into an input event.
*/
#include <linux/device.h>
#include <linux/gpio/consumer.h>
#include <linux/input.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
struct gpio_decoder {
struct gpio_descs *input_gpios;
struct device *dev;
u32 axis;
u32 last_stable;
};
static int gpio_decoder_get_gpios_state(struct gpio_decoder *decoder)
{
struct gpio_descs *gpios = decoder->input_gpios;
unsigned int ret = 0;
int i, val;
for (i = 0; i < gpios->ndescs; i++) {
val = gpiod_get_value_cansleep(gpios->desc[i]);
if (val < 0) {
dev_err(decoder->dev,
"Error reading gpio %d: %d\n",
desc_to_gpio(gpios->desc[i]), val);
return val;
}
val = !!val;
ret = (ret << 1) | val;
}
return ret;
}
static void gpio_decoder_poll_gpios(struct input_dev *input)
{
struct gpio_decoder *decoder = input_get_drvdata(input);
int state;
state = gpio_decoder_get_gpios_state(decoder);
if (state >= 0 && state != decoder->last_stable) {
input_report_abs(input, decoder->axis, state);
input_sync(input);
decoder->last_stable = state;
}
}
static int gpio_decoder_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct gpio_decoder *decoder;
struct input_dev *input;
u32 max;
int err;
decoder = devm_kzalloc(dev, sizeof(*decoder), GFP_KERNEL);
if (!decoder)
return -ENOMEM;
decoder->dev = dev;
device_property_read_u32(dev, "linux,axis", &decoder->axis);
decoder->input_gpios = devm_gpiod_get_array(dev, NULL, GPIOD_IN);
if (IS_ERR(decoder->input_gpios)) {
dev_err(dev, "unable to acquire input gpios\n");
return PTR_ERR(decoder->input_gpios);
}
if (decoder->input_gpios->ndescs < 2) {
dev_err(dev, "not enough gpios found\n");
return -EINVAL;
}
if (device_property_read_u32(dev, "decoder-max-value", &max))
max = (1U << decoder->input_gpios->ndescs) - 1;
input = devm_input_allocate_device(dev);
if (!input)
return -ENOMEM;
input_set_drvdata(input, decoder);
input->name = pdev->name;
input->id.bustype = BUS_HOST;
input_set_abs_params(input, decoder->axis, 0, max, 0, 0);
err = input_setup_polling(input, gpio_decoder_poll_gpios);
if (err) {
dev_err(dev, "failed to set up polling\n");
return err;
}
err = input_register_device(input);
if (err) {
dev_err(dev, "failed to register input device\n");
return err;
}
return 0;
}
#ifdef CONFIG_OF
static const struct of_device_id gpio_decoder_of_match[] = {
{ .compatible = "gpio-decoder", },
{ },
};
MODULE_DEVICE_TABLE(of, gpio_decoder_of_match);
#endif
static struct platform_driver gpio_decoder_driver = {
.probe = gpio_decoder_probe,
.driver = {
.name = "gpio-decoder",
.of_match_table = of_match_ptr(gpio_decoder_of_match),
}
};
module_platform_driver(gpio_decoder_driver);
MODULE_DESCRIPTION("GPIO decoder input driver");
MODULE_AUTHOR("Vignesh R <vigneshr@ti.com>");
MODULE_LICENSE("GPL v2");
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