/* * 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/input-polldev.h>#include <linux/kernel.h>#include <linux/module.h>#include <linux/of.h>#include <linux/platform_device.h> struct gpio_decoder {	struct input_polled_dev *poll_dev;	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_polled_dev *poll_dev){	struct gpio_decoder *decoder = poll_dev->private;	int state; 	state = gpio_decoder_get_gpios_state(decoder);	if (state >= 0 && state != decoder->last_stable) {		input_report_abs(poll_dev->input, decoder->axis, state);		input_sync(poll_dev->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_polled_dev *poll_dev;	u32  max;	int err; 	decoder = devm_kzalloc(dev, sizeof(struct gpio_decoder), GFP_KERNEL);	if (!decoder)		return -ENOMEM; 	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; 	decoder->dev = dev;	poll_dev = devm_input_allocate_polled_device(decoder->dev);	if (!poll_dev)		return -ENOMEM; 	poll_dev->private = decoder;	poll_dev->poll = gpio_decoder_poll_gpios;	decoder->poll_dev = poll_dev; 	poll_dev->input->name = pdev->name;	poll_dev->input->id.bustype = BUS_HOST;	input_set_abs_params(poll_dev->input, decoder->axis, 0, max, 0, 0); 	err = input_register_polled_device(poll_dev);	if (err) {		dev_err(dev, "failed to register polled  device\n");		return err;	}	platform_set_drvdata(pdev, decoder); 	return 0;} #ifdef CONFIG_OFstatic 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");