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