LXR linux/drivers/input/misc/gpio

   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/input-polldev.h>
  21#include <linux/kernel.h>
  22#include <linux/module.h>
  23#include <linux/of.h>
  24#include <linux/platform_device.h>
  25
  26struct gpio_decoder {
  27        struct input_polled_dev *poll_dev;
  28        struct gpio_descs *input_gpios;
  29        struct device *dev;
  30        u32 axis;
  31        u32 last_stable;
  32};
  33
  34static int gpio_decoder_get_gpios_state(struct gpio_decoder *decoder)
  35{
  36        struct gpio_descs *gpios = decoder->input_gpios;
  37        unsigned int ret = 0;
  38        int i, val;
  39
  40        for (i = 0; i < gpios->ndescs; i++) {
  41                val = gpiod_get_value_cansleep(gpios->desc[i]);
  42                if (val < 0) {
  43                        dev_err(decoder->dev,
  44                                "Error reading gpio %d: %d\n",
  45                                desc_to_gpio(gpios->desc[i]), val);
  46                        return val;
  47                }
  48
  49                val = !!val;
  50                ret = (ret << 1) | val;
  51        }
  52
  53        return ret;
  54}
  55
  56static void gpio_decoder_poll_gpios(struct input_polled_dev *poll_dev)
  57{
  58        struct gpio_decoder *decoder = poll_dev->private;
  59        int state;
  60
  61        state = gpio_decoder_get_gpios_state(decoder);
  62        if (state >= 0 && state != decoder->last_stable) {
  63                input_report_abs(poll_dev->input, decoder->axis, state);
  64                input_sync(poll_dev->input);
  65                decoder->last_stable = state;
  66        }
  67}
  68
  69static int gpio_decoder_probe(struct platform_device *pdev)
  70{
  71        struct device *dev = &pdev->dev;
  72        struct gpio_decoder *decoder;
  73        struct input_polled_dev *poll_dev;
  74        u32  max;
  75        int err;
  76
  77        decoder = devm_kzalloc(dev, sizeof(struct gpio_decoder), GFP_KERNEL);
  78        if (!decoder)
  79                return -ENOMEM;
  80
  81        device_property_read_u32(dev, "linux,axis", &decoder->axis);
  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        if (decoder->input_gpios->ndescs < 2) {
  88                dev_err(dev, "not enough gpios found\n");
  89                return -EINVAL;
  90        }
  91
  92        if (device_property_read_u32(dev, "decoder-max-value", &max))
  93                max = (1U << decoder->input_gpios->ndescs) - 1;
  94
  95        decoder->dev = dev;
  96        poll_dev = devm_input_allocate_polled_device(decoder->dev);
  97        if (!poll_dev)
  98                return -ENOMEM;
  99
 100        poll_dev->private = decoder;
 101        poll_dev->poll = gpio_decoder_poll_gpios;
 102        decoder->poll_dev = poll_dev;
 103
 104        poll_dev->input->name = pdev->name;
 105        poll_dev->input->id.bustype = BUS_HOST;
 106        input_set_abs_params(poll_dev->input, decoder->axis, 0, max, 0, 0);
 107
 108        err = input_register_polled_device(poll_dev);
 109        if (err) {
 110                dev_err(dev, "failed to register polled  device\n");
 111                return err;
 112        }
 113
 114        return 0;
 115}
 116
 117#ifdef CONFIG_OF
 118static const struct of_device_id gpio_decoder_of_match[] = {
 119        { .compatible = "gpio-decoder", },
 120        { },
 121};
 122MODULE_DEVICE_TABLE(of, gpio_decoder_of_match);
 123#endif
 124
 125static struct platform_driver gpio_decoder_driver = {
 126        .probe          = gpio_decoder_probe,
 127        .driver         = {
 128                .name   = "gpio-decoder",
 129                .of_match_table = of_match_ptr(gpio_decoder_of_match),
 130        }
 131};
 132module_platform_driver(gpio_decoder_driver);
 133
 134MODULE_DESCRIPTION("GPIO decoder input driver");
 135MODULE_AUTHOR("Vignesh R <vigneshr@ti.com>");
 136MODULE_LICENSE("GPL v2");
 137