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/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");
 141