drivers/input/misc/gpio_decoder.c

   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
  25 struct gpio_decoder {
  26         struct gpio_descs *input_gpios;
  27         struct device *dev;
  28         u32 axis;
  29         u32 last_stable;
  30 };
  31
  32 static 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
  54 static 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
  67 static 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
 122 static const struct of_device_id gpio_decoder_of_match[] = {
 123         { .compatible = "gpio-decoder", },
 124         { },
 125 };
 126 MODULE_DEVICE_TABLE(of, gpio_decoder_of_match);
 127 #endif
 128
 129 static 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 };
 136 module_platform_driver(gpio_decoder_driver);
 137
 138 MODULE_DESCRIPTION("GPIO decoder input driver");
 139 MODULE_AUTHOR("Vignesh R <vigneshr@ti.com>");
 140 MODULE_LICENSE("GPL v2");