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/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
  26 struct 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
  34 static 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
  56 static 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
  69 static 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
 118 static const struct of_device_id gpio_decoder_of_match[] = {
 119         { .compatible = "gpio-decoder", },
 120         { },
 121 };
 122 MODULE_DEVICE_TABLE(of, gpio_decoder_of_match);
 123 #endif
 124
 125 static 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 };
 132 module_platform_driver(gpio_decoder_driver);
 133
 134 MODULE_DESCRIPTION("GPIO decoder input driver");
 135 MODULE_AUTHOR("Vignesh R <vigneshr@ti.com>");
 136 MODULE_LICENSE("GPL v2");