drivers/input/misc/rb532_button.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Support for the S1 button on Routerboard 532
   4  *
   5  * Copyright (C) 2009  Phil Sutter <n0-1@freewrt.org>
   6  */
   7
   8 #include <linux/input-polldev.h>
   9 #include <linux/module.h>
  10 #include <linux/platform_device.h>
  11 #include <linux/gpio.h>
  12
  13 #include <asm/mach-rc32434/gpio.h>
  14 #include <asm/mach-rc32434/rb.h>
  15
  16 #define DRV_NAME "rb532-button"
  17
  18 #define RB532_BTN_RATE 100 /* msec */
  19 #define RB532_BTN_KSYM BTN_0
  20
  21 /* The S1 button state is provided by GPIO pin 1. But as this
  22  * pin is also used for uart input as alternate function, the
  23  * operational modes must be switched first:
  24  * 1) disable uart using set_latch_u5()
  25  * 2) turn off alternate function implicitly through
  26  *    gpio_direction_input()
  27  * 3) read the GPIO's current value
  28  * 4) undo step 2 by enabling alternate function (in this
  29  *    mode the GPIO direction is fixed, so no change needed)
  30  * 5) turn on uart again
  31  * The GPIO value occurs to be inverted, so pin high means
  32  * button is not pressed.
  33  */
  34 static bool rb532_button_pressed(void)
  35 {
  36         int val;
  37
  38         set_latch_u5(0, LO_FOFF);
  39         gpio_direction_input(GPIO_BTN_S1);
  40
  41         val = gpio_get_value(GPIO_BTN_S1);
  42
  43         rb532_gpio_set_func(GPIO_BTN_S1);
  44         set_latch_u5(LO_FOFF, 0);
  45
  46         return !val;
  47 }
  48
  49 static void rb532_button_poll(struct input_polled_dev *poll_dev)
  50 {
  51         input_report_key(poll_dev->input, RB532_BTN_KSYM,
  52                          rb532_button_pressed());
  53         input_sync(poll_dev->input);
  54 }
  55
  56 static int rb532_button_probe(struct platform_device *pdev)
  57 {
  58         struct input_polled_dev *poll_dev;
  59         int error;
  60
  61         poll_dev = input_allocate_polled_device();
  62         if (!poll_dev)
  63                 return -ENOMEM;
  64
  65         poll_dev->poll = rb532_button_poll;
  66         poll_dev->poll_interval = RB532_BTN_RATE;
  67
  68         poll_dev->input->name = "rb532 button";
  69         poll_dev->input->phys = "rb532/button0";
  70         poll_dev->input->id.bustype = BUS_HOST;
  71         poll_dev->input->dev.parent = &pdev->dev;
  72
  73         dev_set_drvdata(&pdev->dev, poll_dev);
  74
  75         input_set_capability(poll_dev->input, EV_KEY, RB532_BTN_KSYM);
  76
  77         error = input_register_polled_device(poll_dev);
  78         if (error) {
  79                 input_free_polled_device(poll_dev);
  80                 return error;
  81         }
  82
  83         return 0;
  84 }
  85
  86 static int rb532_button_remove(struct platform_device *pdev)
  87 {
  88         struct input_polled_dev *poll_dev = dev_get_drvdata(&pdev->dev);
  89
  90         input_unregister_polled_device(poll_dev);
  91         input_free_polled_device(poll_dev);
  92
  93         return 0;
  94 }
  95
  96 static struct platform_driver rb532_button_driver = {
  97         .probe = rb532_button_probe,
  98         .remove = rb532_button_remove,
  99         .driver = {
 100                 .name = DRV_NAME,
 101         },
 102 };
 103 module_platform_driver(rb532_button_driver);
 104
 105 MODULE_AUTHOR("Phil Sutter <n0-1@freewrt.org>");
 106 MODULE_LICENSE("GPL");
 107 MODULE_DESCRIPTION("Support for S1 button on Routerboard 532");
 108 MODULE_ALIAS("platform:" DRV_NAME);