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.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_dev *input)
  50 {
  51         input_report_key(input, RB532_BTN_KSYM, rb532_button_pressed());
  52         input_sync(input);
  53 }
  54
  55 static int rb532_button_probe(struct platform_device *pdev)
  56 {
  57         struct input_dev *input;
  58         int error;
  59
  60         input = devm_input_allocate_device(&pdev->dev);
  61         if (!input)
  62                 return -ENOMEM;
  63
  64         input->name = "rb532 button";
  65         input->phys = "rb532/button0";
  66         input->id.bustype = BUS_HOST;
  67
  68         input_set_capability(input, EV_KEY, RB532_BTN_KSYM);
  69
  70         error = input_setup_polling(input, rb532_button_poll);
  71         if (error)
  72                 return error;
  73
  74         input_set_poll_interval(input, RB532_BTN_RATE);
  75
  76         error = input_register_device(input);
  77         if (error)
  78                 return error;
  79
  80         return 0;
  81 }
  82
  83 static struct platform_driver rb532_button_driver = {
  84         .probe = rb532_button_probe,
  85         .driver = {
  86                 .name = DRV_NAME,
  87         },
  88 };
  89 module_platform_driver(rb532_button_driver);
  90
  91 MODULE_AUTHOR("Phil Sutter <n0-1@freewrt.org>");
  92 MODULE_LICENSE("GPL");
  93 MODULE_DESCRIPTION("Support for S1 button on Routerboard 532");
  94 MODULE_ALIAS("platform:" DRV_NAME);