drivers/video/backlight/gpio_backlight.c

   1 /*
   2  * gpio_backlight.c - Simple GPIO-controlled backlight
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #include <linux/backlight.h>
  10 #include <linux/err.h>
  11 #include <linux/fb.h>
  12 #include <linux/gpio.h>
  13 #include <linux/init.h>
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/platform_data/gpio_backlight.h>
  17 #include <linux/platform_device.h>
  18 #include <linux/slab.h>
  19
  20 struct gpio_backlight {
  21         struct device *dev;
  22         struct device *fbdev;
  23
  24         int gpio;
  25         int active;
  26 };
  27
  28 static int gpio_backlight_update_status(struct backlight_device *bl)
  29 {
  30         struct gpio_backlight *gbl = bl_get_data(bl);
  31         int brightness = bl->props.brightness;
  32
  33         if (bl->props.power != FB_BLANK_UNBLANK ||
  34             bl->props.fb_blank != FB_BLANK_UNBLANK ||
  35             bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
  36                 brightness = 0;
  37
  38         gpio_set_value(gbl->gpio, brightness ? gbl->active : !gbl->active);
  39
  40         return 0;
  41 }
  42
  43 static int gpio_backlight_get_brightness(struct backlight_device *bl)
  44 {
  45         return bl->props.brightness;
  46 }
  47
  48 static int gpio_backlight_check_fb(struct backlight_device *bl,
  49                                    struct fb_info *info)
  50 {
  51         struct gpio_backlight *gbl = bl_get_data(bl);
  52
  53         return gbl->fbdev == NULL || gbl->fbdev == info->dev;
  54 }
  55
  56 static const struct backlight_ops gpio_backlight_ops = {
  57         .options        = BL_CORE_SUSPENDRESUME,
  58         .update_status  = gpio_backlight_update_status,
  59         .get_brightness = gpio_backlight_get_brightness,
  60         .check_fb       = gpio_backlight_check_fb,
  61 };
  62
  63 static int gpio_backlight_probe(struct platform_device *pdev)
  64 {
  65         struct gpio_backlight_platform_data *pdata =
  66                 dev_get_platdata(&pdev->dev);
  67         struct backlight_properties props;
  68         struct backlight_device *bl;
  69         struct gpio_backlight *gbl;
  70         int ret;
  71
  72         if (!pdata) {
  73                 dev_err(&pdev->dev, "failed to find platform data\n");
  74                 return -ENODEV;
  75         }
  76
  77         gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL);
  78         if (gbl == NULL)
  79                 return -ENOMEM;
  80
  81         gbl->dev = &pdev->dev;
  82         gbl->fbdev = pdata->fbdev;
  83         gbl->gpio = pdata->gpio;
  84         gbl->active = pdata->active_low ? 0 : 1;
  85
  86         ret = devm_gpio_request_one(gbl->dev, gbl->gpio, GPIOF_DIR_OUT |
  87                                     (gbl->active ? GPIOF_INIT_LOW
  88                                                  : GPIOF_INIT_HIGH),
  89                                     pdata->name);
  90         if (ret < 0) {
  91                 dev_err(&pdev->dev, "unable to request GPIO\n");
  92                 return ret;
  93         }
  94
  95         memset(&props, 0, sizeof(props));
  96         props.type = BACKLIGHT_RAW;
  97         props.max_brightness = 1;
  98         bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),
  99                                         &pdev->dev, gbl, &gpio_backlight_ops,
 100                                         &props);
 101         if (IS_ERR(bl)) {
 102                 dev_err(&pdev->dev, "failed to register backlight\n");
 103                 return PTR_ERR(bl);
 104         }
 105
 106         bl->props.brightness = pdata->def_value;
 107         backlight_update_status(bl);
 108
 109         platform_set_drvdata(pdev, bl);
 110         return 0;
 111 }
 112
 113 static struct platform_driver gpio_backlight_driver = {
 114         .driver         = {
 115                 .name           = "gpio-backlight",
 116                 .owner          = THIS_MODULE,
 117         },
 118         .probe          = gpio_backlight_probe,
 119 };
 120
 121 module_platform_driver(gpio_backlight_driver);
 122
 123 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
 124 MODULE_DESCRIPTION("GPIO-based Backlight Driver");
 125 MODULE_LICENSE("GPL");
 126 MODULE_ALIAS("platform:gpio-backlight");