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/of.h>
  17 #include <linux/of_gpio.h>
  18 #include <linux/platform_data/gpio_backlight.h>
  19 #include <linux/platform_device.h>
  20 #include <linux/slab.h>
  21
  22 struct gpio_backlight {
  23         struct device *dev;
  24         struct device *fbdev;
  25
  26         int gpio;
  27         int active;
  28         int def_value;
  29 };
  30
  31 static int gpio_backlight_update_status(struct backlight_device *bl)
  32 {
  33         struct gpio_backlight *gbl = bl_get_data(bl);
  34         int brightness = bl->props.brightness;
  35
  36         if (bl->props.power != FB_BLANK_UNBLANK ||
  37             bl->props.fb_blank != FB_BLANK_UNBLANK ||
  38             bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
  39                 brightness = 0;
  40
  41         gpio_set_value_cansleep(gbl->gpio,
  42                                 brightness ? gbl->active : !gbl->active);
  43
  44         return 0;
  45 }
  46
  47 static int gpio_backlight_check_fb(struct backlight_device *bl,
  48                                    struct fb_info *info)
  49 {
  50         struct gpio_backlight *gbl = bl_get_data(bl);
  51
  52         return gbl->fbdev == NULL || gbl->fbdev == info->dev;
  53 }
  54
  55 static const struct backlight_ops gpio_backlight_ops = {
  56         .options        = BL_CORE_SUSPENDRESUME,
  57         .update_status  = gpio_backlight_update_status,
  58         .check_fb       = gpio_backlight_check_fb,
  59 };
  60
  61 static int gpio_backlight_probe_dt(struct platform_device *pdev,
  62                                    struct gpio_backlight *gbl)
  63 {
  64         struct device_node *np = pdev->dev.of_node;
  65         enum of_gpio_flags gpio_flags;
  66
  67         gbl->gpio = of_get_gpio_flags(np, 0, &gpio_flags);
  68
  69         if (!gpio_is_valid(gbl->gpio)) {
  70                 if (gbl->gpio != -EPROBE_DEFER) {
  71                         dev_err(&pdev->dev,
  72                                 "Error: The gpios parameter is missing or invalid.\n");
  73                 }
  74                 return gbl->gpio;
  75         }
  76
  77         gbl->active = (gpio_flags & OF_GPIO_ACTIVE_LOW) ? 0 : 1;
  78
  79         gbl->def_value = of_property_read_bool(np, "default-on");
  80
  81         return 0;
  82 }
  83
  84 static int gpio_backlight_probe(struct platform_device *pdev)
  85 {
  86         struct gpio_backlight_platform_data *pdata =
  87                 dev_get_platdata(&pdev->dev);
  88         struct backlight_properties props;
  89         struct backlight_device *bl;
  90         struct gpio_backlight *gbl;
  91         struct device_node *np = pdev->dev.of_node;
  92         int ret;
  93
  94         if (!pdata && !np) {
  95                 dev_err(&pdev->dev,
  96                         "failed to find platform data or device tree node.\n");
  97                 return -ENODEV;
  98         }
  99
 100         gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL);
 101         if (gbl == NULL)
 102                 return -ENOMEM;
 103
 104         gbl->dev = &pdev->dev;
 105
 106         if (np) {
 107                 ret = gpio_backlight_probe_dt(pdev, gbl);
 108                 if (ret)
 109                         return ret;
 110         } else {
 111                 gbl->fbdev = pdata->fbdev;
 112                 gbl->gpio = pdata->gpio;
 113                 gbl->active = pdata->active_low ? 0 : 1;
 114                 gbl->def_value = pdata->def_value;
 115         }
 116
 117         ret = devm_gpio_request_one(gbl->dev, gbl->gpio, GPIOF_DIR_OUT |
 118                                     (gbl->active ? GPIOF_INIT_LOW
 119                                                  : GPIOF_INIT_HIGH),
 120                                     pdata ? pdata->name : "backlight");
 121         if (ret < 0) {
 122                 dev_err(&pdev->dev, "unable to request GPIO\n");
 123                 return ret;
 124         }
 125
 126         memset(&props, 0, sizeof(props));
 127         props.type = BACKLIGHT_RAW;
 128         props.max_brightness = 1;
 129         bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),
 130                                         &pdev->dev, gbl, &gpio_backlight_ops,
 131                                         &props);
 132         if (IS_ERR(bl)) {
 133                 dev_err(&pdev->dev, "failed to register backlight\n");
 134                 return PTR_ERR(bl);
 135         }
 136
 137         bl->props.brightness = gbl->def_value;
 138         backlight_update_status(bl);
 139
 140         platform_set_drvdata(pdev, bl);
 141         return 0;
 142 }
 143
 144 #ifdef CONFIG_OF
 145 static struct of_device_id gpio_backlight_of_match[] = {
 146         { .compatible = "gpio-backlight" },
 147         { /* sentinel */ }
 148 };
 149 #endif
 150
 151 static struct platform_driver gpio_backlight_driver = {
 152         .driver         = {
 153                 .name           = "gpio-backlight",
 154                 .of_match_table = of_match_ptr(gpio_backlight_of_match),
 155         },
 156         .probe          = gpio_backlight_probe,
 157 };
 158
 159 module_platform_driver(gpio_backlight_driver);
 160
 161 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
 162 MODULE_DESCRIPTION("GPIO-based Backlight Driver");
 163 MODULE_LICENSE("GPL");
 164 MODULE_ALIAS("platform:gpio-backlight");