drivers/video/backlight/gpio_backlight.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * gpio_backlight.c - Simple GPIO-controlled backlight
   4  */
   5
   6 #include <linux/backlight.h>
   7 #include <linux/err.h>
   8 #include <linux/fb.h>
   9 #include <linux/gpio/consumer.h>
  10 #include <linux/init.h>
  11 #include <linux/kernel.h>
  12 #include <linux/module.h>
  13 #include <linux/of.h>
  14 #include <linux/platform_data/gpio_backlight.h>
  15 #include <linux/platform_device.h>
  16 #include <linux/property.h>
  17 #include <linux/slab.h>
  18
  19 struct gpio_backlight {
  20         struct device *fbdev;
  21         struct gpio_desc *gpiod;
  22 };
  23
  24 static int gpio_backlight_get_next_brightness(struct backlight_device *bl)
  25 {
  26         int brightness = bl->props.brightness;
  27
  28         if (bl->props.power != FB_BLANK_UNBLANK ||
  29             bl->props.fb_blank != FB_BLANK_UNBLANK ||
  30             bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
  31                 brightness = 0;
  32
  33         return brightness;
  34 }
  35
  36 static int gpio_backlight_update_status(struct backlight_device *bl)
  37 {
  38         struct gpio_backlight *gbl = bl_get_data(bl);
  39         int brightness = gpio_backlight_get_next_brightness(bl);
  40
  41         gpiod_set_value_cansleep(gbl->gpiod, brightness);
  42
  43         return 0;
  44 }
  45
  46 static int gpio_backlight_check_fb(struct backlight_device *bl,
  47                                    struct fb_info *info)
  48 {
  49         struct gpio_backlight *gbl = bl_get_data(bl);
  50
  51         return gbl->fbdev == NULL || gbl->fbdev == info->dev;
  52 }
  53
  54 static const struct backlight_ops gpio_backlight_ops = {
  55         .options        = BL_CORE_SUSPENDRESUME,
  56         .update_status  = gpio_backlight_update_status,
  57         .check_fb       = gpio_backlight_check_fb,
  58 };
  59
  60 static int gpio_backlight_probe(struct platform_device *pdev)
  61 {
  62         struct device *dev = &pdev->dev;
  63         struct gpio_backlight_platform_data *pdata = dev_get_platdata(dev);
  64         struct device_node *of_node = dev->of_node;
  65         struct backlight_properties props;
  66         struct backlight_device *bl;
  67         struct gpio_backlight *gbl;
  68         int ret, init_brightness, def_value;
  69
  70         gbl = devm_kzalloc(dev, sizeof(*gbl), GFP_KERNEL);
  71         if (gbl == NULL)
  72                 return -ENOMEM;
  73
  74         if (pdata)
  75                 gbl->fbdev = pdata->fbdev;
  76
  77         def_value = device_property_read_bool(dev, "default-on");
  78
  79         gbl->gpiod = devm_gpiod_get(dev, NULL, GPIOD_ASIS);
  80         if (IS_ERR(gbl->gpiod)) {
  81                 ret = PTR_ERR(gbl->gpiod);
  82                 if (ret != -EPROBE_DEFER)
  83                         dev_err(dev,
  84                                 "Error: The gpios parameter is missing or invalid.\n");
  85                 return ret;
  86         }
  87
  88         memset(&props, 0, sizeof(props));
  89         props.type = BACKLIGHT_RAW;
  90         props.max_brightness = 1;
  91         bl = devm_backlight_device_register(dev, dev_name(dev), dev, gbl,
  92                                             &gpio_backlight_ops, &props);
  93         if (IS_ERR(bl)) {
  94                 dev_err(dev, "failed to register backlight\n");
  95                 return PTR_ERR(bl);
  96         }
  97
  98         /* Set the initial power state */
  99         if (!of_node || !of_node->phandle)
 100                 /* Not booted with device tree or no phandle link to the node */
 101                 bl->props.power = def_value ? FB_BLANK_UNBLANK
 102                                             : FB_BLANK_POWERDOWN;
 103         else if (gpiod_get_direction(gbl->gpiod) == 0 &&
 104                  gpiod_get_value_cansleep(gbl->gpiod) == 0)
 105                 bl->props.power = FB_BLANK_POWERDOWN;
 106         else
 107                 bl->props.power = FB_BLANK_UNBLANK;
 108
 109         bl->props.brightness = 1;
 110
 111         init_brightness = gpio_backlight_get_next_brightness(bl);
 112         ret = gpiod_direction_output(gbl->gpiod, init_brightness);
 113         if (ret) {
 114                 dev_err(dev, "failed to set initial brightness\n");
 115                 return ret;
 116         }
 117
 118         platform_set_drvdata(pdev, bl);
 119         return 0;
 120 }
 121
 122 static struct of_device_id gpio_backlight_of_match[] = {
 123         { .compatible = "gpio-backlight" },
 124         { /* sentinel */ }
 125 };
 126
 127 MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
 128
 129 static struct platform_driver gpio_backlight_driver = {
 130         .driver         = {
 131                 .name           = "gpio-backlight",
 132                 .of_match_table = gpio_backlight_of_match,
 133         },
 134         .probe          = gpio_backlight_probe,
 135 };
 136
 137 module_platform_driver(gpio_backlight_driver);
 138
 139 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
 140 MODULE_DESCRIPTION("GPIO-based Backlight Driver");
 141 MODULE_LICENSE("GPL");
 142 MODULE_ALIAS("platform:gpio-backlight");