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