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_update_status(struct backlight_device *bl)
  25 {
  26         struct gpio_backlight *gbl = bl_get_data(bl);
  27
  28         gpiod_set_value_cansleep(gbl->gpiod, backlight_get_brightness(bl));
  29
  30         return 0;
  31 }
  32
  33 static int gpio_backlight_check_fb(struct backlight_device *bl,
  34                                    struct fb_info *info)
  35 {
  36         struct gpio_backlight *gbl = bl_get_data(bl);
  37
  38         return gbl->fbdev == NULL || gbl->fbdev == info->dev;
  39 }
  40
  41 static const struct backlight_ops gpio_backlight_ops = {
  42         .options        = BL_CORE_SUSPENDRESUME,
  43         .update_status  = gpio_backlight_update_status,
  44         .check_fb       = gpio_backlight_check_fb,
  45 };
  46
  47 static int gpio_backlight_probe(struct platform_device *pdev)
  48 {
  49         struct device *dev = &pdev->dev;
  50         struct gpio_backlight_platform_data *pdata = dev_get_platdata(dev);
  51         struct device_node *of_node = dev->of_node;
  52         struct backlight_properties props;
  53         struct backlight_device *bl;
  54         struct gpio_backlight *gbl;
  55         int ret, init_brightness, def_value;
  56
  57         gbl = devm_kzalloc(dev, sizeof(*gbl), GFP_KERNEL);
  58         if (gbl == NULL)
  59                 return -ENOMEM;
  60
  61         if (pdata)
  62                 gbl->fbdev = pdata->fbdev;
  63
  64         def_value = device_property_read_bool(dev, "default-on");
  65
  66         gbl->gpiod = devm_gpiod_get(dev, NULL, GPIOD_ASIS);
  67         if (IS_ERR(gbl->gpiod)) {
  68                 ret = PTR_ERR(gbl->gpiod);
  69                 if (ret != -EPROBE_DEFER)
  70                         dev_err(dev,
  71                                 "Error: The gpios parameter is missing or invalid.\n");
  72                 return ret;
  73         }
  74
  75         memset(&props, 0, sizeof(props));
  76         props.type = BACKLIGHT_RAW;
  77         props.max_brightness = 1;
  78         bl = devm_backlight_device_register(dev, dev_name(dev), dev, gbl,
  79                                             &gpio_backlight_ops, &props);
  80         if (IS_ERR(bl)) {
  81                 dev_err(dev, "failed to register backlight\n");
  82                 return PTR_ERR(bl);
  83         }
  84
  85         /* Set the initial power state */
  86         if (!of_node || !of_node->phandle)
  87                 /* Not booted with device tree or no phandle link to the node */
  88                 bl->props.power = def_value ? FB_BLANK_UNBLANK
  89                                             : FB_BLANK_POWERDOWN;
  90         else if (gpiod_get_direction(gbl->gpiod) == 0 &&
  91                  gpiod_get_value_cansleep(gbl->gpiod) == 0)
  92                 bl->props.power = FB_BLANK_POWERDOWN;
  93         else
  94                 bl->props.power = FB_BLANK_UNBLANK;
  95
  96         bl->props.brightness = 1;
  97
  98         init_brightness = backlight_get_brightness(bl);
  99         ret = gpiod_direction_output(gbl->gpiod, init_brightness);
 100         if (ret) {
 101                 dev_err(dev, "failed to set initial brightness\n");
 102                 return ret;
 103         }
 104
 105         platform_set_drvdata(pdev, bl);
 106         return 0;
 107 }
 108
 109 static struct of_device_id gpio_backlight_of_match[] = {
 110         { .compatible = "gpio-backlight" },
 111         { /* sentinel */ }
 112 };
 113
 114 MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
 115
 116 static struct platform_driver gpio_backlight_driver = {
 117         .driver         = {
 118                 .name           = "gpio-backlight",
 119                 .of_match_table = gpio_backlight_of_match,
 120         },
 121         .probe          = gpio_backlight_probe,
 122 };
 123
 124 module_platform_driver(gpio_backlight_driver);
 125
 126 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
 127 MODULE_DESCRIPTION("GPIO-based Backlight Driver");
 128 MODULE_LICENSE("GPL");
 129 MODULE_ALIAS("platform:gpio-backlight");