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_get_brightness(struct backlight_device *bl)
  48 {
  49         return bl->props.brightness;
  50 }
  51
  52 static int gpio_backlight_check_fb(struct backlight_device *bl,
  53                                    struct fb_info *info)
  54 {
  55         struct gpio_backlight *gbl = bl_get_data(bl);
  56
  57         return gbl->fbdev == NULL || gbl->fbdev == info->dev;
  58 }
  59
  60 static const struct backlight_ops gpio_backlight_ops = {
  61         .options        = BL_CORE_SUSPENDRESUME,
  62         .update_status  = gpio_backlight_update_status,
  63         .get_brightness = gpio_backlight_get_brightness,
  64         .check_fb       = gpio_backlight_check_fb,
  65 };
  66
  67 static int gpio_backlight_probe_dt(struct platform_device *pdev,
  68                                    struct gpio_backlight *gbl)
  69 {
  70         struct device_node *np = pdev->dev.of_node;
  71         enum of_gpio_flags gpio_flags;
  72
  73         gbl->gpio = of_get_gpio_flags(np, 0, &gpio_flags);
  74
  75         if (!gpio_is_valid(gbl->gpio)) {
  76                 if (gbl->gpio != -EPROBE_DEFER) {
  77                         dev_err(&pdev->dev,
  78                                 "Error: The gpios parameter is missing or invalid.\n");
  79                 }
  80                 return gbl->gpio;
  81         }
  82
  83         gbl->active = (gpio_flags & OF_GPIO_ACTIVE_LOW) ? 0 : 1;
  84
  85         gbl->def_value = of_property_read_bool(np, "default-on");
  86
  87         return 0;
  88 }
  89
  90 static int gpio_backlight_probe(struct platform_device *pdev)
  91 {
  92         struct gpio_backlight_platform_data *pdata =
  93                 dev_get_platdata(&pdev->dev);
  94         struct backlight_properties props;
  95         struct backlight_device *bl;
  96         struct gpio_backlight *gbl;
  97         struct device_node *np = pdev->dev.of_node;
  98         int ret;
  99
 100         if (!pdata && !np) {
 101                 dev_err(&pdev->dev,
 102                         "failed to find platform data or device tree node.\n");
 103                 return -ENODEV;
 104         }
 105
 106         gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL);
 107         if (gbl == NULL)
 108                 return -ENOMEM;
 109
 110         gbl->dev = &pdev->dev;
 111
 112         if (np) {
 113                 ret = gpio_backlight_probe_dt(pdev, gbl);
 114                 if (ret)
 115                         return ret;
 116         } else {
 117                 gbl->fbdev = pdata->fbdev;
 118                 gbl->gpio = pdata->gpio;
 119                 gbl->active = pdata->active_low ? 0 : 1;
 120                 gbl->def_value = pdata->def_value;
 121         }
 122
 123         ret = devm_gpio_request_one(gbl->dev, gbl->gpio, GPIOF_DIR_OUT |
 124                                     (gbl->active ? GPIOF_INIT_LOW
 125                                                  : GPIOF_INIT_HIGH),
 126                                     pdata ? pdata->name : "backlight");
 127         if (ret < 0) {
 128                 dev_err(&pdev->dev, "unable to request GPIO\n");
 129                 return ret;
 130         }
 131
 132         memset(&props, 0, sizeof(props));
 133         props.type = BACKLIGHT_RAW;
 134         props.max_brightness = 1;
 135         bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),
 136                                         &pdev->dev, gbl, &gpio_backlight_ops,
 137                                         &props);
 138         if (IS_ERR(bl)) {
 139                 dev_err(&pdev->dev, "failed to register backlight\n");
 140                 return PTR_ERR(bl);
 141         }
 142
 143         bl->props.brightness = gbl->def_value;
 144         backlight_update_status(bl);
 145
 146         platform_set_drvdata(pdev, bl);
 147         return 0;
 148 }
 149
 150 #ifdef CONFIG_OF
 151 static struct of_device_id gpio_backlight_of_match[] = {
 152         { .compatible = "gpio-backlight" },
 153         { /* sentinel */ }
 154 };
 155 #endif
 156
 157 static struct platform_driver gpio_backlight_driver = {
 158         .driver         = {
 159                 .name           = "gpio-backlight",
 160                 .owner          = THIS_MODULE,
 161                 .of_match_table = of_match_ptr(gpio_backlight_of_match),
 162         },
 163         .probe          = gpio_backlight_probe,
 164 };
 165
 166 module_platform_driver(gpio_backlight_driver);
 167
 168 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
 169 MODULE_DESCRIPTION("GPIO-based Backlight Driver");
 170 MODULE_LICENSE("GPL");
 171 MODULE_ALIAS("platform:gpio-backlight");