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> /* Only for legacy support */
  13 #include <linux/gpio/consumer.h>
  14 #include <linux/init.h>
  15 #include <linux/kernel.h>
  16 #include <linux/module.h>
  17 #include <linux/of.h>
  18 #include <linux/of_gpio.h>
  19 #include <linux/platform_data/gpio_backlight.h>
  20 #include <linux/platform_device.h>
  21 #include <linux/slab.h>
  22
  23 struct gpio_backlight {
  24         struct device *dev;
  25         struct device *fbdev;
  26
  27         struct gpio_desc *gpiod;
  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         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_dt(struct platform_device *pdev,
  61                                    struct gpio_backlight *gbl)
  62 {
  63         struct device *dev = &pdev->dev;
  64         struct device_node *np = dev->of_node;
  65         enum gpiod_flags flags;
  66         int ret;
  67
  68         gbl->def_value = of_property_read_bool(np, "default-on");
  69         flags = gbl->def_value ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW;
  70
  71         gbl->gpiod = devm_gpiod_get(dev, NULL, flags);
  72         if (IS_ERR(gbl->gpiod)) {
  73                 ret = PTR_ERR(gbl->gpiod);
  74
  75                 if (ret != -EPROBE_DEFER) {
  76                         dev_err(dev,
  77                                 "Error: The gpios parameter is missing or invalid.\n");
  78                 }
  79                 return ret;
  80         }
  81
  82         return 0;
  83 }
  84
  85 static int gpio_backlight_probe(struct platform_device *pdev)
  86 {
  87         struct gpio_backlight_platform_data *pdata =
  88                 dev_get_platdata(&pdev->dev);
  89         struct backlight_properties props;
  90         struct backlight_device *bl;
  91         struct gpio_backlight *gbl;
  92         struct device_node *np = pdev->dev.of_node;
  93         int ret;
  94
  95         if (!pdata && !np) {
  96                 dev_err(&pdev->dev,
  97                         "failed to find platform data or device tree node.\n");
  98                 return -ENODEV;
  99         }
 100
 101         gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL);
 102         if (gbl == NULL)
 103                 return -ENOMEM;
 104
 105         gbl->dev = &pdev->dev;
 106
 107         if (np) {
 108                 ret = gpio_backlight_probe_dt(pdev, gbl);
 109                 if (ret)
 110                         return ret;
 111         } else {
 112                 /*
 113                  * Legacy platform data GPIO retrieveal. Do not expand
 114                  * the use of this code path, currently only used by one
 115                  * SH board.
 116                  */
 117                 unsigned long flags = GPIOF_DIR_OUT;
 118
 119                 gbl->fbdev = pdata->fbdev;
 120                 gbl->def_value = pdata->def_value;
 121                 flags |= gbl->def_value ? GPIOF_INIT_HIGH : GPIOF_INIT_LOW;
 122
 123                 ret = devm_gpio_request_one(gbl->dev, pdata->gpio, flags,
 124                                             pdata ? pdata->name : "backlight");
 125                 if (ret < 0) {
 126                         dev_err(&pdev->dev, "unable to request GPIO\n");
 127                         return ret;
 128                 }
 129                 gbl->gpiod = gpio_to_desc(pdata->gpio);
 130                 if (!gbl->gpiod)
 131                         return -EINVAL;
 132         }
 133
 134         memset(&props, 0, sizeof(props));
 135         props.type = BACKLIGHT_RAW;
 136         props.max_brightness = 1;
 137         bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),
 138                                         &pdev->dev, gbl, &gpio_backlight_ops,
 139                                         &props);
 140         if (IS_ERR(bl)) {
 141                 dev_err(&pdev->dev, "failed to register backlight\n");
 142                 return PTR_ERR(bl);
 143         }
 144
 145         bl->props.brightness = gbl->def_value;
 146         backlight_update_status(bl);
 147
 148         platform_set_drvdata(pdev, bl);
 149         return 0;
 150 }
 151
 152 #ifdef CONFIG_OF
 153 static struct of_device_id gpio_backlight_of_match[] = {
 154         { .compatible = "gpio-backlight" },
 155         { /* sentinel */ }
 156 };
 157
 158 MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
 159 #endif
 160
 161 static struct platform_driver gpio_backlight_driver = {
 162         .driver         = {
 163                 .name           = "gpio-backlight",
 164                 .of_match_table = of_match_ptr(gpio_backlight_of_match),
 165         },
 166         .probe          = gpio_backlight_probe,
 167 };
 168
 169 module_platform_driver(gpio_backlight_driver);
 170
 171 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
 172 MODULE_DESCRIPTION("GPIO-based Backlight Driver");
 173 MODULE_LICENSE("GPL");
 174 MODULE_ALIAS("platform:gpio-backlight");