LXR linux/drivers/video/backlight/gpio

   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
  22struct gpio_backlight {
  23        struct device *dev;
  24        struct device *fbdev;
  25
  26        int gpio;
  27        int active;
  28        int def_value;
  29};
  30
  31static 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
  47static int gpio_backlight_check_fb(struct backlight_device *bl,
  48                                   struct fb_info *info)
  49{
  50        struct gpio_backlight *gbl = bl_get_data(bl);
  51
  52        return gbl->fbdev == NULL || gbl->fbdev == info->dev;
  53}
  54
  55static const struct backlight_ops gpio_backlight_ops = {
  56        .options        = BL_CORE_SUSPENDRESUME,
  57        .update_status  = gpio_backlight_update_status,
  58        .check_fb       = gpio_backlight_check_fb,
  59};
  60
  61static int gpio_backlight_probe_dt(struct platform_device *pdev,
  62                                   struct gpio_backlight *gbl)
  63{
  64        struct device_node *np = pdev->dev.of_node;
  65        enum of_gpio_flags gpio_flags;
  66
  67        gbl->gpio = of_get_gpio_flags(np, 0, &gpio_flags);
  68
  69        if (!gpio_is_valid(gbl->gpio)) {
  70                if (gbl->gpio != -EPROBE_DEFER) {
  71                        dev_err(&pdev->dev,
  72                                "Error: The gpios parameter is missing or invalid.\n");
  73                }
  74                return gbl->gpio;
  75        }
  76
  77        gbl->active = (gpio_flags & OF_GPIO_ACTIVE_LOW) ? 0 : 1;
  78
  79        gbl->def_value = of_property_read_bool(np, "default-on");
  80
  81        return 0;
  82}
  83
  84static int gpio_backlight_probe(struct platform_device *pdev)
  85{
  86        struct gpio_backlight_platform_data *pdata =
  87                dev_get_platdata(&pdev->dev);
  88        struct backlight_properties props;
  89        struct backlight_device *bl;
  90        struct gpio_backlight *gbl;
  91        struct device_node *np = pdev->dev.of_node;
  92        unsigned long flags = GPIOF_DIR_OUT;
  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                gbl->fbdev = pdata->fbdev;
 113                gbl->gpio = pdata->gpio;
 114                gbl->active = pdata->active_low ? 0 : 1;
 115                gbl->def_value = pdata->def_value;
 116        }
 117
 118        if (gbl->active)
 119                flags |= gbl->def_value ? GPIOF_INIT_HIGH : GPIOF_INIT_LOW;
 120        else
 121                flags |= gbl->def_value ? GPIOF_INIT_LOW : GPIOF_INIT_HIGH;
 122
 123        ret = devm_gpio_request_one(gbl->dev, gbl->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
 130        memset(&props, 0, sizeof(props));
 131        props.type = BACKLIGHT_RAW;
 132        props.max_brightness = 1;
 133        bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),
 134                                        &pdev->dev, gbl, &gpio_backlight_ops,
 135                                        &props);
 136        if (IS_ERR(bl)) {
 137                dev_err(&pdev->dev, "failed to register backlight\n");
 138                return PTR_ERR(bl);
 139        }
 140
 141        bl->props.brightness = gbl->def_value;
 142        backlight_update_status(bl);
 143
 144        platform_set_drvdata(pdev, bl);
 145        return 0;
 146}
 147
 148#ifdef CONFIG_OF
 149static struct of_device_id gpio_backlight_of_match[] = {
 150        { .compatible = "gpio-backlight" },
 151        { /* sentinel */ }
 152};
 153
 154MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
 155#endif
 156
 157static struct platform_driver gpio_backlight_driver = {
 158        .driver         = {
 159                .name           = "gpio-backlight",
 160                .of_match_table = of_match_ptr(gpio_backlight_of_match),
 161        },
 162        .probe          = gpio_backlight_probe,
 163};
 164
 165module_platform_driver(gpio_backlight_driver);
 166
 167MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
 168MODULE_DESCRIPTION("GPIO-based Backlight Driver");
 169MODULE_LICENSE("GPL");
 170MODULE_ALIAS("platform:gpio-backlight");
 171