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/*
* gpio_backlight.c - Simple GPIO-controlled backlight
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/backlight.h>
#include <linux/err.h>
#include <linux/fb.h>
#include <linux/gpio.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/platform_data/gpio_backlight.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
struct gpio_backlight {
struct device *dev;
struct device *fbdev;
int gpio;
int active;
int def_value;
};
static int gpio_backlight_update_status(struct backlight_device *bl)
{
struct gpio_backlight *gbl = bl_get_data(bl);
int brightness = bl->props.brightness;
if (bl->props.power != FB_BLANK_UNBLANK ||
bl->props.fb_blank != FB_BLANK_UNBLANK ||
bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
brightness = 0;
gpio_set_value(gbl->gpio, brightness ? gbl->active : !gbl->active);
return 0;
}
static int gpio_backlight_get_brightness(struct backlight_device *bl)
{
return bl->props.brightness;
}
static int gpio_backlight_check_fb(struct backlight_device *bl,
struct fb_info *info)
{
struct gpio_backlight *gbl = bl_get_data(bl);
return gbl->fbdev == NULL || gbl->fbdev == info->dev;
}
static const struct backlight_ops gpio_backlight_ops = {
.options = BL_CORE_SUSPENDRESUME,
.update_status = gpio_backlight_update_status,
.get_brightness = gpio_backlight_get_brightness,
.check_fb = gpio_backlight_check_fb,
};
static int gpio_backlight_probe_dt(struct platform_device *pdev,
struct gpio_backlight *gbl)
{
struct device_node *np = pdev->dev.of_node;
enum of_gpio_flags gpio_flags;
gbl->gpio = of_get_gpio_flags(np, 0, &gpio_flags);
if (!gpio_is_valid(gbl->gpio)) {
if (gbl->gpio != -EPROBE_DEFER) {
dev_err(&pdev->dev,
"Error: The gpios parameter is missing or invalid.\n");
}
return gbl->gpio;
}
gbl->active = (gpio_flags & OF_GPIO_ACTIVE_LOW) ? 0 : 1;
gbl->def_value = of_property_read_bool(np, "default-on");
return 0;
}
static int gpio_backlight_probe(struct platform_device *pdev)
{
struct gpio_backlight_platform_data *pdata =
dev_get_platdata(&pdev->dev);
struct backlight_properties props;
struct backlight_device *bl;
struct gpio_backlight *gbl;
struct device_node *np = pdev->dev.of_node;
int ret;
if (!pdata && !np) {
dev_err(&pdev->dev,
"failed to find platform data or device tree node.\n");
return -ENODEV;
}
gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL);
if (gbl == NULL)
return -ENOMEM;
gbl->dev = &pdev->dev;
if (np) {
ret = gpio_backlight_probe_dt(pdev, gbl);
if (ret)
return ret;
} else {
gbl->fbdev = pdata->fbdev;
gbl->gpio = pdata->gpio;
gbl->active = pdata->active_low ? 0 : 1;
gbl->def_value = pdata->def_value;
}
ret = devm_gpio_request_one(gbl->dev, gbl->gpio, GPIOF_DIR_OUT |
(gbl->active ? GPIOF_INIT_LOW
: GPIOF_INIT_HIGH),
pdata ? pdata->name : "backlight");
if (ret < 0) {
dev_err(&pdev->dev, "unable to request GPIO\n");
return ret;
}
memset(&props, 0, sizeof(props));
props.type = BACKLIGHT_RAW;
props.max_brightness = 1;
bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),
&pdev->dev, gbl, &gpio_backlight_ops,
&props);
if (IS_ERR(bl)) {
dev_err(&pdev->dev, "failed to register backlight\n");
return PTR_ERR(bl);
}
bl->props.brightness = gbl->def_value;
backlight_update_status(bl);
platform_set_drvdata(pdev, bl);
return 0;
}
#ifdef CONFIG_OF
static struct of_device_id gpio_backlight_of_match[] = {
{ .compatible = "gpio-backlight" },
{ /* sentinel */ }
};
#endif
static struct platform_driver gpio_backlight_driver = {
.driver = {
.name = "gpio-backlight",
.owner = THIS_MODULE,
.of_match_table = of_match_ptr(gpio_backlight_of_match),
},
.probe = gpio_backlight_probe,
};
module_platform_driver(gpio_backlight_driver);
MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
MODULE_DESCRIPTION("GPIO-based Backlight Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:gpio-backlight");
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