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// SPDX-License-Identifier: GPL-2.0-only
/*
* gpio_backlight.c - Simple GPIO-controlled backlight
*/
#include <linux/backlight.h>
#include <linux/err.h>
#include <linux/fb.h>
#include <linux/gpio/consumer.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_data/gpio_backlight.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#include <linux/slab.h>
struct gpio_backlight {
struct device *dev;
struct device *fbdev;
struct gpio_desc *gpiod;
int def_value;
};
static int gpio_backlight_get_next_brightness(struct backlight_device *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;
return brightness;
}
static int gpio_backlight_update_status(struct backlight_device *bl)
{
struct gpio_backlight *gbl = bl_get_data(bl);
int brightness = gpio_backlight_get_next_brightness(bl);
gpiod_set_value_cansleep(gbl->gpiod, brightness);
return 0;
}
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,
.check_fb = gpio_backlight_check_fb,
};
static int gpio_backlight_initial_power_state(struct gpio_backlight *gbl)
{
struct device_node *node = gbl->dev->of_node;
/* Not booted with device tree or no phandle link to the node */
if (!node || !node->phandle)
return gbl->def_value ? FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN;
/* if the enable GPIO is disabled, do not enable the backlight */
if (gpiod_get_direction(gbl->gpiod) == 0 &&
gpiod_get_value_cansleep(gbl->gpiod) == 0)
return FB_BLANK_POWERDOWN;
return FB_BLANK_UNBLANK;
}
static int gpio_backlight_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct gpio_backlight_platform_data *pdata = dev_get_platdata(dev);
struct backlight_properties props;
struct backlight_device *bl;
struct gpio_backlight *gbl;
int ret, init_brightness;
gbl = devm_kzalloc(dev, sizeof(*gbl), GFP_KERNEL);
if (gbl == NULL)
return -ENOMEM;
gbl->dev = dev;
if (pdata)
gbl->fbdev = pdata->fbdev;
gbl->def_value = device_property_read_bool(dev, "default-on");
gbl->gpiod = devm_gpiod_get(dev, NULL, GPIOD_ASIS);
if (IS_ERR(gbl->gpiod)) {
ret = PTR_ERR(gbl->gpiod);
if (ret != -EPROBE_DEFER)
dev_err(dev,
"Error: The gpios parameter is missing or invalid.\n");
return ret;
}
memset(&props, 0, sizeof(props));
props.type = BACKLIGHT_RAW;
props.max_brightness = 1;
bl = devm_backlight_device_register(dev, dev_name(dev), dev, gbl,
&gpio_backlight_ops, &props);
if (IS_ERR(bl)) {
dev_err(dev, "failed to register backlight\n");
return PTR_ERR(bl);
}
bl->props.power = gpio_backlight_initial_power_state(gbl);
bl->props.brightness = 1;
init_brightness = gpio_backlight_get_next_brightness(bl);
ret = gpiod_direction_output(gbl->gpiod, init_brightness);
if (ret) {
dev_err(dev, "failed to set initial brightness\n");
return ret;
}
platform_set_drvdata(pdev, bl);
return 0;
}
static struct of_device_id gpio_backlight_of_match[] = {
{ .compatible = "gpio-backlight" },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, gpio_backlight_of_match);
static struct platform_driver gpio_backlight_driver = {
.driver = {
.name = "gpio-backlight",
.of_match_table = 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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