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// SPDX-License-Identifier: GPL-2.0-only
/*
* Datasheet:
* https://www.kinet-ic.com/uploads/web/KTD2801/KTD2801-04b.pdf
*/
#include <linux/backlight.h>
#include <linux/gpio/consumer.h>
#include <linux/leds-expresswire.h>
#include <linux/platform_device.h>
#include <linux/property.h>
#define KTD2801_DEFAULT_BRIGHTNESS 100
#define KTD2801_MAX_BRIGHTNESS 255
/* These values have been extracted from Samsung's driver. */
static const struct expresswire_timing ktd2801_timing = {
.poweroff_us = 2600,
.detect_delay_us = 150,
.detect_us = 270,
.data_start_us = 5,
.short_bitset_us = 5,
.long_bitset_us = 15,
.end_of_data_low_us = 10,
.end_of_data_high_us = 350
};
struct ktd2801_backlight {
struct expresswire_common_props props;
struct backlight_device *bd;
bool was_on;
};
static int ktd2801_update_status(struct backlight_device *bd)
{
struct ktd2801_backlight *ktd2801 = bl_get_data(bd);
u8 brightness = (u8) backlight_get_brightness(bd);
if (backlight_is_blank(bd)) {
expresswire_power_off(&ktd2801->props);
ktd2801->was_on = false;
return 0;
}
if (!ktd2801->was_on) {
expresswire_enable(&ktd2801->props);
ktd2801->was_on = true;
}
expresswire_write_u8(&ktd2801->props, brightness);
return 0;
}
static const struct backlight_ops ktd2801_backlight_ops = {
.update_status = ktd2801_update_status,
};
static int ktd2801_backlight_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct backlight_device *bd;
struct ktd2801_backlight *ktd2801;
u32 brightness, max_brightness;
int ret;
ktd2801 = devm_kzalloc(dev, sizeof(*ktd2801), GFP_KERNEL);
if (!ktd2801)
return -ENOMEM;
ktd2801->was_on = true;
ktd2801->props.timing = ktd2801_timing;
ret = device_property_read_u32(dev, "max-brightness", &max_brightness);
if (ret)
max_brightness = KTD2801_MAX_BRIGHTNESS;
if (max_brightness > KTD2801_MAX_BRIGHTNESS) {
dev_err(dev, "illegal max brightness specified\n");
max_brightness = KTD2801_MAX_BRIGHTNESS;
}
ret = device_property_read_u32(dev, "default-brightness", &brightness);
if (ret)
brightness = KTD2801_DEFAULT_BRIGHTNESS;
if (brightness > max_brightness) {
dev_err(dev, "default brightness exceeds max\n");
brightness = max_brightness;
}
ktd2801->props.ctrl_gpio = devm_gpiod_get(dev, "ctrl", GPIOD_OUT_HIGH);
if (IS_ERR(ktd2801->props.ctrl_gpio))
return dev_err_probe(dev, PTR_ERR(ktd2801->props.ctrl_gpio),
"failed to get backlight GPIO");
gpiod_set_consumer_name(ktd2801->props.ctrl_gpio, dev_name(dev));
bd = devm_backlight_device_register(dev, dev_name(dev), dev, ktd2801,
&ktd2801_backlight_ops, NULL);
if (IS_ERR(bd))
return dev_err_probe(dev, PTR_ERR(bd),
"failed to register backlight");
bd->props.max_brightness = max_brightness;
bd->props.brightness = brightness;
ktd2801->bd = bd;
platform_set_drvdata(pdev, bd);
backlight_update_status(bd);
return 0;
}
static const struct of_device_id ktd2801_of_match[] = {
{ .compatible = "kinetic,ktd2801" },
{ }
};
MODULE_DEVICE_TABLE(of, ktd2801_of_match);
static struct platform_driver ktd2801_backlight_driver = {
.driver = {
.name = "ktd2801-backlight",
.of_match_table = ktd2801_of_match,
},
.probe = ktd2801_backlight_probe,
};
module_platform_driver(ktd2801_backlight_driver);
MODULE_IMPORT_NS(EXPRESSWIRE);
MODULE_AUTHOR("Duje Mihanović <duje.mihanovic@skole.hr>");
MODULE_DESCRIPTION("Kinetic KTD2801 Backlight Driver");
MODULE_LICENSE("GPL");
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