drivers/video/backlight/ktd2801-backlight.c

// 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");