drivers/leds/leds-expresswire.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Shared library for Kinetic's ExpressWire protocol.
 * This protocol works by pulsing the ExpressWire IC's control GPIO.
 * ktd2692 and ktd2801 are known to use this protocol.
 */

#include <linux/bits.h>
#include <linux/delay.h>
#include <linux/export.h>
#include <linux/gpio/consumer.h>
#include <linux/irqflags.h>
#include <linux/types.h>

#include <linux/leds-expresswire.h>

void expresswire_power_off(struct expresswire_common_props *props)
{
	gpiod_set_value_cansleep(props->ctrl_gpio, 0);
	fsleep(props->timing.poweroff_us);
}
EXPORT_SYMBOL_NS_GPL(expresswire_power_off, "EXPRESSWIRE");

void expresswire_enable(struct expresswire_common_props *props)
{
	unsigned long flags;

	local_irq_save(flags);

	gpiod_set_value(props->ctrl_gpio, 1);
	udelay(props->timing.detect_delay_us);
	gpiod_set_value(props->ctrl_gpio, 0);
	udelay(props->timing.detect_us);
	gpiod_set_value(props->ctrl_gpio, 1);

	local_irq_restore(flags);
}
EXPORT_SYMBOL_NS_GPL(expresswire_enable, "EXPRESSWIRE");

static void expresswire_start(struct expresswire_common_props *props)
{
	gpiod_set_value(props->ctrl_gpio, 1);
	udelay(props->timing.data_start_us);
}

static void expresswire_end(struct expresswire_common_props *props)
{
	gpiod_set_value(props->ctrl_gpio, 0);
	udelay(props->timing.end_of_data_low_us);
	gpiod_set_value(props->ctrl_gpio, 1);
	udelay(props->timing.end_of_data_high_us);
}

static void expresswire_set_bit(struct expresswire_common_props *props, bool bit)
{
	if (bit) {
		gpiod_set_value(props->ctrl_gpio, 0);
		udelay(props->timing.short_bitset_us);
		gpiod_set_value(props->ctrl_gpio, 1);
		udelay(props->timing.long_bitset_us);
	} else {
		gpiod_set_value(props->ctrl_gpio, 0);
		udelay(props->timing.long_bitset_us);
		gpiod_set_value(props->ctrl_gpio, 1);
		udelay(props->timing.short_bitset_us);
	}
}

void expresswire_write_u8(struct expresswire_common_props *props, u8 val)
{
	unsigned long flags;

	local_irq_save(flags);

	expresswire_start(props);
	for (int i = 7; i >= 0; i--)
		expresswire_set_bit(props, val & BIT(i));
	expresswire_end(props);

	local_irq_restore(flags);
}
EXPORT_SYMBOL_NS_GPL(expresswire_write_u8, "EXPRESSWIRE");