backlight.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Miscellaneous procedures for dealing with the PowerMac hardware.
 * Contains support for the backlight.
 *
 *   Copyright (C) 2000 Benjamin Herrenschmidt
 *   Copyright (C) 2006 Michael Hanselmann <[email protected]>
 *
 */

#include <linux/kernel.h>
#include <linux/backlight.h>
#include <linux/adb.h>
#include <linux/of.h>
#include <linux/pmu.h>
#include <linux/atomic.h>
#include <linux/export.h>
#include <asm/backlight.h>

#define OLD_BACKLIGHT_MAX 15

static void pmac_backlight_key_worker(struct work_struct *work);
static void pmac_backlight_set_legacy_worker(struct work_struct *work);

static DECLARE_WORK(pmac_backlight_key_work, pmac_backlight_key_worker);
static DECLARE_WORK(pmac_backlight_set_legacy_work, pmac_backlight_set_legacy_worker);

/* Although these variables are used in interrupt context, it makes no sense to
 * protect them. No user is able to produce enough key events per second and
 * notice the errors that might happen.
 */
static int pmac_backlight_key_queued;
static int pmac_backlight_set_legacy_queued;

/* The via-pmu code allows the backlight to be grabbed, in which case the
 * in-kernel control of the brightness needs to be disabled. This should
 * only be used by really old PowerBooks.
 */
static atomic_t kernel_backlight_disabled = ATOMIC_INIT(0);

/* Protect the pmac_backlight variable below.
   You should hold this lock when using the pmac_backlight pointer to
   prevent its potential removal. */
DEFINE_MUTEX(pmac_backlight_mutex);

/* Main backlight storage
 *
 * Backlight drivers in this variable are required to have the "ops"
 * attribute set and to have an update_status function.
 *
 * We can only store one backlight here, but since Apple laptops have only one
 * internal display, it doesn't matter. Other backlight drivers can be used
 * independently.
 *
 */
struct backlight_device *pmac_backlight;

int pmac_has_backlight_type(const char *type)
{
	struct device_node* bk_node = of_find_node_by_name(NULL, "backlight");
	int i = of_property_match_string(bk_node, "backlight-control", type);

	of_node_put(bk_node);
	return i >= 0;
}

static void pmac_backlight_key_worker(struct work_struct *work)
{
	if (atomic_read(&kernel_backlight_disabled))
		return;

	mutex_lock(&pmac_backlight_mutex);
	if (pmac_backlight) {
		struct backlight_properties *props;
		int brightness;

		props = &pmac_backlight->props;

		brightness = props->brightness +
			((pmac_backlight_key_queued?-1:1) *
			 (props->max_brightness / 15));

		if (brightness < 0)
			brightness = 0;
		else if (brightness > props->max_brightness)
			brightness = props->max_brightness;

		props->brightness = brightness;
		backlight_update_status(pmac_backlight);
	}
	mutex_unlock(&pmac_backlight_mutex);
}

/* This function is called in interrupt context */
void pmac_backlight_key(int direction)
{
	if (atomic_read(&kernel_backlight_disabled))
		return;

	/* we can receive multiple interrupts here, but the scheduled work
	 * will run only once, with the last value
	 */
	pmac_backlight_key_queued = direction;
	schedule_work(&pmac_backlight_key_work);
}

static int __pmac_backlight_set_legacy_brightness(int brightness)
{
	int error = -ENXIO;

	mutex_lock(&pmac_backlight_mutex);
	if (pmac_backlight) {
		struct backlight_properties *props;

		props = &pmac_backlight->props;
		props->brightness = brightness *
			(props->max_brightness + 1) /
			(OLD_BACKLIGHT_MAX + 1);

		if (props->brightness > props->max_brightness)
			props->brightness = props->max_brightness;
		else if (props->brightness < 0)
			props->brightness = 0;

		backlight_update_status(pmac_backlight);

		error = 0;
	}
	mutex_unlock(&pmac_backlight_mutex);

	return error;
}

static void pmac_backlight_set_legacy_worker(struct work_struct *work)
{
	if (atomic_read(&kernel_backlight_disabled))
		return;

	__pmac_backlight_set_legacy_brightness(pmac_backlight_set_legacy_queued);
}

/* This function is called in interrupt context */
void pmac_backlight_set_legacy_brightness_pmu(int brightness) {
	if (atomic_read(&kernel_backlight_disabled))
		return;

	pmac_backlight_set_legacy_queued = brightness;
	schedule_work(&pmac_backlight_set_legacy_work);
}

int pmac_backlight_set_legacy_brightness(int brightness)
{
	return __pmac_backlight_set_legacy_brightness(brightness);
}

int pmac_backlight_get_legacy_brightness(void)
{
	int result = -ENXIO;

	mutex_lock(&pmac_backlight_mutex);
	if (pmac_backlight) {
		struct backlight_properties *props;

		props = &pmac_backlight->props;

		result = props->brightness *
			(OLD_BACKLIGHT_MAX + 1) /
			(props->max_brightness + 1);
	}
	mutex_unlock(&pmac_backlight_mutex);

	return result;
}

void pmac_backlight_disable(void)
{
	atomic_inc(&kernel_backlight_disabled);
}

void pmac_backlight_enable(void)
{
	atomic_dec(&kernel_backlight_disabled);
}

EXPORT_SYMBOL_GPL(pmac_backlight);
EXPORT_SYMBOL_GPL(pmac_backlight_mutex);
EXPORT_SYMBOL_GPL(pmac_has_backlight_type);