Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 779 insertions, 0 deletions

diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
new file mode 100644
index 000000000..b788ff3d0
--- /dev/null
+++ b/drivers/video/backlight/backlight.c
@@ -0,0 +1,779 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Backlight Lowlevel Control Abstraction
+ *
+ * Copyright (C) 2003,2004 Hewlett-Packard Company
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/device.h>
+#include <linux/backlight.h>
+#include <linux/notifier.h>
+#include <linux/ctype.h>
+#include <linux/err.h>
+#include <linux/fb.h>
+#include <linux/slab.h>
+
+#ifdef CONFIG_PMAC_BACKLIGHT
+#include <asm/backlight.h>
+#endif
+
+/**
+ * DOC: overview
+ *
+ * The backlight core supports implementing backlight drivers.
+ *
+ * A backlight driver registers a driver using
+ * devm_backlight_device_register(). The properties of the backlight
+ * driver such as type and max_brightness must be specified.
+ * When the core detect changes in for example brightness or power state
+ * the update_status() operation is called. The backlight driver shall
+ * implement this operation and use it to adjust backlight.
+ *
+ * Several sysfs attributes are provided by the backlight core::
+ *
+ * - brightness         R/W, set the requested brightness level
+ * - actual_brightness  RO, the brightness level used by the HW
+ * - max_brightness     RO, the maximum  brightness level supported
+ *
+ * See Documentation/ABI/stable/sysfs-class-backlight for the full list.
+ *
+ * The backlight can be adjusted using the sysfs interface, and
+ * the backlight driver may also support adjusting backlight using
+ * a hot-key or some other platform or firmware specific way.
+ *
+ * The driver must implement the get_brightness() operation if
+ * the HW do not support all the levels that can be specified in
+ * brightness, thus providing user-space access to the actual level
+ * via the actual_brightness attribute.
+ *
+ * When the backlight changes this is reported to user-space using
+ * an uevent connected to the actual_brightness attribute.
+ * When brightness is set by platform specific means, for example
+ * a hot-key to adjust backlight, the driver must notify the backlight
+ * core that brightness has changed using backlight_force_update().
+ *
+ * The backlight driver core receives notifications from fbdev and
+ * if the event is FB_EVENT_BLANK and if the value of blank, from the
+ * FBIOBLANK ioctrl, results in a change in the backlight state the
+ * update_status() operation is called.
+ */
+
+static struct list_head backlight_dev_list;
+static struct mutex backlight_dev_list_mutex;
+static struct blocking_notifier_head backlight_notifier;
+
+static const char *const backlight_types[] = {
+	[BACKLIGHT_RAW] = "raw",
+	[BACKLIGHT_PLATFORM] = "platform",
+	[BACKLIGHT_FIRMWARE] = "firmware",
+};
+
+static const char *const backlight_scale_types[] = {
+	[BACKLIGHT_SCALE_UNKNOWN]	= "unknown",
+	[BACKLIGHT_SCALE_LINEAR]	= "linear",
+	[BACKLIGHT_SCALE_NON_LINEAR]	= "non-linear",
+};
+
+#if defined(CONFIG_FB) || (defined(CONFIG_FB_MODULE) && \
+			   defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE))
+/*
+ * fb_notifier_callback
+ *
+ * This callback gets called when something important happens inside a
+ * framebuffer driver. The backlight core only cares about FB_BLANK_UNBLANK
+ * which is reported to the driver using backlight_update_status()
+ * as a state change.
+ *
+ * There may be several fbdev's connected to the backlight device,
+ * in which case they are kept track of. A state change is only reported
+ * if there is a change in backlight for the specified fbdev.
+ */
+static int fb_notifier_callback(struct notifier_block *self,
+				unsigned long event, void *data)
+{
+	struct backlight_device *bd;
+	struct fb_event *evdata = data;
+	int node = evdata->info->node;
+	int fb_blank = 0;
+
+	/* If we aren't interested in this event, skip it immediately ... */
+	if (event != FB_EVENT_BLANK)
+		return 0;
+
+	bd = container_of(self, struct backlight_device, fb_notif);
+	mutex_lock(&bd->ops_lock);
+
+	if (!bd->ops)
+		goto out;
+	if (bd->ops->check_fb && !bd->ops->check_fb(bd, evdata->info))
+		goto out;
+
+	fb_blank = *(int *)evdata->data;
+	if (fb_blank == FB_BLANK_UNBLANK && !bd->fb_bl_on[node]) {
+		bd->fb_bl_on[node] = true;
+		if (!bd->use_count++) {
+			bd->props.state &= ~BL_CORE_FBBLANK;
+			bd->props.fb_blank = FB_BLANK_UNBLANK;
+			backlight_update_status(bd);
+		}
+	} else if (fb_blank != FB_BLANK_UNBLANK && bd->fb_bl_on[node]) {
+		bd->fb_bl_on[node] = false;
+		if (!(--bd->use_count)) {
+			bd->props.state |= BL_CORE_FBBLANK;
+			bd->props.fb_blank = fb_blank;
+			backlight_update_status(bd);
+		}
+	}
+out:
+	mutex_unlock(&bd->ops_lock);
+	return 0;
+}
+
+static int backlight_register_fb(struct backlight_device *bd)
+{
+	memset(&bd->fb_notif, 0, sizeof(bd->fb_notif));
+	bd->fb_notif.notifier_call = fb_notifier_callback;
+
+	return fb_register_client(&bd->fb_notif);
+}
+
+static void backlight_unregister_fb(struct backlight_device *bd)
+{
+	fb_unregister_client(&bd->fb_notif);
+}
+#else
+static inline int backlight_register_fb(struct backlight_device *bd)
+{
+	return 0;
+}
+
+static inline void backlight_unregister_fb(struct backlight_device *bd)
+{
+}
+#endif /* CONFIG_FB */
+
+static void backlight_generate_event(struct backlight_device *bd,
+				     enum backlight_update_reason reason)
+{
+	char *envp[2];
+
+	switch (reason) {
+	case BACKLIGHT_UPDATE_SYSFS:
+		envp[0] = "SOURCE=sysfs";
+		break;
+	case BACKLIGHT_UPDATE_HOTKEY:
+		envp[0] = "SOURCE=hotkey";
+		break;
+	default:
+		envp[0] = "SOURCE=unknown";
+		break;
+	}
+	envp[1] = NULL;
+	kobject_uevent_env(&bd->dev.kobj, KOBJ_CHANGE, envp);
+	sysfs_notify(&bd->dev.kobj, NULL, "actual_brightness");
+}
+
+static ssize_t bl_power_show(struct device *dev, struct device_attribute *attr,
+		char *buf)
+{
+	struct backlight_device *bd = to_backlight_device(dev);
+
+	return sprintf(buf, "%d\n", bd->props.power);
+}
+
+static ssize_t bl_power_store(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t count)
+{
+	int rc;
+	struct backlight_device *bd = to_backlight_device(dev);
+	unsigned long power, old_power;
+
+	rc = kstrtoul(buf, 0, &power);
+	if (rc)
+		return rc;
+
+	rc = -ENXIO;
+	mutex_lock(&bd->ops_lock);
+	if (bd->ops) {
+		pr_debug("set power to %lu\n", power);
+		if (bd->props.power != power) {
+			old_power = bd->props.power;
+			bd->props.power = power;
+			rc = backlight_update_status(bd);
+			if (rc)
+				bd->props.power = old_power;
+			else
+				rc = count;
+		} else {
+			rc = count;
+		}
+	}
+	mutex_unlock(&bd->ops_lock);
+
+	return rc;
+}
+static DEVICE_ATTR_RW(bl_power);
+
+static ssize_t brightness_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct backlight_device *bd = to_backlight_device(dev);
+
+	return sprintf(buf, "%d\n", bd->props.brightness);
+}
+
+int backlight_device_set_brightness(struct backlight_device *bd,
+				    unsigned long brightness)
+{
+	int rc = -ENXIO;
+
+	mutex_lock(&bd->ops_lock);
+	if (bd->ops) {
+		if (brightness > bd->props.max_brightness)
+			rc = -EINVAL;
+		else {
+			pr_debug("set brightness to %lu\n", brightness);
+			bd->props.brightness = brightness;
+			rc = backlight_update_status(bd);
+		}
+	}
+	mutex_unlock(&bd->ops_lock);
+
+	backlight_generate_event(bd, BACKLIGHT_UPDATE_SYSFS);
+
+	return rc;
+}
+EXPORT_SYMBOL(backlight_device_set_brightness);
+
+static ssize_t brightness_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	int rc;
+	struct backlight_device *bd = to_backlight_device(dev);
+	unsigned long brightness;
+
+	rc = kstrtoul(buf, 0, &brightness);
+	if (rc)
+		return rc;
+
+	rc = backlight_device_set_brightness(bd, brightness);
+
+	return rc ? rc : count;
+}
+static DEVICE_ATTR_RW(brightness);
+
+static ssize_t type_show(struct device *dev, struct device_attribute *attr,
+		char *buf)
+{
+	struct backlight_device *bd = to_backlight_device(dev);
+
+	return sprintf(buf, "%s\n", backlight_types[bd->props.type]);
+}
+static DEVICE_ATTR_RO(type);
+
+static ssize_t max_brightness_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct backlight_device *bd = to_backlight_device(dev);
+
+	return sprintf(buf, "%d\n", bd->props.max_brightness);
+}
+static DEVICE_ATTR_RO(max_brightness);
+
+static ssize_t actual_brightness_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	int rc = -ENXIO;
+	struct backlight_device *bd = to_backlight_device(dev);
+
+	mutex_lock(&bd->ops_lock);
+	if (bd->ops && bd->ops->get_brightness) {
+		rc = bd->ops->get_brightness(bd);
+		if (rc >= 0)
+			rc = sprintf(buf, "%d\n", rc);
+	} else {
+		rc = sprintf(buf, "%d\n", bd->props.brightness);
+	}
+	mutex_unlock(&bd->ops_lock);
+
+	return rc;
+}
+static DEVICE_ATTR_RO(actual_brightness);
+
+static ssize_t scale_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct backlight_device *bd = to_backlight_device(dev);
+
+	if (WARN_ON(bd->props.scale > BACKLIGHT_SCALE_NON_LINEAR))
+		return sprintf(buf, "unknown\n");
+
+	return sprintf(buf, "%s\n", backlight_scale_types[bd->props.scale]);
+}
+static DEVICE_ATTR_RO(scale);
+
+static struct class *backlight_class;
+
+#ifdef CONFIG_PM_SLEEP
+static int backlight_suspend(struct device *dev)
+{
+	struct backlight_device *bd = to_backlight_device(dev);
+
+	mutex_lock(&bd->ops_lock);
+	if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) {
+		bd->props.state |= BL_CORE_SUSPENDED;
+		backlight_update_status(bd);
+	}
+	mutex_unlock(&bd->ops_lock);
+
+	return 0;
+}
+
+static int backlight_resume(struct device *dev)
+{
+	struct backlight_device *bd = to_backlight_device(dev);
+
+	mutex_lock(&bd->ops_lock);
+	if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) {
+		bd->props.state &= ~BL_CORE_SUSPENDED;
+		backlight_update_status(bd);
+	}
+	mutex_unlock(&bd->ops_lock);
+
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(backlight_class_dev_pm_ops, backlight_suspend,
+			 backlight_resume);
+
+static void bl_device_release(struct device *dev)
+{
+	struct backlight_device *bd = to_backlight_device(dev);
+	kfree(bd);
+}
+
+static struct attribute *bl_device_attrs[] = {
+	&dev_attr_bl_power.attr,
+	&dev_attr_brightness.attr,
+	&dev_attr_actual_brightness.attr,
+	&dev_attr_max_brightness.attr,
+	&dev_attr_scale.attr,
+	&dev_attr_type.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(bl_device);
+
+/**
+ * backlight_force_update - tell the backlight subsystem that hardware state
+ *   has changed
+ * @bd: the backlight device to update
+ * @reason: reason for update
+ *
+ * Updates the internal state of the backlight in response to a hardware event,
+ * and generates an uevent to notify userspace. A backlight driver shall call
+ * backlight_force_update() when the backlight is changed using, for example,
+ * a hot-key. The updated brightness is read using get_brightness() and the
+ * brightness value is reported using an uevent.
+ */
+void backlight_force_update(struct backlight_device *bd,
+			    enum backlight_update_reason reason)
+{
+	int brightness;
+
+	mutex_lock(&bd->ops_lock);
+	if (bd->ops && bd->ops->get_brightness) {
+		brightness = bd->ops->get_brightness(bd);
+		if (brightness >= 0)
+			bd->props.brightness = brightness;
+		else
+			dev_err(&bd->dev,
+				"Could not update brightness from device: %pe\n",
+				ERR_PTR(brightness));
+	}
+	mutex_unlock(&bd->ops_lock);
+	backlight_generate_event(bd, reason);
+}
+EXPORT_SYMBOL(backlight_force_update);
+
+/* deprecated - use devm_backlight_device_register() */
+struct backlight_device *backlight_device_register(const char *name,
+	struct device *parent, void *devdata, const struct backlight_ops *ops,
+	const struct backlight_properties *props)
+{
+	struct backlight_device *new_bd;
+	int rc;
+
+	pr_debug("backlight_device_register: name=%s\n", name);
+
+	new_bd = kzalloc(sizeof(struct backlight_device), GFP_KERNEL);
+	if (!new_bd)
+		return ERR_PTR(-ENOMEM);
+
+	mutex_init(&new_bd->update_lock);
+	mutex_init(&new_bd->ops_lock);
+
+	new_bd->dev.class = backlight_class;
+	new_bd->dev.parent = parent;
+	new_bd->dev.release = bl_device_release;
+	dev_set_name(&new_bd->dev, "%s", name);
+	dev_set_drvdata(&new_bd->dev, devdata);
+
+	/* Set default properties */
+	if (props) {
+		memcpy(&new_bd->props, props,
+		       sizeof(struct backlight_properties));
+		if (props->type <= 0 || props->type >= BACKLIGHT_TYPE_MAX) {
+			WARN(1, "%s: invalid backlight type", name);
+			new_bd->props.type = BACKLIGHT_RAW;
+		}
+	} else {
+		new_bd->props.type = BACKLIGHT_RAW;
+	}
+
+	rc = device_register(&new_bd->dev);
+	if (rc) {
+		put_device(&new_bd->dev);
+		return ERR_PTR(rc);
+	}
+
+	rc = backlight_register_fb(new_bd);
+	if (rc) {
+		device_unregister(&new_bd->dev);
+		return ERR_PTR(rc);
+	}
+
+	new_bd->ops = ops;
+
+#ifdef CONFIG_PMAC_BACKLIGHT
+	mutex_lock(&pmac_backlight_mutex);
+	if (!pmac_backlight)
+		pmac_backlight = new_bd;
+	mutex_unlock(&pmac_backlight_mutex);
+#endif
+
+	mutex_lock(&backlight_dev_list_mutex);
+	list_add(&new_bd->entry, &backlight_dev_list);
+	mutex_unlock(&backlight_dev_list_mutex);
+
+	blocking_notifier_call_chain(&backlight_notifier,
+				     BACKLIGHT_REGISTERED, new_bd);
+
+	return new_bd;
+}
+EXPORT_SYMBOL(backlight_device_register);
+
+/** backlight_device_get_by_type - find first backlight device of a type
+ * @type: the type of backlight device
+ *
+ * Look up the first backlight device of the specified type
+ *
+ * RETURNS:
+ *
+ * Pointer to backlight device if any was found. Otherwise NULL.
+ */
+struct backlight_device *backlight_device_get_by_type(enum backlight_type type)
+{
+	bool found = false;
+	struct backlight_device *bd;
+
+	mutex_lock(&backlight_dev_list_mutex);
+	list_for_each_entry(bd, &backlight_dev_list, entry) {
+		if (bd->props.type == type) {
+			found = true;
+			break;
+		}
+	}
+	mutex_unlock(&backlight_dev_list_mutex);
+
+	return found ? bd : NULL;
+}
+EXPORT_SYMBOL(backlight_device_get_by_type);
+
+/**
+ * backlight_device_get_by_name - Get backlight device by name
+ * @name: Device name
+ *
+ * This function looks up a backlight device by its name. It obtains a reference
+ * on the backlight device and it is the caller's responsibility to drop the
+ * reference by calling backlight_put().
+ *
+ * Returns:
+ * A pointer to the backlight device if found, otherwise NULL.
+ */
+struct backlight_device *backlight_device_get_by_name(const char *name)
+{
+	struct device *dev;
+
+	dev = class_find_device_by_name(backlight_class, name);
+
+	return dev ? to_backlight_device(dev) : NULL;
+}
+EXPORT_SYMBOL(backlight_device_get_by_name);
+
+/* deprecated - use devm_backlight_device_unregister() */
+void backlight_device_unregister(struct backlight_device *bd)
+{
+	if (!bd)
+		return;
+
+	mutex_lock(&backlight_dev_list_mutex);
+	list_del(&bd->entry);
+	mutex_unlock(&backlight_dev_list_mutex);
+
+#ifdef CONFIG_PMAC_BACKLIGHT
+	mutex_lock(&pmac_backlight_mutex);
+	if (pmac_backlight == bd)
+		pmac_backlight = NULL;
+	mutex_unlock(&pmac_backlight_mutex);
+#endif
+
+	blocking_notifier_call_chain(&backlight_notifier,
+				     BACKLIGHT_UNREGISTERED, bd);
+
+	mutex_lock(&bd->ops_lock);
+	bd->ops = NULL;
+	mutex_unlock(&bd->ops_lock);
+
+	backlight_unregister_fb(bd);
+	device_unregister(&bd->dev);
+}
+EXPORT_SYMBOL(backlight_device_unregister);
+
+static void devm_backlight_device_release(struct device *dev, void *res)
+{
+	struct backlight_device *backlight = *(struct backlight_device **)res;
+
+	backlight_device_unregister(backlight);
+}
+
+static int devm_backlight_device_match(struct device *dev, void *res,
+					void *data)
+{
+	struct backlight_device **r = res;
+
+	return *r == data;
+}
+
+/**
+ * backlight_register_notifier - get notified of backlight (un)registration
+ * @nb: notifier block with the notifier to call on backlight (un)registration
+ *
+ * Register a notifier to get notified when backlight devices get registered
+ * or unregistered.
+ *
+ * RETURNS:
+ *
+ * 0 on success, otherwise a negative error code
+ */
+int backlight_register_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&backlight_notifier, nb);
+}
+EXPORT_SYMBOL(backlight_register_notifier);
+
+/**
+ * backlight_unregister_notifier - unregister a backlight notifier
+ * @nb: notifier block to unregister
+ *
+ * Register a notifier to get notified when backlight devices get registered
+ * or unregistered.
+ *
+ * RETURNS:
+ *
+ * 0 on success, otherwise a negative error code
+ */
+int backlight_unregister_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&backlight_notifier, nb);
+}
+EXPORT_SYMBOL(backlight_unregister_notifier);
+
+/**
+ * devm_backlight_device_register - register a new backlight device
+ * @dev: the device to register
+ * @name: the name of the device
+ * @parent: a pointer to the parent device (often the same as @dev)
+ * @devdata: an optional pointer to be stored for private driver use
+ * @ops: the backlight operations structure
+ * @props: the backlight properties
+ *
+ * Creates and registers new backlight device. When a backlight device
+ * is registered the configuration must be specified in the @props
+ * parameter. See description of &backlight_properties.
+ *
+ * RETURNS:
+ *
+ * struct backlight on success, or an ERR_PTR on error
+ */
+struct backlight_device *devm_backlight_device_register(struct device *dev,
+	const char *name, struct device *parent, void *devdata,
+	const struct backlight_ops *ops,
+	const struct backlight_properties *props)
+{
+	struct backlight_device **ptr, *backlight;
+
+	ptr = devres_alloc(devm_backlight_device_release, sizeof(*ptr),
+			GFP_KERNEL);
+	if (!ptr)
+		return ERR_PTR(-ENOMEM);
+
+	backlight = backlight_device_register(name, parent, devdata, ops,
+						props);
+	if (!IS_ERR(backlight)) {
+		*ptr = backlight;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return backlight;
+}
+EXPORT_SYMBOL(devm_backlight_device_register);
+
+/**
+ * devm_backlight_device_unregister - unregister backlight device
+ * @dev: the device to unregister
+ * @bd: the backlight device to unregister
+ *
+ * Deallocates a backlight allocated with devm_backlight_device_register().
+ * Normally this function will not need to be called and the resource management
+ * code will ensure that the resources are freed.
+ */
+void devm_backlight_device_unregister(struct device *dev,
+				struct backlight_device *bd)
+{
+	int rc;
+
+	rc = devres_release(dev, devm_backlight_device_release,
+				devm_backlight_device_match, bd);
+	WARN_ON(rc);
+}
+EXPORT_SYMBOL(devm_backlight_device_unregister);
+
+#ifdef CONFIG_OF
+static int of_parent_match(struct device *dev, const void *data)
+{
+	return dev->parent && dev->parent->of_node == data;
+}
+
+/**
+ * of_find_backlight_by_node() - find backlight device by device-tree node
+ * @node: device-tree node of the backlight device
+ *
+ * Returns a pointer to the backlight device corresponding to the given DT
+ * node or NULL if no such backlight device exists or if the device hasn't
+ * been probed yet.
+ *
+ * This function obtains a reference on the backlight device and it is the
+ * caller's responsibility to drop the reference by calling put_device() on
+ * the backlight device's .dev field.
+ */
+struct backlight_device *of_find_backlight_by_node(struct device_node *node)
+{
+	struct device *dev;
+
+	dev = class_find_device(backlight_class, NULL, node, of_parent_match);
+
+	return dev ? to_backlight_device(dev) : NULL;
+}
+EXPORT_SYMBOL(of_find_backlight_by_node);
+#endif
+
+static struct backlight_device *of_find_backlight(struct device *dev)
+{
+	struct backlight_device *bd = NULL;
+	struct device_node *np;
+
+	if (!dev)
+		return NULL;
+
+	if (IS_ENABLED(CONFIG_OF) && dev->of_node) {
+		np = of_parse_phandle(dev->of_node, "backlight", 0);
+		if (np) {
+			bd = of_find_backlight_by_node(np);
+			of_node_put(np);
+			if (!bd)
+				return ERR_PTR(-EPROBE_DEFER);
+		}
+	}
+
+	return bd;
+}
+
+static void devm_backlight_release(void *data)
+{
+	struct backlight_device *bd = data;
+
+	put_device(&bd->dev);
+}
+
+/**
+ * devm_of_find_backlight - find backlight for a device
+ * @dev: the device
+ *
+ * This function looks for a property named 'backlight' on the DT node
+ * connected to @dev and looks up the backlight device. The lookup is
+ * device managed so the reference to the backlight device is automatically
+ * dropped on driver detach.
+ *
+ * RETURNS:
+ *
+ * A pointer to the backlight device if found.
+ * Error pointer -EPROBE_DEFER if the DT property is set, but no backlight
+ * device is found. NULL if there's no backlight property.
+ */
+struct backlight_device *devm_of_find_backlight(struct device *dev)
+{
+	struct backlight_device *bd;
+	int ret;
+
+	bd = of_find_backlight(dev);
+	if (IS_ERR_OR_NULL(bd))
+		return bd;
+	ret = devm_add_action_or_reset(dev, devm_backlight_release, bd);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return bd;
+}
+EXPORT_SYMBOL(devm_of_find_backlight);
+
+static void __exit backlight_class_exit(void)
+{
+	class_destroy(backlight_class);
+}
+
+static int __init backlight_class_init(void)
+{
+	backlight_class = class_create(THIS_MODULE, "backlight");
+	if (IS_ERR(backlight_class)) {
+		pr_warn("Unable to create backlight class; errno = %ld\n",
+			PTR_ERR(backlight_class));
+		return PTR_ERR(backlight_class);
+	}
+
+	backlight_class->dev_groups = bl_device_groups;
+	backlight_class->pm = &backlight_class_dev_pm_ops;
+	INIT_LIST_HEAD(&backlight_dev_list);
+	mutex_init(&backlight_dev_list_mutex);
+	BLOCKING_INIT_NOTIFIER_HEAD(&backlight_notifier);
+
+	return 0;
+}
+
+/*
+ * if this is compiled into the kernel, we need to ensure that the
+ * class is registered before users of the class try to register lcd's
+ */
+postcore_initcall(backlight_class_init);
+module_exit(backlight_class_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Jamey Hicks <jamey.hicks@hp.com>, Andrew Zabolotny <zap@homelink.ru>");
+MODULE_DESCRIPTION("Backlight Lowlevel Control Abstraction");