// 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_CORE) || (defined(CONFIG_FB_CORE_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;
struct fb_info *info = evdata->info;
struct backlight_device *fb_bd = fb_bl_device(info);
int node = 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->controls_device && !bd->ops->controls_device(bd, info->device))
goto out;
if (fb_bd && fb_bd != bd)
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;
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;
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_CORE */
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);
#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);
static const struct class backlight_class = {
.name = "backlight",
.dev_groups = bl_device_groups,
.pm = &backlight_class_dev_pm_ops,
};
/**
* 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 put_device().
*
* 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_unregister(&backlight_class);
}
static int __init backlight_class_init(void)
{
int ret;
ret = class_register(&backlight_class);
if (ret) {
pr_warn("Unable to create backlight class; errno = %d\n", ret);
return ret;
}
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 <[email protected]>, Andrew Zabolotny <[email protected]>");
MODULE_DESCRIPTION("Backlight Lowlevel Control Abstraction");
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