backlight.c

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/*
 * 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

static const char *const backlight_types[] = {
    [BACKLIGHT_RAW] = "raw",
    [BACKLIGHT_PLATFORM] = "platform",
    [BACKLIGHT_FIRMWARE] = "firmware",
};

#if defined(CONFIG_FB) || (defined(CONFIG_FB_MODULE) && \
               defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE))
/* This callback gets called when something important happens inside a
 * framebuffer driver. We're looking if that important event is blanking,
 * and if it is, we're switching backlight power as well ...
 */
static int fb_notifier_callback(struct notifier_block *self,
                unsigned long event, void *data)
{
    struct backlight_device *bd;
    struct fb_event *evdata = data;

    /* If we aren't interested in this event, skip it immediately ... */
    if (event != FB_EVENT_BLANK && event != FB_EVENT_CONBLANK)
        return 0;

    bd = container_of(self, struct backlight_device, fb_notif);
    mutex_lock(&bd->ops_lock);
    if (bd->ops)
        if (!bd->ops->check_fb ||
            bd->ops->check_fb(bd, evdata->info)) {
            bd->props.fb_blank = *(int *)evdata->data;
            if (bd->props.fb_blank == FB_BLANK_UNBLANK)
                bd->props.state &= ~BL_CORE_FBBLANK;
            else
                bd->props.state |= BL_CORE_FBBLANK;
            backlight_update_status(bd);
        }
    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 backlight_show_power(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 backlight_store_power(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;

    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) {
            bd->props.power = power;
            backlight_update_status(bd);
        }
        rc = count;
    }
    mutex_unlock(&bd->ops_lock);

    return rc;
}

static ssize_t backlight_show_brightness(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);
}

static ssize_t backlight_store_brightness(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 = -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;
            backlight_update_status(bd);
            rc = count;
        }
    }
    mutex_unlock(&bd->ops_lock);

    backlight_generate_event(bd, BACKLIGHT_UPDATE_SYSFS);

    return rc;
}

static ssize_t backlight_show_type(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 ssize_t backlight_show_max_brightness(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 ssize_t backlight_show_actual_brightness(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 = sprintf(buf, "%d\n", bd->ops->get_brightness(bd));
    mutex_unlock(&bd->ops_lock);

    return rc;
}

static struct class *backlight_class;

static int backlight_suspend(struct device *dev, pm_message_t state)
{
    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;
}

static void bl_device_release(struct device *dev)
{
    struct backlight_device *bd = to_backlight_device(dev);
    kfree(bd);
}

static struct device_attribute bl_device_attributes[] = {
    __ATTR(bl_power, 0644, backlight_show_power, backlight_store_power),
    __ATTR(brightness, 0644, backlight_show_brightness,
             backlight_store_brightness),
    __ATTR(actual_brightness, 0444, backlight_show_actual_brightness,
             NULL),
    __ATTR(max_brightness, 0444, backlight_show_max_brightness, NULL),
    __ATTR(type, 0444, backlight_show_type, NULL),
    __ATTR_NULL,
};

void backlight_force_update(struct backlight_device *bd,
                enum backlight_update_reason reason)
{
    mutex_lock(&bd->ops_lock);
    if (bd->ops && bd->ops->get_brightness)
        bd->props.brightness = bd->ops->get_brightness(bd);
    mutex_unlock(&bd->ops_lock);
    backlight_generate_event(bd, reason);
}
EXPORT_SYMBOL(backlight_force_update);

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, 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) {
        kfree(new_bd);
        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

    return new_bd;
}
EXPORT_SYMBOL(backlight_device_register);

void backlight_device_unregister(struct backlight_device *bd)
{
    if (!bd)
        return;

#ifdef CONFIG_PMAC_BACKLIGHT
    mutex_lock(&pmac_backlight_mutex);
    if (pmac_backlight == bd)
        pmac_backlight = NULL;
    mutex_unlock(&pmac_backlight_mutex);
#endif
    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 __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_attrs = bl_device_attributes;
    backlight_class->suspend = backlight_suspend;
    backlight_class->resume = backlight_resume;
    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");