There have been several attempts recently to find ways to disable broken backlight interfaces on laptops, such as [1]. These haven't always worked as well as hoped and tend to be driver-specific, so we're seeing attempts to add an expanding number of interfaces between drivers to try to cope with the situation, such as [2] and [3]. We're also seeing difficulties properly expressing the inter-module dependencies[4].
Rather than trying to address this situation in a piecemeal fashion, we should find a solution that deal with disabling broken backlights more generically. This patch does so by adding an "enabled" attribute to sysfs for backlight devices. Writing 0 to this attribute disables the backlight, blocking most attempts to change the state. Tools like udev can set use this attribute to disable known broken backlight interfaces, and tools like gnome-settings-daemon can query the attribute to avoid using disabled backlights. [1] https://lkml.org/lkml/2012/3/22/156 [2] https://lkml.org/lkml/2012/3/15/529 [3] https://lkml.org/lkml/2012/6/13/48 [4] https://lkml.org/lkml/2012/6/28/159 Cc: Matthew Garrett <[email protected]> Cc: Corentin Chary <[email protected]> Signed-off-by: Seth Forshee <[email protected]> --- I wanted to send this out for comments to see how people felt about this idea. If it's well received I can follow up with patches to remove the acpi_video_unregister() and apple_bl_unregister() calls currently being used for this purpose. Documentation/ABI/stable/sysfs-class-backlight | 10 +++++ drivers/video/backlight/backlight.c | 54 +++++++++++++++++++++--- include/linux/backlight.h | 1 + 3 files changed, 59 insertions(+), 6 deletions(-) diff --git a/Documentation/ABI/stable/sysfs-class-backlight b/Documentation/ABI/stable/sysfs-class-backlight index 70302f3..3b3c477 100644 --- a/Documentation/ABI/stable/sysfs-class-backlight +++ b/Documentation/ABI/stable/sysfs-class-backlight @@ -54,3 +54,13 @@ Description: backlight state. Platform interfaces are mostly a holdover from pre-standardisation of firmware interfaces. + +What: /sys/class/backlight/<backlight>/enabled +Date: May 2012 +KernelVersion: 3.6 +Contact: Seth Forshee <[email protected]> +Description: + Enable or disable this <backlight>. Also shows whether + the backlight is enabled. This can be used by tools like + udev to disable backlights that are known to be broken + on a given platform. diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index 297db2f..5275738 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -53,7 +53,8 @@ static int fb_notifier_callback(struct notifier_block *self, bd->props.state &= ~BL_CORE_FBBLANK; else bd->props.state |= BL_CORE_FBBLANK; - backlight_update_status(bd); + if (!(bd->props.state & BL_CORE_DISABLED)) + backlight_update_status(bd); } mutex_unlock(&bd->ops_lock); return 0; @@ -124,7 +125,7 @@ static ssize_t backlight_store_power(struct device *dev, rc = -ENXIO; mutex_lock(&bd->ops_lock); - if (bd->ops) { + if (!(bd->props.state & BL_CORE_DISABLED) && bd->ops) { pr_debug("set power to %lu\n", power); if (bd->props.power != power) { bd->props.power = power; @@ -159,7 +160,7 @@ static ssize_t backlight_store_brightness(struct device *dev, rc = -ENXIO; mutex_lock(&bd->ops_lock); - if (bd->ops) { + if (!(bd->props.state & BL_CORE_DISABLED) && bd->ops) { if (brightness > bd->props.max_brightness) rc = -EINVAL; else { @@ -206,6 +207,43 @@ static ssize_t backlight_show_actual_brightness(struct device *dev, return rc; } +static ssize_t backlight_show_enabled(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct backlight_device *bd = to_backlight_device(dev); + + return sprintf(buf, "%d\n", !(bd->props.state & BL_CORE_DISABLED)); +} + +static ssize_t backlight_store_enabled(struct device *dev, + struct device_attribute *attr, const char *buf, size_t count) +{ + struct backlight_device *bd = to_backlight_device(dev); + int rc; + unsigned long enabled; + + rc = kstrtoul(buf, 0, &enabled); + if (rc) + return rc; + if (enabled != 0 && enabled != 1) + return -EINVAL; + + mutex_lock(&bd->ops_lock); + + if (enabled) + bd->props.state &= ~BL_CORE_DISABLED; + else + bd->props.state |= BL_CORE_DISABLED; + + if (bd->ops) + backlight_update_status(bd); + + mutex_unlock(&bd->ops_lock); + + sysfs_notify(&bd->dev.kobj, NULL, "enabled"); + return count; +} + static struct class *backlight_class; static int backlight_suspend(struct device *dev, pm_message_t state) @@ -213,7 +251,8 @@ 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) { + if (!(bd->props.state & BL_CORE_DISABLED) && + bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) { bd->props.state |= BL_CORE_SUSPENDED; backlight_update_status(bd); } @@ -227,7 +266,8 @@ 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) { + if (!(bd->props.state & BL_CORE_DISABLED) && + bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) { bd->props.state &= ~BL_CORE_SUSPENDED; backlight_update_status(bd); } @@ -250,6 +290,7 @@ static struct device_attribute bl_device_attributes[] = { NULL), __ATTR(max_brightness, 0444, backlight_show_max_brightness, NULL), __ATTR(type, 0444, backlight_show_type, NULL), + __ATTR(enabled, 0644, backlight_show_enabled, backlight_store_enabled), __ATTR_NULL, }; @@ -265,7 +306,8 @@ 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) + if (!(bd->props.state & BL_CORE_DISABLED) && + bd->ops && bd->ops->get_brightness) bd->props.brightness = bd->ops->get_brightness(bd); mutex_unlock(&bd->ops_lock); backlight_generate_event(bd, reason); diff --git a/include/linux/backlight.h b/include/linux/backlight.h index 5ffc6dd..31917d0 100644 --- a/include/linux/backlight.h +++ b/include/linux/backlight.h @@ -77,6 +77,7 @@ struct backlight_properties { #define BL_CORE_SUSPENDED (1 << 0) /* backlight is suspended */ #define BL_CORE_FBBLANK (1 << 1) /* backlight is under an fb blank event */ +#define BL_CORE_DISABLED (1 << 2) /* backlight disabled by userspace */ #define BL_CORE_DRIVER4 (1 << 28) /* reserved for driver specific use */ #define BL_CORE_DRIVER3 (1 << 29) /* reserved for driver specific use */ #define BL_CORE_DRIVER2 (1 << 30) /* reserved for driver specific use */ -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe platform-driver-x86" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
