Hi Hans,
I've tested it with userspace test application and it seems to work
well both with hardware leds-aat1290 driver and drivers/leds/uleds.c.
Applied to the for-next branch of linux-leds.git.
Thanks,
Jacek Anaszewski
On 11/01/2016 02:37 PM, Hans de Goede wrote:
> Add support for userspace using poll() for POLL_PRI on the sysfs brightness
> attr to watch for brightness changes.
>
> This commit adds a led_notify_brightness_change helper function for
> waking up any poll() waiters; and calls this after any brightness changes
> (after any led_classdev->brightness_set[_blocking] calls have completed).
>
> In some use-cases led hardware may autonomously change its brightness,
> e.g. the keyboard backlight used on some laptops is controlled by a
> hardwired (firmware handled) hotkey. led_notify_brightness_change is
> exported for use by drivers which can detect such autonomous changes.
>
> This commit also updates the Documentation/ABI/testing/sysfs-class-led
> documentation to document that userspace may now poll on the brightness
> attribute.
>
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> ---
> Changes in v2:
> -Wakeup / notify userspace on any brightness changes, not just on
> autonomous changes done by the hw
> Changes in v3:
> -Rebase on linux-leds/for-next
> Changes in v4:
> -No Changes
> ---
> Documentation/ABI/testing/sysfs-class-led | 8 ++++++--
> drivers/leds/led-class.c | 9 +++++++++
> drivers/leds/led-core.c | 16 +++++++++++++++-
> include/linux/leds.h | 12 ++++++++++++
> 4 files changed, 42 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-class-led b/Documentation/ABI/testing/sysfs-class-led
> index 491cdee..0af5191 100644
> --- a/Documentation/ABI/testing/sysfs-class-led
> +++ b/Documentation/ABI/testing/sysfs-class-led
> @@ -1,12 +1,16 @@
> What: /sys/class/leds/<led>/brightness
> -Date: March 2006
> -KernelVersion: 2.6.17
> +Date: March 2006 (poll October 2016)
> +KernelVersion: 2.6.17 (poll since 4.10)
> Contact: Richard Purdie <rpurdie@xxxxxxxxx>
> Description:
> Set the brightness of the LED. Most LEDs don't
> have hardware brightness support, so will just be turned on for
> non-zero brightness settings. The value is between 0 and
> /sys/class/leds/<led>/max_brightness.
> + The file supports poll() to detect brightness changes, in
> + some cases the hardware / firmware may change the brightness
> + autonomously, poll() should be woken up in this case too,
> + but not all drivers may support this.
>
> Writing 0 to this file clears active trigger.
>
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index 731e4eb..c8d2d67 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -204,6 +204,14 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
> dev_warn(parent, "Led %s renamed to %s due to name collision",
> led_cdev->name, dev_name(led_cdev->dev));
>
> + led_cdev->brightness_kn = sysfs_get_dirent(led_cdev->dev->kobj.sd,
> + "brightness");
> + if (!led_cdev->brightness_kn) {
> + dev_err(led_cdev->dev, "Error getting brightness kernfs_node\n");
> + device_unregister(led_cdev->dev);
> + return -ENODEV;
> + }
> +
> #ifdef CONFIG_LEDS_TRIGGERS
> init_rwsem(&led_cdev->trigger_lock);
> #endif
> @@ -255,6 +263,7 @@ void led_classdev_unregister(struct led_classdev *led_cdev)
>
> flush_work(&led_cdev->set_brightness_work);
>
> + sysfs_put(led_cdev->brightness_kn);
> device_unregister(led_cdev->dev);
>
> down_write(&leds_list_lock);
> diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> index 2d0c75a..af78279 100644
> --- a/drivers/leds/led-core.c
> +++ b/drivers/leds/led-core.c
> @@ -33,16 +33,24 @@ static int __led_set_brightness(struct led_classdev *led_cdev,
>
> led_cdev->brightness_set(led_cdev, value);
>
> + led_notify_brightness_change(led_cdev);
> +
> return 0;
> }
>
> static int __led_set_brightness_blocking(struct led_classdev *led_cdev,
> enum led_brightness value)
> {
> + int ret;
> +
> if (!led_cdev->brightness_set_blocking)
> return -ENOTSUPP;
>
> - return led_cdev->brightness_set_blocking(led_cdev, value);
> + ret = led_cdev->brightness_set_blocking(led_cdev, value);
> + if (ret >= 0)
> + led_notify_brightness_change(led_cdev);
> +
> + return ret;
> }
>
> static void led_timer_function(unsigned long data)
> @@ -308,6 +316,12 @@ int led_update_brightness(struct led_classdev *led_cdev)
> }
> EXPORT_SYMBOL_GPL(led_update_brightness);
>
> +void led_notify_brightness_change(struct led_classdev *led_cdev)
> +{
> + sysfs_notify_dirent(led_cdev->brightness_kn);
> +}
> +EXPORT_SYMBOL_GPL(led_notify_brightness_change);
> +
> /* Caller must ensure led_cdev->led_access held */
> void led_sysfs_disable(struct led_classdev *led_cdev)
> {
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index 52993de..f034c2d 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -13,6 +13,7 @@
> #define __LINUX_LEDS_H_INCLUDED
>
> #include <linux/device.h>
> +#include <linux/kernfs.h>
> #include <linux/list.h>
> #include <linux/mutex.h>
> #include <linux/rwsem.h>
> @@ -93,6 +94,8 @@ struct led_classdev {
>
> struct work_struct set_brightness_work;
>
> + struct kernfs_node *brightness_kn;
> +
> #ifdef CONFIG_LEDS_TRIGGERS
> /* Protects the trigger data below */
> struct rw_semaphore trigger_lock;
> @@ -192,6 +195,15 @@ extern int led_set_brightness_sync(struct led_classdev *led_cdev,
> extern int led_update_brightness(struct led_classdev *led_cdev);
>
> /**
> + * led_notify_brightness_change - Notify userspace of brightness changes
> + * @led_cdev: the LED to do the notify on
> + *
> + * Let any users waiting for POLL_PRI on the led's brightness sysfs
> + * atrribute know that the brightness has been changed.
> + */
> +extern void led_notify_brightness_change(struct led_classdev *led_cdev);
> +
> +/**
> * led_sysfs_disable - disable LED sysfs interface
> * @led_cdev: the LED to set
> *
>
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