Re: [PATCH] Let chip-driver set brightness if, software blink not used.

[Jacek Anaszewski]

Hi Tony,

Thanks for the patch. I'd like to improve the commit message.

Please let me know if you have any suggestions related to the below:

    led: core: Fix brightness setting upon hardware blinking enabled

    Commit 76931edd54 ('leds: fix brightness changing when software 
blinking
    is active') changed the semantics of led_set_brightness() which 
according
    to the documentation should disable blinking on any brightness setting.
    Moreover it made it different for soft blink case, where it was allowed
    for blink brightness change, and for hardware blink case, where setting
    any brightness greater than 0 was ignored.

    While the change itself is against the documentation claims, it was 
driven
    also by the fact that timer trigger remained active after turning 
blinking
    off. Fixing that would have required major refactoring in the led-core,
    led-class, and led-triggers because of cyclic dependencies.

    Finally, it has been decided that allowing for brightness change during
    blinking is beneficial as it can be accomplished without disturbing
    blink rhythm.

    The change in brightness setting semantics will not affect existing
    LED class drivers that implement blink_set op thanks to the 
LED_BLINK_SW
    flag introduced by this patch. The flag state will be from now on 
checked
    in led_set_brightness() which will allow to distinguish between 
hardware
    and software blink mode. In the former case the control will be passed
    directly to the drivers which apply their semantics on brightness set,
    which is disable the blinking in case of most such drivers. New drivers
    will apply new semantics and just change the brightness while hardware
    blinking is on, if possible.

    Due to the later LED core improvements this patch can't be applied 
directly
    on the patch that originally introduced the problem, but to the 
later one,
    that touched the affected code.

    Fixes: f1e80c07416a ("leds: core: Add two new LED_BLINK_ flags")
    Signed-off-by: Tony Makkiel <tony.makkiel@xxxxxxxxx>
    Signed-off-by: Jacek Anaszewski <j.anaszewski@xxxxxxxxxxx>


We will need also to modify the documentation, but this can
be done in a separate patch.

On 05/17/2016 06:28 PM, Tony Makkiel wrote:
> With this patch, chip drivers will be given option to
> set brightness while, blink is active.
>
> Signed-off-by: Tony Makkiel <tony.makkiel@xxxxxxxxx>
> ---
>   drivers/leds/led-core.c |  7 +++++--
>   include/linux/leds.h    | 19 ++++++++++---------
>   2 files changed, 15 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> index 3495d5d..b595eb9 100644
> --- a/drivers/leds/led-core.c
> +++ b/drivers/leds/led-core.c
> @@ -53,11 +53,12 @@ static void led_timer_function(unsigned long data)
>
>   	if (!led_cdev->blink_delay_on || !led_cdev->blink_delay_off) {
>   		led_set_brightness_nosleep(led_cdev, LED_OFF);
> +		led_cdev->flags &= ~LED_BLINK_SW;
>   		return;
>   	}
>
>   	if (led_cdev->flags & LED_BLINK_ONESHOT_STOP) {
> -		led_cdev->flags &= ~LED_BLINK_ONESHOT_STOP;
> +		led_cdev->flags &=  ~(LED_BLINK_ONESHOT_STOP | LED_BLINK_SW);
>   		return;
>   	}
>
> @@ -151,6 +152,7 @@ static void led_set_software_blink(struct led_classdev *led_cdev,
>   		return;
>   	}
>
> +	led_cdev->flags |= LED_BLINK_SW;
>   	mod_timer(&led_cdev->blink_timer, jiffies + 1);
>   }
>
> @@ -219,6 +221,7 @@ void led_stop_software_blink(struct led_classdev *led_cdev)
>   	del_timer_sync(&led_cdev->blink_timer);
>   	led_cdev->blink_delay_on = 0;
>   	led_cdev->blink_delay_off = 0;
> +	led_cdev->flags &= ~LED_BLINK_SW;
>   }
>   EXPORT_SYMBOL_GPL(led_stop_software_blink);
>
> @@ -229,7 +232,7 @@ void led_set_brightness(struct led_classdev *led_cdev,
>   	 * In case blinking is on delay brightness setting

We need to make this comment more precise:

s/blinking/soft blink/g

>   	 * until the next timer tick.
>   	 */
> -	if (led_cdev->blink_delay_on || led_cdev->blink_delay_off) {
> +	if (led_cdev->flags & LED_BLINK_SW) {
>   		/*
>   		 * If we need to disable soft blinking delegate this to the
>   		 * work queue task to avoid problems in case we are called
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index d2b1306..99b1f0b 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -42,15 +42,16 @@ struct led_classdev {
>   #define LED_UNREGISTERING	(1 << 1)
>   	/* Upper 16 bits reflect control information */
>   #define LED_CORE_SUSPENDRESUME	(1 << 16)
> -#define LED_BLINK_ONESHOT	(1 << 17)
> -#define LED_BLINK_ONESHOT_STOP	(1 << 18)
> -#define LED_BLINK_INVERT	(1 << 19)
> -#define LED_BLINK_BRIGHTNESS_CHANGE (1 << 20)
> -#define LED_BLINK_DISABLE	(1 << 21)
> -#define LED_SYSFS_DISABLE	(1 << 22)
> -#define LED_DEV_CAP_FLASH	(1 << 23)
> -#define LED_HW_PLUGGABLE	(1 << 24)
> -#define LED_PANIC_INDICATOR	(1 << 25)
> +#define LED_BLINK_SW		(1 << 17)
> +#define LED_BLINK_ONESHOT	(1 << 18)
> +#define LED_BLINK_ONESHOT_STOP	(1 << 19)
> +#define LED_BLINK_INVERT	(1 << 20)
> +#define LED_BLINK_BRIGHTNESS_CHANGE (1 << 21)
> +#define LED_BLINK_DISABLE	(1 << 22)
> +#define LED_SYSFS_DISABLE	(1 << 23)
> +#define LED_DEV_CAP_FLASH	(1 << 24)
> +#define LED_HW_PLUGGABLE	(1 << 25)
> +#define LED_PANIC_INDICATOR	(1 << 26)
>
>   	/* Set LED brightness level
>   	 * Must not sleep. Use brightness_set_blocking for drivers


--
Best regards,
Jacek Anaszewski