Re: [PATCH v4 1/3] led: make led_set_brightness_sync() use led_set_brightness_nosleep()

[Jean-Jacques Hiblot]

Hi Jacek,

On 20/09/2019 23:10, Jacek Anaszewski wrote:
> Hi Jean,
>
> On 9/20/19 2:25 PM, Jean-Jacques Hiblot wrote:
> > Making led_set_brightness_sync() use led_set_brightness_nosleep() has 2
> > advantages:
> > - works for LED controllers that do not provide brightness_set_blocking()
> > - When the blocking callback is used, it uses the workqueue to update the
> >    LED state, removing the need for mutual exclusion between
> >    led_set_brightness_sync() and set_brightness_delayed().
> And third:
>
> - it compromises the "sync" part of the function name :-)

Making it sync is the role of the flush_work() function. It waits until 
the deferred work has been done.

JJ

> This function has been introduced specifically to be blocking
> and have the immediate effect. Its sole client is
> drivers/media/v4l2-core/v4l2-flash-led-class.c.
>
> > Signed-off-by: Jean-Jacques Hiblot <jjhiblot@xxxxxx>
> > ---
> >   drivers/leds/led-core.c | 12 +++++++-----
> >   1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> > index f1f718dbe0f8..50e28a8f9357 100644
> > --- a/drivers/leds/led-core.c
> > +++ b/drivers/leds/led-core.c
> > @@ -294,15 +294,17 @@ EXPORT_SYMBOL_GPL(led_set_brightness_nosleep);
> >   int led_set_brightness_sync(struct led_classdev *led_cdev,
> >   			    enum led_brightness value)
> >   {
> > +	int ret;
> > +
> >   	if (led_cdev->blink_delay_on || led_cdev->blink_delay_off)
> >   		return -EBUSY;
> >   
> > -	led_cdev->brightness = min(value, led_cdev->max_brightness);
> > -
> > -	if (led_cdev->flags & LED_SUSPENDED)
> > -		return 0;
> > +	ret = led_set_brightness_nosleep(led_cdev, value);
> > +	if (!ret)
> > +		return ret;
> >   
> > -	return __led_set_brightness_blocking(led_cdev, led_cdev->brightness);
> > +	flush_work(&led_cdev->set_brightness_work);
> > +	return 0;
> >   }
> >   EXPORT_SYMBOL_GPL(led_set_brightness_sync);
> >