Re: [PATCH v2] leds: core: use deferred probing if default trigger isn't available yet

[Jacek Anaszewski <jacek.anaszewski@gmail.com>]

Hi Heiner,

Thanks for the updated patch.

On 02/24/2017 07:41 AM, Heiner Kallweit wrote:
> When registering a LED device we have the option to set a default trigger.
> Depending on load order of drivers this trigger may not be available yet.
> (affected LED device in my case: a DT-configured GPIO LED)
> So far if the default trigger can't be found this error is silently
> ignored.
> 
> Let's change this to return EPROBE_DEFER if the default trigger can't be
> found. This gives the system the chance to probe the LED device later
> once the trigger is available.
> 
> In addition in led_trigger_set_default break out of the loop when trigger
> has been found.
> 
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> ---
> v2:
> - in led_trigger_set_default break out of loop when trigger has been found
> ---
>  drivers/leds/led-class.c    |  6 +++++-
>  drivers/leds/led-triggers.c | 12 +++++++++---
>  include/linux/leds.h        |  5 +++--
>  3 files changed, 17 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index f2b0a80a..efe4f5a3 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -295,7 +295,11 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
>  	led_init_core(led_cdev);
>  
>  #ifdef CONFIG_LEDS_TRIGGERS
> -	led_trigger_set_default(led_cdev);
> +	ret = led_trigger_set_default(led_cdev);
> +	if (ret) {
> +		led_classdev_unregister(led_cdev);
> +		return ret;
> +	}
>  #endif
>  
>  	dev_dbg(parent, "Registered led device: %s\n",
> diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
> index 431123b0..572ede29 100644
> --- a/drivers/leds/led-triggers.c
> +++ b/drivers/leds/led-triggers.c
> @@ -157,21 +157,27 @@ void led_trigger_remove(struct led_classdev *led_cdev)
>  }
>  EXPORT_SYMBOL_GPL(led_trigger_remove);
>  
> -void led_trigger_set_default(struct led_classdev *led_cdev)
> +int led_trigger_set_default(struct led_classdev *led_cdev)
>  {
>  	struct led_trigger *trig;
> +	int ret = -EPROBE_DEFER;
>  
>  	if (!led_cdev->default_trigger)
> -		return;
> +		return 0;
>  
>  	down_read(&triggers_list_lock);
>  	down_write(&led_cdev->trigger_lock);
>  	list_for_each_entry(trig, &trigger_list, next_trig) {
> -		if (!strcmp(led_cdev->default_trigger, trig->name))
> +		if (!strcmp(led_cdev->default_trigger, trig->name)) {
>  			led_trigger_set(led_cdev, trig);
> +			ret = 0;
> +			break;
> +		}
>  	}
>  	up_write(&led_cdev->trigger_lock);
>  	up_read(&triggers_list_lock);
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL_GPL(led_trigger_set_default);
>  
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index 38c0bd7c..3e36ce31 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -280,7 +280,7 @@ extern void led_trigger_blink_oneshot(struct led_trigger *trigger,
>  				      unsigned long *delay_on,
>  				      unsigned long *delay_off,
>  				      int invert);
> -extern void led_trigger_set_default(struct led_classdev *led_cdev);
> +extern int led_trigger_set_default(struct led_classdev *led_cdev);
>  extern void led_trigger_set(struct led_classdev *led_cdev,
>  			struct led_trigger *trigger);
>  extern void led_trigger_remove(struct led_classdev *led_cdev);
> @@ -326,7 +326,8 @@ static inline void led_trigger_blink_oneshot(struct led_trigger *trigger,
>  				      unsigned long *delay_on,
>  				      unsigned long *delay_off,
>  				      int invert) {}
> -static inline void led_trigger_set_default(struct led_classdev *led_cdev) {}
> +static inline int led_trigger_set_default(struct led_classdev *led_cdev)
> +							{ return 0; }
>  static inline void led_trigger_set(struct led_classdev *led_cdev,
>  				struct led_trigger *trigger) {}
>  static inline void led_trigger_remove(struct led_classdev *led_cdev) {}
> 

Applied to the for-4.12 branch of linux-leds.git.

-- 
Best regards,
Jacek Anaszewski