Re: [PATCH v3 1/2] leds: pwm: Allow automatic labels for DT based devices

[Alexander Dahl <post@lespocky.de>]

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Hei hei,

On Wed, Sep 09, 2020 at 11:07:36AM +0200, Pavel Machek wrote:
> Hi!
> 
> >  	pwm_init_state(led_data->pwm, &led_data->pwmstate);
> >  
> > -	ret = devm_led_classdev_register(dev, &led_data->cdev);
> > +	if (fwnode) {
> > +		init_data.fwnode = fwnode;
> > +		ret = devm_led_classdev_register_ext(dev, &led_data->cdev,
> > +						     &init_data);
> > +	} else {
> > +		ret = devm_led_classdev_register(dev, &led_data->cdev);
> > +	}
> 
> Can you always use _ext version, even with null fwnode? 

I did not try on real hardware, but from reading the code I would say
the following would happen: led_classdev_register_ext() calls
led_compose_name(parent, init_data, composed_name) which itself calls
led_parse_fwnode_props(dev, fwnode, &props); that returns early due to
fwnode==NULL without changing props, thus this stays as initialized
with {}, so led_compose_name() would return -EINVAL which would let
led_classdev_register_ext() fail, too.

> If not, can you fix the core to accept that? Having that conditional
> in driver is ugly.

It is ugly, although the approach is inspired by the leds-gpio driver.
I'll see if I can come up with a change to led-core, but I'm also open
for suggestions. ;-)

fyi: Peter Ujfalusi answered and would give his Ack to the changed
dual license for the yaml file.  You can expect that for v4.

Stay tuned
Alex

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