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

[Jacek Anaszewski]

Hi Alexander,

On 9/9/20 10:29 PM, Alexander Dahl wrote:
> 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. ;-)

devm_led_classdev_register() calls devm_led_classdev_register_ext()
with NULL passed in place of init_data, so you could do something like
below to achieve the same without touching LED core:

struct led_init_data init_data_impl = { .fwnode = fwnode };
struct led_init_data *init_data = NULL;

if (fwnode)
	init_data = &init_data_impl;

devm_led_classdev_register_ext(dev, &led_data->cdev, init_data);

> 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

--
Best regards,
Jacek Anaszewski