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

From: Jacek Anaszewski
Date: Wed Sep 09 2020 - 16:47:55 EST

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:

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

Best regards,
Jacek Anaszewski