Re: Problem with resetting LED in led_classdev_unregister in case of USB LED device removal

[Jacek Anaszewski <j.anaszewski@samsung.com>]

Hi Heiner,

On 01/18/2016 09:52 PM, Heiner Kallweit wrote:

>> Yes, this seems to be the best solution. Driver should set this flag
>> before calling led_classdev_unregister. If the flag is set the -ENODEV
>> error will not be reported. It could be named LED_HW_ABSENT for
>> instance. Feel free to propose other ideas.
>>
> Setting such a flag from the driver might cause significant effort in different layers.
> When we talk about thingm as an example, it uses the hid subsystem with the usbhid low level driver.
> We would need a callback in the usbhid driver (to be notified when the device is unplugged)
> and a way to propagate this event to the hid core.

> Maybe simpler: We could ignore ENODEV errors if a function is called from led_classdev_unregister.
> This way we wouldn't have to touch drivers. I think of something like this:

Ignoring -ENODEV errors for all devices would filter out also valid
error cases and hinder debugging.

How about adding a flag LED_HW_PLUGGABLE in addition to
LED_UNREGISTERING, and make the pluggable LED class drivers having set
it all the time. The -ENODEV error would be reported only
if !(LED_UNREGISTERING && LED_HW_PLUGGABLE).

-- 
Best Regards,
Jacek Anaszewski