Re: [PATCH] Illuminators and status LED controls

[Peter Korsgaard <jacmet@sunsite.dk>]

>>>>> "Hans" == Hans Verkuil <hverkuil@xs4all.nl> writes:

Hi,

 Hans> But I feel I am missing something: who is supposed to use these LEDs?
 Hans> Turning LEDs in e.g. webcams on or off is a job for the driver, never for
 Hans> a userspace application.

Agreed - By default, the driver should just turn on the LED when the
device is active and off again when it is not.

 Hans> For that matter, if the driver handles the LEDs,
 Hans> can we still expose the API to userspace? Wouldn't those two interfere
 Hans> with one another? I know nothing about the LED interface in sysfs, but I
 Hans> can imagine that will be a problem.

Yes, you expose the LED using the LED class, and add a LED trigger per
video device (named something like "videoX-active"). Furthermore you set
the default trigger for that LED to be videoX-active.

So the logic of how to turn on/off the LED is seperated from the policy
about WHEN it should be turned on/off.

 >> Sysfs entry ownership, unix permissions, and ACL permissions consistency
 >> with /dev/videoN will be the immediate usability problem for end users in
 >> any case.

 Hans> Again, why would end users or application need or want to manipulate such
 Hans> LEDs in any case?

In most cases they don't - Not using the LED sysfs or v4l. But if they
do, then they CAN.

-- 
Bye, Peter Korsgaard