On 09/14/2017 01:53 PM, Pavel Machek wrote:

On Thu 2017-09-14 13:01:19, Sylwester Nawrocki wrote:

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On 09/14/2017 12:07 PM, Pavel Machek wrote:

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Isn't the V4L2 subdev/Media Controller API supposed to provide means
for associating flash LEDs with camera sensors? You seem to be insisting
on using the sysfs leds interface for that, which is not a primary
interface for camera flash AFAICT.

a) subdev/media controller API currently does not provide such means.

Yes, but it should, that's what it was designed for AFAIK.

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b) if we have /sys/class/leds interface to userland, it should be
useful.

At the same time we shouldn't overcomplicate it with the camera
functionality.

I'm advocating adding label = "main_camera" into the .dts. That's all.

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c) having flashlight application going through media controller API is
a bad joke.

It doesn't have to, maybe I misunderstood what you exactly ask for.
Nevertheless what's missing is some user visible name/label for each
flash LED, right? Currently enumerating flash LEDs can be done by looking
at the function part of /sys/class/leds/<led-controller>:<colour>:
<function> path.

Could additional information be appended to the <function> part, so
user can identify which LED is which? E.g. "flash(rear)", "flash(front)",
etc. This could be achieved by simply adding label property in DT.
Or is the list of supported <function> strings already standardized?

label = "flash_main_camera" would work for me, yes. And yes, I'd
prefer to do this before 4.14 release, so that userland-visible
interface does not change.

Looking at existing label entries in DT (git grep label.*led
-- arch/arm/boot/dts | sed 's\^.*label\label\' | sort | uniq)
I can't see why something like this couldn't be added.
Or label = "as3645a::flash_main_camera" so we abide the LED device
naming rules described in Documentation/leds/leds-class.txt.

-- 
Regards,
Sylwester