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leds: TODO: Add documentation about possible subsystem improvements

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Help welcome :-).

Signed-off-by: Pavel Machek <pavel@ucw.cz>
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Pavel Machek 2020-09-25 11:29:17 +02:00
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commit 364682d1bc
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-*- org -*-
* On/off LEDs should have max_brightness of 1
* Get rid of enum led_brightness
It is really an integer, as maximum is configurable. Get rid of it, or
make it into typedef or something.
* Review atomicity requirements in LED subsystem
Calls that may and that may not block are mixed in same structure, and
semantics is sometimes non-intuitive. (For example blink callback may
not sleep.) Review the requirements for any bugs and document them
clearly.
* LED names are still a mess
No two LEDs have same name, so the names are probably unusable for the
userland. Nudge authors into creating common LED names for common
functionality.
? Perhaps check for known LED names during boot, and warn if there are
LEDs not on the list?
* Split drivers into subdirectories
The number of drivers is getting big, and driver for on/off LED on a
i/o port is really quite different from camera flash LED, which is
really different from driver for RGB color LED that can run its own
microcode. Split the drivers somehow.
* Figure out what to do with RGB leds
Multicolor is a bit too abstract. Yes, we can have
Green-Magenta-Ultraviolet LED, but so far all the LEDs we support are
RGB, and not even RGB-White or RGB-Yellow variants emerged.
Multicolor is not a good fit for RGB LED. It does not really know
about LED color. In particular, there's no way to make LED "white".
Userspace is interested in knowing "this LED can produce arbitrary
color", which not all multicolor LEDs can.
Proposal: let's add "rgb" to led_colors in drivers/leds/led-core.c,
add corresponding device tree defines, and use that, instead of
multicolor for RGB LEDs.
We really need to do that now; "white" stuff can wait.
RGB LEDs are quite common, and it would be good to be able to turn LED
white and to turn it into any arbitrary color. It is essential that
userspace is able to set arbitrary colors, and it might be good to
have that ability from kernel, too... to allow full-color triggers.
* Command line utility to manipulate the LEDs?
/sys interface is not really suitable to use by hand, should we have
an utility to perform LED control?
In particular, LED names are still a mess (see above) and utility
could help there by presenting both old and new names while we clean
them up.
In future, I'd like utility to accept both old and new names while we
clean them up.
It would be also nice to have useful listing mode -- name, type,
current brightness/trigger...
In future, it would be good to be able to set rgb led to particular
color.
And probably user-friendly interface to access LEDs for particular
ethernet interface would be nice.