Hi,
Well, the ACPI spec says this (section B.5.2):
"
The OEM may define the number 0 as "Zero brightness" that can mean
to turn off the lighting (e.g. LCD panel backlight) in the device.
This may be useful in the case of an output device that can still be
viewed using only ambient light, for example, a transflective LCD.
"
My interpretation of this is that the value 0 is supposed to still
be visible. I'm pretty sure I saw a statement that 0 is supposed to
mean "barely visible" somewhere, but can't find it at the moment.
I'll search for the source of it.
I think that's a stretch - "This may be useful" isn't normative
language, "The OEM may define" is. But even if we do assert it for the
ACPI backlight, it's not true for other interfaces - zero backlight
intensity is supposed to be screen off on Apple hardware, for instance.
OK, I see. And there is user space depending on that behaviour? And
again - how is user space supposed to know about the behavioral
differences? Is it something like 'if type is raw, don't expect anything'?
The reason for my question is that I want to determine what a) the
correct place to fix this and b) the correct fix is. As Xrandr abstracts
away the used backlight interface, I see no way for user space using
Xrandr (e.g. KDE) to meaningfully handle this.
Thanks,
Danny
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