[Bug 86936] Facilitate override on minimum brightness level

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=86936

--- Comment #5 from Aurabindo J <mail at aurabindo.in> ---
(In reply to Jani Nikula from comment #3)
> A few additional things to consider.
> 
> First, does 5% brightness running a kernel before the offending commit
> correspond to lowest brightness running a kernel after the offending commit?

No, since 5% (of 255)  brightness is at 12 and the new minimum in current
kernel is 64.

> 
> Second, there might be a catch here. The brightness UI, whichever it may be,
> might provide you with an arbitrary number of steps. The UI might not let
> you choose the lowest non-zero brightness. E.g. going up from 0, it probably
> jumps to something other than 1.

Yes the brightness UI always goes in steps, though not linearly. It seems to be
exponential since at times I see very lower brightness states (before offending
commits) between the usually-smallest and turned-off state when I am pressing
holding brightness down key from the highest brightness level. I dont get this
intermediate level when for going down from other states, for example second
lowest.

However, it is letting me choose the smallest level of 64 (in  newer kernels). 
Since I cannot read the actual_brightness to know the current level (it is
always 0 in new kernel). But I confirmed it by manually echoing the test case
values and visually inspecting for any change in brightness for the minimum
value supported  by UI. For all values above 64, the UI was able to reduce the
brightness by a some amount.

> 
> See if this gives you more desirable results:
> 
> # echo 1 > /sys/class/brightness/intel_backlight/brightness

This still puts the current level to 64, which is a bit on the high side.

Please let me know other details you need

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