RE: drm2 regression: backlight adjustment on ivybridge no longer works

From: Andrew Wilcox <AWilcox_at_Wilcox-Tech.com>
Date: Sun, 1 Feb 2015 03:35:15 -0600
Lars Engels sent: 01 February 2015 03:18:
> With acpi_video I get some interesting sysctl:
> hw.acpi.video.lcd0.levels: 100 100 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
> 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39
> 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
> 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87
> 88 89 90 91 92 93 94 95 96 97 98 99 100
> 
> I guess it should not be 100 100 0 ... 100?

Actually, the "standard" internal ACPI brightness level struct (BRTN in the DSDT) is laid out as:

* "Full power" value (one byte, the value at which the brightness should be set on AC by default)
* "Economy" value (one byte, the value at which the brightness should be set on battery by default)
* Actual values (N bytes, up to Max but frequently not)

So, no, that value indeed sounds correct.  On my laptop the value is:
80 47 0 7 13 20 27 33 40 47 53 60 67 73 80 87 93 100

What revision of -CURRENT are you running?  What is the outcome of trying the patch posted Saturday morning (UTC) from Elizabeth Myers (message ID <54CC5311.9070604_at_interlinked.me>)?

Andrew
--
Andrew Wilcox, C/C++/Python developer, kernel hacker
Blog:   http://blog.foxkit.us/  WWW: http://foxkit.us/
GitHub: https://github.com/awilfox
Received on Sun Feb 01 2015 - 08:35:23 UTC

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