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

On Sun, Feb 01, 2015 at 11:23:47AM +0100, Lars Engels wrote:
> On 1. Februar 2015 11:20:26 MEZ, Alexandr Krivulya <shuriku_at_shurik.kiev.ua> wrote:
> >01.02.2015 12:12, Lars Engels пишет:
> >> On Sun, Feb 01, 2015 at 10:41:25AM +0100, Lars Engels wrote:
> >>> On Sun, Feb 01, 2015 at 03:35:15AM -0600, Andrew Wilcox wrote:
> >>>> 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
> >>> Thank you for the explanation.
> >>> FWIW, here is the full output from sysctl hw.acpi.video.lcd0:
> >>>
> >>> hw.acpi.video.lcd0.active: 1
> >>> hw.acpi.video.lcd0.brightness: 11
> >>> hw.acpi.video.lcd0.fullpower: 100
> >>> hw.acpi.video.lcd0.economy: 100
> >>> 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
> >>> hw.acpi.video.crt0.active: 1
> >>> hw.acpi.video.ext0.active: 1
> >>> hw.acpi.video.ext1.active: 1
> >>> hw.acpi.video.ext2.active: 1
> >>> hw.acpi.video.ext3.active: 1
> >>> hw.acpi.video.ext4.active: 1
> >>> hw.acpi.video.ext5.active: 1
> >>>
> >>>> 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>)?
> >>>>
> >>> I'm currently running r277858 and haven't tried the patch, yet. But
> >will
> >>> do now and report back.
> >>>
> >> So now I have a new sysctl hw.dri.0.i915_backlight. But no matter
> >what
> >> value I pass to it, the brightness doesn't change.
> >>
> >> It's a Ivy Brigde notebook where drm shows some errors in dmesg.
> >Please
> >> see: http://pastie.org/9877917
> >>
> >>
> >
> >Please try to boot with acpi_ibm and without acpi_video. This way all
> >works for me.
> 
> That‘s already what I do. Also tried it with acpi_video without luck.

For the records: With r278102 brightness controls are working again.
Thanks all for helping.