Apple Backlight Injector Brightness not saved

[KNNSpeed]

@hitman478 You do have a device ACPI0008, and it's called ALSD in the DSDT, so whatever fix we figure out is best to use in this thread should apply to you.


@RehabMan Removing the device from the DSDT did nothing. See attached. So I think _STA really was already returning 0. Recall, it's not a real ALS: it's this so-called CABC thing.

 

[RehabMan]

@RehabMan Removing the device from the DSDT did nothing. See attached. So I think _STA really was already returning 0.

Ummm... your config.plist is corrupt.

SPEEDY-NUC:RehabMan rehabman$ plutil -lint /Users/rehabman/Downloads/Brightness\ Configuration\ \[Problem\ Report\ Files\]\ v3/Non-working\ \(Modded\ DSDT\)/Modded\ FakeSMC/CLOVER/config.plist
/Users/rehabman/Downloads/Brightness Configuration [Problem Report Files] v3/Non-working (Modded DSDT)/Modded FakeSMC/CLOVER/config.plist: Encountered unexpected character 6 on line 344 while looking for close tag

I have a question though on the details of this problem that I don't think anyone has mentioned...

If it was some under the covers hardware change going on without macOS actions (brightness changing behind the scenes...), then the behavior would be as follows:
- reboot with known brightness level
- brightness level does not restore
- but upon pressing a brightness up or brightness down key, the backlight would jump to one level above or below the saved but lost value

Can you verify?

 

[KNNSpeed]

That's weird. It's just this part:

                <string>0x19160000/etc, 19MB framebuffer 9MB cursor bytes (credit RehabMan), will need if Dell ever changes DVMT to <64MB in BIOS</string>

Opens up fine in Atom.io, though it seems bdmesg has an issue with it, too. But it's just that line (for a patch I don't even have enabled). The rest seems OK.

EDIT: Oh, lol. just open it up in TextEdit and delete the < in front of <64MB. I used to mean a less than sign, but that's apparently a no-no.

 

[KNNSpeed]

Ummm... your config.plist is corrupt.

SPEEDY-NUC:RehabMan rehabman$ plutil -lint /Users/rehabman/Downloads/Brightness\ Configuration\ \[Problem\ Report\ Files\]\ v3/Non-working\ \(Modded\ DSDT\)/Modded\ FakeSMC/CLOVER/config.plist
/Users/rehabman/Downloads/Brightness Configuration [Problem Report Files] v3/Non-working (Modded DSDT)/Modded FakeSMC/CLOVER/config.plist: Encountered unexpected character 6 on line 344 while looking for close tag

I have a question though on the details of this problem that I don't think anyone has mentioned...

If it was some under the covers hardware change going on without macOS actions (brightness changing behind the scenes...), then the behavior would be as follows:
- reboot with known brightness level
- brightness level does not restore
- but upon pressing a brightness up or brightness down key, the backlight would jump to one level above or below the saved but lost value

Can you verify?

Almost. What actually happens is it jumps to a value that's at about 75% brightness (in every non-working situation). I edited my post above, but recall, it's not a real ALS: it's this so-called CABC thing.

 

[RehabMan]

EDIT: Oh, lol. just open it up in TextEdit and delete the < in front of <64MB. I used to mean a less than sign, but that's apparently a no-no.

This is why you should avoid editing plist files in text editors...
(such characters need escaping).

 

[RehabMan]

Almost. What actually happens is it jumps to a value that's at about 75% brightness (in every non-working situation). I edited my post above, but recall, it's not a real ALS: it's this so-called CABC thing.

The "about 75%" would make sense if the previously set value (before reboot) was near 75%.

What about if you had brightness set at something else, say 25%... does it still jump to 75%?
If it jumps to something near 25%, it implies the system was unaware of the brightness change (eg. a change that happened due to ACPI code executing).

If it jumps to 75%, then something else weird is happening... potentially two different weird things (brightness setting got confused somewhere and was set to something other than what the system expected it to be set to, and brightness restore value process went bad too)

 

[hitman478]

@KNNSpeed : Now I have found my ACPI0008 Device. I just have searched with an old DSDTEditor for Windows because I wasn't able to start OS X correctly. I think this was the reason why I didn't find it. I will just test your Solution with Replacing the FakeSMC.kext and adding your SSDT to see if it also will work for me.

 

[KNNSpeed]

What about if you had brightness set at something else, say 25%... does it still jump to 75%?

Yes.

If it jumps to 75%, then something else weird is happening... potentially two different weird things (brightness setting got confused somewhere and was set to something other than what the system expected it to be set to, and brightness restore value process went bad too)

A note on CABC:

This laptop suffers from display CABC. It's not fixable for FHD screens, because it's embedded in display firmware that is not flashable via OS.
The only solutions seems to swap the display. The part number should be Sharp LQ133M1JW01. If I won't be able to live with CABC, I'll try the swap with a non XPS13-specific OEM display.

That's for the XPS 13, but it seems like all 9x50/9x60 XPS models have it. Gotta give Dell props for creativity for reusing the ALS subsystem for that purpose, haha.

 

[RehabMan]

Yes.

Fun.

That's for the XPS 13, but it seems like all 9x50/9x60 XPS models have it. Gotta give Dell props for creativity for reusing the ALS subsystem for that purpose, haha.

This article says CABC can be disabled with a patch from Dell:
http://www.anandtech.com/show/9869/...ent-adaptive-brightness-control-on-the-xps-13

 

[bozma88]

Yes.




That's for the XPS 13, but it seems like all 9x50/9x60 XPS models have it. Gotta give Dell props for creativity for reusing the ALS subsystem for that purpose, haha.

A few more details on the CABC thing, just to avoid spreading incomplete or incorrect info.

9343, 9350, 9360, 9550, 9560 do not have ALS. They have it in DSDT, but it's disabled. They definitely don't have it.
CABC is embedded in display controllar's firmware, it's not a BIOS thing.
On 9350 and 9360, the FHD display is NOT flashable, so you cannot disable CABC.
On 9350, 9360 UHD display, you can flash a new display firmware via windows and CABC will go away.
On 9365 FHD+UHD you can flash a new firmware and disable it.
On 9550, 9560 FHD and UHD I think it's disabled by default.

Anyway, it all happens at firmware level, it's not a BIOS thing and BIOS / OS has no way to see the brightness change reported. So if you see the backlight reported level change, it's not CABC.