[Guide] Laptop backlight control using AppleBacklightFixup.kext

[RehabMan]

Here are my test results on this Kaby Lake system so far...

First, I follow post #1 as written (SSDT-PNLF, generic AppleBacklight patch, current AppleBacklightInjector.kext).
Then, I observe P profile is being selected (this is Kaby, so "F12Pxxxx"), brightness controls broken.
Next, change display-id with config.plist/Graphics/Inject/EDID/Inject=true, config.plist/Graphics/Inject/EDID/ProductID=0x9c7c.
Reboot.
I observe P profile is still selected (and I verified EDID patch was correct/successful), brightness still broken.
Next, remove the matching P profile from the injector kext (made F12Pxxxx -> #F12Pxxxx).
Rebuild cache and reboot.
Observe "F12TxxxxM" is selected. Brightness controls work.

Conclusion: Having "P" profiles present in the injector are helpful in identifying the P profile problem, but P profiles need to be removed from the injector to have a chance of selecting the T profile, even with patched EDID. All T profiles should probably remain in the injector kext. And clearly, certain configurations prefer the P profile if available.

I will conduct a few more science experiments later today to further nail down the behavior.
And hopefully, I can find a way to avoid patching EDID...

 

[RehabMan]

Here is 2 more set. I removed P profile from Kext and installed it.

First Set
======
Fixed EDID
First restart --> Default Profile
Fix kextcache second restart --> T Profile

Second Set
=======
Changed EDID back to original
Profile --> T Profile but brightness controls doesn't have any effect on brightness.

I think for successful brightness, EDID or productId must be changed and P profile must be removed. That is my conclusion.

Thanks for the test and provided results. It confirms my results in #261.

 

[RehabMan]

For my next science experiment, I followed from this scenario...
(eg. by guide, inject fake display-id, remove P profiles from injector)

First, I follow post #1 as written (SSDT-PNLF, generic AppleBacklight patch, current AppleBacklightInjector.kext).
Then, I observe P profile is being selected (this is Kaby, so "F12Pxxxx"), brightness controls broken.
Next, change display-id with config.plist/Graphics/Inject/EDID/Inject=true, config.plist/Graphics/Inject/EDID/ProductID=0x9c7c.
Reboot.
I observe P profile is still selected (and I verified EDID patch was correct/successful), brightness still broken.
Next, remove the matching P profile from the injector kext (made F12Pxxxx -> #F12Pxxxx).
Rebuild cache and reboot.
Observe "F12TxxxxM" is selected. Brightness controls work.

and then I changed config.plist/Graphics/Inject/EDID/Inject=false.
(eg. go back to native display-id)

Result: Working backlight, and still F12TxxxxM profile selected.

Conclusion: Patching display-id in EDID, at least on this system is not needed. Without P profile, the system selected a T profile, although it is an FxxTxxxxM profile. The original injector proposed by the guide didn't have this particular T profile (only FxxTxxxx). When I responded to that by adding all the profiles, including the P profiles, the system then selected an incompatible P profile instead of the desired T profile (M). Key is adding the other T profiles, but not having the P profiles...

Fix: Remove all P profiles from the injector. Then no EDID hacking required.

I will make the change (DONE), and we will test like that for a while...

 

[johnnync21]

Hello @RehabMan, how i can compile your kext?, i know your bitbucket but i would like compile your work

 

[RehabMan]

Hello @RehabMan, how i can compile your kext?, i know your bitbucket but i would like compile your work

What kext are you referring to?
With this guide, there is no kext to compile.

 

[maromi]

here is the report to get the P to T

 

[iAnil]

Got Brightness control after installing applebacklight.kext using this guide:-
Native Brightness working without 'blinkscreen' using patched AppleBacklight.kext
before restart

but after restart the brightness level goes back to higher.

My dsdt & ssdts and config file

 

[RehabMan]

here is the report to get the P to T

I think you will have the same result if you follow post #1 as now written.

Changes from what you currently have:
- use AppleIntelBacklightInjector.kext as per post #1 (current version)
- remove patched EDID if you're using one (no way for me to know whether the EDID you're injecting is native or not)

 

[RehabMan]

Got Brightness control after installing applebacklight.kext using this guide:-
Native Brightness working without 'blinkscreen' using patched AppleBacklight.kext
before restart
View attachment 246827
but after restart the brightness level goes back to higher.
View attachment 246828
My dsdt & ssdts and config file

Off-topic.
The guide in post #1 is based on that original work, but is being refined to be simpler and to apply to more graphics hardware.

 

[maromi]

I think you will have the same result if you follow post #1 as now written.

Changes from what you currently have:
- use AppleIntelBacklightInjector.kext as per post #1 (current version)
- remove patched EDID if you're using one (no way for me to know whether the EDID you're injecting is native or not)

i don't see any changes that would be helpful as i have already tested that scenario yesterday and it did not work. i had disable more profiles to get to to regular T.

the EDID is the native EDID and also without it i lose qe/ci.

tell me onwhen you finally figure it out cause profile switching has been proven already in least 4 of many of my past reports. its done.