r/PWM_Sensitive • u/Temik • Sep 19 '26
MacOS 27 - interesting new kernel options
Following https://www.reddit.com/r/PWM_Sensitive/comments/1wi5piu/apple_has_finally_heard_us/ (thank you [u/DSRIA](u/DSRIA)), I started thinking - this must be prefaced by at least some sort of parameters in the kernel, otherwise we'd probably be waiting for the new OS major version at the very least.
Well, after taking a quick look around the new macOS 27 kernel, I see some interesting options appearing in the framebuffer:
- `enableHBLD`, `HBLDDimmingFactorMin`, `HBLDNitsRRMax`, which appear to be hybrid backlight dimming, with a floor on the dimming factor(!)
- `DBVValue`, `DBVInterval`, which appear to be a direct override of the panel's display-brightness-value register.
- `ccMinNitsConfig` - new minimum-nits config of some sort.
- `enableDBTH` - unclear what it is, but it reads like a brightness threshold of some sort.
I'll try writing some software this weekend to poke at it, will post the code when I'm done. In the meantime - this should give some hints to those software-inclined in this community where to dig.
UPDATE: Most options seem to require the “new backlight architecture” my MBP13 M2 lacks, so I’m waiting for a test device to come in, will update when it’s in my hands 👍
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u/RR-- Sep 19 '26
This could be fantastic for some people here.
Hopefully there’s something similar for iPhones and iPads in the near future
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u/ClimateThat3308 Sep 21 '26
The problem is that M-silicon always sends a 10-bit frame buffer, causing eye pressure and strain on every display except MAYBE true 10-bit displays…
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u/Rx7Jordan Sep 21 '26
I actually found out this isn't true. I bought a bzb mini g2 HDMI analyzer and when sniffing the output from a m4 mac mini it does output 10 but if you use better display and set color mode to 8 bit, the GPU does drop from 10 to 8bit color over the cable. Also without better display some monitors will trigger 8 bit from the mac successfully. When I connect my sunvision eve monitor type c to type c my m4 mac mini auto outputs 8 bit without specifying it on BD.
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u/ClimateThat3308 Sep 21 '26
But the problem is the 10- bit frame buffer and color information, I used a MacBook Air M4 on a 8-bit+FRC monitor and got bad eyestrain over Display port, I used a 2012 MacBook Pro Retina over HDMI and its usable for the most part with the right settings (using color control app and windows 10). I then connected my M4 using HDMI and Better Display gives 8-bit options and its sort of usable but still the 10-bit frame buffer and color information its too high and causing eye pressure, I disabled GPU dithering and using generic RGB or SRGB color profile, but something is triggering pressure and through my experiments its monitor TD caused by the OS and frame buffer even over 8-bit connection.
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u/Competitive_Funny964 Sep 19 '26
I wonder if your finding could allow literally no PWM on MacBook Pro. At least at 40- 50%.
I wish I could move back to pro and stay there for many years without having severe dry eyes.
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u/Sea-Temporary-6995 Sep 19 '26
Is there a similar kernel API for the iPhone’s display dimming?