5 ms·

Unfortunately we don't have access to lower level communication on macOS. Kexts (Kernel Extensions) have been deprecated and now need System Integrity Protectio

by alin23 4y ago

Unfortunately we don't have access to lower level communication on macOS. Kexts (Kernel Extensions) have been deprecated and now need System Integrity Protection (SIP) to be disabled. Even with that, you wouldn't have a way to send raw I2C signals to the monitor like ddcctl does on Linux. I do discuss these challenges regularly on HN, it's very possible you have read one of my comments. Lunar provides a Raspberry Pi solution for cases where DDC is really needed and doesn't work from the Mac: https://lunar.fyi/#displaylink-control https://lunar.fyi/#displaylink-control The guide leans toward DisplayLink but in fact it works on any monitor, and it was the only solution for DDC when the first M1 Macs appeared: https://alinpanaitiu.com/blog/journey-to-ddc-on-m1-macs/#the-raspberry-pi-idea https://alinpanaitiu.com/blog/journey-to-ddc-on-m1-macs/#the...

solardev 4y ago
Ah... thank you for all your work digging into that! Sorry it's such a pain :( That Pi solution is really interesting. Does that mean monitors will generally accept DDC commands from inputs other than the active one? Like having the Pi connected to a second HDMI port lets you control brightness without switching inputs? That would be neat. I wonder if there's some programmable dial type thing...
- alin23 4y ago
  Yes, in my experience, most monitors do accept DDC commands even if the video signal comes from another input as long as the other input keeps the line busy. For example, on the Pi this was not possible in past, we had to wait for the vc4-kms-v3d GPU driver to get this functionality. Thankfully it’s beta version coincided with the M1 release :) There’s no DDC dial available, but it’s something I tried doing in the past using an ESP32 that gets Power-over-HDMI [1] and sends DDC through the I2C wires of the HDMI cable [2] Unfortunately I had to put that on hold as I started a Mac app studio [3] which took most of my time away. (and I also realized I don’t have the means to sell and distribute a hardware project) [1] https://www.hdmi.org/spec21sub/cablepower https://www.hdmi.org/spec21sub/cablepower [2] https://github.com/tttttx2/ddcvcp https://github.com/tttttx2/ddcvcp [3] https://lowtechguys.com/ https://lowtechguys.com/

by alin23 4y ago

solardev 4y ago

Ah... thank you for all your work digging into that! Sorry it's such a pain :( That Pi solution is really interesting. Does that mean monitors will generally accept DDC commands from inputs other than the active one? Like having the Pi connected to a second HDMI port lets you control brightness without switching inputs? That would be neat. I wonder if there's some programmable dial type thing...

alin23 4y ago
Yes, in my experience, most monitors do accept DDC commands even if the video signal comes from another input as long as the other input keeps the line busy. For example, on the Pi this was not possible in past, we had to wait for the vc4-kms-v3d GPU driver to get this functionality. Thankfully it’s beta version coincided with the M1 release :) There’s no DDC dial available, but it’s something I tried doing in the past using an ESP32 that gets Power-over-HDMI [1] and sends DDC through the I2C wires of the HDMI cable [2] Unfortunately I had to put that on hold as I started a Mac app studio [3] which took most of my time away. (and I also realized I don’t have the means to sell and distribute a hardware project) [1] https://www.hdmi.org/spec21sub/cablepower https://www.hdmi.org/spec21sub/cablepower [2] https://github.com/tttttx2/ddcvcp https://github.com/tttttx2/ddcvcp [3] https://lowtechguys.com/ https://lowtechguys.com/