Progress Report: Linux 6.19 – Asahi Linux / Blog / Progress Report: Linux 6.19 Progress Report: Linux 6.19 Previous Happy belated new year! Linux 6.19 is now out in the wild and… ah, let’s just cut to the chase. We know what you’re here for. The big one Asahi Linux turns 5 this year. In those five years, we’ve gone from Hello World over a serial port to being one of the best supported desktop-grade AArch64 platform in the Linux ecosystem. The sustained interest in Asahi was the push many developers needed to start taking AArch64 seriously, with a whole slew of platform-specific bugs in popular software being fixed specifically to enable their use on Apple Silicon devices running Linux. We are immensely proud of what we have achieved and consider the project a resounding and continued success. And yet, there has remained one question seemingly on everyone’s lips. Every announcement, every upstreaming victory, every blog post has drawn this question out in one way or another. It is asked at least once a week on IRC and Matrix, and we even occasionally receive emails asking it. “When will display out via USB-C be supported?” “Is there an ETA for DisplayPort Alt Mode?” “Can I use an HDMI adapter on my MacBook Air yet?” Despite repeated polite requests to not ask us for specific feature ETAs, the questions kept coming. In an effort to try and curtail this, we toyed with setting a “minimum” date for the feature and simply doubling it every time the question was asked. This very quickly led to the date being after the predicted heat death of the universe. We fell back on a tried and tested response pioneered by id Software; DP Alt Mode will be done when it’s done. And, well, it’s done. Kind of. In December, Sven gave a talk at 39C3 recounting the Asahi story so far, our reverse engineering process, and what the immediate future looks like for us. At the end, he revealed that the slide deck had been running on an M1 MacBook Air, connected to the venue’s AV system via a USB-C to HDMI adapter! At the same time, we quietly pushed the fairydust branch to our downstream Linux tree. This branch is the culmination of years of hard work from Sven, Janne and marcan, wrangling and taming the fragile and complicated USB and display stacks on this platform. Getting a display signal out of a USB-C port on Apple Silicon involves four distinct hardware blocks; DCP 1 , DPXBAR 2 , ATCPHY 3 , and ACE 4 . These four pieces of hardware each required reverse engineering, a Linux driver, and then a whole lot of convincing to play nicely with each other. All of that said, there is still work to do. Currently, the fairydust branch “blesses” a specific USB-C port on a machine for use with DisplayPort, meaning that multiple USB-C displays is still not possible. There are also some quirks regarding both cold and hot plug of displays. Moreover, some users have reported that DCP does not properly handle certain display setups, variously exhibiting incorrect or oversaturated colours

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