Enable Android Binder (binderfs) for Waydroid Support ⭐⭐⭐⭐⭐

[detox-slxsh]

Would you consider enabling Android Binder (CONFIG_ANDROID_BINDER_IPC and binderfs) in the Podroid kernel? Alpine already packages Waydroid, and Podroid already supports LXC.

[ExTV]

Binderfs is in. The guest kernel is built with CONFIG_ANDROID_BINDER_IPC=y, CONFIG_ANDROID_BINDERFS=y and CONFIG_ANDROID_BINDER_DEVICES="binder,hwbinder,vndbinder" since v1.2.8, and the kernel build fails if any of them is ever demoted, so they cannot silently disappear in a later build.

That turned out not to be enough for Waydroid. @Peterlovesvscode got it working in a fork, and the missing piece was PSI: the stock kernel had CONFIG_PSI off, so /proc/pressure did not exist, and Android's lmkd needs it.

PSI is now enabled in the kernel for the next release. Verified in the guest on a current build:

CONFIG_PSI=y
$ ls /proc/pressure
cpu  io  irq  memory

One thing that is still manual: binderfs is not mounted at boot, so you need

mkdir -p /dev/binderfs
mount -t binder binder /dev/binderfs

If you get Waydroid running on the next release without a fork, please say so here, and likewise if something else is still missing. Thanks to @Peterlovesvscode for finding the actual cause.

[ExTV]

The kernel option Waydroid was still missing, pressure stall information (CONFIG_PSI, /proc/pressure), shipped in v1.2.9. Together with the binderfs support from v1.2.8 that means the stock guest kernel now has what Waydroid asks for, with no custom build. Updating installs in place and keeps your VM. Thanks again to @Peterlovesvscode for the report and the working fork.