Core Kernel Requirements

Android 8.0 and higher mandate a minimum kernel version and kernel configuration, which are verified by the Vendor Test Suite (VTS) and over-the-air (OTA) updates. Android device kernels must enable kernel .config support and the option to read the kernel configuration at runtime through the procfs file system.

Kernel .config support

All device kernels must enable the entirety of android-base.cfg, which must include the following kernel-config options (or their kernel-version equivalent): 

CONFIG_IKCONFIG=y
CONFIG_IKCONFIG_PROC=y

Kernel version

For Android 9, the minimum Long Term Support (LTS) kernel version requirements are 4.4.107, 4.9.84, and 4.14.42.

  • All SoCs productized in 2018 must launch with kernel 4.9.84 or higher.
  • All other SoCs launching Android devices running Android 9 must use kernel 4.4.107 or higher.
  • Device kernels based on 4.14 must include the 4.14.42 or higher LTS release.
  • Regardless of launch date, all SoCs with device launches on Android 8.0 and higher remain subject to the kernel changes required to enable Treble.
  • Older Android devices upgrading to Android 8.0 or higher can continue to use their original base kernel version.

For details on LTS kernels, see Long-term stable kernels and Android Common Kernels

Devicetree support

If the platform doesn't support the Advanced Configuration and Power Interface (ACPI) specification, devicetree support in the kernel must be enabled and bootloaders must pass the hardware description in the form of a devicetree to the kernel. The devicetree must also be available for Android to read, and it must be able to pass vendor- and ODM-specific parameters to Android. CONFIG_OF is mandatory, along with all other device- and subsystem-specific CONFIG_OF_* kernel config options.

Using DebugFS

The implementation of the vendor interface can't rely on the DebugFS file system to access debug information. That's because in Android 7.0–10, DebugFS can be enabled, but VTS testing might be done with DebugFS unmounted.

In Android 11, DebugFS can't be accessed or mounted on production devices, so device manufacturers must remove it. Before Android 11, dumpstate accessed binder statistics from DebugFS. Because user builds launching with Android 11 or higher can’t access DebugFS, dumpstate accesses binder statistics from binderfs. To enable Binderfs, enable the kernel config CONFIG_ANDROID_BINDERFS.

In Android 11, VTS enforces these two requirements:

  • CONFIG_DEBUG_FS isn't enabled in the device’s kernel config.
  • DebugFS isn't listed under /proc/filesystems.

DebugFS in Android 11

The following table describes how each of these three categories is supported in Android 11. Note that the following only applies to userdebug builds since DebugFS can’t be mounted in user builds. Never mount DebugFS in user builds for devices launching on Android 11.

Use case Android 11 userdebug build
One-time DebugFS files initialization, during startup. This access happens only once during boot time. Vendor init does this.
Bugreport generation: The dumpstate HAL reads DebugFS files, which become part of the bug report. Done by dumpstate HAL within DumpstateBoard() when invoked by the dumpstate tool.
Device-specific testing and validation Adb root and shell