by strcat | 2025-04-13 03:53:59+00:00
> But they're drivers that are not upstreamed and which therefore make it hard to move to a newer kernel, right?

It's no harder than it would be dealing with them if they were upstream. Google ports all the Pixel drivers to newer LTS branches and a recent branch of the mainline kernel themselves.

With the recent Android 15 QPR2 release last month (March 2025), 6th/7th generation Pixels moved from the 5.10 branch to 6.1 and 8th generation Pixels moved from 5.15 to 6.1. 6th, 7th, 8th and 9th generation Pixels share the same kernel and kernel driver source tree now. They have them ported to 6.6 and mainline kernels too, it's just not ready to ship yet. 6.6 is used for virtual machines run on the devices and the emulator. 6.12 will be what's used for Android 16.

You can see at https://android.googlesource.com/kernel/google-modules/aoc/+... that they still port the 6th gen Pixel drivers to newer mainline kernels. They're ported to 6.13 and probably moving along to 6.14 soon. It doesn't mean they're going to ship them. Only LTS branches make sense to ship and they need long term stabilization first. The likely model is going to become ~12 months of stabilization and then ~12 months of usage since LTS kernel branches are moving back to 2 years of support. It was essentially increased to 6 years for 6th gen Pixels having 5 years of support, but they moved along to upgrading to newer LTS branches for 8th gen Pixels moving to 7 years of support. Greg KH works for and with Google on the LTS kernel maintenance / testing so it's actually quite Android centric rather than server centric. Long term support desktop/server distributions historically maintain their own LTS branches so they're not really the ones involved in that for the most part.

Drivers that are upstream don't actually get much free maintenance and testing. People making API changes blindly update the drivers without testing them. They get lots of updates and refactoring, but not much ongoing maintenance. Maintainers still need to deal with it. It's very common for upstream drivers to continuously regress. They can go a long time without actually working properly across releases due to how few people use them. Most people are using distributions with frozen package versions like Debian, not a rolling, and people using a rolling release like Arch Linux can use an LTS kernel branch to avoid a lot of this. The drivers for embedded hardware and things not used much by enthusiasts on desktops often break without it being noticed.

Android made a Generic Kernel Image system with ABI stability for drivers which does not benefit Pixels because they update the drivers to match the latest GKI kernel they ship. Similarly, Pixels don't really need the Treble HAL ABI forwards compatibility because they update all the vendor code to the latest monthly, quarterly and yearly OS releases anyway. It's helpful that drivers don't need to add all the new standard features to keep providing working support for new OS versions though. It's nice having it all nearly all neatly standardized and stable. We like Treble because of the sandboxing. The forwards compatibility benefits are largely unrealized because the vendors needing it aren't doing updates much anyway. Qualcomm is moving to 8 years of full update support for Snapdragon to partially match Pixels anyway.