Intel Working On Slim Bootloader Integration Improvements For The Linux Kernel

Slim Bootloader is the open-source initiative Intel announced in Q3'2018 for providing a very bare bones BSD-licensed open-source firmware implementation. We're now seeing new Linux patches for improving the integration with the Slim Bootloader.

The Slim Bootloader has been designed from the start to be a very lightweight EFI implementation that is derived from Coreboot and designed to be secure as much as it is optimized and lightweight. Recently we haven't heard too much about Slim Bootloader but it's fortunately alive and well.

The code remains in development by Intel. The documentation further spells out the project's intentions and goals. So Far Slim Bootloader is supported by just a small number of embedded/development platforms based on the likes of Apollo Lake / Whiskey Lake / Coffee Lake Refresh.

The latest on the Linux front with regards to Slim Bootloader is a signal handling driver. Due to Slim Bootloader not being UEFI compliant, its firmware update handling cannot be done using existing UEFI infrastructure so this specialized driver was written. And in trying to be slim and as fast as possible, the firmware doesn't check by default for new updates each boot.

So this new SBL_FWU_WMI driver aims to fulfill this purpose of providing notification when to check/apply a firmware update on the system. This driver is responsible for asserting a firmware update signal when there is a Slim Bootloader update that should be applied, which in turn via sysfs can be triggered by user-space.

Hopefully Slim Bootloader continues progressing nicely along with the other Intel efforts on providing more open-source firmware.