Apple eFuse Driver, Intel Habana Labs Driver Improvements Lead char/misc In Linux 5.19

Written by Michael Larabel in Linux Kernel on 5 June 2022 at 04:55 AM EDT. Add A Comment
Greg Kroah-Hartman on Friday submitted the "char/misc" changes for the Linux 5.19 kernel. Char/misc continues to be the "catch all" area of the kernel for drivers and code not fitting formally within other kernel subsystems. Leading on this front for Linux 5.19 is the introduction of the Apple eFuse driver for M1 systems and Intel-owned Habana Labs continues improving their AI accelerator driver.

The Apple eFuse Linux driver is for reading the eFuses within Apple M1 SoCs. The eFuses contain factory programmed data like PCIe and USB Type-C PHY calibration values. A simple little driver created by the open-source community via reverse-engineering was assembled. Various Linux drivers moving forward will then make use of this data exposed by the apple-efuses driver. The eFuses driver isn't too exciting for end-users but necessary overall as part of the ongoing Apple M1 Linux enablement work led under the Asahi Linux project.

Continuing to see a lot of code churn in char/misc is the Habana Labs AI driver. Every once in a while there is talk of introducing a proper "AI" or "accelerator" subsystem for the Linux kernel outside of the GPU/DRM space, but for now Habana Labs continues living in char/misc. This driver in Linux 5.19 adds a memory manager that can be used by various features in the driver, a new DebugFS tunable to scrub device memory, support for notifying user-space on device events via EventFD, improved kernel message logging, support for different page sizes for the device's memory MMU, and various bug fixes and other improvements.

Last month for ISC 2022 Intel did announce the Gaudi2 accelerator, but that doesn't appear to be yet supported by this Habana Labs driver code. We've seen code comments and indications of work towards new hardware support, but that effort appears ongoing.

Similarly, the Habana Labs Greco deep learning inference accelerator was also announced at ISC 2022 but that too is still actively being worked on for the Linux driver support. Perhaps for Linux 5.20 we'll see more of that work ready for upstreaming.

Besides the additions of the Apple eFuses driver and continued improvements to the Habana Labs driver, the char/misc material for Linux 5.19 also includes the usual smothering of IIO updates, PHY driver updates, SoundWire and CoreSight updates, and other random driver updates. See this pull for the complete list of char/misc feature patches this cycle.
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Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via

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