Hardware Timestamping Engine Subsystem Merged For Linux 5.19

While just a day prior Linus Torvalds was questioning the proposed "HTE" subsystem, today on this final day of the Linux 5.19 merge window he decided to land this new subsystem.

The Hardware Timestamping Engine "HTE" is for being able to efficiently associate hardware timestamps with certain events like from GPIOs and IRQs. Linux kernel drivers can register as hardware timestamp providers while other areas of the kernel can request the events they are interested in to be timestamped by said providers. With Linux 5.19 the initial launch "customer" of the HWE subsystem is a NVIDIA Tegra Xavier driver and integration with GPIOs. Expanding the coverage of the HWE support is expected over the coming kernel cycles.

As written about in yesterday's article, Linus Torvalds was concerned over just having this one provider implementation (NVIDIA Tegra), the pull request coming late in the merge window, and not being fond of the subsystem name.

His concerns though seemed to have largely passed -- with Intel at least possibly adding to the HWE subsystem in the future -- and today he merged the initial 3k lines of new kernel code.

Linus commented on the mailing list he remains unhappy with the "HTE" name. NVIDIA's Thierry Reding raised the idea of still possibly renaming the HTE subsystem with the Linux 5.20 kernel cycle later this summer.