A few years ago, one of our customers came to us with what sounded like a reasonably straightforward request: adding support for the Precision Time Protocol to an existing Linux kernel Ethernet PHY driver, namely the Marvell PHY driver.
Not only this sounded reasonably easy, but someone had actually already done the work: Russell King, a famous Linux kernel developer, maintainer of the ARM 32-bit support and prolific contributor to the networking subsystem, had already sent to the netdev mailing list a patch series implementing exactly this. With this existing series, we initially expected that a few review rounds and some testing would be enough to get it merged. Task done, move on.
It turned out to be much more complicated.
We started this work in March 2023. Three years later, we only have posted a second revision of the Marvell PHY PTP support, and that happened only after a significant change to the PTP core API. Read on for a deep dive into this real-life story of Linux kernel development and contribution.
Continue reading “Linux PTP mainline development war story and new features”