CXL PORT(9)

💅 cxl port (9) — the manual page, bestie edition

okay so like, welcome to the cxl port page, section 9, Kernel API Manual vibes ✨ this is the whole glow-up of the port driver and honestly? she's iconic.

✨ cxl port

so the ✨port driver✨ is the main character here, and what she does is enumerate dport via PCI — yep, through PCI, no cap — and then she scans for HDM (Host-managed-Device-Memory) decoder resources via the component_reg_phys value 🎀 and where does that value come from?? from the agent that registered the port, obviously 💅 iykyk.

and like, all descendant ports of a CXL root port (which is described by platform firmware, tyvm 🌸) are managed inside this driver's context. periodt. every single one of them.

each driver instance is responsible for tearing down the driver context of immediate descendant ports 😭 like yes bestie, you brought them into this world, you clean them up. and the locking for all of this? validated by CONFIG_PROVE_LOCKING — she does NOT play about locking, fr fr 🔥

🦋 the main service (her actual job)

the primary service this driver provides is:

• presenting APIs to other drivers so they can utilize the decoders 🫶
• indicating to userspace (via bind status, bestie 💖) the connectivity of the CXL.mem protocol throughout the PCIe topology 🌈

like she's literally the group chat relay between the kernel and userspace, keeping everyone updated on who's connected to who. main character energy honestly 👑

🌟 SEE ALSO

• Kernel file ./drivers/cxl/port.c — go read it, it's giving source code realness 💜

and that's the whole page!! mwah 💋 this lil rewrite lives in ./drivers/cxl, dated October 2026, and it's officially cxl port(9) — go forth and slay, bestie 🧚‍♀️🎀