pci_vc_enable(9)

📦 version 7.3.1, in nixpkgs unstable

💅 pci_vc_enable(9) — from the Kernel API Manual

okay so bestie, welcome to pci_vc_enable(9), straight out of the Kernel API Manual ✨ this lil function is your girl for turning on a virtual channel, and we're gonna walk through it together, no cap 🫶

🌸 NAME

pci_vc_enable — Enable virtual channel 💫

🎀 SYNOPSIS

void pci_vc_enable (struct pci_dev *dev , int pos , int res );

like, that's the whole thing. void return, three args, go off 👑

🦋 ARGUMENTS

  • dev — the device 💻 that's your main character here
  • pos — the starting position of the VC capability, and just so we're clear that's VC/VC9/MFVC 🧚
  • res — the VC res number, i.e. VCn and n is 0-7, so pick your fave 🍓

💜 DESCRIPTION

so the whole vibe is: a VC gets enabled by setting the enable bit in the matching resource control registers on both sides of a link 🔥 both sides. not one. both. got it? 💅

which means we literally have to go find the opposite end of the link 🌈 we can't just enable on one side and call it a day, that's not how any of this works.

to keep it simple (and honestly, iconic of them), we enable from the downstream device ✨ but plot twist 😭 — RC devices do not have an upstream device, and it also doesn't seem like VC9 does either (the spec is unclear on that one, and not me side-eyeing the spec 🙈).

so once we do find the upstream device, we match the VC ID to get the correct resource, and then we disable and enable on both ends 🫶 that's the whole ritual, periodt.

⭐ SEE ALSO

kernel file ./drivers/pci/vc.c plus the whole friend group 💖:

and that's the page bestie 🎀 shoutout to ./drivers/pci for holding it down — this one's dated October 2026, so like, mark your calendars 📅💜 go enable some virtual channels, ily, bye 🦋✨

📦 where this page comes from