__pci_request_region(9)

📦 version 7.3.1, in nixpkgs unstable

💅 __pci_request_region(9) — like, the Kernel API Manual page, bestie

okay so picture this: you're deep in the kernel, you've got a PCI device, and you need to claim its I/O or memory region before you touch a single byte in it. that's this function. it's from the Kernel API Manual, and it's genuinely iconic. no cap.

✨ SYNOPSIS ✨

int __pci_request_region (struct pci_dev *pdev , int bar , const char
*name , int exclusive );

look at her. four args. flawless. let's meet them 💖

🎀 ARGUMENTS 🎀

  • pdev — the PCI device whose resources you're about to reserve. your main character device, basically 👑
  • bar — the BAR you want reserved. yes, that BAR. pick one 🫶
  • name — the name of the driver that's requesting the resource. it's literally your name on the reservation, like a little table card at a restaurant 🎀
  • exclusive — whether the region access is exclusive or not. exclusive is a vibe (more on that below) 💅

⭐ RETURN ⭐

0 on success, negative error code on failure. that's it. that's the whole story. 😭

🌸 DESCRIPTION 🌸

okay so here's the tea 🍓 — this marks the PCI region associated with the PCI device pdev, BAR bar, as being reserved by owner name.

the way this is non-negotiable: do not access any address inside the PCI regions unless this call returns successfully. like, at all. no peeking. 🙈

if exclusive is set, the region gets marked so that userspace is explicitly not allowed to map the resource via /dev/mem or sysfs MMIO access. so it's giving "reserved for me only", and honestly? respect. 💅

returns 0 on success, or EBUSY on error. and bestie — a warning message is also printed on failure, so if you're wondering why your dmesg is yelling at you, it's probably this 😭

🦋 SEE ALSO 🦋

kernel file ./drivers/pci/pci.c — that's where the magic lives, iykyk. and then there's the whole friend group, all 133 of them, all showing up to the group chat. slay 🔥

and that's the whole page, bestie 💜 go reserve your regions responsibly, do NOT touch addresses before the call succeeds, and remember — if it fails, it will tell on you in the logs 😭✨

🫶 this one came to you from ./drivers/pci (that's the source/version, and it's dated October 2026) — mwah, see you in the next manpage 🌈

📦 where this page comes from