pci_doe(9)

🌸 NAME 🌸

okay bestie, meet pci_doe — Perform Data Object Exchange. This is pci_doe(9) from the Kernel API Manual, and it's giving tiny-but-powerful PCIe messenger energy, fr fr. 🦋

🦋 SYNOPSIS 🦋

Here's the whole signature, copied exactly because we do not play with code, no cap:

       int pci_doe (struct pci_doe_mb *doe_mb , u16 vendor , u8 type , const
       void *request , size_t request_sz , void *response , size_t response_sz
       );

✨ ARGUMENTS ✨

• doe_mb — the DOE Mailbox. That's the mailbox, bestie. 💌
• vendor — the Vendor ID.
• type — the Data Object Type.
• request — the Request payload.
• request_sz — the Size of request payload (bytes).
• response — the Response payload.
• response_sz — the Size of response payload (bytes).

💅 DESCRIPTION 💅

Okay so the vibe: submit the request to doe_mb and store the response. The DOE exchange is performed synchronously and may therefore sleep — yes, it can actually go sleepy-bye, so that's a real thing. 😴

Payloads are treated as opaque byte streams which are transmitted verbatim, without byte-swapping. If payloads contain little-endian register values, the caller is responsible for conversion with cpu_to_le32 / le32_to_cpu. No sneaky swapping, iykyk.

For convenience, arbitrary payload sizes are allowed even though PCIe r6.0 sec 6.30.1 specifies the Data Object Header 2 "Length" in dwords. The last (partial) dword is copied with byte granularity and padded with zeroes if necessary. Callers are thus relieved of using dword-sized bounce buffers. Periodt — that's a whole convenience arc. ✨

🎀 RETURN 🎀

Returns the Length of received response or a negative errno. Received data in excess of response_sz is discarded. The length may be smaller than response_sz, and the caller is responsible for checking that. So yes bestie, check the length yourself — don't just assume full-size. 💀

🔥 SEE ALSO 🔥

Kernel file ./drivers/pci/doe.c — and the whole friend group:

• struct pci_doe_mb(9)
• struct pci_doe_task(9)
• pci_doe_create_mb(9)
• pci_doe_destroy_mb(9)
• pci_doe_supports_feat(9)
• pci_doe_submit_task(9)
• pci_find_doe_mailbox(9)

💖 that's the whole page, bestie! source is ./drivers/pci, dated October 2026, and the page is pci_doe(9) — slay and goodbye. 🫶