ntb_peer_db_addr(9)

📦 version 7.3.1, in nixpkgs unstable

💅 ntb_peer_db_addr(9) — from the Kernel API Manual, bestie

okay so this is a page from the Kernel API Manual and it's literally about getting the address and size of the peer doorbell register. yes, doorbell, like ringing someone's door but in a computer way 🔔✨

🎀 NAME 🎀

ntb_peer_db_addr — address and size of the peer doorbell register

✨ SYNOPSIS ✨

int ntb_peer_db_addr (struct ntb_dev *ntb , phys_addr_t *db_addr ,
resource_size_t *db_size , u64 *db_data , int db_bit );

not me just dropping the function signature like it's nothing 💅 that's the whole vibe, keep it exact, don't touch it.

🫶 ARGUMENTS 🫶

  • ntb — the NTB device context. your main character struct, basically 👑
  • db_addr — OUT — the address of the peer doorbell register. this one gets written out, so it's the answer spot 📍
  • db_size — OUT — the number of bytes to write the peer doorbell register. like, how big is this thing, we need the exact byte count 🧮
  • db_data — OUT — the data of peer doorbell register. no notes, that's what it says 🍓
  • db_bit — door bell bit number. which specific bit, bestie, pick one 🔢

🌈 DESCRIPTION 🌈

so the function returns the address of the peer doorbell register. that's the whole job, and it does it slayfully 💖

and like, who actually uses this? drivers that offload memory copy operations to a dma engine, that's who. those drivers may wish to ring the peer doorbell at the completion of memory copy operations — literally "hey bestie, i'm done" but a register write 📣

the fun part is the efficiency trick. for efficiency, and to simplify ordering of operations between the dma memory copies and the ringing doorbell, the driver may append one additional dma memory copy with the doorbell register as the destination, after the memory copy operations. so you're not doing a separate doorbell thing — you just yeet the doorbell into the copy queue as the destination and let the dma engine handle it. that's giving lowkey genius ✨ iykyk

⭐ RETURN ⭐

Zero on success, otherwise an error number. so 0 = slay, anything else = read the number and go fix something 😭

🦋 SEE ALSO 🦋

Kernel file ./include/linux/ntb.h — and here's the whole extended friend group, no one gets left out 🫶

that's the whole list, every single one, periodt 💅

lowkey reminder: the OUT args are outputs, so the function is the one filling them in for you — don't pre-fill them and expect the vibes to work out 🙈

and that's the page, bestie 🎀 this one came from the source tree at ./include/linux, dated October 2026 — go forth and ring those doorbells responsibly 💜🦋

📦 where this page comes from