usb4_switch_drom_read(9)

📦 version 7.3.1, in nixpkgs unstable

💅 usb4_switch_drom_read — a kernel API manual, but make it cute

okay so this is usb4_switch_drom_read(9) from the Kernel API Manual, and honestly? she's a little icon. let's get into it 🎀

✨ NAME ✨

usb4_switch_drom_read — read arbitrary bytes from a USB4 router DROM. that's it. that's the whole job. and she does it beautifully 🦋

🌸 SYNOPSIS 🌸

int usb4_switch_drom_read (struct tb_switch *sw , unsigned int address ,
void *buf , size_t size );

literally just hand her a router, an address, a buffer and a size and she'll go get your bytes bestie 💖

🎀 ARGUMENTS 🎀

  • sw — the USB4 router. your main character, the device you're reading from 👑
  • address — byte address inside the DROM where the reading starts. like a little bookmark, but for bytes 🔖
  • buf — the buffer where the DROM content ends up getting stored. she fills it. that's the vibe 🫶
  • size — how many bytes to read from the DROM. be precise, be slay ✨

💅 DESCRIPTION 💅

so the way this works: it uses USB4 router operations to read the router DROM. no cap, that's the mechanism 🧚

for devices this should always work. always always. but for hosts? ok don't panic — it may return -EOPNOTSUPP, and in that case it's because the host router simply does not have a DROM. not a bug, not a her-problem, it's giving "nothing to read here" energy 💀

heads up bestie: that -EOPNOTSUPP is a real possibility on hosts, so check your return value like the responsible little kernel dev you are 🙈

⭐ RETURN ⭐

  • 0 on success — ate, no notes 💯
  • negative errno otherwise — she's telling you something went sideways, listen to her 😭

🌈 SEE ALSO 🌈

the kernel file lives at ./drivers/thunderbolt/usb4.c — go say hi 💜

and here is the entire friend group, all of them, nobody left behind (fr fr this is the whole list):

and that's the whole page, bestie 🫶 this lil manual lives over in ./drivers/thunderbolt and it's dated October 2026 — go read some DROM bytes, you've got this 💖✨👑

📦 where this page comes from