tsi721_lcwrite(9)

📦 version 7.3.1, in nixpkgs unstable

💅 tsi721_lcwrite — the kernel API manual, but make it make sense

okay so hi bestie 🫶 welcome to tsi721_lcwrite(9), a page straight out of the Kernel API Manual. yes it's a kernel function, no it's not scary, and yes we're gonna get through it together. it lives over in ./drivers/rapidio/devices and the version we're reading is the October 2026 one, so. fresh.

🌸 NAME 🌸

tsi721_lcwrite — write into local SREP config space. that's the whole vibe. it writes. locally. into SREP config space. iconique.

✨ SYNOPSIS ✨

no cap, here's the signature, exactly as it is:

int tsi721_lcwrite (struct rio_mport *mport , int index , u32 offset ,
int len , u32 data );

that's five arguments and an int coming back at you. easy.

🎀 ARGUMENTS 🎀

here's the cast of characters, and yes every single one of them matters:

  • mport — RapidIO master port info. it's the port, it's the master, it's giving main character energy tbh.
  • index — ID of RapdiIO interface. (yes bestie that's genuinely how it's spelled in the original 😭 copying it exactly, no edits, we don't "fix" things here.)
  • offset — Offset into configuration space. where in the config space we're poking. 📍
  • len — Length (in bytes) of the maintenance transaction. how many bytes we're moving, fr fr.
  • data — Value to be written. the actual good stuff going in. 💖

🦋 DESCRIPTION 🦋

so what does it do? it generates a local write into SREP configuration space. that's it. that's the whole job. it's not doing a little extra on the side, it's not doing vibes-based guesses — it just generates that local write. slay. ✨

🔥 RETURN 🔥

  • 0 on success 🎉
  • -EINVAL on failure 💀

two possible outcomes, no in-between. a very simple vibe check.

👑 SEE ALSO 👑

if you're the kind of bestie who likes to read ahead (and honestly? respect), the kernel file lives at ./drivers/rapidio/devices/tsi721.c, and here's the entire friend group, no one left out:

ok that's the whole page, bestie. go write some SREP config space, responsibly. 💜

and a lil sign-off to close it out: this one's from ./drivers/rapidio/devices, dated October 2026. periodt. 🎀

📦 where this page comes from