scmi_xfer_token_set(9)

📦 version 7.3.1, in nixpkgs unstable

💅 scmi_xfer_token_set — from the Kernel API Manual, bestie

okay so this is scmi_xfer_token_set, and it lives in the Kernel API Manual, and honestly? it's lowkey the bouncer at the club for transfer tokens. let's get into it 🎀

✨ NAME ✨

scmi_xfer_token_set — reserve and set a shiny new token for the xfer at hand 🫶

🌸 SYNOPSIS 🌸

int scmi_xfer_token_set (struct scmi_xfers_info *minfo , struct
       scmi_xfer *xfer );

🦋 ARGUMENTS 🦋

  • minfo — pointer to the Tx/Rx Message management info, based on channel type. the vibe-checked context, basically 💅
  • xfer — the xfer we're acting upon. the main character of this function ✨

💖 DESCRIPTION 💖

okay so what it does: pick the next unused monotonically increasing token and set it into xfer->hdr.seq. and why monotonic, you ask? because picking a monotonically increasing value avoids immediate reuse of freshly completed or timed-out xfers — which mitigates the risk of incorrectly associating a late and expired xfer with a live in-flight transaction, when both happen to re-use the same token identifier. no cap, that's the whole safety rationale 🔥

since the platform is NOT required to answer our request in-order, we should account for a few rare but possible scenarios:

  • exactly 'next_token' may be NOT available, so pick xfer_id >= next_token using find_next_zero_bit starting from the candidate next_token bit 🧚
  • all tokens ahead up to (MSG_TOKEN_ID_MASK - 1) are used in-flight, but we are plenty of free tokens at start, so try a second pass using find_next_zero_bit and starting from 0 🔁

X = used in-flight

Normal — the chill one 😌

|- xfer_id picked
-----------+---------------------------------------------------------- |
| |X|X|X| | | | | | ... ... ... ... ... ... ... ... ... ... ...|X|X|
---------------------------------------------------------------------- ^
|- next_token

Out-of-order pending at start — the plot twist 🌪️

|- xfer_id picked, last_token fixed
-----+----------------------------------------------------------------
|X|X| | | | |X|X| ... ... ... ... ... ... ... ... ... ... ... ...|X| |
---------------------------------------------------------------------- ^
|- next_token

Out-of-order pending at end — the finale 🎬

|- xfer_id picked, last_token fixed
-----+----------------------------------------------------------------
|X|X| | | | |X|X| ... ... ... ... ... ... ... ... ... ... |X|X|X||X|X|
---------------------------------------------------------------------- ^
|- next_token

🔒 CONTEXT 🔒

assumes to be called with xfer_lock already acquired. like, the lock is already in the group chat, don't re-add it 🙈

⭐ RETURN ⭐

0 on success, or an error 💀

👑 SEE ALSO 👑

kernel file ./drivers/firmware/arm_scmi/driver.c and honestly the whole extended friend group:

and that's the whole page, bestie 🫶 this one's straight out of ./drivers/firmware/arm_scmi, dated October 2026, and yeah — it's literally scmi_xfer_token_set(9) signing off 💜✨slay✨

📦 where this page comes from