qrtr_tx_wait(9)

💅 qrtr_tx_wait(9) — like, the flow control one, from the Kernel API Manual

okay so bestie, gather round, because today we're talking about qrtr_tx_wait — flow control for outgoing packets ✨ (yes that's the whole NAME section, and yes it's iconic, we move).

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🌸 SYNOPSIS 🌸

int qrtr_tx_wait (struct qrtr_node *node , int dest_node , int dest_port
, int type );

that's the whole signature, no notes, she ate 💅

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🎀 ARGUMENTS 🎀

• node — the qrtr_node that the packet is to be send to 🫶
• dest_node — node id of the destination, iykyk
• dest_port — port number of the destination, the lil address of it all
• type — type of message

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🦋 DESCRIPTION 🦋

okay so the whole vibe here is flow control, and it's built around the low and high "watermarks". think of them like the little lines on your duolingo streak bar but for packets 🔥

the way it works: when the low watermark is passed, the confirm_rx flag gets set on the outgoing message. that lowkey triggers the remote to send a control message of the type QRTR_TYPE_RESUME_TX, which resets the counter. slay, communication 💖

and then — if the high watermark is hit? further transmision should be paused. periodt. that's the whole point, bestie, that's the guardrail 🌈

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💀 RETURN 💀

• 1 if confirm_rx should be set
• 0 otherwise
• or errno failure 😭 (we don't love that for us but it happens)

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✨ SEE ALSO ✨

go look at the Kernel file ./net/qrtr/af_qrtr.c, plus these absolute main characters:

• struct qrtr_hdr_v1(9)
• struct qrtr_hdr_v2(9)
• struct qrtr_node(9)
• struct qrtr_tx_flow(9)
• qrtr_tx_resume(9)
• qrtr_tx_flow_failed(9)
• qrtr_endpoint_post(9)
• qrtr_alloc_ctrl_packet(9)
• qrtr_endpoint_register(9)
• qrtr_endpoint_unregister(9)

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ngl bestie, read the whole friend group, they all reference each other for a reason 👑

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and that's the page!! 🎀 this lil number lives in ./net/qrtr and the version/date stamp on it is October 2026 — so yeah, mark your calendar, mwah 💋🫶