ipa_endpoint_init_hdr(9)

📦 version 7.3.1, in nixpkgs unstable

💅 ipa_endpoint_init_hdr(9) 💅

okay so bestie, welcome to the kernel API manual — this one's ipa_endpoint_init_hdr, and it's literally the glow-up routine for the HDR endpoint configuration register ✨ no cap.

🌸 NAME 🌸

ipa_endpoint_init_hdr — Initialize HDR endpoint configuration register 🎀

✨ SYNOPSIS ✨

void ipa_endpoint_init_hdr (struct ipa_endpoint *endpoint );

🦋 ARGUMENTS 🦋

  • endpoint — Endpoint pointer. that's it, that's the whole argument, she's lowkey simple like that 🫶

💖 DESCRIPTION 💖

okay so here's the vibe: we program QMAP endpoints so that every single packet received is preceded by a QMAP header structure. like, the header walks in first, main character energy, and then the packet shows up 🌈

The QMAP header contains a 1-byte mux_id and a 2-byte packet size field, and we have the IPA hardware populate both of them for each received packet. yes bestie, the hardware does the work — the header is configured (in the HDR_EXT register) to use big endian format 🔥

The packet size gets written into the QMAP header's pkt_len field. That location is defined right here using the HDR_OFST_PKT_SIZE field. slay, positioning is everything 💅

Now the mux_id — she comes from a 4-byte metadata value supplied with each packet by the modem. and listen: it is *not* a QMAP header, but it does contain the mux_id value that we want, chillin' in its low-order byte 🍓

A bitmask defined in the endpoint's METADATA_MASK register defines which byte within the modem metadata actually contains the mux_id. And the OFST_METADATA field programmed here indicates where the extracted byte should be placed within the QMAP header. it's giving "find her, then put her exactly where she belongs" 🧚

👑 SEE ALSO 👑

the whole friend group fr fr 🫶

ok that's the page!! source: ./drivers/net/ipa · version/date: October 2026 · catch u later bestie, go init those headers 💜🎀🦋
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