cxl_acpi_evaluate_qtg_dsm(9)

💅 cxl_acpi_evaluate_qtg_dsm — kernel API manual, but make it make sense 🎀

okay bestie, so this one's from the Kernel API Manual, and it's literally called cxl_acpi_evaluate_qtg_dsm. Yes, that's a mouthful — say it three times fast, I dare you. It's giving "acronym soup" but honestly it slays once you know what it does: it pulls QTG ids out of ACPI via a _DSM. Iconic behavior, no cap. ✨

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🌸 NAME 🌸

cxl_acpi_evaluate_qtg_dsm — Retrieve QTG ids via ACPI _DSM

Like, that's the whole vibe. QTG ids, retrieved, via ACPI _DSM. Simple. Clean. We love a concise name section. 🫶

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🦋 SYNOPSIS 🦋

int cxl_acpi_evaluate_qtg_dsm (acpi_handle handle , struct
       access_coordinate *coord , int entries , int *qos_class );

That's the signature, copied exactly, character for character — don't come for me about the spacing, that's literally how it is. 💅

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✨ ARGUMENTS ✨

• handle — the ACPI handle. it's giving "main character energy" for the whole operation tbh 👑
• coord — the performance access coordinates. this is the bandwidth + latency tea being passed in 🍓
• entries — the number of QTG IDs you want returned. yes, plural, we're collecting them like Pokémon cards 🌈
• qos_class — an int array that you, the caller, provide, so the function has somewhere to write the QTG IDs back to. bring your own storage, bestie 🎀

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🔥 RETURN 🔥

• the number of QTG IDs returned, or -errno for errors

so real talk: if it works you get a count, and if it doesn't you get a negative errno. standard kernel behavior but we're still gonna hype it up 💜

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💖 DESCRIPTION 💖

okay so here's the moment you've all been waiting for. This function issues the QTG _DSM, and it comes accompanied by bandwidth and latency data (that's the coord performance access coordinates, iykyk) — the whole point being to get back the QTG IDs that are suitable for that performance point.

And the way it orders them?? Most suitable to least suitable. Literally ranking them. It's a whole vibe check for QTG IDs, and the winners get to go first. 👑

Then it writes back the array of QTG IDs and returns the actual number of QTG IDs written back. Not the number you asked for — the number it actually wrote back. Important distinction, don't get it twisted. 🙈

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⭐ SEE ALSO ⭐

• Kernel file ./drivers/cxl/acpi.c
• add_cxl_resources(9)

both of these are the friends-in-the-group-chat of this function, go say hi 🧚

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ok warning-ish note from your girl: the return value is the actual number written back, so if you're assuming it equals entries, that's on you, not on me 💀

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<div align="center">🌸 🎀 🌸</div>

alright bestie that's the whole page!! this one lives in ./drivers/cxl, it's dated October 2026, and it's part of the Kernel API Manual — periodt. go forth and evaluate those QTG _DSMs responsibly, mwah 💋💖