to_dpa(9)

✨ to_dpa(9) ✨

okay bestie, welcome to the <pink>Kernel API Manual</pink> 💅 this one's called to_dpa, and honestly it's giving "tiny function, big lore."

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🌸 NAME 🌸

to_dpa — translate an HPA offset to a DPA offset 🦋

like, host brain → device brain. iykyk.

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🎀 SYNOPSIS 🎀

u64 to_dpa (u64 hpa_offset , u8 r_eiw , u16 r_eig , u8 hb_ways , u8 math );

that's the whole vibe. five args, one u64 back. slay.

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💖 ARGUMENTS 💖

so the manpage is literally no help here — every single one of these says -- undescribed -- 😭 not me reading the DESCRIPTION to figure out what anything means:

• hpa_offset — -- undescribed -- 🙈 (the DESCRIPTION spills it tho: host physical address offset)
• r_eiw — -- undescribed -- 🙈 (DESCRIPTION says region encoded interleave ways)
• r_eig — -- undescribed -- 🙈 (DESCRIPTION says region encoded interleave granularity)
• hb_ways — -- undescribed -- 🙈 (DESCRIPTION says host bridge interleave ways)
• math — -- undescribed -- 🙈 (DESCRIPTION says interleave arithmetic, aka MODULO_MATH or XOR_MATH)

no cap, the argument list just gave up. but the description ate, so we move 💅

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🔥 DESCRIPTION 🔥

here's the real tea, laid out exactly like the page has it:

• hpa_offset: host physical address offset
• r_eiw: region encoded interleave ways
• r_eig: region encoded interleave granularity
• hb_ways: host bridge interleave ways
• math: interleave arithmetic (MODULO_MATH or XOR_MATH)

so it takes where you are in host-physical land, plus all the interleave deets — the ways, the granularity, the host bridge ways — plus which math flavor you're vibing with (MODULO_MATH or XOR_MATH, pick one bestie, those are the options), and it hands you back the device side. main character energy fr fr 👑

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⭐ RETURN ⭐

device physical address offset 💜

that's it. that's what you get back. a u64 of pure device-physical destination. 🫶

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🌈 SEE ALSO 🌈

• Kernel file ./tools/testing/cxl/test/cxl_translate.c — yes the actual file, go read it 🍓
• to_hpa(9) — the reverse girly 🔁
• to_pos(9)
• run_translation_test(9)
• parse_test_vector(9)

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vibe check: the arguments section is literally all -- undescribed --, so if you're confused, that's not you, that's the page. the DESCRIPTION is the only one doing homework here 😭✨

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and that's the whole page, bestie 🧚 from <purple>./tools/testing/cxl/test</purple> with much love, dated <cyan>October 2026</cyan>, to_dpa(9)` signing off — mwah 💋🎀