calculate_hu...rt_end_lines(9)

🎀 NAME 🎀

ok so this page is from the Kernel API Manual (the header up top literally says calculate_hu...rt_end_lines(9), it's giving truncated filename energy, we love a mysterious queen 💅), and the actual vibe is:

calculate_hubp_start_end_lines — a function that calculates svp parameters given a target p-state line. that's it, that's the whole thing ✨

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✨ SYNOPSIS ✨

void calculate_hubp_start_end_lines (struct
calculate_hubp_start_end_lines_params *p );

like yes bestie it returns void, we're doing side effects today 🫶

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💅 ARGUMENTS 💅

• p — so the manual literally just says -- undescribed -- for this one 😭 no cap, that's the entire entry. it's a struct calculate_hubp_start_end_lines_params * and that's all we're told. iconic of the docs team tbh.

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🦋 DESCRIPTION 🦋

okok so here's the tea 🍓: this function calculates the svp parameters (that's the vp0 and vp1 programming, keep up bestie) in terms of swath index and number of swaths, given an otg p-state target.

🚨 real talk: this function should be called per plane. don't be out here calling it once and thinking you're done, it's not that kind of function 💀

The manual says there are 5 steps. The list below has six items. Not me counting 🙈 but like, we're reporting the facts exactly as given, so here's literally everything:

1. Calculate svp0_start_dst_line and svp0_end_dst_line.
2. Calculate svp1_start_dst_line and svp1_end_dst_line
3. Calculate svp0_swath_start_idx and svp0_swath_end_idx
4. Calculate svp1_swath_start_idx and svp1_swath_end_idx
5. Convert to start swath index and number of swaths (for height)
6. Convert swath indices to START_LINE and HEIGHT

and then, because the source material felt dramatic:

***********************************************************************************************************

(mood. same energy as a group chat "anyway—")

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🌈 SEE ALSO 🌈

ok so the Kernel file this all lives in is:

./drivers/gpu/drm/amd/display/dc/dml2_0/dml21/src/dml2_standalone_libraries/alternate_pstate_shared_lib.c

and here's the whole friend group, go say hi 👋:

• in_circular_range(9)
• apply_svp1_workaround(9)
• calculate_start_line_and_height_from_swath(9)
• get_swath_deadlines(9)
• calculate_swath_deadline_dst(9)
• is_dst_in_next_frame(9)
• is_end_swath_in_next_frame(9)
• is_svp_dst_in_next_frame(9)
• calculate_swath_idx_from_dst(9)
• populate_svp_params(9)
• populate_start_index_num_swaths_helper(9)
• calculate_start_index_num_swaths(9)
• get_prefetch_end_line(9)
• get_effective_vblank_start(9)

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aaaand that's the page bestie 💖 source is ./drivers/gpu/drm/amd/display/... and it's dated October 2026 — yes, the future, we're ahead of schedule, slay 👑✨