get_effective_vblank_start(9)

✨ get_effective_vblank_start(9) ✨

okay bestie, welcome to the Kernel API Manual 💖 and yes, get_effective_vblank_start(9) is the main character today 👑

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🌸 NAME 🌸

get_effective_vblank_start — a little helper that calculates the effective vblank start 🎀

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🦋 SYNOPSIS 🦋

uint16_t get_effective_vblank_start (uint16_t vblank_start , uint16_t
vblank_end , uint16_t recout_y , uint16_t recout_height );

that's it, that's the whole signature, no cap ✨ it hands you back a uint16_t 🫶

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💅 ARGUMENTS 💅

so... bestie... the source doc is literally not giving 😭 every single one of these says the exact same thing:

• vblank_start — -- undescribed -- 🙈
• vblank_end — -- undescribed -- 🙈
• recout_y — -- undescribed -- 🙈
• recout_height — -- undescribed -- 🙈

not me copying the same placeholder four times 💀 that's genuinely what's on the page though, i don't gatekeep, i don't invent lore. iykyk 🧚

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🌈 DESCRIPTION 🌈

okay so here's the vibe 👑 this one is to be used by FW (firmware, bestie, it's giving embedded) to calculate and store the effective vblank start — specifically so it doesn't need to be computed multiple times ✨ like, cache your girl, she's not doing that math twice 💅

and what is the effective vblank start? literally the end of the recout in OTG timing space 🎀 slay.

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⭐ RETURN ⭐

it calculates effective vblank start given the input timing params 🔥

and then, because the source page said so, there's this absolutely iconic wall of asterisks right after it — keeping it verbatim because i fear her 🌸:

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

main character energy honestly 💀

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🍓 SEE ALSO 🍓

first up, the Kernel file, no thoughts just path:

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

and then the whole friend group showed up to the group chat 🫶 go read these next bestie:

• 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)
• calculate_hubp_start_end_lines(9)
• get_prefetch_end_line(9)

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lowkey a whole squad, and they all live in ./drivers/gpu/drm/amd/display/... 🦋

and that's the whole page, bestie, tysm for reading 🫶 this came from ./drivers/gpu/drm/amd/display/..., dated October 2026, and the title on the tin is get_effective_vblank_start(9) — periodt 💜✨🎀