calculate_st...t_from_swath(9)

💅 calculate_st...t_from_swath(9) — Kernel API Manual ✨

okay so bestie, welcome to the group chat for calculate_st...t_from_swath(9) — that's the Kernel API manual, and yes the title is literally truncated like that, it's giving "my name got cut off in the GC nickname" energy 😭. Anyway. Sit down, hydrate, let's get into it.

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🌸 NAME 🌸

calculate_start_line_and_height_from_swath — okay so this icon takes the output from calculate_hubp_start_end_lines and calculates hardware programming values. Which values? SVP0/1_START_LINE and SVP0/1_HEIGHT. That's the whole vibe, periodt.

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✨ SYNOPSIS ✨

void calculate_start_line_and_height_from_swath (uint32_t
svp0_start_sw_idx_curr , uint32_t svp0_num_swaths_curr , uint32_t
svp0_start_sw_idx_next , uint32_t svp0_num_swaths_next , uint32_t
svp1_start_sw_idx_curr , uint32_t svp1_num_swaths_curr , uint32_t
svp1_start_sw_idx_next , uint32_t svp1_num_swaths_next , uint16_t
rec_start_dst , uint16_t svp0_start_dst , uint32_t svp0_frame_count ,
uint32_t program_go_line , uint32_t program_go_frame_count , uint16_t
viewport_start , uint16_t viewport_size , uint8_t access_direction ,
uint16_t vstartup , uint16_t swath_height , uint16_t *svp0_start_line ,
uint16_t *svp0_height , uint16_t *svp0_height_next , uint16_t
*svp1_start_line , uint16_t *svp1_height , uint16_t *svp1_height_next );

it's a void function, she returns nothing, she simply does 💅. twenty-four parameters. twenty-four. not me counting them twice to make sure 🫶.

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🎀 ARGUMENTS 🎀

okay so here's the part where the manpage simply Did Not Do The Reading 🙈. Every single one of these says -- undescribed -- in the original, and I'm not about to make stuff up, so I'm passing that message along verbatim, bestie. no cap.

• svp0_start_sw_idx_curr — -- undescribed --
• svp0_num_swaths_curr — -- undescribed --
• svp0_start_sw_idx_next — -- undescribed --
• svp0_num_swaths_next — -- undescribed --
• svp1_start_sw_idx_curr — -- undescribed --
• svp1_num_swaths_curr — -- undescribed --
• svp1_start_sw_idx_next — -- undescribed --
• svp1_num_swaths_next — -- undescribed --
• rec_start_dst — -- undescribed --
• svp0_start_dst — -- undescribed --
• svp0_frame_count — -- undescribed --
• program_go_line — -- undescribed --
• program_go_frame_count — -- undescribed --
• viewport_start — -- undescribed --
• viewport_size — -- undescribed --
• access_direction — -- undescribed --
• vstartup — -- undescribed --
• swath_height — -- undescribed --
• svp0_start_line — -- undescribed --
• svp0_height — -- undescribed --
• svp0_height_next — -- undescribed --
• svp1_start_line — -- undescribed --
• svp1_height — -- undescribed --
• svp1_height_next — -- undescribed --

like, the way that literally all twenty-four of them are just sitting there undescribed... the manpage said "figure it out" and dipped 😭💀. (the types are in the synopsis though, so at least we know which ones are uint32_t, which are uint16_t, which is the lone uint8_t access_direction, and which six are uint16_t * out-pointers. slay for that, at least 👑)

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🦋 DESCRIPTION 🦋

okay so the actual tea ☕: this function takes the output from calculate_hubp_start_end_lines and calculates the values for START_LINE and HEIGHT — and those are the values that get used to program directly into hardware. direct. into. hardware. main character energy fr fr 🔥.

and then the original drops this absolute wall of asterisks, which I am preserving in its full chaotic glory because it's iconic and I refuse to edit it:

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

that's it. that's the description. she's mysterious, she's got a star divider, she ate ✨

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🌈 SEE ALSO 🌈

first up, the kernel file itself — located at:

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

and the whole friend group, in the original order, no cap:

• in_circular_range(9)
• apply_svp1_workaround(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)
• get_effective_vblank_start(9)

go read all of them, bestie, they're all in the same little dml2 friend group 🫶

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heads up: this page came from the source path ./drivers/gpu/drm/amd/display/... (yes, truncated just like the title — the manpage generator was in a hurry okay 😭) and it's dated October 2026. that's the whole footer, and I'm folding it in here instead of copy-pasting the line, as promised 💖

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and that's the page!! 💜 calculate_st...t_from_swath(9) out. twenty-four arguments, zero descriptions, one star divider, infinite swag. mwah 🎀✨🌸💅