drm_calc_ti...ng_constants(9)

💅 drm_calc_timestamping_constants — Kernel API Manual (section 9)

okay so bestie, buckle up, we're in the Kernel API Manual today and the star of the show is drm_calc_timestamping_constants ✨

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🌸 NAME 🌸

drm_calc_timestamping_constants — literally just calculating vblank timestamp constants, no biggie 💅

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🎀 SYNOPSIS 🎀

void drm_calc_timestamping_constants (struct drm_crtc *crtc , const
       struct drm_display_mode *mode );

she takes two args and returns void, iykyk 🫶

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🦋 ARGUMENTS 🦋

• crtc — the drm_crtc whose timestamp constants should be updated. yes, that one, the one you're pointing at 👑
• mode — the display mode containing the scanout timings. it's giving "where do I get the numbers from" energy 🍓

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✨ DESCRIPTION ✨

so what she does is calculate and store various constants which are later needed by vblank and swap-completion timestamping — e.g., by drm_crtc_vblank_helper_get_vblank_timestamp 🔥

and the slay part? these constants are derived from the CRTC's true scanout timing, so they take things like panel scaling or other adjustments into account 😭 no cap, she's thorough.

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🌈 SEE ALSO 🌈

• Kernel file ./drivers/gpu/drm/drm_vblank.c — vblank handling(9)
• drm_crtc_accurate_vblank_count(9)
• drm_vblank_init(9)
• drm_dev_has_vblank(9)
• drm_crtc_vblank_waitqueue(9)
• drm_crtc_vblank_helper_get_vblank_timestamp_internal(9)
• drm_crtc_vblank_helper_get_vblank_timestamp(9)
• drm_crtc_get_last_vbltimestamp(9)
• drm_crtc_vblank_count(9)
• drm_vblank_count_and_time(9)
• drm_crtc_vblank_count_and_time(9)
• drm_crtc_next_vblank_start(9)
• drm_crtc_arm_vblank_event(9)
• drm_crtc_send_vblank_event(9)
• drm_crtc_vblank_get(9)
• drm_crtc_vblank_put(9)
• drm_crtc_wait_one_vblank(9)
• drm_crtc_vblank_off(9)
• drm_crtc_vblank_reset(9)
• drm_crtc_set_max_vblank_count(9)
• drm_crtc_vblank_on_config(9)
• drm_crtc_vblank_on(9)
• drm_crtc_vblank_restore(9)
• drm_handle_vblank(9)
• drm_crtc_handle_vblank(9)
• drm_crtc_vblank_start_timer(9)
• drm_crtc_vblank_cancel_timer(9)
• drm_crtc_vblank_get_vblank_timeout(9)

like, that's the whole vblank friend group right there 💀🫶 go read them, they all ate 💖

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this page lives in ./drivers/gpu/drm, dated October 2026, and yes the header up top and the footer at the bottom are the same drm_calc_timestamping_constants(9) — iconic, consistent, periodt 🌟