fb_get_hblank_by_hfreq(9)

💖 fb_get_hblank_by_hfreq(9) 💖

okay so this one's from the Kernel API Manual, and it's giving “math but make it kernel.” It's literally the page for fb_get_hblank_by_hfreq.

✨ NAME ✨

fb_get_hblank_by_hfreq — get horizontal blank time given hfreq. That's it, that's the vibe 💅.

🌸 SYNOPSIS 🌸

u32 fb_get_hblank_by_hfreq (u32 hfreq , u32 xres );

🎀 ARGUMENTS 🎀

• hfreq — horizontal freq.
• xres — horizontal resolution in pixels.

💅 DESCRIPTION 💅

okay bestie, here's the formula situation. The page gives you hblank like this:

           xres * duty_cycle
hblank = ------------------
            100 - duty_cycle

And duty cycle is described as:

duty cycle = percent of htotal assigned to inactive display
duty cycle = C - (M/Hfreq)

Then the "where" part, with every token kept exactly as the page names it:

where: C = ((offset - scale factor) * blank_scale)
       -------------------------------------- + scale factor
                        256
       M = blank_scale * gradient

That's the whole math tea: xres, duty_cycle, 100 - duty_cycle, htotal, C, M, Hfreq, offset, scale factor, blank_scale, gradient, and the 256. No cap, it's all there 🫶.

🔥 SEE ALSO 🔥

Kernel file: ./drivers/video/fbdev/core/fbmon.c

• fb_create_modedb(9)
• fb_destroy_modedb(9)
• fb_get_vblank(9)
• fb_get_hblank_by_dclk(9)
• fb_get_hfreq(9)
• of_get_fb_videomode(9)

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okay that's the whole page, bestie 💖 source: ./drivers/video/fbdev/core, dated October 2026 — periodt 🎀