drm_fb_dma_...anout_buffer(9)

💅 drm_fb_dma_get_scanout_buffer(9) 💅

okay so this is a page from the Kernel API Manual bestie, and it's about one very specific little function that has a very specific little job. it's giving "emergency era" energy, and honestly? iconic.

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✨ NAME ✨

drm_fb_dma_get_scanout_buffer — provide a scanout buffer in case of panic 🫶

like, the whole point: panic happens, screen still needs to show something, this is the hook that hands over the buffer.

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🦋 SYNOPSIS 🦋

int drm_fb_dma_get_scanout_buffer (struct drm_plane *plane , struct
drm_scanout_buffer *sb );

that's the whole signature, no cap. two args, one int coming back at you.

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🌸 ARGUMENTS 🌸

• plane — the DRM primary plane. yes, the primary one. main character plane energy 👑
• sb — the scanout buffer, but specifically for the panic handler. it's the buffer that gets to shine when everything else has gone sideways 💀

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⭐ RETURN ⭐

0, or a negative error code. that's it, that's the vibe check. zero means slay, negative means uh oh 🙈

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🎀 DESCRIPTION 🎀

so this is the generic get_scanout_buffer implementation — the one for drivers that use the drm_fb_dma_helper. if that's your driver, congrats, this is your girl 💖

here's the important part, and I need you to actually read it: it won't call vmap in the panic context. like, literally will not. so the driver has to make sure the primary plane is already vmapped — otherwise the panic screen won't get displayed. no vmapped plane, no panic screen, and that's a whole mess you do not want 😭

⚠️ warning bestie: forgetting the vmap is not a cute look. this is panic-context code, there's no second chances, no do-overs, no "let me just fix that real quick." make sure the primary plane is vmapped or your panic screen is simply not happening 💅

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🌈 SEE ALSO 🌈

• Kernel file ./drivers/gpu/drm/drm_fb_dma_helper.c framebuffer dma helper functions(9)
• drm_fb_dma_get_gem_obj(9)
• drm_fb_dma_get_gem_addr(9)
• drm_fb_dma_sync_non_coherent(9)

go read the whole squad, they're all in their helper era together 🧚✨

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and that's the page, fr fr 🍓 this one's from ./drivers/gpu/drm, dated October 2026 — mwah, go forth and vmap your planes 💜🦋