dma_buf_mmap(9)

📦 version 7.3.1, in nixpkgs unstable

💅 dma_buf_mmap — like, the Kernel API Manual, bestie

Okay so this is dma_buf_mmap(9) from the Kernel API Manual and it's genuinely the moment your userspace memory gets to touch a dma-buf. Sit down, this one's cute.

✨ NAME ✨

dma_buf_mmap — Setup up a userspace mmap with the given vma 🫶 (yes, "Setup up", that's what it says, we don't edit the original text, we respect the original text)

🌸 SYNOPSIS 🌸

int dma_buf_mmap (struct dma_buf *dmabuf , struct vm_area_struct *vma ,
unsigned long pgoff );

Three args, one int back, that's the whole vibe. 💅

🎀 ARGUMENTS 🎀

  • dmabuf — [in] — the buffer that should back the vma. Like, the actual dma-buf that's gonna be the main character underneath your mapping. 👑
  • vma — [in] — the vma for the mmap. This is the thing getting adjusted, so heads up, it's not staying exactly how you handed it over. 🙈
  • pgoff — [in] — offset in pages where this mmap should start within the dma-buf buffer. Pages, bestie, not bytes. Don't do bytes. 😭

🦋 DESCRIPTION 🦋

So what this function does is, like, a whole little glow-up routine on the vma you pass in:

  • it adjusts the passed-in vma so that it points at the file of the dma_buf operation ✨
  • it also adjusts the starting pgoff 🧚
  • and it does bounds checking on the size of the vma (safety first, always) 🔥

Then — and this is the slay part — it calls the exporter's mmap function to actually set up the mapping. So it's giving middle-manager energy: it does the setup and validation, then hands the real work off to whoever exported the buffer. 💜

It can return negative error values, and it returns 0 on success. That's the contract. Negative = something went sideways, 0 = we ate and left no crumbs. ⭐

🌈 SEE ALSO 🌈

The kernel file for this is ./drivers/dma-buf/dma-buf.c — go read it, it's right there and it's iconic. Then the whole extended friend group:

Fr fr, that's all of them — do not skip the list, every single one of those (9) pages is part of the lore. iykq 😌

And that's the whole page, bestie! 💖 Cute little sign-off below: this one lives in ./drivers/dma-buf, it's dated October 2026, and it's from the Kernel API Manual. Mwah, go mmap something responsibly. 🍓🎀🫶

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