dma_free_contiguous(9)

💖 dma_free_contiguous — like, the kernel API manual, section 9, bestie 💖

Okay so before we even start — this is from the Kernel API Manual, section 9, and yes we are absolutely getting into it. Sit down, grab a strawberry 🍓, and let's talk about giving memory back.

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✨ NAME ✨

dma_free_contiguous — release allocated pages 🎀

Like, it's the cleanup crew. The "ok bestie, party's over, everybody out" of contiguous DMA pages. No cap.

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🦋 SYNOPSIS 🦋

void dma_free_contiguous (struct device *dev , struct page *page ,
       size_t size );

That's it. That's the whole vibe check. Three things in, nothing out — it returns void, so don't be out here expecting a status report. 🙈

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🌸 ARGUMENTS 🌸

• dev — Pointer to the device for which the pages were allocated. Like, which device's memory are we handing back? Gotta be specific, bestie. 👑
• page — Pointer to the allocated pages. This is the actual stuff you're freeing. Your main character. ✨
• size — Size of allocated pages. Yes, you have to tell it how much. It's not a mind reader. 💅

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💜 DESCRIPTION 💜

So here's the tea, fr fr: this function releases memory that was allocated by dma_alloc_contiguous. It's the ✨ reverse ✨ of that one. Cleanup arc. We love to see it. 🧚

Now, the way it actually works is genuinely kind of iconic: cma_release returns false when the pages you provided do not belong to the contiguous area, and true otherwise. So the function checks that return value, and — plot twist — upon a false-return it does a fallback __free_pages. 🫶

Lowkey important: that false path means your pages weren't from the contiguous area, so it just frees them the regular way instead. Not me being dramatic — that's literally what the manpage says. 😭

So: true → CMA handled it. false → fallback __free_pages swings in and saves the day. Either way, the pages get freed. Slay. 🔥

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⭐ SEE ALSO ⭐

• Kernel file ./kernel/dma/contiguous.c 👀 (yes, that's where the source lives)
• dma_contiguous_get_area_by_idx(9)
• dma_contiguous_reserve(9)
• dma_contiguous_reserve_area(9)
• dma_alloc_from_contiguous(9)
• dma_release_from_contiguous(9)
• dma_alloc_contiguous(9)

All the siblings. The whole contiguous-family group chat. 🌈

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Okay that's the whole page, bestie — no filler, all facts. This lil' beauty comes to you courtesy of the source path ./kernel/dma, dated October 2026, in section 9 of the Kernel API Manual. Go free your pages responsibly. 🎀💅🦋