dma_release...dev_coherent(9)

💅 dma_release_from_dev_coherent(9) — from the Kernel API Manual

okay so bestie, we're in the Kernel API Manual today and this one's a little function with main character energy — it's literally the "hey, this memory belongs to our pool, lemme hand it back" vibe check for device coherent memory. 🧚

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✨ NAME ✨

dma_release_from_dev_coherent — free memory back to the device coherent memory pool. that's it, that's the whole job. 💖

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🌸 SYNOPSIS 🌸

int dma_release_from_dev_coherent(struct device *dev, int order, void *vaddr);

like, three args, one int coming back at you. no cap. ✨

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🎀 ARGUMENTS 🎀

• dev — the device whose memory we're talking about, i.e. the one this memory was originally allocated from 🫶
• order — the order of the pages that were allocated. yes, order, like the buddy allocator kind, not like a coffee order 😭
• vaddr — the virtual address of the allocated pages. the actual pointer, the real one 💅

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💅 DESCRIPTION 💅

so here's the tea: this function checks whether that memory came out of the per-device coherent memory pool, and if it did — slay — it releases it. that's the whole loop, bestie. 🦋

the return value is doing a whole little two-party situation:

• returns 1 if we correctly released the memory 👑 (iconic, we did it)
• returns 0 if the caller should go ahead and release memory from the generic pools instead 🙈 (not our memory, not our problem)

literally just: "is this mine? yes → free it, return 1. no → return 0 and let the caller handle it elsewhere." periodt. 💀

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🌈 SEE ALSO 🌈

• Kernel file ./kernel/dma/coherent.c — the whole source neighborhood, go snoop 👀
• dma_alloc_from_dev_coherent(9) — the alloc counterpart, the origin story ⭐
• dma_mmap_from_dev_coherent(9) — the mmap one, for when you wanna map it too 🍓

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and that's the page!! source is ./kernel/dma, dated October 2026, and the footer's just echoing the same title back at you because the kernel doc build said so 💜 mwah, go free that coherent memory responsibly ✨🎀