arm_iommu_unmap_sg(9)

📦 version 7.3.1, in nixpkgs unstable

💫 arm_iommu_unmap_sg 💫

okay bestie, welcome to the Kernel API Manual — this little page is all about arm_iommu_unmap_sg, and fr fr it's the cleanup queen of the scatter-gather world 🧹✨

🌸 NAME 🌸

arm_iommu_unmap_sg — unmaps a whole set of SG buffers that were mapped by dma_map_sg 🫶

✨ SYNOPSIS ✨

void arm_iommu_unmap_sg (struct device *dev , struct scatterlist *sg ,
int nents , enum dma_data_direction dir , unsigned long attrs );

no cap, that's the whole signature — five params, one vibe 💅

🎀 ARGUMENTS 🎀

  • dev — a valid struct device pointer. like, valid valid, don't be out here passing nonsense 🙈
  • sg — the list of buffers. the whole little squad of them 🦋
  • nents — how many buffers to unmap. and bestie, it has to be the same number that was passed to dma_map_sg, okay? no matching game 💀
  • dir — the DMA transfer direction. again, same as what was passed to dma_map_sg — it's giving "consistency is the moment" ⭐
  • attrs — -- undescribed -- 😭 literally the manpage itself said nothing about this one, so I'm not gonna invent lore that isn't there. she's mysterious, she's undefined, we respect her privacy 🎭

🔥 DESCRIPTION 🔥

So what does she actually do? She unmaps a set of streaming mode DMA translations. that's the whole job, and she ate 💅

And again — the CPU access rules concerning calls here are the same as for dma_unmap_single. so if you already know how that one behaves around CPU access, you already know this one too. iykyk 🌈

⚠️ quick vibe check: that "same rules as dma_unmap_single" thing is the real tea — treat the CPU access constraints here exactly like you would there, no shortcuts 🍓

👑 SEE ALSO 👑

Kernel file ./arch/arm/mm/dma-mapping.c, plus the whole friend group:

go read them, they're iconic, each and every one 🌟

and that's the page!! mwah 💖 this little gem lives over in ./arch/arm/mm, dated October 2026, and it's filed right under arm_iommu_unmap_sg(9) in the Kernel API Manual — go unmap those buffers responsibly, bestie, ily 🫶🎀

📦 where this page comes from