dma_direct_set_offset(9)

✨ NAME ✨

okay so bestie, this is from the Kernel API Manual — the function is dma_direct_set_offset, and its whole thing is assigning a scalar offset for a single DMA range. iconic behavior, honestly 💅

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🦋 SYNOPSIS 🦋

int dma_direct_set_offset (struct device *dev , phys_addr_t cpu_start ,
       dma_addr_t dma_start , u64 size );

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🎀 ARGUMENTS 🎀

• dev — a device pointer; it’s needed to "own" the alloced memory.
• cpu_start — the beginning of the memory region covered by this offset.
• dma_start — the beginning of the DMA/PCI region covered by this offset.
• size — the size of the region.

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🌸 DESCRIPTION 🌸

This is for the simple case of a uniform offset which cannot be discovered by "dma-ranges". lowkey straightforward, highkey specific 🫶

It returns -ENOMEM if out of memory, -EINVAL if a map already exists, 0 otherwise. periodt.

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💀 NOTE 💀

⚠️ bestie, listen: any call to this from a driver is a bug. The mapping needs to be described by the device tree or other firmware interfaces. not me stressing this, it’s literally in the note 😭

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🔥 SEE ALSO 🔥

• Kernel file ./kernel/dma/direct.c — go look, iykyk 👑

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byeee 🫶 — source/version: ./kernel/dma, date: October 2026, page: dma_direct_set_offset(9) 💖