CONFIG_ARM_DMA_IOMMU_ALIGNMENT: Maximum PAGE_SIZE order of alignment for DMA IOMMU buffers

General informations

The Linux kernel configuration item CONFIG_ARM_DMA_IOMMU_ALIGNMENT:

• prompt: Maximum PAGE_SIZE order of alignment for DMA IOMMU buffers
• type: int
• depends on: (none)
• defined in arch/arm/Kconfig
• found in Linux kernels: 3.9–3.19, 4.0–4.20, 5.0–5.19, 6.0–6.8, 6.9-rc+HEAD

Help text

DMA mapping framework by default aligns all buffers to the smallest PAGE_SIZE order which is greater than or equal to the requested buffer size. This works well for buffers up to a few hundreds kilobytes, but for larger buffers it just a waste of address space. Drivers which has relatively small addressing window (like 64Mib) might run out of virtual space with just a few allocations.

With this parameter you can specify the maximum PAGE_SIZE order for DMA IOMMU buffers. Larger buffers will be aligned only to this specified order. The order is expressed as a power of two multiplied by the PAGE_SIZE.

Hardware

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Sources

This page is automaticly generated with free (libre, open) software lkddb(see lkddb-sources).

The data is retrived from:

• Linux kernel
• Linux Kernel Driver DataBase (LKDDb)

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