Re: Split bulk transfers

On Wednesday 09 May 2007, Laurent Pinchart wrote:

> Could you elaborate a bit on the subject ? Which allocator calls should I 
> use ? Just kmalloc ? When does a USB driver need cache coherent buffers ?

Using kmalloc() should be fine.

The original use-case for cache-coherent DMA buffers was HID on SPARC,
for keyboard and mouse.  The HID report buffers are about 8 bytes, and
using dma-coherent buffers was a *lot* cheaper than IOMMU operation for
dma map/unmap on every keystroke or mouse gesture.

- Dave

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