On Wednesday 09 May 2007, David Brownell wrote: > 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.
Thanks for the explanation. Shouldn't the usb_buffer_alloc mention that most drivers don't need cache-coherent DMA buffers ? Documentation/usb/dma.txt states that usb_buffer_alloc should be used as a generic USB memory allocator. Should that be changed as well ? Laurent Pinchart ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
