Re: New USB stack on FreeBSD w/Linux emulation layer coming

Am Dienstag, 22. Mai 2007 17:23 schrieb Alan Stern:
> On Tue, 22 May 2007, Laurent Pinchart wrote:
> 
> > The usb_buffer_alloc name is misleading. Many USB driver developers believe it 
> > is a generic purpose buffer allocator.
> > 
> > I'd like to change usb_buffer_alloc to make it a general purpose allocator. A 
> > parameter would tell the function to just allocate memory (default behaviour) 
> > or to allocate a DMA coherent mapping as well. We could even pass the URB 
> > pointer to the function to set the URB_TRANSFER_NO_DMA_MAP automatically 
> > (although usb_buffer_alloc can be used to allocate the setup buffer, so the 
> > API might have to be a little different).
> 
> It would be simpler and less objectionable to just change the name of 
> the routine.  If it were called usb_alloc_coherent_DMA_buffer() then 
> people wouldn't be tempted to think it was a general-purpose allocator.

I thought a bit about this. Maybe there _is_ room for an allocator that
will provide memory the HCD can get at, but without the full overhead
of allocating a coherent buffer.

	Regards
		Oliver

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