Re: New USB stack on FreeBSD w/Linux emulation layer coming
David Brownell <[email protected]>
| Newsgroups | gmane.linux.usb.devel |
|---|---|
| Message-ID | <[email protected]> |
On Wednesday 16 May 2007, Hans Petter Selasky wrote:
> On the BSD platform there is something called BUS-DMA. Memory is allocated
> according to PCI device capabilities. This is because sometimes the PCI
> device is not capable of addressing the complete memory. Also you need to
> sync memory, like on the SUN architecture. Then you need to send specific
> commands to the PCI-bridge, for example "pshyco". From what I see your model
> will not work in all cases.
Those issues are handled by the DMA framework, transparently to USB.
> > Transfer descriptors are an artifact of one kind of host controller;
> > it'd be wrong to assume all HCDs use them.
>
> As long as the core information is not in the header of an USB transfer, like
> IP-packets have an header, you cannot ignore this.
Strange how it seems to work already though, having factored the
problem differently ... I think that word ("cannot") doesn't mean
what you think it means!!
- Dave
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