Am Donnerstag, 28. Oktober 2004 17:01 schrieb Alan Stern:
> On Thu, 28 Oct 2004, Axel Waggershauser wrote:
>
> > Hi,
> >
> > I have to write a custom driver for a FX2 based camera module that
> > should be able to reach a bulk throughput of about 30 MBytes/sec from
> > the device to user space memory. The available CPU performance is less
> > than a 1GHz VIA EDEN. Is the libusb capable to provide this performance?
> >
> > If not, I guess I would have to write a driver that definitely makes
> > usage of scatter-gather lists to avoid unnecessary cpu involvement, is
> > that right? Is there a good starting point (documentation/examples) for
> > a "state of the art" sg-based usb driver?
> >
> > Thanks,
> > Axel
>
> I have no idea how fast libusb will run on your system, but it shouldn't
> be hard for you to test it.
30 MB/s is 45% of nominal PCI bandwidth and 50% of nominal USB2 throughput.
It would be interesting to see what libusb can do, but nobody should even
be slightly disappointed or surprised if it turns out to be significantly
less.
> AFAIK the only driver that uses sg-based transfers is usb-storage. The sg
> library routines are called from with drivers/usb/storage/transport.c, and
> they are well documented in drivers/usb/core/message.c.
You might have a look at usbvideo_StartDataPump() of usbvideo.c
Regards
Oliver
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