Re: MAX_USBFS_BUFFER_SIZE

[Greg KH <greg@kroah.com>]

On Wed, Mar 01, 2006 at 10:42:35PM +0100, Ren? Rebe wrote:
> Hi,
> 
> On Wednesday 01 March 2006 22:32, Greg KH wrote:
> > On Wed, Mar 01, 2006 at 09:16:25PM +0100, Ren?? Rebe wrote:
> > > Hi,
> > > 
> > > I wonder if:
> > > 
> > > drivers/usb/core/devio.c:86
> > > #define MAX_USBFS_BUFFER_SIZE   16384
> > > 
> > > is some random, or outdated limit or if there really is some code path that could
> > > not handle bigger URBs.
> > > 
> > > For performance reasons I would like to use bigger packages for an image
> > > aquisition device.
> > 
> > Why not just send down 2 urbs with that size then, that would keep the
> > pipe quite full.
> 
> Because that requires even more modifications to libusb and sane (i_usb) ...

No, do it in your application I mean.

> So, queing alot URBs is the recommended way to sustain the bus? Allowing
> way bigger buffers will not be realistic?

16Kb is "way big" in the USB scheme of things aready.  Look at the size
of your endpoint.  It's probably _very_ small compared to that.  So no,
larger buffer sizes is not realistic at all.

thanks,

greg k-h