Re: MAX_USBFS_BUFFER_SIZE

[Olivier Galibert]

On Wed, Mar 01, 2006 at 01:54:23PM -0800, Greg KH wrote:
> On Wed, Mar 01, 2006 at 10:42:35PM +0100, Ren? Rebe wrote:
> > 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.

As a data point, I have traces of a scanner session including a
download of a 26Mb binary image using 524288 bytes logical blocks
physically transferred with 61440 bytes bulk_in frames.  Seems stable
enough.  IIRC the scanner-side controller chip has some advanced
buffering just to handle that kind of bandwidth.

ISTR a preliminary linux userland driver using libusb having problems
keeping up with the scanner too.  May very well have been an issue
with the driver itself though, so I wouldn't read too much into that.

  OG.

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