linux-kernel - Re: [Patch] Increase USBFS Bulk Transfer size

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Date:	Sun, 16 Oct 2011 10:18:28 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Johannes Stezenbach <js@...21.net>
cc:	Markus Rechberger <mrechberger@...il.com>,
	Greg KH <gregkh@...e.de>, USB list <linux-usb@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [Patch] Increase USBFS Bulk Transfer size

On Sun, 16 Oct 2011, Johannes Stezenbach wrote:

> On Sat, Oct 15, 2011 at 03:04:28PM -0400, Alan Stern wrote:
> > On Sat, 15 Oct 2011, Johannes Stezenbach wrote:
> > 
> > > What I meant to say is Markus' statement that the device only
> > > works at a certain transfer size cannot be true since
> > > this size is not visible to the device via the USB bus.
> > 
> > That's what I would expect, too.  But did you take a look at the usbmon 
> > traces Markus acquired?
> > 
> > 	http://marc.info/?l=linux-usb&m=131845614819045&w=2
> 
> I glanced at them for 3 seconds, but I cannot be bothered
> to analyze them in detail.  The ASCII usbmon traces don't
> show full USB packet contents anyway so you can't see if
> partial MPEG TS packets are missing.

> The device transfers data in the "not working" case, it's just that
> the MPEG TS sync byte is not where Markus expects it, which could
> be explained by a partial MPEG TS packet left in the device's FIFO
> from previous interaction.

But why does this happen only when the transfer size is different from
24064?  Why doesn't it also happen when the transfer size _is_ 24064?

Alan Stern

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