Re: REGRESSION: usbdevfs:Use-scatter-gather-lists-for-large-bulk-transfers

[Henrik Rydberg]

On Wed, Oct 10, 2012 at 10:34:59PM +0200, Peter Stuge wrote:
> Hej Henrik,
> 
> Henrik Rydberg wrote:
> > commit 3d97ff63f8997761f12c8fbe8082996c6eeaba1a
> > Author: Hans de Goede <hdegoede@xxxxxxxxxx>
> > Date:   Wed Jul 4 09:18:03 2012 +0200
> > 
> >     usbdevfs: Use scatter-gather lists for large bulk transfers
> >     
> > breaks an usb programming cable over here. The problem is reported as
> > "bulk tranfer failed" [sic] by the tool, and bisection leads to this
> > commit. Reverting on top of 3.6 solves it for me.
> > 
> > I am happy to test alternatives.
> 
> In order to make full use of the new kernel commit you also need
> changes in libusb, if the tool uses libusb, but I agree that the
> kernel change must under no circumstance cause existing userland
> software to regress.

Indeed.

> What is the programming cable and software that uses it?

The programmer is impact, using libusbx-1.0.14-1. The device runs the
xusbdfwu firmware. The (usb 2.0) bulk endpoint says wMaxPacketSize
1x512 bytes, and bInterval 0.

The patch is pretty generic, so I am suprised the problem has not
shown up earlier.

Henrik
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