Re: uvcvideo failure under xHCI

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Sarah,

On Friday 17 June 2011 20:19:01 Sarah Sharp wrote:
> On Fri, Jun 17, 2011 at 07:01:10PM +0200, Laurent Pinchart wrote:
> > On Friday 17 June 2011 18:46:20 Sarah Sharp wrote:
> > > On Fri, Jun 17, 2011 at 10:18:39AM +0200, Laurent Pinchart wrote:
> > > > On Thursday 16 June 2011 22:20:22 Alan Stern wrote:
> > > > > On Thu, 16 Jun 2011, Sarah Sharp wrote:
> > > > > > On Thu, Jun 16, 2011 at 03:39:11PM -0400, Alan Stern wrote:
> > > > > > > That's appropriate.  But nobody should ever set an isochronous
> > > > > > > URB's status field to -EPROTO, no matter whether the device is
> > > > > > > connected or not and no matter whether the host controller is
> > > > > > > alive or not.
> > > > > > 
> > > > > > But the individual frame status be set to -EPROTO, correct? 
> > > > > > That's what Alex was told to do when an isochronous TD had a
> > > > > > completion code of "Incompatible Device Error".
> > > > > 
> > > > > Right.  -EPROTO is a perfectly reasonable code for a frame's
> > > > > status. But not for an isochronous URB's status.  There's no
> > > > > reason for uvcvideo to test for it.
> > > > 
> > > > The uvcvideo driver tests for -EPROTO for interrupt URBs only. For
> > > > isochronous URBs it tests for -ENOENT, -ECONNRESET and -ESHUTDOWN.
> > > 
> > > So is uvc_status_complete() shared between interrupt and isochronous
> > > URBs then?
> > 
> > No, uvc_status_complete() handles status URBs (interrupt only), and
> > uvc_video_complete() handles video URBs (isochronous or bulk, depending
> > on the device).
> 
> Huh, that's very odd then.  I could have sworn I was getting missed
> service interval events (which are only for isochronous transfers) and
> then seeing the "Non-zero" message.  And the userspace video definitely
> froze before my patch and did not freeze after the patch was applied.
> I'll have to look more closely at the logs.

The log excerpt message you posted was

Jun 15 17:37:11 talon kernel: [  117.987769] uvcvideo: Non-zero status (-18) 
in video completion handler.

That's printed by uvc_video_complete(). uvc_status_complete() would have 
printed "Non-zero status (-18) in status completion handler". There's nothing 
wrong with your analysis of the problem, you just picked the wrong uvcvideo 
function.

-- 
Regards,

Laurent Pinchart