linux-kernel - Re: [PATCH 1/1] usb: gadget: Don't attempt to dequeue requests for a disabled USB endpoint on Freescale hardware

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Message-ID: <20121026081448.GD23501@arwen.pp.htv.fi>
Date:	Fri, 26 Oct 2012 11:14:48 +0300
From:	Felipe Balbi <balbi@...com>
To:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
CC:	<balbi@...com>, Li Yang-R58472 <r58472@...escale.com>,
	Simon Haggett <simon.haggett@...lvnc.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] usb: gadget: Don't attempt to dequeue requests for a
 disabled USB endpoint on Freescale hardware

Hi,

On Thu, Oct 25, 2012 at 02:36:24AM +0200, Laurent Pinchart wrote:
> Hi Felipe,
> 
> On Monday 22 October 2012 13:56:01 Felipe Balbi wrote:
> > On Mon, Oct 22, 2012 at 12:47:21PM +0200, Laurent Pinchart wrote:
> > > On Monday 22 October 2012 03:33:19 Li Yang-R58472 wrote:
> > > > On Saturday, October 20, 2012 1:37 AM Felipe Balbi wrote:
> > > > > On Fri, Oct 19, 2012 at 06:19:26PM +0100, Simon Haggett wrote:
> > > > > > Some gadget drivers may attempt to dequeue requests for an endpoint
> > > > > > that has already been disabled. For example, in the UVC gadget
> > > > > > driver, uvc_function_set_alt() will call usb_ep_disable() when alt
> > > > > > setting 0 is selected. When the userspace application subsequently
> > > > > > issues the VIDIOC_STREAMOFF ioctl, uvc_video_enable() invokes
> > > > > > usb_ep_dequeue() to ensure that all requests have been cancelled.
> > > > > 
> > > > > bug is on uvc gadget, then. Laurent ?
> > > 
> > > We've discussed this topic a couple of months before. I believe that's not
> > > a bug.
> > > 
> > > http://68.183.106.108/lists/linux-usb/msg68869.html
> > 
> > fair enough :-)
> > 
> > That's a different case, however. At the link above we're discussing
> > dequeueing a request which is already being dequeued. $SUBJECT is trying
> > to fix dequeueing of a request for an endpoint which isn't even enabled.
> 
> You've got a point there :-) That's a different case indeed, I'm open to (at 
> least evaluating) a fix in the UVC gadget driver if you think that's better.

I _do_ think that's better. If the endpoint isn't even enabled, why are
you trying to dequeue a request ? :-)

cheers

-- 
balbi

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