Re: g_webcam Isoch high bandwidth transfer

[Bin Liu <b-liu@ti.com>]

On Fri, Sep 23, 2016 at 10:49:57AM +0300, Felipe Balbi wrote:
> 
> Hi,
> 
> Bin Liu <b-liu@ti.com> writes:
> > +Fengwei Yin per his request.
> >
> > On Thu, Sep 22, 2016 at 10:48:40PM +0300, Felipe Balbi wrote:
> >> 
> >> Hi,
> >> 
> >> Bin Liu <b-liu@ti.com> writes:
> >> 
> >> [...]
> >> 
> >> >> Here's one that actually compiles, sorry about that.
> >> >
> >> > No worries, I was sleeping ;-)
> >> >
> >> > I will test it out early next week. Thanks.
> >> 
> >> meanwhile, how about some instructions on how to test this out myself?
> >> How are you using g_webcam and what are you running on host side? Got a
> >> nice list of commands there I can use? I think I can get to bottom of
> >> this much quicker if I can reproduce it locally ;-)
> >
> > On device side:
> > - first patch g_webcam as in my first email in this thread to enable
> >   640x480@30fps;
> > - # modprobe g_webcam streaming_maxpacket=3072
> > - then run uvc-gadget to feed the YUV frames;
> > 	http://git.ideasonboard.org/uvc-gadget.git
> 
> as is, g_webcam never enumerates to the host. It's calls to

Right, on mainline kernel (I tested 4.8.0-rc7) g_webcam is broken with
DWC3, g_webcam does not enumerate on the host. But it works on v4.4.21.

[snip]

> 
> uvc-gadget keeps printing this error message:
> 
>  159         if ((ret = ioctl(dev->fd, VIDIOC_DQBUF, &buf)) < 0) {
>  160                 printf("Unable to dequeue buffer: %s (%d).\n", strerror(errno),
>  161                         errno);
>  162                 return ret;
>  163         }

I removed this printf, since it floods the console if start uvc-gadget
before connect to the host.

BTY, you don't have to start uvc-gadget first then connect usb cable. I
keep the cable always connected.

Regards,
-Bin.