Re: video: USB webcam fails since kernel 3.2

[Hans de Goede]

Hi,

On 07/09/2012 01:33 PM, Martin-Ãric Racine wrote:

<snip>

> > Hmm, this is then likely caused by the new isoc bandwidth negotiation code
> > in 3.2, unfortunately the vc032x driver is one of the few gspca drivers
> > for which I don't have a cam to test with. Can you try to build your own
> > kernel from source?
> >
> > Boot into your own kernel, and verify the regression is still there,
> > then edit drivers/media/video/gspca/gspca.c and go to the which_bandwidth
> > function, and at the beginning of this function add the following line:
> >
> > return 2000 * 2000 * 120;
> >
> > Then rebuild and re-install the kernel and try again.
> >
> > If that helps, remove the added
> > return 2000 * 2000 * 120;
> > line, and also remove the following lines from which_bandwidth:
> >
> >          /* if the image is compressed, estimate its mean size */
> >          if (!gspca_dev->cam.needs_full_bandwidth &&
> >              bandwidth < gspca_dev->cam.cam_mode[i].width *
> >                                  gspca_dev->cam.cam_mode[i].height)
> >                  bandwidth = bandwidth * 3 / 8;  /* 0.375 */
> >
> > And try again if things still work this way.
> >
> > Once you've tested this I can try to write a fix for this.
>
> Hans,
>
> Thank you for your reply.
>
> Just to eliminate the possibility of mistakes on my part while trying
> to perform the above changes, could you send me a patch against Linux
> 3.2.21 that I could apply as-is, before building myself a test kernel
> package?

Erm, that is quite a bit of work from my side for something which you
can easily do yourself, edit gspca.c, search for which_bandwidth
and then under the following lines:
        u32 bandwidth;
        int i;

Add a line like this:
	return 2000 * 2000 * 120;

Regards,

Hans
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