Re: [RFC, PATCH] gspca pac7302: propagate footer to userspace

[Hans de Goede <hdegoede@redhat.com>]

Hi Németh,

On 01/24/2010 06:20 PM, Németh Márton wrote:
> Hi,
>
> I'm dealing with Labtec Webcam 2200 and I found that the pac7302 driver does not
> forward the image footer information to userspace. This footer contains some information
> which might be interesting to the userspace. What exactly this footer means is
> not clear as of this writing, but it is easier to analyze the data in
> userspace than in kernel space.
>
> I modified the sd_pkt_scan() in order the footer is transfered to the userspace together
> with the image. This, however, breaks the image decoding in libv4lconvert. This is
> can be easily solved by passing the image buffer to v4lconvert_convert() truncated by
> 0x4f bytes.
>
> What do you think the right way would be to transfer image footer to userspace?

I agree that in retrospect sending the footer to userspace is a good
idea, but see below.

> Is it necessary to add a new V4L2_PIX_FMT_* format in order not to brake userspace
> programs?
>

Yes that is the only sensible way I see to do this, which IMHO is a too high price
to pay for just getting this info out of the kernel while we are not doing anything
with it. Now if we actually find a good use for this in userspace, then I think
we can do this, but until then I think you need to do this with a local
patch.

Regards,

Hans