[Bug 735660] v4l2: fix new v4l2 code not working with certain devices (regression)

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=735660
  GStreamer | gst-plugins-good | 1.4.1

--- Comment #24 from Hans de Goede <jwrdegoede at fedoraproject.org> 2014-08-30 13:43:34 UTC ---
Erm, should have waited a second before hitting commit.

So with old drivers all reqbufs(0) does is free kernel memory. But once it got
introduced, new drivers started requiring it to be done before doing a s_fmt,
as that makes resource management easier (no need to wait with returning an
error because the buffers are to small till the first qbuf)l, so it is very
much necessary for userspace to this now a days if it wants to re-negotiate the
fmt.

For old drivers which use the old videobuf, I would expect them to handle
things like bttv, as the whole notion of requiring userspace to explicitly
freeing buffers before changing fmt through a s_fmt call did not exist in the
old model, while re-negotiation was a normal thing to do back then too.

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