[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

Nicolas Dufresne <nicolas.dufresne> changed:

           What    |Removed                     |Added
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 Attachment #284882|none                        |reviewed
             status|                            |

--- Comment #21 from Nicolas Dufresne <nicolas.dufresne at collabora.co.uk> 2014-08-30 12:49:55 UTC ---
Review of attachment 284882:
 --> (https://bugzilla.gnome.org/review?bug=735660&attachment=284882)

::: sys/v4l2/gstv4l2allocator.c
@@ +651,1 @@
+  GST_OBJECT_FLAG_SET (allocator, flags);

Thanks good catch

@@ +783,3 @@
         "error releasing buffers buffers: %s", g_strerror (errno));
+    /* Not all drivers support freeing buffers by requesting 0 buffers, so
+       we don't set ret to an error here. */

This has the side effect, as we won't be able to restart the allocator. Maybe
we should empty the atomic queue and deactivate the allocator even if freeing
buffers didn't work ?

Note, for all this to be useful, we'd need S_FMT to succeed even if there is
buffers allocated. Hans V. seemed to think this won't work. He said said the
only way we could change the format after having allocated buffers would be to
close and re-open. Would it be possible to double check that ?

If this is the case, we'd keep the code has is, I would simply like to add
something in the warning, so developers will know that re-negotiation isn't
possible for this device. They would then have the choice between trying to
port to VB2, or implement a close/re-open work around (both are fair amount of
work).

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