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authorHans Verkuil <hans.verkuil@cisco.com>2011-11-07 08:30:20 -0300
committerMauro Carvalho Chehab <mchehab@redhat.com>2011-11-25 15:07:22 -0200
commit0fb6ec6b1c185a1d99bf238880cc265d72ab111b (patch)
tree3a42dbfd3deafd638ce8706e9c362e4e49dd401e /Documentation/DocBook/media/v4l
parent146d35b00db270054378de17ca33eb54b0b78311 (diff)
[media] V4L2 Spec: clarify usage of V4L2_FBUF_FLAG_PRIMARY
As per discussion during the 2011 V4L-DVB workshop. Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'Documentation/DocBook/media/v4l')
-rw-r--r--Documentation/DocBook/media/v4l/vidioc-g-fbuf.xml10
1 files changed, 6 insertions, 4 deletions
diff --git a/Documentation/DocBook/media/v4l/vidioc-g-fbuf.xml b/Documentation/DocBook/media/v4l/vidioc-g-fbuf.xml
index 055718231bc..109d7294d35 100644
--- a/Documentation/DocBook/media/v4l/vidioc-g-fbuf.xml
+++ b/Documentation/DocBook/media/v4l/vidioc-g-fbuf.xml
@@ -295,7 +295,8 @@ set this field to zero.</entry>
<entry>The device is capable of non-destructive overlays.
When the driver clears this flag, only destructive overlays are
supported. There are no drivers yet which support both destructive and
-non-destructive overlays.</entry>
+non-destructive overlays. Video Output Overlays are in practice always
+non-destructive.</entry>
</row>
<row>
<entry><constant>V4L2_FBUF_CAP_CHROMAKEY</constant></entry>
@@ -356,7 +357,9 @@ with the chroma-key colors are replaced by video pixels, which is exactly opposi
<entry><constant>V4L2_FBUF_FLAG_PRIMARY</constant></entry>
<entry>0x0001</entry>
<entry>The framebuffer is the primary graphics surface.
-In other words, the overlay is destructive. [?]</entry>
+In other words, the overlay is destructive. This flag is typically set by any
+driver that doesn't have the <constant>V4L2_FBUF_CAP_EXTERNOVERLAY</constant>
+capability and it is cleared otherwise.</entry>
</row>
<row>
<entry><constant>V4L2_FBUF_FLAG_OVERLAY</constant></entry>
@@ -366,9 +369,8 @@ size as the capture. [?]</entry>
</row>
<row>
<entry spanname="hspan">The purpose of
-<constant>V4L2_FBUF_FLAG_PRIMARY</constant> and
<constant>V4L2_FBUF_FLAG_OVERLAY</constant> was never quite clear.
-Most drivers seem to ignore these flags. For compatibility with the
+Most drivers seem to ignore this flag. For compatibility with the
<wordasword>bttv</wordasword> driver applications should set the
<constant>V4L2_FBUF_FLAG_OVERLAY</constant> flag.</entry>
</row>