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[media] V4L2 Spec: clarify usage of V4L2_FBUF_FLAG_PRIMARY

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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>
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Hans Verkuil 2011-11-07 08:30:20 -03:00 committed by Mauro Carvalho Chehab
parent 146d35b00d
commit 0fb6ec6b1c
1 changed files with 6 additions and 4 deletions
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Documentation/DocBook/media/v4l/vidioc-g-fbuf.xml
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@ -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>