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authorPawel Osciak <p.osciak@samsung.com>2010-04-28 07:05:23 (GMT)
committerMauro Carvalho Chehab <mchehab@redhat.com>2010-05-19 15:58:38 (GMT)
commit21636363be97725432591071d26dc0dca088ecbb (patch)
tree3448192f320a6385fb57c2e4585d4443dcd11696 /Documentation/DocBook
parentb2dfd1a45f014e24f0eecc50a7edc954425c348a (diff)
V4L/DVB: Add documentation for the new error flag
Add documentation for V4L2_BUF_FLAG_ERROR. Signed-off-by: Pawel Osciak <p.osciak@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'Documentation/DocBook')
-rw-r--r--Documentation/DocBook/v4l/io.xml10
-rw-r--r--Documentation/DocBook/v4l/vidioc-qbuf.xml14
2 files changed, 22 insertions, 2 deletions
diff --git a/Documentation/DocBook/v4l/io.xml b/Documentation/DocBook/v4l/io.xml
index bb685ed..d424886 100644
--- a/Documentation/DocBook/v4l/io.xml
+++ b/Documentation/DocBook/v4l/io.xml
@@ -702,6 +702,16 @@ They can be both cleared however, then the buffer is in "dequeued"
state, in the application domain to say so.</entry>
</row>
<row>
+ <entry><constant>V4L2_BUF_FLAG_ERROR</constant></entry>
+ <entry>0x0040</entry>
+ <entry>When this flag is set, the buffer has been dequeued
+ successfully, although the data might have been corrupted.
+ This is recoverable, streaming may continue as normal and
+ the buffer may be reused normally.
+ Drivers set this flag when the <constant>VIDIOC_DQBUF</constant>
+ ioctl is called.</entry>
+ </row>
+ <row>
<entry><constant>V4L2_BUF_FLAG_KEYFRAME</constant></entry>
<entry>0x0008</entry>
<entry>Drivers set or clear this flag when calling the
diff --git a/Documentation/DocBook/v4l/vidioc-qbuf.xml b/Documentation/DocBook/v4l/vidioc-qbuf.xml
index b843bd7..ab691eb 100644
--- a/Documentation/DocBook/v4l/vidioc-qbuf.xml
+++ b/Documentation/DocBook/v4l/vidioc-qbuf.xml
@@ -111,7 +111,11 @@ from the driver's outgoing queue. They just set the
and <structfield>reserved</structfield>
fields of a &v4l2-buffer; as above, when <constant>VIDIOC_DQBUF</constant>
is called with a pointer to this structure the driver fills the
-remaining fields or returns an error code.</para>
+remaining fields or returns an error code. The driver may also set
+<constant>V4L2_BUF_FLAG_ERROR</constant> in the <structfield>flags</structfield>
+field. It indicates a non-critical (recoverable) streaming error. In such case
+the application may continue as normal, but should be aware that data in the
+dequeued buffer might be corrupted.</para>
<para>By default <constant>VIDIOC_DQBUF</constant> blocks when no
buffer is in the outgoing queue. When the
@@ -158,7 +162,13 @@ enqueue a user pointer buffer.</para>
<para><constant>VIDIOC_DQBUF</constant> failed due to an
internal error. Can also indicate temporary problems like signal
loss. Note the driver might dequeue an (empty) buffer despite
-returning an error, or even stop capturing.</para>
+returning an error, or even stop capturing. Reusing such buffer may be unsafe
+though and its details (e.g. <structfield>index</structfield>) may not be
+returned either. It is recommended that drivers indicate recoverable errors
+by setting the <constant>V4L2_BUF_FLAG_ERROR</constant> and returning 0 instead.
+In that case the application should be able to safely reuse the buffer and
+continue streaming.
+ </para>
</listitem>
</varlistentry>
</variablelist>

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