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-rw-r--r--Documentation/DocBook/v4l/vidioc-qbuf.xml14
1 files changed, 12 insertions, 2 deletions
diff --git a/Documentation/DocBook/v4l/vidioc-qbuf.xml b/Documentation/DocBook/v4l/vidioc-qbuf.xml
index b843bd7b3897..ab691ebf3b93 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
111and <structfield>reserved</structfield> 111and <structfield>reserved</structfield>
112fields of a &v4l2-buffer; as above, when <constant>VIDIOC_DQBUF</constant> 112fields of a &v4l2-buffer; as above, when <constant>VIDIOC_DQBUF</constant>
113is called with a pointer to this structure the driver fills the 113is called with a pointer to this structure the driver fills the
114remaining fields or returns an error code.</para> 114remaining fields or returns an error code. The driver may also set
115<constant>V4L2_BUF_FLAG_ERROR</constant> in the <structfield>flags</structfield>
116field. It indicates a non-critical (recoverable) streaming error. In such case
117the application may continue as normal, but should be aware that data in the
118dequeued buffer might be corrupted.</para>
115 119
116 <para>By default <constant>VIDIOC_DQBUF</constant> blocks when no 120 <para>By default <constant>VIDIOC_DQBUF</constant> blocks when no
117buffer is in the outgoing queue. When the 121buffer is in the outgoing queue. When the
@@ -158,7 +162,13 @@ enqueue a user pointer buffer.</para>
158 <para><constant>VIDIOC_DQBUF</constant> failed due to an 162 <para><constant>VIDIOC_DQBUF</constant> failed due to an
159internal error. Can also indicate temporary problems like signal 163internal error. Can also indicate temporary problems like signal
160loss. Note the driver might dequeue an (empty) buffer despite 164loss. Note the driver might dequeue an (empty) buffer despite
161returning an error, or even stop capturing.</para> 165returning an error, or even stop capturing. Reusing such buffer may be unsafe
166though and its details (e.g. <structfield>index</structfield>) may not be
167returned either. It is recommended that drivers indicate recoverable errors
168by setting the <constant>V4L2_BUF_FLAG_ERROR</constant> and returning 0 instead.
169In that case the application should be able to safely reuse the buffer and
170continue streaming.
171 </para>
162 </listitem> 172 </listitem>
163 </varlistentry> 173 </varlistentry>
164 </variablelist> 174 </variablelist>