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authorHans Verkuil <hverkuil@xs4all.nl>2018-09-17 07:37:18 -0400
committerMauro Carvalho Chehab <mchehab+samsung@kernel.org>2018-10-04 14:26:10 -0400
commit1611c686c1245408c3ddb451b2a5fff1dc088d6e (patch)
treef1b267cf456b8481fea55e7466b0b06723a6c7ff /Documentation/media
parent85e4af0a7ae2f146769b7475ae531bf8a3f3afb4 (diff)
downloadlinux-1611c686c1245408c3ddb451b2a5fff1dc088d6e.tar.bz2
media: vidioc-dqevent.rst: clarify V4L2_EVENT_SRC_CH_RESOLUTION
Clarify that when you receive V4L2_EVENT_SOURCE_CHANGE with flag V4L2_EVENT_SRC_CH_RESOLUTION set, and the new resolution appears identical to the old resolution, then you still must restart the streaming I/O. Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Diffstat (limited to 'Documentation/media')
-rw-r--r--Documentation/media/uapi/v4l/vidioc-dqevent.rst12
1 files changed, 11 insertions, 1 deletions
diff --git a/Documentation/media/uapi/v4l/vidioc-dqevent.rst b/Documentation/media/uapi/v4l/vidioc-dqevent.rst
index cb3565f36793..04416b6943c0 100644
--- a/Documentation/media/uapi/v4l/vidioc-dqevent.rst
+++ b/Documentation/media/uapi/v4l/vidioc-dqevent.rst
@@ -379,7 +379,17 @@ call.
- 0x0001
- This event gets triggered when a resolution change is detected at
an input. This can come from an input connector or from a video
- decoder.
+ decoder. Applications will have to query the new resolution (if
+ any, the signal may also have been lost).
+
+ *Important*: even if the new video timings appear identical to the old
+ ones, receiving this event indicates that there was an issue with the
+ video signal and you must stop and restart streaming
+ (:ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>`
+ followed by :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>`). The reason is
+ that many devices are not able to recover from a temporary loss of
+ signal and so restarting streaming I/O is required in order for the
+ hardware to synchronize to the video signal.
Return Value