linux-kernel - [PATCH] v4l: Add source change event for colorimetry

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Date:   Thu,  2 Jul 2020 13:00:17 +0300
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Tomasz Figa <tfiga@...omium.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Stanimir Varbanov <stanimir.varbanov@...aro.org>
Subject: [PATCH] v4l: Add source change event for colorimetry

This event indicate that the source colorspace is changed
during run-time. The client has to retrieve the new colorspace
identifiers by getting the format (G_FMT).

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@...aro.org>
---
 .../userspace-api/media/v4l/vidioc-dqevent.rst        | 11 ++++++++++-
 .../userspace-api/media/videodev2.h.rst.exceptions    |  1 +
 include/uapi/linux/videodev2.h                        |  1 +
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/Documentation/userspace-api/media/v4l/vidioc-dqevent.rst b/Documentation/userspace-api/media/v4l/vidioc-dqevent.rst
index a9a176d5256d..3f69c753db58 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-dqevent.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-dqevent.rst
@@ -381,7 +381,16 @@ call.
 	that many Video Capture 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.
-
+    * - ``V4L2_EVENT_SRC_CH_COLORIMETRY``
+      - 0x0002
+      - This event gets triggered when a colorspace change is detected at
+	an input. By colorspace change here we include also changes in the
+	colorspace specifiers (transfer function, Y'CbCr encoding and
+	quantization). This event can come from an input or from video decoder.
+	Once the event has been send to the client the driver has to update
+	the colorspace specifiers internally so that they could be retrieved by
+	client. In that case queue re-negotiation is not needed as this change
+	only reflects on the interpretation of the data.
 
 Return Value
 ============
diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
index ca05e4e126b2..54fc21af852d 100644
--- a/Documentation/userspace-api/media/videodev2.h.rst.exceptions
+++ b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
@@ -492,6 +492,7 @@ replace define V4L2_EVENT_CTRL_CH_FLAGS ctrl-changes-flags
 replace define V4L2_EVENT_CTRL_CH_RANGE ctrl-changes-flags
 
 replace define V4L2_EVENT_SRC_CH_RESOLUTION src-changes-flags
+replace define V4L2_EVENT_SRC_CH_COLORIMETRY src-changes-flags
 
 replace define V4L2_EVENT_MD_FL_HAVE_FRAME_SEQ :c:type:`v4l2_event_motion_det`
 
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 303805438814..b5838bc4e3a3 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -2351,6 +2351,7 @@ struct v4l2_event_frame_sync {
 };
 
 #define V4L2_EVENT_SRC_CH_RESOLUTION		(1 << 0)
+#define V4L2_EVENT_SRC_CH_COLORIMETRY		(1 << 1)
 
 struct v4l2_event_src_change {
 	__u32 changes;
-- 
2.17.1