LinuxTV Patchwork [v6,2/4] media: videodev2: add V4L2_FMT_FLAG_FIXED_RESOLUTION

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Submitter Maxime Jourdan
Date May 14, 2019, 1:56 p.m.
Message ID <>
Download mbox | patch
Permalink /patch/56156/
State New
Delegated to: Hans Verkuil
Headers show


Maxime Jourdan - May 14, 2019, 1:56 p.m.
When a v4l2 driver exposes V4L2_EVENT_SOURCE_CHANGE, some (usually
OUTPUT) formats may not be able to trigger this event.

For instance, MPEG2 on Amlogic hardware does not support resolution
switching on the fly, and a decode session must operate at a set
resolution defined before the decoding start.

Add a enum_fmt format flag to tag those specific formats.

Signed-off-by: Maxime Jourdan <>
 Documentation/media/uapi/v4l/vidioc-enum-fmt.rst | 6 ++++++
 include/uapi/linux/videodev2.h                   | 5 +++--
 2 files changed, 9 insertions(+), 2 deletions(-)


diff --git a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
index 822d6730e7d2..b11448a1848b 100644
--- a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
+++ b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
@@ -127,6 +127,12 @@  one until ``EINVAL`` is returned.
       - This format is not native to the device but emulated through
 	software (usually libv4l2), where possible try to use a native
 	format instead for better performance.
+      - 0x0004
+      - Dynamic resolution switching is not supported for this format,
+        even if the event ``V4L2_EVENT_SOURCE_CHANGE`` is supported by
+        the device.
 Return Value
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 1050a75fb7ef..9b0a7f82dd92 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -768,8 +768,9 @@  struct v4l2_fmtdesc {
 	__u32		    reserved[4];
-#define V4L2_FMT_FLAG_COMPRESSED 0x0001
-#define V4L2_FMT_FLAG_EMULATED   0x0002
+#define V4L2_FMT_FLAG_COMPRESSED	0x0001
+#define V4L2_FMT_FLAG_EMULATED		0x0002
 	/* Frame Size and frame rate enumeration */

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