linux-kernel - [PATCH v5 2/4] media: videodev2: add V4L2_FMT_FLAG_FIXED

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Date:   Mon,  1 Apr 2019 15:38:43 +0200
From:   Maxime Jourdan <mjourdan@...libre.com>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     Maxime Jourdan <mjourdan@...libre.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org
Subject: [PATCH v5 2/4] media: videodev2: add V4L2_FMT_FLAG_FIXED_RESOLUTION

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 <mjourdan@...libre.com>
---
 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.
+    * - ``V4L2_FMT_FLAG_FIXED_RESOLUTION``
+      - 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 1db220da3bcc..9c8a2d2e7bc6 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -751,8 +751,9 @@ 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
+#define V4L2_FMT_FLAG_FIXED_RESOLUTION	0x0004
 
 	/* Frame Size and frame rate enumeration */
 /*
-- 
2.21.0