For drivers that expose both an OUTPUT queue and
V4L2_EVENT_SRC_CH_RESOLUTION such as video decoders, it is
possible that support for this event is limited to a subset
of the enumerated OUTPUT formats.
This adds V4L2_CID_SUPPORTS_CH_RESOLUTION that allows such a driver to
notify userspace of per-format support for this event.
RFC notes: This patch is motivated by the work I'm doing on the Amlogic
video decoder where the firmwares allow me to support
V4L2_EVENT_SRC_CH_RESOLUTION for newer formats (H.264, HEVC..) but
can't support it for older ones (MPEG2, MPEG4, MJPEG..).
For the latter formats, userspace is expected to set the resolution via
S_FMT prior to decoding.
Signed-off-by: Maxime Jourdan <mjour...@baylibre.com>
---
Documentation/media/uapi/v4l/control.rst | 7 +++++++
drivers/media/v4l2-core/v4l2-ctrls.c | 3 +++
include/uapi/linux/v4l2-controls.h | 4 +++-
3 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/Documentation/media/uapi/v4l/control.rst
b/Documentation/media/uapi/v4l/control.rst
index c1e6adbe83d7..029a4e88bfd5 100644
--- a/Documentation/media/uapi/v4l/control.rst
+++ b/Documentation/media/uapi/v4l/control.rst
@@ -297,6 +297,13 @@ Control IDs
set the alpha component value of all pixels for further processing
in the device.
+``V4L2_CID_SUPPORTS_CH_RESOLUTION`` ``(boolean)``
+ This is a read-only control that can be read by the application when
+ the driver exposes an OUTPUT queue and event
+ ``V4L2_EVENT_SRC_CH_RESOLUTION`` but doesn't support it for every
+ OUTPUT format. It returns true if the currently selected OUTPUT format
+ supports this event.
+
``V4L2_CID_LASTP1``
End of the predefined control IDs (currently
``V4L2_CID_ALPHA_COMPONENT`` + 1).
diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c
b/drivers/media/v4l2-core/v4l2-ctrls.c
index 599c1cbff3b9..a8037ff3935a 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -739,6 +739,7 @@ const char *v4l2_ctrl_get_name(u32 id)
case V4L2_CID_MIN_BUFFERS_FOR_OUTPUT: return "Min Number of Output
Buffers";
case V4L2_CID_ALPHA_COMPONENT: return "Alpha Component";
case V4L2_CID_COLORFX_CBCR: return "Color Effects, CbCr";
+ case V4L2_CID_SUPPORTS_CH_RESOLUTION: return "Supports Change
Resolution";
/* Codec controls */
/* The MPEG controls are applicable to all codec controls
@@ -1074,6 +1075,8 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum
v4l2_ctrl_type *type,
*flags = 0;
switch (id) {
+ case V4L2_CID_SUPPORTS_CH_RESOLUTION:
+ *flags |= V4L2_CTRL_FLAG_READ_ONLY;
case V4L2_CID_AUDIO_MUTE:
case V4L2_CID_AUDIO_LOUDNESS:
case V4L2_CID_AUTO_WHITE_BALANCE:
diff --git a/include/uapi/linux/v4l2-controls.h
b/include/uapi/linux/v4l2-controls.h
index e4ee10ee917d..c874fdd28f40 100644
--- a/include/uapi/linux/v4l2-controls.h
+++ b/include/uapi/linux/v4l2-controls.h
@@ -141,8 +141,10 @@ enum v4l2_colorfx {
#define V4L2_CID_ALPHA_COMPONENT (V4L2_CID_BASE+41)
#define V4L2_CID_COLORFX_CBCR (V4L2_CID_BASE+42)
+#define V4L2_CID_SUPPORTS_CH_RESOLUTION (V4L2_CID_BASE+43)
+
/* last CID + 1 */
-#define V4L2_CID_LASTP1 (V4L2_CID_BASE+43)
+#define V4L2_CID_LASTP1 (V4L2_CID_BASE+44)
/* USER-class private control IDs */
--
2.19.0
