[PATCH v6 2/5] media: uapi: Introduce new control for video encoder ROI

[Deepa Guthyappa Madivalara <deepa.madivalara@oss.qualcomm.com>]

Add array control, V4L2_CID_MPEG_VIDEO_ROI_MB_DELTA_QP for
video encoder Region of Interest to allow applications to specify
different quality levels for specific regions in video frames. Define
V4L2_CID_MPEG_VIDEO_ROI_MB_SIZE to retrieve supported MB size based on
codec from the hardware encoder and set the corresponding ROI MB delta_qp
map that adjusts quantization relative to the frame QP's base value.

This enables use cases like prioritizing quality for faces in video
conferencing or important objects in surveillance footage while reducing
bitrate for less critical areas.

Signed-off-by: Deepa Guthyappa Madivalara <deepa.madivalara@oss.qualcomm.com>
---
 .../userspace-api/media/v4l/ext-ctrls-codec.rst    | 26 ++++++++++++++++++++++
 drivers/media/v4l2-core/v4l2-ctrls-core.c          |  3 +++
 drivers/media/v4l2-core/v4l2-ctrls-defs.c          | 10 +++++++++
 include/uapi/linux/v4l2-controls.h                 |  2 ++
 4 files changed, 41 insertions(+)

diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
index ab865a1a6ba929f1725ce2ab0fd3aeee4a69329a..a02ec20ec18f0e684973964d2de1759ad179b819 100644
--- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
+++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
@@ -1674,6 +1674,32 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
     Codecs need to always use the specified range, rather then a HW custom range.
     Applicable to encoders
 
+``V4L2_CID_MPEG_VIDEO_ROI_MB_DELTA_QP (__s8 array)``
+    This control is a dynamically sized 1-dimensional array,
+    V4L2_CTRL_FLAG_DYNAMIC_ARRAY flag must be set when using it.
+    This array control is used to set ROI MB map delta_Qp for the whole frame.
+    The frame is divided into a grid of MB Size by MB Size pixels (MB Size is
+    obtained from querying ``V4L2_CID_MPEG_VIDEO_ROI_MB_SIZE``). Each block
+    is configured with delta_Qp in raster order. The valid range for delta_Qp
+    is encoder dependent.
+    Applicable to encoders.
+
+``V4L2_CID_MPEG_VIDEO_ROI_MB_SIZE`` (integer)
+    A read-only control that reports the MB Size used for the ROI delta_QP map.
+    The supported MB Size depends on the encoder codec.
+    Only square MBs are supported. The value returned represents the
+    width and height of each block in pixels. The ROI delta_QP map provided
+    through the ROI control must use the MB Size reported by this control.
+    The number of entries in the ROI delta_QP array is determined by the
+    frame resolution and the reported MB Size. If frame_width or frame_height
+    is not MB Size aligned, they must be ceiled using ceil(frame_width/MB Size)
+    ceil(frame_height/MB Size) for calculating the array size.
+    For example, for a QCIF frame if reported MB Size is 16,
+    the delta_QP array must contain 99 entries, ceil(176/16) * ceil(144/16) = 99.
+    For frame resolutions that are not aligned to the MB size, for example
+    1920x1080, if the reported MB size is 32, the delta_qp array
+    must contain ceil(1920/32) * ceil(1080/32) = 2040 entries.
+
 .. raw:: latex
 
     \normalsize
diff --git a/drivers/media/v4l2-core/v4l2-ctrls-core.c b/drivers/media/v4l2-core/v4l2-ctrls-core.c
index b78992e32e21c79b1c70ec673b81759c9ca84206..e7376b52bd75dd5800d58941aee21534ce0b502e 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls-core.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls-core.c
@@ -1410,6 +1410,9 @@ static int std_validate_compound(const struct v4l2_ctrl *ctrl, u32 idx,
 			return -EINVAL;
 		break;
 
+	case V4L2_CID_MPEG_VIDEO_ROI_MB_DELTA_QP:
+		break;
+
 	default:
 		return -EINVAL;
 	}
diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
index e062f2088490470c42d6c579ff7675be454a29b0..8f895060799ea13443143edd398dfb97f4ba0085 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
@@ -974,6 +974,8 @@ const char *v4l2_ctrl_get_name(u32 id)
 	case V4L2_CID_MPEG_VIDEO_AVERAGE_QP:			return "Average QP Value";
 	case V4L2_CID_FWHT_I_FRAME_QP:				return "FWHT I-Frame QP Value";
 	case V4L2_CID_FWHT_P_FRAME_QP:				return "FWHT P-Frame QP Value";
+	case V4L2_CID_MPEG_VIDEO_ROI_MB_DELTA_QP:		return "Encoder ROI MB Delta QP";
+	case V4L2_CID_MPEG_VIDEO_ROI_MB_SIZE:			return "Encoder ROI MB Size";
 
 	/* VPX controls */
 	case V4L2_CID_MPEG_VIDEO_VPX_NUM_PARTITIONS:		return "VPX Number of Partitions";
@@ -1622,6 +1624,14 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
 	case V4L2_CID_COLORIMETRY_HDR10_MASTERING_DISPLAY:
 		*type = V4L2_CTRL_TYPE_HDR10_MASTERING_DISPLAY;
 		break;
+	case V4L2_CID_MPEG_VIDEO_ROI_MB_DELTA_QP:
+		*type = V4L2_CTRL_TYPE_S8;
+		*flags |= V4L2_CTRL_FLAG_DYNAMIC_ARRAY;
+		break;
+	case V4L2_CID_MPEG_VIDEO_ROI_MB_SIZE:
+		*type = V4L2_CTRL_TYPE_U8;
+		*flags |= V4L2_CTRL_FLAG_READ_ONLY;
+		break;
 	default:
 		*type = V4L2_CTRL_TYPE_INTEGER;
 		break;
diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
index d17e41d51d2ec1ccb9e8ceb3ccc89ebc4381a4cd..be484156ed35a19229be23ad24fd224cb5a8a0cc 100644
--- a/include/uapi/linux/v4l2-controls.h
+++ b/include/uapi/linux/v4l2-controls.h
@@ -941,6 +941,8 @@ enum v4l2_mpeg_video_av1_level {
 };
 
 #define V4L2_CID_MPEG_VIDEO_AVERAGE_QP  (V4L2_CID_CODEC_BASE + 657)
+#define V4L2_CID_MPEG_VIDEO_ROI_MB_DELTA_QP  (V4L2_CID_CODEC_BASE + 658)
+#define V4L2_CID_MPEG_VIDEO_ROI_MB_SIZE  (V4L2_CID_CODEC_BASE + 659)
 
 /*  MPEG-class control IDs specific to the CX2341x driver as defined by V4L2 */
 #define V4L2_CID_CODEC_CX2341X_BASE				(V4L2_CTRL_CLASS_CODEC | 0x1000)

-- 
2.34.1