[PATCH v7 6/7] media: uapi: Add controls for NPCM video driver

[Marvin Lin]

Create controls for Nuvoton NPCM video driver to support setting
capture mode of Video Capture/Differentiation (VCD) engine and getting
the count of HEXTILE rectangles that is compressed by Encoding
Compression Engine (ECE).

Signed-off-by: Marvin Lin <milkfafa@xxxxxxxxx>
---
 .../userspace-api/media/drivers/index.rst     |  1 +
 .../media/drivers/npcm-video.rst              | 68 +++++++++++++++++++
 include/uapi/linux/npcm-video.h               | 41 +++++++++++
 3 files changed, 110 insertions(+)
 create mode 100644 Documentation/userspace-api/media/drivers/npcm-video.rst
 create mode 100644 include/uapi/linux/npcm-video.h

diff --git a/Documentation/userspace-api/media/drivers/index.rst b/Documentation/userspace-api/media/drivers/index.rst
index 32f82aed47d9..27ce108b15e1 100644
--- a/Documentation/userspace-api/media/drivers/index.rst
+++ b/Documentation/userspace-api/media/drivers/index.rst
@@ -37,5 +37,6 @@ For more details see the file COPYING in the source distribution of Linux.
 	imx-uapi
 	max2175
 	meye-uapi
+	npcm-video
 	omap3isp-uapi
 	uvcvideo
diff --git a/Documentation/userspace-api/media/drivers/npcm-video.rst b/Documentation/userspace-api/media/drivers/npcm-video.rst
new file mode 100644
index 000000000000..3041122fe299
--- /dev/null
+++ b/Documentation/userspace-api/media/drivers/npcm-video.rst
@@ -0,0 +1,68 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+.. include:: <isonum.txt>
+
+NPCM video driver
+=================
+
+This driver is used to control the Video Capture/Differentiation (VCD) engine
+and Encoding Compression Engine (ECE) present on Nuvoton NPCM SoCs. The VCD can
+capture and differentiate video data from digital or analog sources, then the
+ECE will compress the data into HEXTILE format.
+
+Driver-specific Controls
+------------------------
+
+V4L2_CID_NPCM_CAPTURE_MODE
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The VCD engine supports two modes:
+
+- COMPLETE mode:
+
+  Capture the next complete frame into memory.
+
+- DIFF mode:
+
+  Compare the incoming frame with the frame stored in memory, and updates the
+  differentiated frame in memory.
+
+Application can use ``V4L2_CID_NPCM_CAPTURE_MODE`` control to set the VCD mode
+with different control values (enum v4l2_npcm_capture_mode):
+
+- ``V4L2_NPCM_CAPTURE_MODE_COMPLETE``: will set VCD to COMPLETE mode.
+- ``V4L2_NPCM_CAPTURE_MODE_DIFF``: will set VCD to DIFF mode.
+
+V4L2_CID_NPCM_RECT_COUNT
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+After frame data is captured, the ECE will compress the data into HEXTILE format
+and store these HEXTILE rectangles data in V4L2 video buffer with the layout
+defined in Remote Framebuffer Protocol:
+::
+
+           (RFC 6143, https://www.rfc-editor.org/rfc/rfc6143.html#section-7.6.1)
+
+           +--------------+--------------+-------------------+
+           | No. of bytes | Type [Value] | Description       |
+           +--------------+--------------+-------------------+
+           | 2            | U16          | x-position        |
+           | 2            | U16          | y-position        |
+           | 2            | U16          | width             |
+           | 2            | U16          | height            |
+           | 4            | S32          | encoding-type (5) |
+           +--------------+--------------+-------------------+
+           |             HEXTILE rectangle data              |
+           +-------------------------------------------------+
+
+Application can get these video buffers through V4L2 interfaces and use
+``V4L2_CID_NPCM_RECT_COUNT`` control to get the count of compressed HEXTILE
+rectangles that can be put in the field number-of-rectangles of
+FramebufferUpdate header.
+
+References
+----------
+include/uapi/linux/npcm-video.h
+
+**Copyright** |copy| 2022 Nuvoton Technologies
+
diff --git a/include/uapi/linux/npcm-video.h b/include/uapi/linux/npcm-video.h
new file mode 100644
index 000000000000..6d9c77068e45
--- /dev/null
+++ b/include/uapi/linux/npcm-video.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
+/*
+ * Controls header for NPCM video driver
+ *
+ * Copyright (C) 2022 Nuvoton Technologies
+ */
+
+#ifndef _UAPI_LINUX_NPCM_VIDEO_H
+#define _UAPI_LINUX_NPCM_VIDEO_H
+
+#include <linux/v4l2-controls.h>
+
+/*
+ * Check Documentation/userspace-api/media/drivers/npcm-video.rst for control
+ * details.
+ */
+
+/*
+ * This control is meant to set the mode of NPCM Video Capture/Differentiation
+ * (VCD) engine.
+ *
+ * The VCD engine supports two modes:
+ * COMPLETE - Capture the next complete frame into memory.
+ * DIFF	    - Compare the incoming frame with the frame stored in memory, and
+ *	      updates the differentiated frame in memory.
+ */
+#define V4L2_CID_NPCM_CAPTURE_MODE	(V4L2_CID_USER_NPCM_BASE + 0)
+
+enum v4l2_npcm_capture_mode {
+	V4L2_NPCM_CAPTURE_MODE_COMPLETE	= 0, // COMPLETE mode
+	V4L2_NPCM_CAPTURE_MODE_DIFF	= 1, // DIFF mode
+};
+
+/*
+ * This control is meant to get the count of compressed HEXTILE rectangles which
+ * is relevant to the number of differentiated frames if VCD is in DIFF mode.
+ * And the count will always be 1 if VCD is in COMPLETE mode.
+ */
+#define V4L2_CID_NPCM_RECT_COUNT	(V4L2_CID_USER_NPCM_BASE + 1)
+
+#endif /* _UAPI_LINUX_NPCM_VIDEO_H */
-- 
2.34.1