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kernel
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linux
media: uapi: Add controls for NPCM video driver
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@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
authored by
Marvin Lin
and committed by
Hans Verkuil
1568583b
2817154c
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Documentation/userspace-api/media/drivers/index.rst
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Documentation/userspace-api/media/drivers/index.rst
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Documentation/userspace-api/media/drivers/npcm-video.rst
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Documentation/userspace-api/media/drivers/npcm-video.rst
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.. SPDX-License-Identifier: GPL-2.0
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.. include:: <isonum.txt>
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NPCM video driver
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=================
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This driver is used to control the Video Capture/Differentiation (VCD) engine
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and Encoding Compression Engine (ECE) present on Nuvoton NPCM SoCs. The VCD can
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capture a frame from digital video input and compare two frames in memory, and
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the ECE can compress the frame data into HEXTILE format.
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Driver-specific Controls
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------------------------
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V4L2_CID_NPCM_CAPTURE_MODE
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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The VCD engine supports two modes:
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- COMPLETE mode:
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Capture the next complete frame into memory.
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- DIFF mode:
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Compare the incoming frame with the frame stored in memory, and updates the
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differentiated frame in memory.
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Application can use ``V4L2_CID_NPCM_CAPTURE_MODE`` control to set the VCD mode
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with different control values (enum v4l2_npcm_capture_mode):
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- ``V4L2_NPCM_CAPTURE_MODE_COMPLETE``: will set VCD to COMPLETE mode.
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- ``V4L2_NPCM_CAPTURE_MODE_DIFF``: will set VCD to DIFF mode.
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V4L2_CID_NPCM_RECT_COUNT
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~~~~~~~~~~~~~~~~~~~~~~~~
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If using V4L2_PIX_FMT_HEXTILE format, VCD will capture frame data and then ECE
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will compress the data into HEXTILE rectangles and store them in V4L2 video
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buffer with the layout defined in Remote Framebuffer Protocol:
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::
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(RFC 6143, https://www.rfc-editor.org/rfc/rfc6143.html#section-7.6.1)
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+--------------+--------------+-------------------+
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| No. of bytes | Type [Value] | Description |
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+--------------+--------------+-------------------+
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| 2 | U16 | x-position |
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| 2 | U16 | y-position |
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| 2 | U16 | width |
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| 2 | U16 | height |
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| 4 | S32 | encoding-type (5) |
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+--------------+--------------+-------------------+
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| HEXTILE rectangle data |
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+-------------------------------------------------+
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Application can get the video buffer through VIDIOC_DQBUF, and followed by
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calling ``V4L2_CID_NPCM_RECT_COUNT`` control to get the number of HEXTILE
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rectangles in this buffer.
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References
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----------
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include/uapi/linux/npcm-video.h
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**Copyright** |copy| 2022 Nuvoton Technologies
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include/uapi/linux/npcm-video.h
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include/uapi/linux/npcm-video.h
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/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
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/*
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* Controls header for NPCM video driver
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*
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* Copyright (C) 2022 Nuvoton Technologies
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*/
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#ifndef _UAPI_LINUX_NPCM_VIDEO_H
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#define _UAPI_LINUX_NPCM_VIDEO_H
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#include <linux/v4l2-controls.h>
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/*
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* Check Documentation/userspace-api/media/drivers/npcm-video.rst for control
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* details.
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*/
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/*
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* This control is meant to set the mode of NPCM Video Capture/Differentiation
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* (VCD) engine.
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*
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* The VCD engine supports two modes:
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* COMPLETE - Capture the next complete frame into memory.
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* DIFF - Compare the incoming frame with the frame stored in memory, and
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* updates the differentiated frame in memory.
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*/
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#define V4L2_CID_NPCM_CAPTURE_MODE (V4L2_CID_USER_NPCM_BASE + 0)
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enum v4l2_npcm_capture_mode {
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V4L2_NPCM_CAPTURE_MODE_COMPLETE = 0, /* COMPLETE mode */
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V4L2_NPCM_CAPTURE_MODE_DIFF = 1, /* DIFF mode */
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};
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/*
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* This control is meant to get the count of compressed HEXTILE rectangles which
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* is relevant to the number of differentiated frames if VCD is in DIFF mode.
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* And the count will always be 1 if VCD is in COMPLETE mode.
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*/
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#define V4L2_CID_NPCM_RECT_COUNT (V4L2_CID_USER_NPCM_BASE + 1)
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#endif /* _UAPI_LINUX_NPCM_VIDEO_H */