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-rw-r--r--Documentation/userspace-api/media/drivers/aspeed-video.rst65
-rw-r--r--Documentation/userspace-api/media/drivers/index.rst1
-rw-r--r--Documentation/userspace-api/media/v4l/buffer.rst11
-rw-r--r--Documentation/userspace-api/media/v4l/pixfmt-reserved.rst17
4 files changed, 86 insertions, 8 deletions
diff --git a/Documentation/userspace-api/media/drivers/aspeed-video.rst b/Documentation/userspace-api/media/drivers/aspeed-video.rst
new file mode 100644
index 000000000000..1b0cb1e3eba8
--- /dev/null
+++ b/Documentation/userspace-api/media/drivers/aspeed-video.rst
@@ -0,0 +1,65 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+.. include:: <isonum.txt>
+
+ASPEED video driver
+===================
+
+ASPEED Video Engine found on AST2400/2500/2600 SoC supports high performance
+video compressions with a wide range of video quality and compression ratio
+options. The adopted compressing algorithm is a modified JPEG algorithm.
+
+There are 2 types of compressions in this IP.
+
+* JPEG JFIF standard mode: for single frame and management compression
+* ASPEED proprietary mode: for multi-frame and differential compression.
+ Support 2-pass (high quality) video compression scheme (Patent pending by
+ ASPEED). Provide visually lossless video compression quality or to reduce
+ the network average loading under intranet KVM applications.
+
+VIDIOC_S_FMT can be used to choose which format you want. V4L2_PIX_FMT_JPEG
+stands for JPEG JFIF standard mode; V4L2_PIX_FMT_AJPG stands for ASPEED
+proprietary mode.
+
+More details on the ASPEED video hardware operations can be found in
+*chapter 6.2.16 KVM Video Driver* of SDK_User_Guide which available on
+AspeedTech-BMC/openbmc/releases.
+
+The ASPEED video driver implements the following driver-specific control:
+
+``V4L2_CID_ASPEED_HQ_MODE``
+---------------------------
+ Enable/Disable ASPEED's High quality mode. This is a private control
+ that can be used to enable high quality for aspeed proprietary mode.
+
+.. flat-table::
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 4
+
+ * - ``(0)``
+ - ASPEED HQ mode is disabled.
+ * - ``(1)``
+ - ASPEED HQ mode is enabled.
+
+``V4L2_CID_ASPEED_HQ_JPEG_QUALITY``
+-----------------------------------
+ Define the quality of ASPEED's High quality mode. This is a private control
+ that can be used to decide compression quality if High quality mode enabled
+ . Higher the value, better the quality and bigger the size.
+
+.. flat-table::
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 4
+
+ * - ``(1)``
+ - minimum
+ * - ``(12)``
+ - maximum
+ * - ``(1)``
+ - step
+ * - ``(1)``
+ - default
+
+**Copyright** |copy| 2022 ASPEED Technology Inc.
diff --git a/Documentation/userspace-api/media/drivers/index.rst b/Documentation/userspace-api/media/drivers/index.rst
index 32f82aed47d9..46a494e00b72 100644
--- a/Documentation/userspace-api/media/drivers/index.rst
+++ b/Documentation/userspace-api/media/drivers/index.rst
@@ -31,6 +31,7 @@ For more details see the file COPYING in the source distribution of Linux.
:maxdepth: 5
:numbered:
+ aspeed-video
ccs
cx2341x-uapi
dw100
diff --git a/Documentation/userspace-api/media/v4l/buffer.rst b/Documentation/userspace-api/media/v4l/buffer.rst
index 4638ec64db00..04dec3e570ed 100644
--- a/Documentation/userspace-api/media/v4l/buffer.rst
+++ b/Documentation/userspace-api/media/v4l/buffer.rst
@@ -187,10 +187,8 @@ struct v4l2_buffer
on the negotiated data format and may change with each buffer for
compressed variable size data like JPEG images. Drivers must set
this field when ``type`` refers to a capture stream, applications
- when it refers to an output stream. If the application sets this
- to 0 for an output stream, then ``bytesused`` will be set to the
- size of the buffer (see the ``length`` field of this struct) by
- the driver. For multiplanar formats this field is ignored and the
+ when it refers to an output stream. For multiplanar formats this field
+ is ignored and the
``planes`` pointer is used instead.
* - __u32
- ``flags``
@@ -327,10 +325,7 @@ struct v4l2_plane
- ``bytesused``
- The number of bytes occupied by data in the plane (its payload).
Drivers must set this field when ``type`` refers to a capture
- stream, applications when it refers to an output stream. If the
- application sets this to 0 for an output stream, then
- ``bytesused`` will be set to the size of the plane (see the
- ``length`` field of this struct) by the driver.
+ stream, applications when it refers to an output stream.
.. note::
diff --git a/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst b/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst
index 0ff68cd8cf62..73cd99828010 100644
--- a/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst
+++ b/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst
@@ -258,6 +258,23 @@ please make a proposal on the linux-media mailing list.
and it is used by various multimedia hardware blocks like GPU, display
controllers, ISP and video accelerators.
It contains four planes for progressive video.
+ * .. _V4L2-PIX-FMT-AJPG:
+
+ - ``V4L2_PIX_FMT_AJPG``
+ - 'AJPG'
+ - ASPEED JPEG format used by the aspeed-video driver on Aspeed platforms,
+ which is generally adapted for remote KVM.
+ On each frame compression, I will compare the new frame with previous
+ one to decide which macroblock's data is changed, and only the changed
+ macroblocks will be compressed.
+
+ The implementation is based on AST2600 A3 datasheet, revision 0.9, which
+ is not publicly available. Or you can reference Video stream data format
+ – ASPEED mode compression of SDK_User_Guide which available on
+ AspeedTech-BMC/openbmc/releases.
+
+ Decoder's implementation can be found here,
+ `aspeed_codec <https://github.com/AspeedTech-BMC/aspeed_codec/>`__
.. raw:: latex
\normalsize

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