[PATCH v6 09/14] media: Documentation: dw100: Add user documentation for the DW100 driver

From: Xavier Roumegue <xavier.roumegue@oss.nxp.com>
To: mchehab@kernel.org, hverkuil-cisco@xs4all.nl,
	stanimir.varbanov@linaro.org, laurent.pinchart@ideasonboard.com,
	tomi.valkeinen@ideasonboard.com, robh+dt@kernel.org,
	nicolas@ndufresne.ca, alexander.stein@ew.tq-group.com
Cc: Xavier Roumegue <xavier.roumegue@oss.nxp.com>,
	linux-media@vger.kernel.org, devicetree@vger.kernel.org
Subject: [PATCH v6 09/14] media: Documentation: dw100: Add user documentation for the DW100 driver
Date: Thu, 23 Jun 2022 16:31:10 +0200	[thread overview]
Message-ID: <20220623143115.3185297-10-xavier.roumegue@oss.nxp.com> (raw)
In-Reply-To: <20220623143115.3185297-1-xavier.roumegue@oss.nxp.com>

Add user documentation for the DW100 driver.

while at it, replace spaces with tab on drivers list.

Signed-off-by: Xavier Roumegue <xavier.roumegue@oss.nxp.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 .../userspace-api/media/drivers/dw100.rst     | 69 +++++++++++++++++++
 .../userspace-api/media/drivers/index.rst     |  3 +-
 2 files changed, 71 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/userspace-api/media/drivers/dw100.rst

diff --git a/Documentation/userspace-api/media/drivers/dw100.rst b/Documentation/userspace-api/media/drivers/dw100.rst
new file mode 100644
index 000000000000..1ca6fa55f539
--- /dev/null
+++ b/Documentation/userspace-api/media/drivers/dw100.rst
@@ -0,0 +1,69 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+DW100 dewarp driver
+===================
+
+The Vivante DW100 Dewarp Processor IP core found on i.MX8MP SoC applies a
+programmable geometrical transformation on the input image to correct distortion
+introduced by lenses.
+
+The transformation function is exposed by the hardware as a grid map with 16x16
+pixel macroblocks indexed using X, Y vertex coordinates.
+::
+
+                          Image width
+           <--------------------------------------->
+
+      ^    .-------.-------.-------.-------.-------.
+      |    | 16x16 |       |       |       |       |
+   I  |    | pixel |       |       |       |       |
+   m  |    | block |       |       |       |       |
+   a  |    .-------.-------.-------.-------.-------.
+   g  |    |       |       |       |       |       |
+   e  |    |       |       |       |       |       |
+      |    |       |       |       |       |       |
+   h  |    .-------.-------.-------.-------.-------.
+   e  |    |       |       |       |       |       |
+   i  |    |       |       |       |       |       |
+   g  |    |       |       |       |       |       |
+   h  |    .-------.-------.-------.-------.-------.
+   t  |    |       |       |       |       |       |
+      |    |       |       |       |       |       |
+      |    |       |       |       |       |       |
+      v    '-------'-------'-------'-------'-------'
+
+            Grid of Image Blocks for Dewarping Map
+
+
+Each x, y coordinate register uses 16 bits to record the coordinate address in
+an unsigned 12.4 fixed point format (UQ12.4).
+::
+
+    .----------------------.--------..----------------------.--------.
+    |         31~20        | 19~16  ||         15~4         |  3~0   |
+    |       (integer)      | (frac) ||       (integer)      | (frac) |
+    '----------------------'--------''----------------------'--------'
+    <-------------------------------><------------------------------->
+                Y coordinate                     X coordinate
+
+                           Remap Register Layout
+
+The dewarping map is set from applications using the
+V4L2_CID_DW100_DEWARPING_16x16_VERTEX_MAP control. The control contains
+an array of u32 values storing (x, y) destination coordinates for each
+vertex of the grid. The x coordinate is stored in the 16 LSBs and the y
+coordinate in the 16 MSBs.
+
+The number of elements in the array must match the image size:
+
+.. code-block:: C
+
+    elems = (DIV_ROUND_UP(width, 16) + 1) * (DIV_ROUND_UP(height, 16) + 1);
+
+If the control has not been set by the application, the driver uses an identity
+map.
+
+More details on the DW100 hardware operations can be found in
+*chapter 13.15 DeWarp* of IMX8MP_ reference manual.
+
+.. _IMX8MP: https://www.nxp.com/webapp/Download?colCode=IMX8MPRM
diff --git a/Documentation/userspace-api/media/drivers/index.rst b/Documentation/userspace-api/media/drivers/index.rst
index 12e3c512d718..0c720ca1a27d 100644
--- a/Documentation/userspace-api/media/drivers/index.rst
+++ b/Documentation/userspace-api/media/drivers/index.rst
@@ -33,7 +33,8 @@ For more details see the file COPYING in the source distribution of Linux.
 
 	ccs
 	cx2341x-uapi
-        hantro
+	dw100
+	hantro
 	imx-uapi
 	max2175
 	meye-uapi
-- 
2.36.1

