[PATCH v10 3/8] media: Documentation: dw100: Add user documentation for the DW100 driver
From: Xavier Roumegue <xavier.roumegue@oss.nxp.com>
Date: 2022-07-30 15:49:16
Also in:
linux-media
Subsystem:
media input infrastructure (v4l/dvb), nxp i.mx 8mp dw100 v4l2 driver, the rest · Maintainers:
Mauro Carvalho Chehab, Xavier Roumegue, Linus Torvalds
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 0000000000000..1ca6fa55f539e
--- /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 12e3c512d7185..0c720ca1a27d2 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
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2.37.1