Add user documentation for the DW100 driver. while at it, replace spaces with tab on drivers list. Signed-off-by: Xavier Roumegue <xavier.roumegue@xxxxxxxxxxx> --- .../userspace-api/media/drivers/dw100.rst | 90 +++++++++++++++++++ .../userspace-api/media/drivers/index.rst | 3 +- 2 files changed, 92 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..1e606459cf47 --- /dev/null +++ b/Documentation/userspace-api/media/drivers/dw100.rst @@ -0,0 +1,90 @@ +.. 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 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 remap contains two interpolations: coordinate interpolation and +pixel interpolation as shown in the figure below. +:: + + P1 P2 + (x1, y1) (x2, y2) + .-----------------. + | | + | P | + | (x, y) | + | * | + | | + | | + '-----------------' + P3 P4 + (x3, y3) (x4, y4) + + Remap with Coordinate + and Pixel Interpolation + + +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 doesn't contain the correct number of elements, 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 -- 2.35.1
