Commit bdbb016d authored by Xavier Roumegue's avatar Xavier Roumegue Committed by Mauro Carvalho Chehab
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media: Documentation: dw100: Add user documentation for the DW100 driver 



Add user documentation for the DW100 driver.

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

Signed-off-by: default avatarXavier Roumegue <xavier.roumegue@oss.nxp.com>
Reviewed-by: default avatarLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: default avatarHans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@kernel.org>
parent f1739ec4

Documentation/userspace-api/media/drivers/dw100.rst

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.. 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

Documentation/userspace-api/media/drivers/index.rst

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@@ -33,6 +33,7 @@ For more details see the file COPYING in the source distribution of Linux. 


	ccs

	cx2341x-uapi

	dw100

	imx-uapi

	max2175

	meye-uapi