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diff --git a/Documentation/media/uapi/v4l/selection-api-vs-crop-api.rst b/Documentation/media/uapi/v4l/selection-api-vs-crop-api.rst deleted file mode 100644 index 79b3abca341a..000000000000 --- a/Documentation/media/uapi/v4l/selection-api-vs-crop-api.rst +++ /dev/null @@ -1,46 +0,0 @@ -.. Permission is granted to copy, distribute and/or modify this -.. document under the terms of the GNU Free Documentation License, -.. Version 1.1 or any later version published by the Free Software -.. Foundation, with no Invariant Sections, no Front-Cover Texts -.. and no Back-Cover Texts. A copy of the license is included at -.. Documentation/media/uapi/fdl-appendix.rst. -.. -.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections - -.. _selection-vs-crop: - -******************************** -Comparison with old cropping API -******************************** - -The selection API was introduced to cope with deficiencies of the -older :ref:`CROP API <crop>`, that was designed to control simple -capture devices. Later the cropping API was adopted by video output -drivers. The ioctls are used to select a part of the display were the -video signal is inserted. It should be considered as an API abuse -because the described operation is actually the composing. The -selection API makes a clear distinction between composing and cropping -operations by setting the appropriate targets. - -The CROP API lacks any support for composing to and cropping from an -image inside a memory buffer. The application could configure a -capture device to fill only a part of an image by abusing V4L2 -API. Cropping a smaller image from a larger one is achieved by setting -the field ``bytesperline`` at struct :c:type:`v4l2_pix_format`. -Introducing an image offsets could be done by modifying field -``m_userptr`` at struct :c:type:`v4l2_buffer` before calling -:ref:`VIDIOC_QBUF <VIDIOC_QBUF>`. Those operations should be avoided -because they are not portable (endianness), and do not work for -macroblock and Bayer formats and mmap buffers. - -The selection API deals with configuration of buffer -cropping/composing in a clear, intuitive and portable way. Next, with -the selection API the concepts of the padded target and constraints -flags are introduced. Finally, struct :c:type:`v4l2_crop` and struct -:c:type:`v4l2_cropcap` have no reserved fields. Therefore there is no -way to extend their functionality. The new struct -:c:type:`v4l2_selection` provides a lot of place for future -extensions. - -Driver developers are encouraged to implement only selection API. The -former cropping API would be simulated using the new one. |