media: Documentation: userspace-api: media: drop clipping, destructive overlays

Support for clipping for overlays has been removed, update the
documentation.

Support for destructive overlay support has been removed as well,
also update the documentation for this.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Documentation/userspace-api/media/v4l/dev-overlay.rst

@@ -67,6 +67,7 @@ ioctls must be supported by all video overlay devices.
 Setup
 =====
 
+*Note: support for this has been removed.*
 Before overlay can commence applications must program the driver with
 frame buffer parameters, namely the address and size of the frame buffer
 and the image format, for example RGB 5:6:5. The
@@ -92,11 +93,13 @@ A driver may support any (or none) of five clipping/blending methods:
 1. Chroma-keying displays the overlaid image only where pixels in the
    primary graphics surface assume a certain color.
 
-2. A bitmap can be specified where each bit corresponds to a pixel in
+2. *Note: support for this has been removed.*
+   A bitmap can be specified where each bit corresponds to a pixel in
    the overlaid image. When the bit is set, the corresponding video
    pixel is displayed, otherwise a pixel of the graphics surface.
 
-3. A list of clipping rectangles can be specified. In these regions *no*
+3. *Note: support for this has been removed.*
+   A list of clipping rectangles can be specified. In these regions *no*
    video is displayed, so the graphics surface can be seen here.
 
 4. The framebuffer has an alpha channel that can be used to clip or
@@ -185,6 +188,7 @@ struct v4l2_window
     be 0xRRGGBB on a little endian, 0xBBGGRR on a big endian host.
 
 ``struct v4l2_clip * clips``
+    *Note: support for this has been removed.*
     When chroma-keying has *not* been negotiated and
     :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>` indicated this capability,
     applications can set this field to point to an array of clipping
@@ -201,6 +205,7 @@ struct v4l2_window
     are undefined.
 
 ``__u32 clipcount``
+    *Note: support for this has been removed.*
     When the application set the ``clips`` field, this field must
     contain the number of clipping rectangles in the list. When clip
     lists are not supported the driver ignores this field, its contents
@@ -208,6 +213,7 @@ struct v4l2_window
     supported but no clipping is desired this field must be set to zero.
 
 ``void * bitmap``
+    *Note: support for this has been removed.*
     When chroma-keying has *not* been negotiated and
     :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>` indicated this capability,
     applications can set this field to point to a clipping bit mask.

Documentation/userspace-api/media/v4l/vidioc-g-fbuf.rst

@@ -49,6 +49,9 @@ of a graphics card. A non-destructive overlay blends video images into a
 VGA signal or graphics into a video signal. *Video Output Overlays* are
 always non-destructive.
 
+Destructive overlay support has been removed: with modern GPUs and CPUs
+this is no longer needed, and it was always a very dangerous feature.
+
 To get the current parameters applications call the :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>`
 ioctl with a pointer to a struct :c:type:`v4l2_framebuffer`
 structure. The driver fills all fields of the structure or returns an
@@ -63,18 +66,12 @@ this structure, the driver prepares for the overlay and returns the
 framebuffer parameters as :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>` does, or it returns an error
 code.
 
-To set the parameters for a *non-destructive Video Overlay*,
+To set the parameters for a *Video Capture Overlay*
 applications must initialize the ``flags`` field, the ``fmt``
 substructure, and call :ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>`. Again the driver prepares for
 the overlay and returns the framebuffer parameters as :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>`
 does, or it returns an error code.
 
-For a *destructive Video Overlay* applications must additionally provide
-a ``base`` address. Setting up a DMA to a random memory location can
-jeopardize the system security, its stability or even damage the
-hardware, therefore only the superuser can set the parameters for a
-destructive video overlay.
-
 .. tabularcolumns:: |p{3.5cm}|p{3.5cm}|p{3.5cm}|p{6.6cm}|
 
 .. c:type:: v4l2_framebuffer
@@ -100,17 +97,14 @@ destructive video overlay.
       - ``base``
       -
       - Physical base address of the framebuffer, that is the address of
-	the pixel in the top left corner of the framebuffer. [#f1]_
+	the pixel in the top left corner of the framebuffer.
-    * -
+	For :ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>` this field is no longer supported
-      -
+	and the kernel will always set this to NULL.
-      -
+	For *Video Output Overlays*
-      - This field is irrelevant to *non-destructive Video Overlays*. For
+	the driver will return a valid base address, so applications can
-	*destructive Video Overlays* applications must provide a base
-	address. The driver may accept only base addresses which are a
-	multiple of two, four or eight bytes. For *Video Output Overlays*
-	the driver must return a valid base address, so applications can
 	find the corresponding Linux framebuffer device (see
-	:ref:`osd`).
+	:ref:`osd`). For *Video Capture Overlays* this field will always be
+	NULL.
     * - struct
       - ``fmt``
       -
@@ -136,8 +130,7 @@ destructive video overlay.
     * -
       -
       -
-      - For *destructive Video Overlays* applications must initialize this
+      - For *Video Output Overlays* the driver must return a valid
-	field. For *Video Output Overlays* the driver must return a valid
 	format.
     * -
       -
@@ -165,13 +158,6 @@ destructive video overlay.
 
 	This field is irrelevant to *non-destructive Video Overlays*.
 
-	For *destructive Video Overlays* both applications and drivers can
-	set this field to request padding bytes at the end of each line.
-	Drivers however may ignore the requested value, returning
-	``width`` times bytes-per-pixel or a larger value required by the
-	hardware. That implies applications can just set this field to
-	zero to get a reasonable default.
-
 	For *Video Output Overlays* the driver must return a valid value.
 
 	Video hardware may access padding bytes, therefore they must
@@ -190,9 +176,8 @@ destructive video overlay.
     * -
       - __u32
       - ``sizeimage``
-      - This field is irrelevant to *non-destructive Video Overlays*. For
+      - This field is irrelevant to *non-destructive Video Overlays*.
-	*destructive Video Overlays* applications must initialize this
+	For *Video Output Overlays* the driver must return a valid
-	field. For *Video Output Overlays* the driver must return a valid
 	format.
 
 	Together with ``base`` it defines the framebuffer memory
@@ -232,9 +217,11 @@ destructive video overlay.
     * - ``V4L2_FBUF_CAP_LIST_CLIPPING``
       - 0x0004
       - The device supports clipping using a list of clip rectangles.
+        Note that this is no longer supported.
     * - ``V4L2_FBUF_CAP_BITMAP_CLIPPING``
       - 0x0008
       - The device supports clipping using a bit mask.
+        Note that this is no longer supported.
     * - ``V4L2_FBUF_CAP_LOCAL_ALPHA``
       - 0x0010
       - The device supports clipping/blending using the alpha channel of
@@ -342,10 +329,3 @@ EPERM
 
 EINVAL
     The :ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>` parameters are unsuitable.
-
-.. [#f1]
-   A physical base address may not suit all platforms. GK notes in
-   theory we should pass something like PCI device + memory region +
-   offset instead. If you encounter problems please discuss on the
-   linux-media mailing list:
-   `https://linuxtv.org/lists.php <https://linuxtv.org/lists.php>`__.