@@ -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.
@@ -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]_
- * -
- -
- -
- - This field is irrelevant to *non-destructive Video Overlays*. For
- *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
+ 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*
+ the driver will 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
- field. For *Video Output Overlays* the driver must return a valid
+ - 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
- *destructive Video Overlays* applications must initialize this
- field. For *Video Output Overlays* the driver must return a valid
+ - This field is irrelevant to *non-destructive Video Overlays*.
+ 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>`__.
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> --- .../userspace-api/media/v4l/dev-overlay.rst | 10 +++- .../userspace-api/media/v4l/vidioc-g-fbuf.rst | 52 ++++++------------- 2 files changed, 24 insertions(+), 38 deletions(-)