[Mesa-dev] [RFC-PATCH 00/11] add support for GL_OES_EGL_image_external

[Chia-I Wu]

From: Chia-I Wu <olv at lunarg.com>

Hi,

This patch series adds support for the OpenGL ES specific
GL_OES_EGL_image_external extension[1].  It is enabled in st/mesa.

The extension adds a new texture target, GL_TEXTURE_EXTERNAL_OES.  It can only
be specified with an EGLImage.  Calling gl*Tex*Image* to manipulate an
external texture will result in GL_INVALID_ENUM.  Because of the restrictions,
it allows formats that are not otherwise supported to be sampled from.

The extension is written with YUV formats in mind.  It describes two possible
ways to to support them.  One is to insert extra instructions to the shaders
to let GPU perform the necessary color conversions on the fly.  The other is
to allocate an internal storage to perform the conversions when the EGLImage
is specified.  Neither is supported for this series.  It effectively makes the
implementation a subset of GL_OES_EGL_image function-wise.

Later, I plan to adopt the latter, also easier, approach to support NV21 and
YV12 formats[2] (for Android, but haven't started).  The changes will be
limitied to the winsys code.  The idea is that the pixel format of an EGLImage
is winsys dependent.  There are too many formats, well defined or not, to be
enumerated in pipe_format or gl_format.

This series is tested with piglit quick.tests on i965 and llvmpipe without
regressions.  I am unfamiliar with more than a couple of areas touched by this
series.  Comments are appreciated.

[1]
http://www.khronos.org/registry/gles/extensions/OES/OES_EGL_image_external.txt
[2] http://www.fourcc.org/yuv.php