GPU client side changes for GpuMemoryBuffers

gpu/GLES2/extensions/CHROMIUM/CHROMIUM_gpu_memory_buffer.txt

+Name
+
+    CHROMIUM_gpu_memory_buffer
+
+Name Strings
+
+    GL_CHROMIUM_gpu_memory_buffer
+
+Version
+
+    Last Modifed Date: April 26, 2013
+
+Dependencies
+
+    OpenGL ES 2.0 is required.
+
+Overview
+
+    This extension allows for more efficiently uploading of buffer or texture
+    data through Chromium's OpenGL ES 2.0 implementation.
+
+    For security reasons Chromium accesses the GPU from a separate process. User
+    processes are not allowed to access the GPU directly. This multi-process
+    architechure has the advantage that GPU operations can be secured and
+    pipelined but it has the disadvantage that all data that is going to be
+    passed to GPU must first be made available to the separate GPU process.
+
+    Chromium's OpenGL ES 2.0 implementation hides this issue when using the
+    standard OpenGL functions BufferData, BufferSubData, TexImage2D, and
+    TexSubImage2D by first copying the user's data to shared memory and then
+    telling the GPU process to use that shared memory to upload the data.
+
+    This extension helps avoid that extra copy from user memory to shared memory

[greggman, 2013/05/03 23:48:01]

This extension is, at least at the moment, specifically for Images. Does that
need mentioning?

[kaanb, 2013/05/06 18:20:53]

I'll go over this document once we finalize the names.

+    in a safe and secure manner by allowing the client to directly allocate
+    GPU memory. After allocating the memory the client of this interface
+    can use methods in CHROMIUM_map_sub extension to map the GPU buffer into
+    the user memory and modify the pixels.
+
+Issues
+
+    The initial use of this extension was designed for the single process
+    mode of Chromium where OpenGL ES 2.0 and GPU implementations share the
+    same process. Some additions may be required to support the case where
+    OpenGL ES 2.0 and GPU implementations live in different processes.
+
+New Tokens
+
+    None
+
+New Procedures and Functions
+
+    void ImageBufferDataCHROMIUM (GLenum target, GLsizei width, GLsizei height,
+                                  GLenum format, GLenum type)
+
+    Allocates GPU memory for the currently bound buffer with width equal to
+    <width> and height equal to <height>. If any memory was previously allocated
+    to the bound buffer it is freed before new GPU memory is allocated. If
+    <width> and <height> are both 0 no allocation takes place. Similarly if no
+    buffer was bound with a call to BindBuffer this method returns immediately
+    without allocating any buffers.
+
+    INVALID_ENUM is generated if <target> is not GL_IMAGE_BUFFER_CHROMIUM
+
+    INVALID_VALUE is generated if <width> or <height> is negative
+
+    INVALID_ENUM is generated if <format> is not GL_RGBA
+
+    INVALID_ENUM is generated if <type> is not GL_UNSIGNED_BYTE
+
+Errors
+
+    None.
+
+New State
+
+    None.
+
+Revision History
+
+    4/26/2013    Documented the extension