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4358 Serge 1 
Name
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    MESA_drm_image
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Name Strings
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    EGL_MESA_drm_image
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Contact
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    Kristian Høgsberg
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Status
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    Proposal
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Version
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    Version 2, August 25, 2010
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Number
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    EGL Extension #not assigned
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Dependencies
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    Requires EGL 1.4 or later.  This extension is written against the
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    wording of the EGL 1.4 specification.
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    EGL_KHR_base_image is required.
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Overview
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    This extension provides entry points for integrating EGLImage with the
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    Linux DRM mode setting and memory management drivers.  The extension
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    lets applications create EGLImages without a client API resource and
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    lets the application get the DRM buffer handles.
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IP Status
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    Open-source; freely implementable.
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New Procedures and Functions
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    EGLImageKHR eglCreateDRMImageMESA(EGLDisplay dpy,
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                                      const EGLint *attrib_list);
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    EGLBoolean eglExportDRMImageMESA(EGLDisplay dpy,
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                                     EGLImageKHR image,
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                                     EGLint *name,
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				     EGLint *handle,
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				     EGLint *stride);
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New Tokens
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    Accepted in the  parameter of eglCreateDRMImageMESA:
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        EGL_DRM_BUFFER_FORMAT_MESA		0x31D0
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        EGL_DRM_BUFFER_USE_MESA			0x31D1
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    Accepted as values for the EGL_IMAGE_FORMAT_MESA attribute:
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        EGL_DRM_BUFFER_FORMAT_ARGB32_MESA	0x31D2
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    Bits accepted in EGL_DRM_BUFFER_USE_MESA:
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        EGL_DRM_BUFFER_USE_SCANOUT_MESA		0x0001
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        EGL_DRM_BUFFER_USE_SHARE_MESA		0x0002
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        EGL_DRM_BUFFER_USE_CURSOR_MESA		0x0004
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    Accepted in the  parameter of eglCreateImageKHR:
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        EGL_DRM_BUFFER_MESA			0x31D3
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    Use when importing drm buffer:
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        EGL_DRM_BUFFER_STRIDE_MESA		0x31D4
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        EGL_DRM_BUFFER_FORMAT_MESA		0x31D0
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Additions to the EGL 1.4 Specification:
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    To create a DRM EGLImage, call
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        EGLImageKHR eglCreateDRMImageMESA(EGLDisplay dpy,
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                                          const EGLint *attrib_list);
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    In the attribute list, pass EGL_WIDTH, EGL_HEIGHT and format and
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    use in the attrib list using EGL_DRM_BUFFER_FORMAT_MESA and
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    EGL_DRM_BUFFER_USE_MESA.  The only format specified by this
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    extension is EGL_DRM_BUFFER_FORMAT_ARGB32_MESA, where each pixel
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    is a CPU-endian, 32-bit quantity, with alpha in the upper 8 bits,
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    then red, then green, then blue.  The bit values accepted by
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    EGL_DRM_BUFFER_USE_MESA are EGL_DRM_BUFFER_USE_SCANOUT_MESA,
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    EGL_DRM_BUFFER_USE_SHARE_MESA and EGL_DRM_BUFFER_USE_CURSOR_MESA.
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    EGL_DRM_BUFFER_USE_SCANOUT_MESA requests that the created EGLImage
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    should be usable as a scanout buffer with the DRM kernel
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    modesetting API.  EGL_DRM_BUFFER_USE_SHARE_MESA requests that the
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    EGLImage can be shared with other processes by passing the
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    underlying DRM buffer name.  EGL_DRM_BUFFER_USE_CURSOR_MESA
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    requests that the image must be usable as a cursor with KMS.  When
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    EGL_DRM_BUFFER_USE_CURSOR_MESA is set, width and height must both
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    be 64.
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    To create a process local handle or a global DRM name for a
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    buffer, call
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        EGLBoolean eglExportDRMImageMESA(EGLDisplay dpy,
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                                         EGLImageKHR image,
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                                         EGLint *name,
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                                         EGLint *handle,
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                                         EGLint *stride);
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    If  is non-NULL, a global name is assigned to the image and
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    written to , the handle (local to the DRM file descriptor,
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    for use with DRM kernel modesetting API) is written to  if
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    non-NULL and the stride (in bytes) is written to , if
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    non-NULL.
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    Import a shared buffer by calling eglCreateImageKHR with
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    EGL_DRM_BUFFER_MESA as the target, using EGL_WIDTH, EGL_HEIGHT,
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    EGL_DRM_BUFFER_FORMAT_MESA, EGL_DRM_BUFFER_STRIDE_MESA
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    in the attrib list.
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Issues
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    1.  Why don't we use eglCreateImageKHR with a target that
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        indicates that we want to create an EGLImage from scratch?
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        RESOLVED: The eglCreateImageKHR entry point is reserved for
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        creating an EGLImage from an already existing client API
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        resource.  This is fine when we're creating the EGLImage from
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        an existing DRM buffer name, it doesn't seem right to overload
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        the function to also allocate the underlying resource.
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    2.  Why don't we use an eglQueryImageMESA type functions for
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        querying the DRM EGLImage attributes (name, handle, and stride)?
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        RESOLVED: The eglQueryImage function has been proposed often,
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        but it goes against the EGLImage design.  EGLImages are opaque
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        handles to a 2D array of pixels, which can be passed between
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        client APIs.  By referencing an EGLImage in a client API, the
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        EGLImage target (a texture, a renderbuffer or such) can be
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        used to query the attributes of the EGLImage.  We don't have a
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        full client API for creating and querying DRM buffers, though,
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        so we use a new EGL extension entry point instead.
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Revision History
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    Version 1, June 3, 2010
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        Initial draft (Kristian Høgsberg)
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    Version 2, August 25, 2010
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        Flesh out the extension a bit, add final EGL tokens, capture
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        some of the original discussion in the issues section.