Name

    EXT_image_dma_buf_import_modifiers

Name Strings

    EGL_EXT_image_dma_buf_import_modifiers

Contributors

    Pekka Paalanen, Collabora Ltd.
    Louis-Francis Ratté-Boulianne
    Daniel Stone, Collabora Ltd.
    Kristian Høgsberg

Contacts

    Pekka Paalanen (pq 'at' collabora 'dot' com)
    Daniel Stone (daniels 'at' collabora 'dot' com)

Status

    Complete

Version

    Version 4, October 20, 2016

Number

    EGL Extension #105

Dependencies

    EGL 1.2 is required.

    EGL_KHR_image_base is required.
    EGL_EXT_image_dma_buf_import is required.

    The EGL implementation must be running on a Linux kernel supporting the
    dma_buf buffer sharing mechanism.

    This extension is written against the wording of the EGL 1.2 Specification.

    In order to support imports for the GL_TEXTURE_EXTERNAL_OES target, a
    compatible OpenGL ES implementation supporting GL_OES_EGL_image_external
    must be present.

Overview

    This extension builds on EGL_EXT_image_dma_buf_import, in order to support
    format modifiers used for tiling, compression, and additional non-linear
    modes. It also adds support for a fourth auxiliary plane, and queries for
    the implementation-supported types.

New Types

    None

New Procedures and Functions

    EGLBoolean eglQueryDmaBufFormatsEXT(
                            EGLDisplay dpy,
                            EGLint max_formats,
                            EGLint *formats,
                            EGLint *num_formats)


    EGLBoolean eglQueryDmaBufModifiersEXT(
                            EGLDisplay dpy,
                            EGLint format,
                            EGLint max_modifiers,
                            EGLuint64KHR *modifiers,
                            EGLBoolean *external_only,
                            EGLint *num_modifiers)

New Tokens

    Accepted as an attribute in the <attrib_list> parameter of
    eglCreateImageKHR:

        EGL_DMA_BUF_PLANE0_MODIFIER_LO_EXT 0x3443
        EGL_DMA_BUF_PLANE0_MODIFIER_HI_EXT 0x3444
        EGL_DMA_BUF_PLANE1_MODIFIER_LO_EXT 0x3445
        EGL_DMA_BUF_PLANE1_MODIFIER_HI_EXT 0x3446
        EGL_DMA_BUF_PLANE2_MODIFIER_LO_EXT 0x3447
        EGL_DMA_BUF_PLANE2_MODIFIER_HI_EXT 0x3448
        EGL_DMA_BUF_PLANE3_FD_EXT          0x3440
        EGL_DMA_BUF_PLANE3_OFFSET_EXT      0x3441
        EGL_DMA_BUF_PLANE3_PITCH_EXT       0x3442
        EGL_DMA_BUF_PLANE3_MODIFIER_LO_EXT 0x3449
        EGL_DMA_BUF_PLANE3_MODIFIER_HI_EXT 0x344A

New Types

    This extension uses the 64-bit unsigned integer type EGLuint64KHR
    first introduced by the EGL_KHR_stream extension, but does not
    depend on that extension. The typedef may be reproduced separately
    for this extension, if not already present in eglext.h.

    typedef khronos_uint64_t EGLuint64KHR;


Additions to Chapter 2 of the EGL 1.2 Specification (EGL Operation)

    Add to section 2.5.1 "EGLImage Specification" (as defined by the
    EGL_KHR_image_base specification), in the description of
    eglCreateImageKHR:

    If <target> is EGL_LINUX_DMA_BUF_EXT, both or neither of the following
    attribute values may be given. These attribute values together form an
    unsigned 64-bit value called a format modifier. Format modifiers are
    specified by drm_fourcc.h and used as the modifier parameter of the
    drm_mode_fb_cmd2 ioctl. If neither of the two attributes are given, the
    format modifier is assumed to be zero. The two attributes are:

        * EGL_DMA_BUF_PLANE0_MODIFIER_LO_EXT: The lowest 32 bits of the
          64-bit format modifier.

        * EGL_DMA_BUF_PLANE0_MODIFIER_HI_EXT: The highest 32 bits of the
          64-bit format modifier.

    For semi-planar and planar YUV formats, or other formats which require
    multiple memory planes, planes 1, 2 and 3 are specified by the following
    attributes, which have the same meanings as defined above for plane 0:

        * EGL_DMA_BUF_PLANE1_MODIFIER_LO_EXT
        * EGL_DMA_BUF_PLANE1_MODIFIER_HI_EXT
        * EGL_DMA_BUF_PLANE2_MODIFIER_LO_EXT
        * EGL_DMA_BUF_PLANE2_MODIFIER_HI_EXT
        * EGL_DMA_BUF_PLANE3_FD_EXT
        * EGL_DMA_BUF_PLANE3_OFFSET_EXT
        * EGL_DMA_BUF_PLANE3_PITCH_EXT
        * EGL_DMA_BUF_PLANE3_MODIFIER_LO_EXT
        * EGL_DMA_BUF_PLANE3_MODIFIER_HI_EXT

    Modifiers may modify any attribute of a buffer import, including but not
    limited to adding extra planes to a format which otherwise does not have
    those planes. As an example, a modifier may add a plane for an external
    compression buffer to a single-plane format. The exact meaning and effect
    of any modifier is canonically defined by drm_fourcc.h, not as part of this
    extension.

    Implementations are required to validate the full combination of base
    format and per-plane modifiers, and reject any combination which is not
    explicitly supported.

    Add to the list of error conditions for eglCreateImageKHR:

       * If <target> is EGL_LINUX_DMA_BUF_EXT, and the list of attributes
         contains EGL_DMA_BUF_PLANE0_MODIFIER_LO_EXT but not
         EGL_DMA_BUF_PLANE0_MODIFIER_HI_EXT or vice versa, EGL_BAD_PARAMETER
         is generated. This applies similarly for planes 1, 2, and 3 also.

    Add section 2.5.3 "EGLImage dma_buf formats and modifiers"

    The command

        EGLBoolean eglQueryDmaBufFormatsEXT(
                            EGLDisplay dpy,
                            EGLint max_formats,
                            EGLint *formats,
                            EGLint *num_formats)

    is used to query the dma_buf formats supported by <dpy>. Each format is
    returned using its FourCC format as defined in the drm_fourcc.h header file.
    EGL_TRUE is returned if QueryDmaBufFormatsEXT succeeds, EGL_FALSE indicates
    failure to query.

       * If <dpy> is not the handle of a valid EGLDisplay object, the error
         EGL_BAD_DISPLAY is generated.

       * If <max_formats> is 0, no formats are returned, but the total number
         of formats is returned in <num_formats>, and no error is generated.

       * If <max_formats> has a negative value, the error EGL_BAD_PARAMETER
         is generated.

       * If <max_formats> is a positive integer but <formats> is NULL, the error
         EGL_BAD_PARAMETER is generated.

    The command

        EGLBoolean eglQueryDmaBufModifiersEXT(
                            EGLDisplay dpy,
                            EGLint format,
                            EGLint max_modifiers,
                            EGLuint64KHR *modifiers,
                            EGLBoolean *external_only,
                            EGLint *num_modifiers)

    is used to query the dma_buf format modifiers supported by <dpy> for the
    given format. The format must be one of those returned by the
    eglQueryDmaBufFormatsEXT command. The returned modifiers should be
    defined in the canonical drm_fourcc.h header file. If the user also
    passes an array for <external_only>, this will be populated with whether
    the requested format and modifier combination is only supported for use
    with the GL_TEXTURE_EXTERNAL_OES texture target. If <dpy> cannot support
    any context with GL_OES_EGL_image_external, the array will be populated with
    EGL_FALSE. EGL_TRUE is returned if QueryDmaBufModifiersEXT succeeds,
    EGL_FALSE indicates failure.

       * If <dpy> is not the handle of a valid EGLDisplay object, the error
         EGL_BAD_DISPLAY is generated.

       * If <max_modifiers> is 0, no modifiers are returned, but the total
         number of modifiers is returned in <num_modifiers>, and no error is
         generated.

       * If <max_modifiers> has a negative value, the error EGL_BAD_PARAMETER
         is generated.

       * If <max_modifiers> is a positive integer but <modifiers> is NULL, the
         error EGL_BAD_PARAMETER is generated.

       * If <format> is not one of the formats advertised by
         QueryDmaBufFormatsEXT for the same <dpy>, the error EGL_BAD_PARAMETER
         is generated.


Revision History

#4 (Daniel Stone, October 20, 2016)
   - Switch to EGLuint64KHR for modifier types.

#3 (Daniel Stone, October 20, 2016)
   - Clarify that the effect that modifiers can have.
   - Disambiguate references to displays.
   - Explicitly refer to max_formats/max_modifiers behaviour when zero.

#2 (Daniel Stone, September 29, 2016)
   - Add missing tokens for plane 3 FD/offset/pitch.
   - Fix description.
   - Allow max_formats/max_modifiers to be zero, to get the counter.
   - Add external_only to modifiers query.

#1 (Pekka Paalanen, October 14, 2015)
   - Initial draft.