docs/specs/EGL_MESA_drm_image_formats.txt

Name

    MESA_drm_image_formats

Name Strings

    EGL_MESA_drm_image_formats

Contributors

    Nicolai Hähnle <Nicolai.Haehnle@amd.com>
    Qiang Yu <Qiang.Yu@amd.com>

Contact

    Nicolai Hähnle <Nicolai.Haehnle@amd.com>

Status

    Proposal

Version

    Version 1, January 26, 2017

Number

    EGL Extension #??

Dependencies

    This extension requires the EGL_MESA_drm_image extension.

    This extension is written against the wording of EGL_MESA_drm_image
    specification.

Overview

    This extension extends the functionality of EGL_MESA_drm_image by adding
    additional formats required by Glamor for use with DRM buffers.

IP Status

    Open-source; freely implementable.

New Procedures and Functions

    None

New Tokens

    Accepted as values for the EGL_IMAGE_FORMAT_MESA attribute:

        EGL_DRM_BUFFER_FORMAT_ARGB2101010_MESA  0x3290
        EGL_DRM_BUFFER_FORMAT_ARGB1555_MESA     0x3291
        EGL_DRM_BUFFER_FORMAT_RGB565_MESA       0x3292

Additions to the EGL_MESA_drm_image Specification:

    Remove the sentence "The only format specified ..." from the paragraph
    describing eglCreateDRMImageMESA and add the following paragraph:

        The formats specified for use with EGL_DRM_BUFFER_FORMAT_MESA are:

      * EGL_DRM_BUFFER_FORMAT_ARGB32_MESA, where each pixel is a CPU-endian
        32-bit quantity, with alpha in the upper 8 bits, then red, then green,
        then blue,

      * EGL_DRM_BUFFER_FORMAT_ARGB2101010_MESA, where each pixel is a CPU-
        endian, 32-bit quantity, with alpha in the most significant 2 bits,
        followed by 10 bits each for red, green, and blue,

      * EGL_DRM_BUFFER_FORMAT_ARGB1555_MESA, where each pixel is a CPU-endian
        16-bit quantity, with alpha in the most significant bit, followed by
        5 bits each for red, green, and blue, and

      * EGL_DRM_BUFFER_FORMAT_RGB565_MESA, where each pixel is a CPU-endian
        16-bit quantity, with red in the 5 most significant bits, followed by
        6 bits of green and 5 bits of blue.

Issues

    1. Should we expose the full set of channel permutations for the formats,
       e.g. ABGR2101010, RGBA1010102, and BGRA1010102 in addition to
       ARGB2101010?

       RESOLVED: No.

       DISCUSSION: The original extension sets a precedent of only exposing one
       of the possible permutations of 8-bit channel formats. It is also not
       clear where the additional permutations would be used. For example,
       Glamor has a fixed mapping from pixmap/screen depth to format that
       doesn't allow for the other permutations.

Revision History

    Version 1, January, 2017
        Initial draft (Nicolai Hähnle)