New subject: [Linaro-mm-sig] [RFC] New dma_buf -> EGLImage EGL extension

2 Oct 2012

      Hey,
Bit late reply, hopefully not too late.
Op 30-08-12 16:00, Tom Cooksey schreef:
...
Hi All,
Over the last few months I've been working on & off with a few people from
Linaro on a new EGL extension. The extension allows constructing an EGLImage
from a (set of) dma_buf file descriptors, including support for multi-plane
YUV. I envisage the primary use-case of this extension to be importing video
frames from v4l2 into the EGL/GLES graphics driver to texture from.
Originally the intent was to develop this as a Khronos-ratified extension.
However, this is a little too platform-specific to be an officially
sanctioned Khronos extension. It also goes against the general "EGLStream"
direction the EGL working group is going in. As such, the general feeling
was to make this an EXT "multi-vendor" extension with no official stamp of
approval from Khronos. As this is no-longer intended to be a Khronos
extension, I've re-written it to be a lot more Linux & dma_buf specific. It
also allows me to circulate the extension more widely (I.e. To those outside
Khronos membership).
ARM are implementing this extension for at least our Mali-T6xx driver and
likely earlier drivers too. I am sending this e-mail to solicit feedback,
both from other vendors who might implement this extension (Mesa3D?) and
from potential users of the extension. However, any feedback is welcome.
Please find the extension text as it currently stands below. There several
open issues which I've proposed solutions for, but I'm not really happy with
those proposals and hoped others could chip-in with better ideas. There are
likely other issues I've not thought about which also need to be added and
addressed.
Once there's a general consensus or if no-one's interested, I'll update the
spec, move it out of Draft status and get it added to the Khronos registry,
which includes assigning values for the new symbols.
Cheers,
Tom
---------8<---------
Name
EXT_image_dma_buf_import

Name Strings
EGL_EXT_image_dma_buf_import

Contributors
Jesse Barker
Rob Clark
Tom Cooksey

Contacts
Jesse Barker (jesse 'dot' barker 'at' linaro 'dot' org)
Tom Cooksey (tom 'dot' cooksey 'at' arm 'dot' com)

Status
DRAFT

Version
Version 3, August 16, 2012

Number
EGL Extension ???

Dependencies
EGL 1.2 is required.

EGL_KHR_image_base 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.
Overview
This extension allows creating an EGLImage from a Linux dma_buf file
descriptor or multiple file descriptors in the case of multi-plane YUV
images.

New Types
None

New Procedures and Functions
None

New Tokens
Accepted by the <target> parameter of eglCreateImageKHR:

    EGL_LINUX_DMA_BUF_EXT

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

    EGL_LINUX_DRM_FOURCC_EXT
    EGL_DMA_BUF_PLANE0_FD_EXT
    EGL_DMA_BUF_PLANE0_OFFSET_EXT
    EGL_DMA_BUF_PLANE0_PITCH_EXT
    EGL_DMA_BUF_PLANE1_FD_EXT
    EGL_DMA_BUF_PLANE1_OFFSET_EXT
    EGL_DMA_BUF_PLANE1_PITCH_EXT
    EGL_DMA_BUF_PLANE2_FD_EXT
    EGL_DMA_BUF_PLANE2_OFFSET_EXT
    EGL_DMA_BUF_PLANE2_PITCH_EXT

You might want to add PLANE3 just in case someone wants to import a AYUV image.
...
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:

"Values accepted for <target> are listed in Table aaa, below.
+-------------------------+--------------------------------------------+
      |  <target>               |  Notes
|
+-------------------------+--------------------------------------------+
      |  EGL_LINUX_DMA_BUF_EXT  |   Used for EGLImages imported from Linux
|
      |                         |   dma_buf file descriptors
|
+-------------------------+--------------------------------------------+
       Table aaa.  Legal values for eglCreateImageKHR <target> parameter
...

If <target> is EGL_LINUX_DMA_BUF_EXT, <dpy> must be a valid display,

<ctx>
    must be EGL_NO_CONTEXT, and <buffer> must be NULL, cast into the type
    EGLClientBuffer. The details of the image is specified by the attributes
    passed into eglCreateImageKHR. Required attributes and their values are
as
    follows:
    * EGL_WIDTH & EGL_HEIGHT: The logical dimensions of the buffer in

pixels
    * EGL_LINUX_DRM_FOURCC_EXT: The pixel format of the buffer, as

specified
          by drm_fourcc.h and used as the pixel_format parameter of the
          drm_mode_fb_cmd2 ioctl.
    * EGL_DMA_BUF_PLANE0_FD_EXT: The dma_buf file descriptor of plane 0

of
          the image.
    * EGL_DMA_BUF_PLANE0_OFFSET_EXT: The offset from the start of the
      dma_buf of the first sample in plane 0, in bytes.

    * EGL_DMA_BUF_PLANE0_PITCH_EXT: The number of bytes between the

start of
          subsequent rows of samples in plane 0. May have special meaning
for
          non-linear formats.
For images in an RGB color-space or those using a single-plane YUV

format,
    only the first plane's file descriptor, offset & pitch should be
specified.
    For semi-planar YUV formats, the chroma samples are stored in plane 1
and
    for fully planar formats, U-samples are stored in plane 1 and V-samples
are
    stored in plane 2. Planes 1 & 2 are specified by the following
attributes,
    which have the same meanings as defined above for plane 0:
Nitpick, Y'CbCr not YUV.
How do you want to deal with the case where Y' and CbCr are different hardware buffers?
Could some support for 2d arrays be added in case Y' and CbCr are separated into top/bottom fields?
How are semi-planar/planar formats handled that have a different width/height for Y' and CbCr? (YUV420)
~Maarten

Re: [Linaro-mm-sig] [RFC] New dma_buf -> EGLImage EGL extension