NV_stream_dma

Name

NV_stream_dma

Name Strings

EGL_NV_stream_dma

Contributors

Santanu Thangaraj
Daniel Kartch
Arihant Jejani
  

Contacts

Santanu Thangaraj, NVIDIA (sthangaraj 'at' nvidia.com)
Arihant Jejani, NVIDIA (ajejani 'at' nvidia.com)
  

Status

Draft

Version

Version 1 - April 15, 2019

Number

Extension Type

EGL display extension

Dependencies

Requires EGL_NV_stream_remote extension.

Requires EGL_NV_stream_cross_system extension.

Interacts with EGL_NV_stream_socket extensions.

Overview:

This extension provides the framework for performing DMA transfers
between opposite ends of a single stream, if there is no shared
memory available between them. 

In case of cross system streams the buffer contents of one end of
the stream is transferred to other end using sockets by
EGL_NV_stream_socket extension. Transferring buffer contents
through sockets is slower compared to DMA transfers. Since DMA
transfers have higher throughput compared to sockets, using 
EGL_NV_stream_dma extension, applications can request EGL to
utilize DMA channels to perform buffer copies.
  

New types

None

New Procedures and functions

None

New Tokens

Accepted as attribute names in eglCreateStreamKHR,
eglCreateStreamAttribKHR, eglQueryStreamKHR, and
eglQueryStreamAttribKHR:

EGL_STREAM_DMA_NV                         0x3371
EGL_STREAM_DMA_SERVER_NV                  0x3372
  

Add to list of failures in section "3.10.1 Creating an EGLStream" in EGL_KHR stream: - EGL_BAD_MATCH is generated if the value of EGL_STREAM_DMA_NV is neither EGL_TRUE nor EGL_FALSE. - EGL_BAD_MATCH is generated if the value of EGL_STREAM_DMA_SERVER_NV is not EGL_DONT_CARE or a valid DMA server identifier as defined by the platform.

Add to "Table 3.10.4.4 EGLStream Attributes" in EGL_KHR_stream:

Attribute                 Read/Write   Type              Section
------------------------ -----------   ------            ----------
EGL_STREAM_DMA_NV            io       EGLint             3.10.4.x
EGL_STREAM_DMA_SERVER_NV     io       platform dependent 3.10.4.x+1
  

Add new subsections to the end of section "3.10.4 EGLStream Attributes" in EGL_KHR_stream:

3.10.4.x EGL_STREAM_DMA_NV Attribute

The EGL_STREAM_DMA_NV attribute may be set when the stream is 
created, and indicates whether the DMA channels have to be used to
transfer the buffer contents from producer to consumer. Legal 
values are EGL_TRUE or EGL_FALSE. The default value is EGL_FALSE.

A value of EGL_TRUE indicates that EGL has to use DMA channels to
transfer buffers from producer to consumer.

If EGL_FALSE is specified, DMA channels will not be utilized for
buffer transfers.

3.10.4.x+1 EGL_STREAM_DMA_SERVER_NV Attribute

The EGL_STREAM_DMA_SERVER_NV attribute is a platform dependent
identifier which may be set when the stream is created and it
indicates the server, which must be contacted to handle DMA 
transfers, if that server is not local. Legal values, aside from
EGL_DONT_CARE, are determined by the implementation. The default
value is EGL_DONT_CARE.
  

Issues

1.  What happens when application requests DMA copy using 
    EGL_STREAM_DMA_NV attribute in eglCreateStreamKHR or 
    eglCreateStreamAttribKHR API, but the system does not support 
    access to DMA channels?

    RESOLVED: The functions return EGL_NO_STREAM_KHR and 
    EGL_BAD_ATTRIBUTE error is set.
    
2.  What happens when application requests DMA copy using 
    EGL_STREAM_DMA_NV attribute in eglCreateStreamKHR or 
    eglCreateStreamAttribKHR API, and the system supports DMA 
    channels, but currently none of the channels are available for
    use?
    
    RESOLVED: The functions return EGL_NO_STREAM_KHR and
    EGL_BAD_ATTRIBUTE error is set.
  

Revision History

#1  (April 15, 2019) Santanu Thangaraj
    - Initial version
  