Name
NV_stream_socket
NV_stream_socket_unix
NV_stream_socket_inet
Name Strings
EGL_NV_stream_socket
EGL_NV_stream_socket_unix
EGL_NV_stream_socket_inet
Contributors
Daniel Kartch
Bogdan Naodovic
James Jones
Zander Clucas
Tarun Bansal
Contacts
Daniel Kartch, NVIDIA (dkartch 'at' nvidia.com)
Status
Draft
Version
Version 6 - October 27, 2016
Number
EGL Extension #115
Extension Type
EGL display extension
Dependencies
EGL_NV_stream_socket requires EGL_NV_stream_remote.
EGL_NV_stream_socket_unix requires EGL_NV_stream_socket.
EGL_NV_stream_socket_inet requires EGL_NV_stream_socket.
Overview
These extensions build on the framework for remote streams provided
in EGL_NV_stream_remote to define a means for two EGLStream objects
representing opposite ends of a single stream to establish
communication using a socket. The application is expected to create
and connnect both ends of the socket before creating the stream
objects.
The base EGL_NV_stream_socket extension defines most of the
attributes required to initialize the stream objects. The
EGL_NV_stream_socket_unix and EGL_NV_stream_socket_inet extensions
indicate support for UNIX domain and internet protocol socket types,
respectively. Additional extensions may provide support for other
socket types. The type of socket is important, as certain operations
are only available with certain types, which may influence how the
streams are implemented. For instance, UNIX domain sockets allow
file descriptors to be passed between processes, while internet
protocol sockets do not. This ability may allow more efficient
sharing of resources between the socket endpoints.
An application using this extension will bear some similarity to the
example code from the EGL_KHR_stream_cross_process_fd extension,
which also uses sockets to establish the communication between two
processes and then create a pair of EGLStream objects. The key
difference is that in that case, the sockets are merely a temporary
means to an end to pass a file descriptor between the processes.
Once that is accomplished, the sockets are discarded.
The file descriptor used by that extension may represent an
underlying object such as shared memory which allows more efficient
communication than the sockets themselves. However, there is nothing
preventing an implementation of EGL_NV_stream_socket from creating
and passing such a file descriptor as well, gaining the same
efficiency. Therefore, a protocol based on sockets will work at
least as well as one based on file descriptors, with the added
benefit of being more portable.
New Types
None
New Functions
None
New Tokens for EGL_NV_stream_socket
Accepted by eglCreateStreamKHR and returned by eglQueryStreamKHR
when attribute is EGL_STREAM_PROTOCOL_NV:
EGL_STREAM_PROTOCOL_SOCKET_NV 0x324B
Accepted as attribute names by eglCreateStreamKHR and
eglQueryStreamKHR functions
EGL_SOCKET_HANDLE_NV 0x324C
EGL_SOCKET_TYPE_NV 0x324D
New Tokens for EGL_NV_stream_socket_unix
Accepted by eglCreateStreamKHR and returned by eglQueryStreamKHR
when attribute is EGL_SOCKET_TYPE_NV:
EGL_SOCKET_TYPE_UNIX_NV 0x324E
New Tokens for EGL_NV_stream_socket_inet
Accepted by eglCreateStreamKHR and returned by eglQueryStreamKHR
when attribute is EGL_SOCKET_TYPE_NV:
EGL_SOCKET_TYPE_INET_NV 0x324F
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_PROTOCOL_NV
is EGL_STREAM_PROTOCOL_SOCKET_NV and values are not provided for
EGL_SOCKET_HANDLE_NV and EGL_SOCKET_TYPE_NV.
Add to "Table 3.10.4.4 EGLStream Attributes" in EGL_KHR_stream:
Attribute Read/Write Type Section
-------------------------- ---------- ------ ----------
EGL_SOCKET_HANDLE_NV io EGLint 3.10.4.y
EGL_SOCKET_TYPE_NV io EGLint 3.10.4.y+1
In section "3.10.4.x+1 EGL_STREAM_PROTOCOL_NV Attribute" of
EGL_NV_stream_remote, add EGL_STREAM_PROTOCOL_SOCKET_NV to the list of
legal values and add
A value of EGL_STREAM_PROTOCOL_SOCKET_NV indicates that the stream
is a remote stream whose communication is established using a socket
connection provided by the application. The details of the messages
passed through the socket are implementation dependent, and may be
influenced by the stream and socket types. This value for the
EGL_STREAM_PROTOCOL_NV attribute is compatible with values of
EGL_STREAM_CROSS_OBJECT_NV, EGL_STREAM_CROSS_DISPLAY_NV,
EGL_STREAM_CROSS_PROCESS_NV, and EGL_STREAM_CROSS_PARTITION_NV for
the EGL_STREAM_TYPE_NV attribute.
Add new subsections to the end of section "3.10.4 EGLStream Attributes"
in EGL_KHR_stream:
3.10.4.y EGL_SOCKET_HANDLE_NV Attribute
The EGL_SOCKET_HANDLE_NV attribute may be set when the stream
is created, and provides the handle to a blocking socket which will
be used to communicate with the other endpoint of the stream. If the
value of EGL_STREAM_PROTOCOL_NV is not EGL_STREAM_PROTOCOL_SOCKET_NV,
this attribute is ignored.
The type of this value is operating system dependent, and the
default value will be an invalid socket handle for the operating
system. In particular, for unix-like operating systems, the value is
a socket file descriptor as returned by socket() and related
functions, and the default value is -1.
Prior to creating the EGLStream object, the application may use the
socket handle as it wishes. But once the EGLStream object has been
successfully created, it assumes full ownership of this socket. If
the application subsequently writes to, reads from, or closes the
socket, undefined behavior will result. Furthermore, if any data
sent over the socket prior to creating the EGLStream object is not
consumed before the opposite EGLStream object is created, undefined
behavior will result.
When the EGLStream object is deleted, the socket handle will be
closed by the stream.
3.10.4.y+1 EGL_SOCKET_TYPE_NV Attribute
The EGL_SOCKET_TYPE_NV attribute may be set when the stream is
created, and indicates the type of the socket provided by the
EGL_STREAM_SOCKET_HANDLE_NV attribute. If the value of
EGL_STREAM_PROTOCOL_NV is not EGL_STREAM_PROTOCOL_SOCKET_NV this
attribute is ignored.
The default value is EGL_NONE.
If EGL_NV_stream_socket_unix is present, add to section "3.10.4.y+1
EGL_SOCKET_TYPE_NV Attribute" above:
A value of EGL_SOCKET_TYPE_UNIX_NV indicates that the socket handle
represents a Unix domain socket, created with SOCK_STREAM type.
If EGL_NV_stream_socket_inet is present, add to section "3.10.4.y+1
EGL_SOCKET_TYPE_NV Attribute" above:
A value of EGL_SOCKET_TYPE_INET_NV indicates that the socket handle
represents an internet protocol socket, created with SOCK_STREAM
type.
Issues
None
Revision History
#6 (October 27, 2016) Daniel Kartch
- Indicate that the socket handle provided should represent
a blocking socket.
#5 (June 7, 2016) Daniel Kartch
- Add contact and clean up in preparation for publication.
#4 (September 16, 2015) Zander Clucas
- Indicated STREAM_SOCKET_PROTOCOL as compatible with socket
type CROSS_PROCESS.
#3 (December 16, 2014) Daniel Kartch
- Refined overview to clarify comparison with
EGL_KHR_cross_process_fd.
- Indicated SOCK_STREAM as a requirement for the socket types.
#2 (December 11, 2014) Daniel Kartch
- Rewrote as NV draft for earlier release.
- Reserved enum values.
#1 (October 10, 2014) Daniel Kartch
- Initial EXT draft
