On 02/19/13 19:45, Keith Packard wrote:
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Here's the spec for DRI3:
The DRI3 Extension
Version 1.0
2013-2-19
Keith Packard
kei...@keithp.com
Intel Corporation
1. Introduction
The DRI3 extension provides mechanisms to translate between direct
rendered buffers and X pixmaps. When combined with the Swap extension,
a complete direct rendering solution for OpenGL is provided.
The direct rendered buffers are passed across the protocol via
standard POSIX file descriptor passing mechanisms. On Linux, these
buffers are DMA-BUF objects.
1.1. Acknowledgments
Eric Anholt <e...@anholt.net>
Dave Airlie <airl...@redhat.com>
Kristian Høgsberg <k...@bitplanet.net>
❄ ❄ ❄ ❄ ❄ ❄ ❄
2. Data Types
The DRI3 extension uses the RandR extension Provider to select among
multiple GPUs on a single screen.
❄ ❄ ❄ ❄ ❄ ❄ ❄
4. Errors
No errors are defined by the DRI3 extension.
❄ ❄ ❄ ❄ ❄ ❄ ❄
5. Events
No events are defined by the DRI3 extension.
❄ ❄ ❄ ❄ ❄ ❄ ❄
6. Protocol Types
DRI3DRIVER { DRI3DriverDRI
DRI3DriverVDPAU }
These values describe the type of driver the client will want
to load. The server sends back the name of the driver to use
for the screen in question.
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7. Extension Initialization
The name of this extension is "DRI3" (third time is the charm?).
┌───
DRI3QueryVersion
client-major-version: CARD32
client-minor-version: CARD32
▶
major-version: CARD32
minor-version: CARD32
└───
The client sends the highest supported version to the server
and the server sends the highest version it supports, but no
higher than the requested version. Major versions changes can
introduce incompatibilities in existing functionality, minor
version changes introduce only backward compatible changes.
It is the clients responsibility to ensure that the server
supports a version which is compatible with its expectations.
Backwards compatible changes included addition of new
requests.
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8. Extension Requests
┌───
DRI3Open
drawable: DRAWABLE
driverType: DRI3DRIVER
provider: PROVIDER
▶
driver: STRING
device: FD
└───
Errors: Drawable, Value, Match
This requests that the X server open the direct rendering
device associated with drawable, driverType and RandR
provider. The provider must support SourceOutput or SourceOffload.
The direct rendering library used to implement the specified
driverType is returned in the driver value. The file
descriptor for the device is returned in FD.
┌───
DRI3PixmapFromBuffer
pixmap: PIXMAP
drawable: DRAWABLE
width, height, stride: CARD16
Why is there a stride here if all it is is an indirect way of
calculating a total size? If the total size is what the server cares
about, then it seems like the client should just send that.
Not all tiled formats fit nicely into a height * "stride" = total
equation with "stride" being an integer.
depth, bpp: CARD8
buffer: FD
└───
Errors: Alloc, Drawable, IDChoice, Value, Match
Creates a pixmap for the direct rendering object associated
with buffer. width, height and stride specify the geometry (in
pixels) of the underlying buffer. The pixels within the buffer
may not be arranged in a simple linear fashion, but the total
byte size of the buffer must be height * stride * bpp /
8. Precisely how any additional information about the buffer
is shared is outside the scope of this extension.
If buffer cannot be used with the screen associated with
drawable, a Match error is returned.
If depth or bpp are not supported by the screen, a Value error
is returned.
┌───
DRI3BufferFromPixmap
pixmap: PIXMAP
▶
depth: CARD8
width, height, stride: CARD16
depth, bpp: CARD8
buffer: FD
└───
Errors: Pixmap, Match
Pass back a direct rendering object associated with
pixmap. Future changes to pixmap will be visible in that
direct rendered object.
The pixel format and geometry of the buffer are returned along
with a file descriptor referencing the underlying direct
rendering object.
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9. Extension Events
The DRI3 extension defines no events
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10. Extension Versioning
The DRI3 extension is adapted from the DRI2 extension.
1.0: First published version
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11. Relationship with other extensions
As an extension designed to support other extensions, there is
naturally some interactions with other extensions.
11.1 GLX
GLX has no direct relation with DRI3, but a direct rendering OpenGL
application will presumably use both, and target
11.2 Swap
The Swap extension provides a way to synchronize the display of pixmap
contents to the screen. When used in conjunction with DRI3, they
provide a complete direct rendering solution for OpenGL or other APIs.
11.3 DRI2
DRI3 provides similar functionality to the DRI2Connect and
DRI2GetBuffersWithFormat requests, however DRI3 uses file descriptors
to refer to the direct rendering device and buffers.
Swap and DRI3 are designed in conjunction to replace DRI2
11.2 XvMC / Xv
It might be nice to be able to reference YUV formatted direct rendered
objects from the X server.
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Appendix A. Protocol Encoding
Syntactic Conventions
This document uses the same syntactic conventions as the core X
protocol encoding document.
A.1 Common Types
┌───
DRI3DRIVER
0x0 DRI3DriverDRI
0x1 DRI3DriverVDPAU
└───
Note that these match the DRI2 values.
A.2 Protocol Requests
┌───
DRI3QueryVersion
1 CARD8 major opcode
1 0 DRI3 opcode
2 3 length
4 CARD32 major version
4 CARD32 minor version
▶
1 1 Reply
1 unused
2 CARD16 sequence number
4 0 reply length
4 CARD32 major version
4 CARD32 minor version
16 unused
└───
┌───
DRI3Open
1 CARD8 major opcode
1 1 DRI3 opcode
2 4 length
4 DRAWABLE drawable
4 PROVIDER provider
4 CARD32 driver type
▶
1 1 Reply
1 CARD8 n
2 CARD16 sequence number
4 (n + p) / 4 reply length
n CARD8 driver name
p unused, p=pad(n)
0 FD device
└───
┌───
DRI3PixmapFromBuffer
1 CARD8 major opcode
1 2 DRI3 opcode
2 5 length
4 Pixmap pixmap
4 Drawable drawable
2 CARD16 width
2 CARD16 height
2 CARD16 stride
1 CARD8 depth
1 CARD8 bpp
0 FD buffer
└───
┌───
DRI3BufferFromPixmap
1 CARD8 major opcode
1 3 DRI3 opcode
2 length
4 Pixmap pixmap
▶
1 1 Reply
1 unused
2 CARD16 sequence number
4 0 reply length
2 CARD16 width
2 CARD16 height
2 CARD16 stride
1 CARD8 depth
1 CARD8 bpp
16 unused
0 FD buffer
└───
A.3 Protocol Events
The DRI3 extension defines no events
A.4 Protocol Errors
The Swap extension defines no errors.
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