Hi,
Keith talked me intro writing a spec for DRI2, which I grudgingly must
admit is a good idea. I used the randr spec as a template, except I
replaced the flowery section dividers with a more fitting gears motif.
It's still a work in progress, mostly the introductory/background
sections though. The requests and wire encoding sections are mostly
complete and is close to what's in the git repos at this point. The
implementation isn't fully uptodate with the spec yet, but I figured
it would be wise to circulate the spec before doing more code churn,
so here it is.
cheers,
Kristian
The DRI2 Extension
Version 2.0
2008-09-04
Kristian Høgsberg
[EMAIL PROTECTED]
Red Hat, Inc
1. Introduction
DRI2 blurb
1.1 Acknowledgements
kem, keithp, anholt, keithw, glisse, idr
â â â â â â
2. DRI2 Concepts
The DRI2 extension is designed to associate and access auxillary
buffers with an X drawable.
DRI2 is a essentially a helper extension to support implementation of
direct rendering drivers/libraries/technologies.
Relation to XF86DRI
Attachment points
Assumes an underlying kernel video memory manager that can provide 32
bit integer handles to buffers, that can be passed between processes.
No ordering between swap buffers and X rendering. X rendering to src
buffers will block if they have a vblank pending.
Relies on DRM, not memory manager specific, but designed to work with GEM.
Authentication model.
â â â â â â
3. Data Types
The subpixel order is shared with the Render extension, and is documented
there. The only datatype defined is the screen size, defined in the normal
(0 degree) orientation.
â â â â â â
4. Errors
Errors are sent using core X error reports.
Authenticate
The X server failed to authenticate the client.
â â â â â â
5. Protocol Types
DRI2ATTACHMENT { DRI2_BUFFER_FRONT_LEFT
DRI2_BUFFER_BACK_LEFT
DRI2_BUFFER_FRONT_RIGHT
DRI2_BUFFER_BACK_RIGHT
DRI2_BUFFER_DEPTH
DRI2_BUFFER_STENCIL
DRI2_BUFFER_ACCUM
DRI2_BUFFER_FAKE_FRONT_LEFT
DRI2_BUFFER_FAKE_FRONT_RIGHT }
These values describe various attachment points for DRI2
buffers.
DRI2BUFFER { attachment: CARD32
name: CARD32
pitch: CARD32
cpp: CARD32
flags: CARD32 }
â â â â â â
6. Extension Initialization
The name of this extension is "DRI2".
ââââ
DRI2QueryVersion
client-major-version: CARD32
client-minor-version: CARD32
â¶
major-version: CARD32
minor-version: CARD32
ââââ
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.
â â â â â â
7. Extension Requests
ââââ
DRI2Connect
window: WINDOW
type: STRING
â¶
driver: STRING
device: STRING -- device file name
group: CARD32
ââââ
Returns the driver name and device file to use for the
specified driver type for the screen associated with 'window'.
'type' identifies the type of driver to query for.
'driver' is the name of the driver to load. The client is
assumed to know where to look for the drivers and what to do
with it.
'device' is the filename of the drm device file.
'group' is the authentication group the server uses.
If the client is not local, or the request driver type is
unknown or not available, 'driver' and 'device' will be empty
strings, 'group' will be '0'. We are not using an regular X
error here to indicate failure, which will allow the client
fall back to other options more easily.
Implementation notes: For the GEM memory manager, use the
GEM_INVITE ioctl to create a token for requesting access to
the servers authentication group.
ââââ
DRI2Authenticate
window: WINDOW
token: CARD32
ââââ
Errors: Window, Authenticate
Request that the X server authenticates 'token', allowing the
client to access the drm buffers created by the X server on
the screen associated with 'window'.
Authentication shouldn't fail at this point, except if an
invalid token is passed, in which case an Authenticate error
is generated.
ââââ
DRI2GetBuffers
drawable: DRAWABLE
attachments: LISTofDRI2ATTACHMENTS
â¶
width, height: CARD32
buffers: LISTofDRI2BUFFER
ââââ
Errors: Window
Get buffers for the provided attachment points for the given
drawable.
If the DDX driver does not support one or more of the
specified attachment points, a Value error is generated, with
the first unsupported attachment point as the error value.
'width' and 'height' describes the dimensions of the drawable.
'buffers'
ISSUES: Do we need the position of the window as well so that
ââââ
DRI2CopyRegion
drawable: DRAWABLE
region: REGION
source: DRI2ATTACHMENT
destination: DRI2ATTACHMENT
flags: CARD32
sequence: CARD32
ââââ
Errors: Window
Returns the range of possible screen sizes. The screen may be set to
any size within this range.
'flags' VSYNC: perform copy at the start of the vertical
retrace specified by sequence, COPY: keep src contents, for
copy region and , otherwise unspecified, which allows
glXSwapBuffer to do pageflip.
sequence: the vblank sequence number where the swap should be
scheduled, if the VSYNC flag is set.
â â â â â â
8. Extension Versioning
The RandR extension was developed in parallel with the implementation
to ensure the feasibility of various portions of the design. As
portions of the extension are implemented, the version number of the
extension has changed to reflect the portions of the standard provided.
This document describes the version 1.2 of the specification, the
partial implementations have version numbers less than that. Here's a
list of what each version provided:
1.0: Released, but never used. Relied on a number of
constructs from the XF86DRI extension, such as a
shared memory area (SAREA) to communicate changes in
cliprects and window sizes, and
1.99.1: Move the swap buffer functionality into the X server,
introduce SwapBuffer request to copy back buffer
contents to the X drawable.
1.99.2: Rethink the SwapBuffer request as an asynchronous
request to copy a region between DRI2 buffers. Drop
CreateDrawable and DestroyDrawable, update Connect to
support different driver types and to send the
authentication group.
2.0: Awesomeness!
Compatibility up to 2.0 is not preserved, but was also never released.
â â â â â â
10. Relationship with other extensions
As an extension designed to support other extensions, there is
naturally some interactions with other extensions.
10.1 GLX
The GL auxilary buffers map directly to the DRI2 buffers... eh
10.2 DBE
The DBE back buffer must correspond to the DRI2_BUFFER_FRONT_LEFT
DRI2 buffer for servers that support both DBE and DRI2.
10.3 XvMC
We might add a DRI2_BUFFER_YUV to do vsynced colorspace conversion
blits. Maybe... not really sure.
â â â â â â
Appendix A. Protocol Encoding
Syntactic Conventions
This document uses the same syntactic conventions as the core X
protocol encoding document.
A.1 Common Types
ââââ
DRI2ATTACHMENT
0x0 DRI2_BUFFER_FRONT_LEFT
0x1 DRI2_BUFFER_BACK_LEFT
0x2 DRI2_BUFFER_FRONT_RIGHT
0x3 DRI2_BUFFER_BACK_RIGHT
0x4 DRI2_BUFFER_DEPTH
0x5 DRI2_BUFFER_STENCIL
0x6 DRI2_BUFFER_ACCUM
0x7 DRI2_BUFFER_FAKE_FRONT_LEFT
0x8 DRI2_BUFFER_FAKE_FRONT_RIGHT_LEFT
ââââ
Used to encode the possible attachment points.
ââââ
DRI2BUFFER
4 CARD32 attachment
4 CARD32 name
4 CARD32 pitch
4 CARD32 cpp
4 CARD32 flags
ââââ
A DRI2 buffer specifies the attachment, the kernel memory
manager name, the pitch and chars per pixel for a buffer
attached to a given drawable.
A.2 Protocol Requests
ââââ
DRI2QueryVersion
1 CARD8 major opcode
1 0 DRI2 opcode
2 3 length
4 CARD32 major version
4 CARD32 minor version
â¶
1 1 Reply
1 unused
2 CARD16 sequence number
4 0 reply length
4 CARD32 major version
4 CARD32 minor version
16 unused
ââââ
ââââ
DRI2Connect
1 CARD8 major opcode
1 1 DRI2 opcode
2 3+(n+p)/4 length
4 WINDOW window
4 CARD32 driver type name length
n CARD8 driver type name
p unused, p=pad(n)
â¶
1 1 Reply
1 unused
2 CARD16 sequence number
4 (n+m+p)/4 reply length
4 n driver name length
4 m device name length
4 CARD32 group
12 unused
n CARD8 driver name
m CARD8 device name
p unused, p=pad(n)
ââââ
ââââ
DRI2Authenticate
1 CARD8 major opcode
1 2 DRI2 opcode
2 3 length
4 WINDOW window
4 CARD32 authentication token
ââââ
ââââ
DRI2GetBuffers
1 CARD8 major opcode
1 3 DRI2 opcode
2 3 length
4 DRAWABLE drawable
4 n number of attachments
4n LISTofDRI2ATTACHMENTS attachments
â¶
4 CARD32 width of drawable
4 CARD32 height of drawable
5n LISTofDRI2BUFFER buffers
ââââ
ââââ
DRI2CopyRegion
1 CARD8 major opcode
1 4 DRI2 opcode
2 3 length
4 DRAWABLE drawable
4 REGION region
4 DRI2ATTACHMENT source
4 DRI2ATTACHMENT destination
4 CARD32 flags
4 CARD32 sequence
ââââ
A.3 Protocol Events
The DRI2 extension specifies no events.
A.4 Protocol Errors
ââââ
ERRORS
Base + 0 Authenticate
ââââ
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