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Direct Rendering Infrastructure Alpha release
---------------------------------------------
Patches for the final sample implementation (SI) of Precision Insight's
Direct Rendering Infrastructure (DRI) have been submitted to XFree86.
Please direct all comments about this release to glx@xfree86.org.
* What comes with this release?
There are four main parts of this patch:
1. the client- and server-side DRI,
2. a 2D DDX driver for 3Dlabs' GMX2000,
3. an OpenGL client side direct rendering driver for the GMX2000, and
4. a generic kernel driver for Linux 2.2.x (x <= 10) and Linux 2.3.y (y
<= 8).
The DRI handles the communication and synchronization between the X
server, the client driver and the kernel driver.
The 3Dlabs XFree86 DDX driver has been enhanced to support the
GMX2000. It has also been extended to communicate with and provide
callbacks for the DRI.
The client driver implements a subset of OpenGL. The subset required
for id Software's Quake 2 was chosen to demonstrate the capabilities
of the DRI. This driver communicates with the device by filling DMA
buffers and sending them to the kernel driver. Note that the Gamma
chip implements OpenGL 1.1 in hardware, and therefore, does not use
the Mesa internals at this time. However, support for the majority of
current generation of 3D hardware devices will require integration
with Mesa, so an example DRI driver using the Mesa software-only
pipeline was implemented (and is mostly complete for the alpha
release).
The generic kernel driver handles the allocation of the DMA buffers,
distribution of the buffers to the clients, sending the buffers to the
device, and the management of synchronization between the client
driver, the X server, and the kernel driver (this includes the device
lock and a shared memory region). Note that hardware that does not
support DMA or that does support special synchronization methods will
only make use of a subset of these capabilities.
* What changed between the alpha release and the sample implementation?
- Dynamic loading of the OpenGL client driver is implemented
- 3D client death while holding the drawable lock does not cause deadlock
- The kernel module works with Linux 2.2.x [x <= 10] and 2.3.y [y <= 8]
- A better authentication mechanism has been implemented
- XF86Config options for the DRI are supported
* What are the known problems and/or limitations of the sample
implementation?
Here are other problems that we did not have time to fix for the SI.
However, we and other open source developers could continue developing
and extending the DRI in follow-on projects.
- The X server seg faults due to a context switching bug when there
are 10 or more 3D clients running simultaneously
- A better DMA buffer queuing algorithm needs to be implemented
- A device specific shared memory region needs to be added to SAREA
- The DRI protocol request for the framebuffer layout needs to be
extended to support FB width and depth information (for 24 vs. 32
bpp, 8+24 layouts, etc)
- Direct rendering to a pixmap is not supported
- A more sophisticated texture management routine is required to
handle texture swapping efficiently
- Multi-threaded OpenGL clients are not supported
- glXCopyContext and glXUseXFont are not supported in the DRI
- SwapBuffers does not wait on vertical retrace
- Support wait for vertical retrace in kernel driver
- Handling overlays is not currently supported
- Integrate with DBE
- Completing the software-only Mesa example driver
- Completing the other OpenGL paths for the GMX2000
- Support for video modes other than 640x480 in both the GMX2000 2D
DDX driver and the 3D client driver
- More than minimal 2D acceleration of the GMX2000 2D DDX driver
should be implemented
- Implement finer grained locking scheme in X server to improve
interactivity
- Only grab the drawable lock and update the drawable stamp when a 3D
window is altered
- The viewport does not scale properly when a 3D window is resized
- Double buffered 3D windows are not clipped to the screen
- glXSwapBuffers is not clipped to the client's viewport
- Only one client is allowed to use texture memory
- glFinish does not wait until the HW completes processing the
outstanding DMA buffers
- Version numbers of the DDX and kernel driver are not verified
- Make lock available during SIGSTOP
- Make drmFinish work while holding the device lock
- Improve /proc/drm
- Improve documentation
- Improve example device-specific kernel driver (not used for SI)
* Where can I get more information?
We have made our design and implementation documents available on our
website:
http://www.precisioninsight.com/piinsights.html
More documentation will be available with the SI release.
* Where should I send comments?
Please send all comments and questions to the glx@xfree86.org list
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