Gallium3D is Mesa's new driver model that addresses issues with the classic model. It separates driver responsibilities into reusable components: a state tracker handles APIs like OpenGL, a pipe driver abstracts the hardware, and a pipe winsys interfaces with the operating system. This makes drivers more portable and easier to develop while supporting multiple graphics APIs on a single hardware driver.

1. Gallium3D - Mesa’s New Driver Model
Chia-I Wu
olvaffe@gmail.com
Mar 27, 2011
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 1 / 24

2. Agenda
Who Am I?
main developer of Mesa EGL stack
Android(-x86) port of Mesa
experiences in OpenGL stacks
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 2 / 24

3. Agenda
Who Am I?
main developer of Mesa EGL stack
Android(-x86) port of Mesa
experiences in OpenGL stacks
a member of 0xlab
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 2 / 24

4. Agenda
Agenda
OpenGL and Linux: DRI
classic and Gallium3D driver models
how does it make a developer happy
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 3 / 24

5. OpenGL and Linux
Mesa v.s. Proprietary Drivers
Isn’t this the case?
Mesa Proprietary
stability . v
performance . v
feature set . v
it’s free v .
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 4 / 24

6. OpenGL and Linux
Not Always
Figure: nouveau v.s. nVidia binary driver (phronix)
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 5 / 24

7. OpenGL and Linux
People
BIG TEAMS / BIG BUDGET
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 6 / 24

8. OpenGL and Linux
DRI
Direct Rendering Infrastructure, DRI
direct rendering
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 7 / 24

9. OpenGL and Linux
DRI
Direct Rendering Infrastructure, DRI
direct rendering
core X rendering
indirect rendering
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 7 / 24

10. OpenGL and Linux
DRI Components
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 8 / 24

11. OpenGL and Linux
DRI Components
<hw> dri.so is the DRI or 3D driver
<hw> drv.so is the DDX or 2D driver
<hw>.ko is the DRM kernel module
libdrm <hw>.so is the user space library for the DRM module
GLX and DRI2 are X11 protocols
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 8 / 24

12. OpenGL and Linux
They are all complex
DRM driver for buffer management, mode setting, ... (radeon has ∼70k LoC)
DDX driver for 2D operations, video, mode setting, ... (radeon has ∼100k LoC)
DRI driver for OpenGL (radeon has ∼90k LoC)
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 9 / 24

13. OpenGL and Linux
OpenGL under Mesa Classic Driver Model
libGL.so <hw>_dri.so libdrm_<hw>.so
DRI driver interface Mesa common code HW code
In the classic model,
there is common code that checks the arguments of an OpenGL call and updates
internal states
it then calls into the HW code using the function table implemented there
There is an almost one-to-one mapping between OpenGL API and the function table that
the HW code implements.
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 10 / 24

14. OpenGL and Linux
Dissection of the DRI driver
libGL.so <hw>_dri.so libdrm_<hw>.so
DRI driver interface Mesa common code HW code
OS dependent: the HW code
display server dependent: none
OpenGL dependent: the common and HW code
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 11 / 24

15. OpenGL and Linux
Problems with the Classic Model
The problems with the classic model are
it is OpenGL(ES) only; even the hardware can support OpenVG, OpenCL, ...
the driver uses OpenGL data types and objects
the driver must handle the differences between OpenGL and the hardware
an implementation issue instead of a design issue in view of the DRI architecture
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 12 / 24

16. Gallium3D
Ideal Model
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 13 / 24

17. Gallium3D
Gallium3D
libGL.so <hw>_dri.so libdrm_<hw>.so
DRI state tracker
pipe driver pipe winsys
OpenGL state tracker
OS dependent: the pipe winsys
display server dependent: none
OpenGL dependent: OpenGL state tracker
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 14 / 24

18. Gallium3D
Gallium3D
libGL.so <hw>_dri.so libdrm_<hw>.so
DRI state tracker
pipe driver pipe winsys
OpenGL state tracker
OS dependent: the pipe winsys
display server dependent: none
OpenGL dependent: OpenGL state tracker
The pipe driver is highly protable and has a well-defined interface!
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 14 / 24

19. Gallium3D
Classic Model to Gallium3D Model
libGL.so <hw>_dri.so libdrm_<hw>.so
DRI driver interface Mesa common code HW code
DRI state tracker
pipe driver pipe winsys
OpenGL state tracker
This is a non-trivial process
DRI and OpenGL state trackers are written once and shared
the pipe driver and winsys must be written for each HW
new drivers should adopt the Gallium3D model from beginning
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 15 / 24

20. Gallium3D
Gallium3D: examples
libEGL.so egl_dri2.so <hw>_dri.so libdrm_<hw>.so
DRI state tracker
pipe driver pipe winsys
OpenVG state tracker
libOpenCL.so <hw>_dri.so libdrm_<hw>.so
DRI state tracker
pipe driver pipe winsys
OpenCL state tracker
(You can also have all OpenGL, OpenVG, and OpenCL state trackers inside a single DRI
driver)
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 16 / 24

21. Gallium3D
Gallium3D: even for DDX
Xorg <hw>_drv.so (DDX) libdrm_<hw>.so
DDX state tracker pipe driver pipe winsys
A modern DDX driver is more than a 2D driver
EXA/UXA
Xrender
video decoding
mode setting KMS
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 17 / 24

22. Gallium3D
Gallium3D: SVGA
VMWare has a virtual GPU named SVGA. The aquisition of Tungsten Graphics gives
vmwgfx.ko DRM module
Gallium3D based DRI driver
Gallium3D based DDX driver
Gallium3D based D3D9 driver (D3D9 state tracker + Windows winsys)
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 18 / 24

23. Developers
Gallium3D core
Gallium3D core consists of
two interfaces: struct pipe screen and struct pipe context
helper functions for format conversions, buffer management, vertex processing, and
etc.
wrappers of OS or compiler dependent functions, such as threads, timing, I/O
Pipe drivers implement struct pipe screen and struct pipe context interfaces.
State trackers are users of the interfaces.
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 19 / 24

24. Developers
struct pipe screen
The pipe screen is an abstraction of the adapter. It is used for
querying adapter capabilities/limitations
creating resources
fencing
and other misc operations
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 20 / 24

25. Developers
struct pipe context
The pipe context is an abstraction of the graphics pipeline (and some misc operations)
vertex buffers vertex fetcher
vertex shader
geometry shader stream output buffers
textures and
constant buffers rasterizer
fragment shader
per-fragment ops color and depth buffers
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 21 / 24

26. Developers
Pseudo Code
/∗ c r e a t e t h e p i p e s c r e e n ∗/
s t r u c t p i p e s c r e e n ∗ s c r e e n = o p e n h w d e v i c e ( dev name ) ;
/∗ c r e a t e a p i p e c o n t e x t ∗/
s t r u c t p i p e s c r e e n ∗ p i p e = s c r e e n −>c o n t e x t c r e a t e ( / ∗ . . . ∗ / ) ;
struct pipe resource ∗ res ;
/∗ c r e a t e a r e s o u r c e from t h e s c r e e n ∗/
r e s = s c r e e n −>r e s o u r c e c r e a t e ( / ∗ . . . ∗ / ) ;
/∗ s e t t h e r e s o u r c e a s t h e f r a m e b u f f e r ∗/
p i p e −>s e t f r a m e b u f f e r s t a t e ( / ∗ . . . ∗ / ) ;
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 22 / 24

27. Developers
It is easier
Gallium3D driver model
has well-defined interfaces and types
is close to the hardware
has reusable state trackers
has lots of helper functions
supports pipe screen/context wrapping: trace, rbug, galahad
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 23 / 24

28. Q&A
Q&A
Questions?
Chia-I Wu (olvaffe@gmail.com) Gallium3D - Mesa’s New Driver Model Mar 27, 2011 24 / 24