xref: /aosp_15_r20/external/mesa3d/src/gallium/frontends/xa/README (revision 6104692788411f58d303aa86923a9ff6ecaded22)

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 * Authors:
 * Zack Rusin <zackr-at-vmware-dot-com>
 * Thomas Hellstrom <thellstrom-at-vmware-dot-com>
 */

The XA gallium frontend is intended as a versioned interface to gallium for
xorg driver writers. Initially it's mostly based on Zack Rusin's
composite / video work for the Xorg gallium frontend.

The motivation behind this gallium frontend is that the Xorg gallium frontend has
a number of interfaces to work with:

1) The Xorg sdk (versioned)
2) Gallium3D (not versioned)
3) KMS modesetting (versioned)
4) Driver-private (hopefully versioned)

Since Gallium3D is not versioned, the Xorg gallium frontend needs to be compiled
with Gallium, but it's really beneficial to be able to compile xorg drivers
standalone.

Therefore the xa gallium frontend is intended to supply the following
functionality:

1) Versioning.
2) Surface functionality (creation and copying for a basic dri2 implementation)
3) YUV blits for textured Xv.
4) Solid fills without ROP functionality.
5) Copies with format conversion and - reinterpretation but without ROP
6) Xrender- type compositing for general acceleration.


The first user will be the vmwgfx xorg driver. When there are more users,
we need to be able to load the appropriate gallium pipe driver, and we
should investigate sharing the loadig mechanism with the EGL gallium frontend.

IMPORTANT:
Version compatibilities:
While this library remains OUTSIDE any mesa release branch,
and the major version number is still 0. Any minor bump should be viewed as
an incompatibility event, and any user of this library should test for that
and refuse to use the library if minor versions differ.
As soon as the library enters a mesa release branch, if not earlier, major
will be bumped to 1, and normal incompatibility rules (major bump)
will be followed.
It is allowed to add function interfaces while only bumping minor. Any
user that uses these function interfaces must therefore use lazy symbol
lookups and test minor for compatibility before using such a function.