Hi!
Vladimir Dergachev wrote:
On the Unichrome it's possible to do quite a lot using AGP DMA. Some of the things that can be done are not disclosed by VIA, but apparently you can blit memory contents from more or less anywhere to more or less anywhere....This has just been implemented in the Unichrome driver, and I'm not sure wether it's the best or most appopriate way to do it but it works as follows:
1. The Mesa driver fills a "malloced" system memory buffer with vertex data.
2. The Mesa driver then calls the DRM through a via-specific IOCTL. (via_ioctl.c)
3. The via drm copies the buffer to another buffer in kernel system memory ( static storage ), (via_dma.c)
4. The via drm verifies the content of the buffer to reject buffers that contain commands that are considered harmful. (via_verifier.c)
5. The buffer is copied to AGP space, and the engine pointers are updated. (via_dma.c)
The reason for 3. is that running the verifier directly on AGP memory is very slow.
Hi Thomas,
Thank you very much for the explanation :)
What kind of verification of vertex data does unichrome need ?
thank you !
Vladimir Dergachev
What the command verifier does is that it lets commands thrugh that is knows:
1. Only accesses the 2D-engine or Mpeg engine through writes. (Other areas are blocked).
2. Does not attempt to fetch memory contents from system memory.
3. Does not attempt to fetch memory contents from AGP memory that is outside the user-mappable range (textures).
Frame-buffer memory is considered open territory, as is the user-mappable part of AGP-memory. Note that the AGP command buffers must NOT reside in the user-mappable parts of AGP-memory.
Regards /Thomas
/Thomas
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