Hi!

Vladimir Dergachev wrote:

Hi all,

   Can someone more knowledgable explain to me how to properly access AGP
space from within Mesa driver ?

What I want to do is to copy vertex data (i.e. coordinates, colors, etc) into an array in AGP space so that R300 engine can fetch it from there. Ideally, I would be able to tell Mesa to just store them there to begin with.

I looked at R200 MAOS code and I do not understand it - it looks like it does not use GART memory for vertex buffers, but instead users indirect buffers.

                        thank you

                              Vladimir Dergachev

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.

/Thomas









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