57 lines
2.2 KiB
Plaintext
57 lines
2.2 KiB
Plaintext
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Quick Voodoo/Voodoo2 Crash Course (mostly Alan's notes to save looking
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stuff up in the docs all the time)
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Voodoo and Voodoo 2 appear as multimedia devices. They may be on a "dual
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function" board in which case we should not 'borrow' the Voodoo as we will
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blank the main video card. That is reported in the PCI config space.
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Voodoo/Voodoo2 hardware may not always be initialized by the host OS because
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it is not video.
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The voodoo memory is split into two pools. A 1-4Mb pool holds the frame
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buffer, an optional second buffer, zbuffers, and alpha. A second 2-8Mb
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memory area holds all the textures.
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Texture ram is directly writable but not important for the current 2D
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driver. Video RAM is 16bit depth and tiled. The view of the video memory
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area is "magic", it doesn't contain a mapping of the video RAM into PCI
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space but contains pixel poking functionality.
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The frame buffer always appears untiled and 1024 pixels wide. For write
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there are some 16 different write modes including 24/32bit. The hardware
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does not support 24/32bit - these are provided for software rendering
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fallback. Read back is always 16bit. Endian conversion is hardware. Byte
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aligned access is not supported, only word aligned. Also watch how you
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access data - you can't access out of frame buffer space and if you get
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the control bits wrong you also get zbuffered, fogged and other fun.
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LFB writes have depth and alpha if you want.
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The real hardware is RGB565, how it sets stuff up internally is out of
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our hands - which means X memory alloc/pixmap cache is a little
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constrained.
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[IDEA: Should we put the mouse and framebuffer at different Z values so
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that we don't have to erase it to draw under it - less flicker]
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Acceleration:
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All Voodoo
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Fast Fill - Solid 2D rectangle fill
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(Also depth buffer clear for 3D)
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Supports a constant alpha option
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Requires a running 3D engine
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Voodoo2 and later
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Screen to screen blit
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CPU to screen blit
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Ultra fast fill to some alignments
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Monochrome to colour expansion (cpu to screen only)
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(and they finally made the 2D and 3D state independant
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if someone ever gets drunk enough to do DRI...)
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Colour conversion on blit
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Dither
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Chroma testing (src/dst) and selection of op by colour
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raster ops are the usual 16 suspects
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Other bits supported
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CLUT Gamma correction
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