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Diffstat (limited to 'Documentation/fb/cyblafb/whycyblafb')
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diff --git a/Documentation/fb/cyblafb/whycyblafb b/Documentation/fb/cyblafb/whycyblafb deleted file mode 100644 index a123bc1..0000000 --- a/Documentation/fb/cyblafb/whycyblafb +++ /dev/null @@ -1,85 +0,0 @@ -I tried the following framebuffer drivers: - - - TRIDENTFB is full of bugs. Acceleration is broken for Blade3D - graphics cores like the cyberblade/i1. It claims to support a great - number of devices, but documentation for most of these devices is - unfortunately not available. There is _no_ reason to use tridentfb - for cyberblade/i1 + CRT users. VESAFB is faster, and the one - advantage, mode switching, is broken in tridentfb. - - - VESAFB is used by many distributions as a standard. Vesafb does - not support mode switching. VESAFB is a bit faster than the working - configurations of TRIDENTFB, but it is still too slow, even if you - use ypan. - - - EPIAFB (you'll find it on sourceforge) supports the Cyberblade/i1 - graphics core, but it still has serious bugs and developement seems - to have stopped. This is the one driver with TV-out support. If you - do need this feature, try epiafb. - -None of these drivers was a real option for me. - -I believe that is unreasonable to change code that announces to support 20 -devices if I only have more or less sufficient documentation for exactly one -of these. The risk of breaking device foo while fixing device bar is too high. - -So I decided to start CyBlaFB as a stripped down tridentfb. - -All code specific to other Trident chips has been removed. After that there -were a lot of cosmetic changes to increase the readability of the code. All -register names were changed to those mnemonics used in the datasheet. Function -and macro names were changed if they hindered easy understanding of the code. - -After that I debugged the code and implemented some new features. I'll try to -give a little summary of the main changes: - - - calculation of vertical and horizontal timings was fixed - - - video signal quality has been improved dramatically - - - acceleration: - - - fillrect and copyarea were fixed and reenabled - - - color expanding imageblit was newly implemented, color - imageblit (only used to draw the penguine) still uses the - generic code. - - - init of the acceleration engine was improved and moved to a - place where it really works ... - - - sync function has a timeout now and tries to reset and - reinit the accel engine if necessary - - - fewer slow copyarea calls when doing ypan scrolling by using - undocumented bit d21 of screen start address stored in - CR2B[5]. BIOS does use it also, so this should be safe. - - - cyblafb rejects any attempt to set modes that would cause vclk - values above reasonable 230 MHz. 32bit modes use a clock - multiplicator of 2, so fbset does show the correct values for - pixclock but not for vclk in this case. The fbset limit is 115 MHz - for 32 bpp modes. - - - cyblafb rejects modes known to be broken or unimplemented (all - interlaced modes, all doublescan modes for now) - - - cyblafb now works independant of the video mode in effect at startup - time (tridentfb does not init all needed registers to reasonable - values) - - - switching between video modes does work reliably now - - - the first video mode now is the one selected on startup using the - vga=???? mechanism or any of - - 640x480, 800x600, 1024x768, 1280x1024 - - 8, 16, 24 or 32 bpp - - refresh between 50 Hz and 85 Hz, 1 Hz steps (1280x1024-32 - is limited to 63Hz) - - - pci retry and pci burst mode are settable (try to disable if you - experience latency problems) - - - built as a module cyblafb might be unloaded and reloaded using - the vfb module and con2vt or might be used together with vesafb - |