As there are a number of confirmed bug reports with the viafb kernel driver, and I've been working on openchrome VX855 support, as well as OLPC XO1.5 support for viafb as well as openchrome, I've decided to write some better tool for debugging graphics problems.
The userspace tool will dump all the registers (currently only CRT / LVDS / DVI / Sequencer / Power management) and parse them into human-readable form. This way we can set a certain mode or display configuration, and verify what the respective driver[s] have actually done in the hardware.
The idea is to ssh into the respective system and run that tool, even if the actual monitor is no longer showing any userful output.
viafb still needs quite a bit of re-work, I'm not really happy with e.g. how it directly uses the I2C controllers rather than registering proper i2c client drivers. What's also sad is that it doesn't use the common kernel interface for modelines (modedb). Also, there are _way_ too many module parameters. I guess close to nobody but the original authors understand how to set all this correctly.
Since I actually have a CLE266 and CX700 system at home, I'll be able to test any new code or changes on those two as well as VX800 and VX855, which should cover all the major generations of VIA integrated graphics hardware out there.
You can see the early beginnings of that tool at svn.gnumonks.org/trunk/via-chrome-tool. Theres lots of uncommitted code not yet in that repository, will push it tomorrow after I'm back to Germany.