Validating modes should be more fuzzy

[Matthias Hopf]

While testing the current Xserver + drivers it occurred to us that a
mode wasn't accepted though it looked perfectly sane. It turned out,
that its refresh rate (60.01fps) was *just* above the nominal maximum
refresh rate of the monitor (60fps).

As PLLs cannot be programmed exactly to any given value, there should be
a certain fuzziness in mode validation, like the attached patch will do
(in this case +/- 0.5Hz for vrefresh, +/- 0.5kHz for hrefresh, +/-
0.5MHz for clock).

I chose these values arbitrarily, and it should be discussed what to use
here (absolute/relative? How much?). I would suggest going for 0.5
absolute like in this patch (because people tend to specify integer
values for limits), or 0.1% to 1% relative.

If nobody cares, I will commit it the way it is.

Matthias

-- 
Matthias Hopf <mhopf at suse.de>      __        __   __
Maxfeldstr. 5 / 90409 Nuernberg   (_   | |  (_   |__          mat at mshopf.de
Phone +49-911-74053-715           __)  |_|  __)  |__  R & D   www.mshopf.de
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