kms howto - is there one?

Felix Miata mrmazda at earthlink.net
Fri Mar 19 17:32:42 UTC 2010


On 2010/03/19 09:05 (GMT-0700) Adam Williamson composed:

> On Fri, 2010-03-19 at 08:09 -0400, Felix Miata wrote:

>> > In fact, even the Modes line may not be necessary, looking at the X log.

>> Without both modes and modelines in xorg.conf, only the anachronistic
>> 1024x768 and worse are available modes. Xorg.0.log lies. The "probed" modes
>> above 1024x768 are not there unless present in xorg.conf, unless I'm using
>> mga, or Factory, Knoppix, Lucid, Cooker or previous Fedora releases.

> But the Mode you wind up using is 2048x1536_60.00 , so I don't see where
> having 2048x1536 listed in your Modes line helps. *shrug*

If I understand your puzzlement correctly, it "helps" in that the absence of
a modes line means, until typing a bunch of unmemorable xrandr stuff at a
prompt, the highest available mode actually available, and shown by xrandr,
is 1024x768.

>> > (Although I note "VertRefresh  56-61" - don't you get headaches?!)

>> The only headaches I get are from having to play with the device's physical
>> controls every time another driver comes up with yet another set of
>> auto-generated mode specifications that haven't been entered in the device's
>> memory, resulting in errant sizing and/or positioning of the output. By
>> limiting refresh to that narrow range the auto-generation usually matches a
>> generic spec that's already in the device's memory, resulting in correct
>> centering and sizing of the output.

> ...at 60Hz. On a CRT. Yikes. 

Different people have different flicker sensitivity. I have to get it down
below 56 to detect it, and down around 48 or 50 for it to be a bother.

>> Again I think you're missing the major point that this is _new_ behavior.
>> Only in F13 (so far, using intel & radeon at least, but not when using mga)
>> does what worked previously work no longer. Until now, and for those for whom
>> lowfi resolution is not acceptable, explicit modelines in xorg.conf hadn't
>> been necessary with broken/missing DDC/EDID for many many moons.

> And as I said, that behaviour is equally 'wrong'. The other distros
> you've tried probably aren't using kernel modesetting, hence the
> differing behaviour.

I'm having a problem understanding how something that has long been
functioning acceptably can be considered wrong. I posit that KMS
configurations simply aren't yet mature enough to deal with absent DDC/EDID.
AFAICT, KMS is in all the 2.6.33 I've used, but might not yet be used by
default, or enforced, in the non-Fedora variants or their interdependent
driver versions.

>> And BTW, actually switching modes without restarting X must be done by typing
>> xrandr commands. Attempting to select another mode from krandrtray corrupts
>> everything such that CAD or the reset button (or I suppose remote login) are
>> required to recover.

> I don't know anything about krandrtray, I use GNOME.

I know about you and Gnome, but I'm pretty sure I've seen evidence you're not
the only one besides me following this thread. :-)

> Actually I think krandrtray was written by one of Mandriva's Brazilian guys :)

Gotta be something easier than a command prompt and typing a whole big bunch
of xrandr and cvt stuff to get an acceptable configuration that persists. ;-)
-- 
"The wise are known for their understanding, and pleasant
words are persuasive." Proverbs 16:21 (New Living Translation)

 Team OS/2 ** Reg. Linux User #211409

Felix Miata  ***  http://fm.no-ip.com/


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