Bug#281286: xserver-xfree86: Starting X with USB mouse unpluged hardlocks system when Option "AGPMode" "4" used.
On Sun, 2005-01-16 at 17:38 -0500, Slaven Peles wrote:
> On January 16, 2005 17:05, Michel Dänzer wrote:
> > On Sun, 2005-01-09 at 14:52 -0500, Slaven Peles wrote:
> > > Perhaps it would be a good idea to put in X documentation that options
> > > such as AGPMode, AGPFastWrite and EnablePageFlip are experimental and may
> > > cause unpredictable problems when nondefault values are used.
> >
> > Where did you get the idea that this is _not_ the case for at least the
> > majority of X server driver options? There's usually a reason why
> > something is an option with a certain default value.
>
> I got the idea from man pages. For example it says:
> Option "AGPMode" "integer"
> Set AGP data transfer rate. (used only when DRI is enabled)
> 1 -- x1 (default)
> 2 -- x2
> 4 -- x4
> English is not my first language, but I understood this as I actually _should_
> set AGP mode to x4 if this is the transfer rate my chipset supports.
> The sentence is written in imperative form.
You mean 'Set AGP data transfer rate.'? I can see the same wording being
used as an imperative (shouldn't there be an exclamation mark in that
case though?), but it's definitely only intended to be a description of
what the option does in this case. Most if not all option descriptions
are worded similarly, but that doesn't mean you have to use every single
one of them. That's why they're called 'options'.
That being said, English isn't my first language either, so it's
possible that the above is indeed as misleading as you say. I'll leave
that to the resident master of the subtleties of the English language,
Branden Robinson. :)
> My understanding was that the default value was set to x1 only to
> include older chipsets which do not support higher rates.
No, the kernel automatically clamps the rate to the maximum supported.
This option merely defines the maximum rate you'd like to use. The
default value is 1x because that's considered safest. Same goes (or
should) for all options.
> Besides, there is a lot of unofficial documentation on the net which actually
> recommends users to enable these options,
There's a lot of unofficial documentation that says a lot of silly
things... (not that this is a particularly silly example)
> and since there were no explicit warnings in official XFree86 docs I
> concluded these optios were safe.
>
> Furthermore, when I set AGP mode to 4 I experienced problems that didn't look
> like X problems at all. I suspected IRQ conflict, proper kernel modules not
> loaded, hotplug bugs etc. So, I think that perhaps mentioning somewhere in
> documentation that changing default options may cause very weird system
> behavior may be helpful.
Sounds to me like you want some kind of 'if you do anything, something
else may happen' style disclaimer that seems typical for North America?
I don't like those in general, but if you really think it's necessary, I
suspect a patch won't be rejected.
--
Earthling Michel Dänzer | Debian (powerpc), X and DRI developer
Libre software enthusiast | http://svcs.affero.net/rm.php?r=daenzer
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