Re: Linux 2.6.31-rc7

From: Dave Airlie
Date: Tue Aug 25 2009 - 23:48:00 EST

On Wed, Aug 26, 2009 at 1:33 PM, Linus
Torvalds<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Wed, 26 Aug 2009, Zhenyu Wang wrote:
>> > In my experience, the BIOS setup doesn't reflect what outputs should be
>> > used at runtime, and certainly not the correct configuration of the
>> > enabled outputs.  For example, if we went to this, the giant monitor
>> > attached to my laptop that I actually look at would go unused.
>> yeah, normally VBIOS startup just needs or only can driver one pipe, so
>> we don't have any pre knowledge except detect everything.
> Umm. What's your guys point, exactly?
> The fact is, as-is, YOU DETECT THE WRONG OUTPUTS!
> If you actually detected things _right_, none of this would be an issue.
> But you don't. And you seem to have a really hard time even admitting
> that. You try to re-detect things, and you SCREW UP.

This isn't anything to do with redetection, and in the Mac case there isn't
even a BIOS table that you can really rely on since Apple hard coded all
this stuff into their EFI and Mac OSX drivers.

Now you probably get a video bios using Apples bios layer, but it also
is most likely not telling anything close to the truth about the hw layout.

Just because the BIOS manages to light up an output in now way effects
whether the driver can do the same.

>> we already have some mac relate bugs open, but please report on it so we
>> do have people with hardware to try and response. We have recently got a
>> MacBook, yakui is looking after the modesetting issue on it.
> Quite frankly, I've reported these things several times. I've been open to
> try patches. Nothing has ever come out of it.
> I have a Mac Mini that I reported as broken over a month ago. I have a
> Westemere I've reported as not doing any DDC probing - and that I have to
> disable the LVDS probing on entirely in order to not make KMS set up the
> display to go to a non-existent LVDS port.
> You claim that you "detect everything", but quite frankly, you don't. The
> KMS code seems to assume that if it's a mobile chipset, it should have an
> LVDS output - and whether anything is connected to that or not is totally
> immaterial. There's clearly _zero_ "detection" going on.
> And the thing is, X seems to get it right, at least more often than KMS
> does.

I'm not sure why the mac-mini hack hasn't been merged I asked for it a
few times,
I'd rather the proper solution was merged but that seems to not have
happened either.

You have two special cases here,
a) mac mini - apple hw, needs hacks to workaround the fact that they
do something
nobody else does with the hw and then don't tell you about it in the
hw. the hack
from userspace should have been ported to the kernel but I keep not seeing it.

b) pre-production SDV hardware for a mobile chipset without LVDS,
here's both pieces
you get to keep them. LVDS isn't detectable on any hw, the sanity
assumption so far
are you have a mobile chipset you must have LVDS, you have an ACPI lid
button you
might have LVDS. You cannot reliably detect LVDS since DDC on LVDS panels isn't
mandatory. most BIOSes have an LVDS table, guess what I'd bet your BIOS claims
you have LVDS. So yes it nice you get free shiny hw but if it doesn't
work, its not nice
to give out about it.

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