Re: [RFC] i915/acpi: add lid status notification and detection

[Zhang Rui <rui.zhang@intel.com>]

On Wed, 2009-05-20 at 01:15 +0800, Matthew Garrett wrote:
> > > There's also a policy question here.  On some machines, a lid close
> > > will cause the ACPI firmware to program the GPU, disabling the pipe
> > > associated with the panel.  Should we detect this and turn it back on
> > > at open time?  That could be dangerous if userspace has received the
> > > LVDS hotplug event and changed the config out from under us...
> > > 
> > > Comments?
> > It seems that the LID status is used to determine whether the LVDS is
> > connected.
> > It is not reliable. On some boxes the initial LID status is incorrect.
> > Maybe the LID status is open. But the ACPI returns that the LID is
> > close. In such case the LVDS is not initialized and user can't get the
> > output.
> 
> Really? I haven't seen any cases of this. They'll fail in all sorts of 
> fun ways with modern userland.
> 
This is rare, and if this happens, a bug should be filed against ACPI.
BTW: we have fixed/root caused all such kind of bugs that have been
reported.
So I think it makes sense to trust the Lid state reported by ACPI button
driver.

thanks,
rui