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Re: [Xen-devel] vm86 - DCC probes don't work

  • To: Rik van Riel <riel@xxxxxxxxxx>
  • From: Jon Smirl <jonsmirl@xxxxxxxxx>
  • Date: Tue, 22 Feb 2005 17:54:03 -0500
  • Cc: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxxx, ian.pratt@xxxxxxxxxxxx
  • Delivery-date: Tue, 22 Feb 2005 22:58:04 +0000
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On Tue, 22 Feb 2005 17:31:36 -0500 (EST), Rik van Riel <riel@xxxxxxxxxx> wrote:
> On Tue, 22 Feb 2005, Ian Pratt wrote:
> > > ddcprobe is trying to read hardware I2C buses. On a radeon card these
> > > are part of the mmio address space. Not sure where they appear on the
> > > i915 but it should be easy to find in the source.
> >
> > I suspect the i915 driver is going at the address using __va rather than
> > using isa_bus_to_virt. Please can someone investigate and send a .patch
> > (and feed upstream too).
> Dccprobe is trying to do BIOS calls from vm86 mode.
> I wonder if we're just not mapping certain physical addresses
> into vm86 mode (in domain 0) that the program expects there to
> be ...

Intel has not released the source to the i915 VBIOS. You'll have to
debug it the hard way with breakpoints on the emulation hooks in vm86.
It might be going for ioports instead of pci memory. lspci -v should
tell you all of the hardware on the i915.

I also believe the only way to set a video mode on the i915 is with a
call to the VBIOS. That will probably be broken too.

Radeon hardware would be easier to get running. All of the source for
it is in the X tree.

> --
> "Debugging is twice as hard as writing the code in the first place.
> Therefore, if you write the code as cleverly as possible, you are,
> by definition, not smart enough to debug it." - Brian W. Kernighan

Jon Smirl

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